First observed interaction of the circumstellar envelope of an S-star with the environment of Sgr A*
Florian Pei?ker, Basel Ali, Michal Zaja?ek, Andreas Eckart, S. Elaheh Hosseini, Vladimír Karas, Yann Clénet, Nadeen B. Sabha, Lucas Labadie, Matthias Subroweit
DDraft version January 7, 2021
Typeset using L A TEX twocolumn style in AASTeX63
First observed interaction of the circumstellar envelope of an S-star with the environment of Sgr A*
Florian Pei β ker , Basel Ali , Michal Zajaˇcek ,
2, 1, 3
Andreas Eckart ,
1, 3
S. Elaheh Hosseini ,
1, 3
Vladim´ır Karas , Yann Cl´enet , Nadeen B. Sabha, Lucas Labadie, and Matthias Subroweit I.Physikalisches Institut der Universit¨at zu K¨oln, Z¨ulpicher Str. 77, 50937 K¨oln, Germany Center for Theoretical Physics, Al. Lotnik´ow 32/46, 02-668 Warsaw, Poland Max-Plank-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, 53121 Bonn, Germany Astronomical Institute, Czech Academy of Sciences, Boˇcn´ı II 1401, CZ-14100 Prague, Czech Republic LESIA, Observatoire de Paris, Universit´e PSL, CNRS, Sorbonne Universit´e, Universit´e de Paris, 5 place Jules Janssen, 92195 Meudon,France Institut f¨ur Astro- und Teilchenphysik, Universit¨at Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria (Received June 1, 2019; Revised January 10, 2019; Accepted January 7, 2021)
Submitted to ApJABSTRACTSeveral publications highlight the importance of the observations of bow shocks to learn more aboutthe surrounding interstellar medium and radiation field. We revisit the most prominent dusty andgaseous bow shock source, X7, close to the supermassive black hole, Sgr A*, using multiwavelengthanalysis. For the purpose of this study, we use SINFONI (H+K-band) and NACO ( L (cid:48) - and M (cid:48) -band)data-sets between 2002 and 2018 with additional COMIC/ADONIS+RASOIR ( L (cid:48) -band) data of 1999.By analyzing the line maps of SINFONI, we identify a velocity of ∼
200 km/s from the tip to thetail. Furthermore, a combination of the multiwavelength data of NACO and SINFONI in the H -, K -, L (cid:48) -, and M (cid:48) -band results in a two-component black-body fit that implies that X7 is a dust-enshroudedstellar object. The observed ongoing elongation and orientation of X7 in the Br γ line maps and theNACO L (cid:48) -band continuum indicate a wind arising at the position of Sgr A* or at the IRS16 complex.Observations after 2010 show that the dust and the gas shell seems to be decoupled in projectionfrom its stellar source S50. The data also implies that the tail of X7 gets thermally heated up due tothe presence of S50. The gas emission at the tip is excited because of the related forward scattering(Mie-scattering), which will continue to influence the shape of X7 in the near future. In addition, wefind excited [FeIII] lines, which underline together with the recently analyzed dusty sources and theBr γ -bar the uniqueness of this source. Keywords: editorials, notices — miscellaneous — catalogs — surveys INTRODUCTIONIn the center of our Galaxy, the prominent variableradio source Sgr A* is located (Balick & Brown 1974).This source emits across a broad range of wavelengths,ranging from the radio up to the X-ray domain, with thepeak at submillimeter wavelengths (see e.g. Genzel et al.2010; Eckart et al. 2017, and references therein). Al-though Sgr A* is a low-luminosity source, its monitoring
Corresponding author: Florian Peiß[email protected] has been of high interest because of order-of-magnitudeflares in the near-infrared and X-ray domains (Witzelet al. 2012; Do et al. 2019). Because of its nonthermal ra-diative properties, compact nature, variability, and posi-tion at the Galactic center, it has been associated witha supermassive black hole (SMBH) since its discovery(Lynden-Bell & Rees 1971), with most of the alterna-tives being ruled out based on the current observationaldata (Eckart et al. 2017).Sgr A* is also the only SMBH to date, where we candetect and monitor orbiting stars. Some of them are lo-cated inside the S-cluster, hence, they are called S-stars.These stars show pericentre distances of several 100 AU a r X i v : . [ a s t r o - ph . GA ] J a n Pei β ker et al. (Gillessen et al. 2009; Parsa et al. 2017; Ali et al. 2020).Recently discovered stars push this distance an order ofmagnitude closer to the SMBH (Peißker et al. 2020a,d).These S-stars are widely covered by many publications.For example, Eckart & Genzel (1996) derived from thestellar proper motion a direct mass estimate of Sgr A*.In addition, Ghez et al. (2002) and Eckart et al. (2002)found stellar accelerations based on the orbital curva-ture. Genzel et al. (2000) derived a velocity dispersionas a function of the distance of S-stars and found valuesof up to several hundred km/s.One of the controversial but also interesting sourcesin the field of view (FOV) is the Galactic center (GC)gas cloud G2 (Gillessen et al. 2012; Eckart, A. et al.2013; Valencia-S. et al. 2015; Shahzamanian et al. 2017;Zajaˇcek et al. 2017; Peißker et al. 2020b) also knownas the Dusty S-cluster Object (DSO) . This object wasfound on its way approaching Sgr A* in the Dopplershifted Br γ maps of SINFONI, a near-infrared (NIR)instrument mounted at the Very Large Telescope (VLT,Chile/Paranal). In combination with the observed dustemission in the L (cid:48) -band (3 . µm ) with NACO (also op-erating in the NIR, mounted at the VLT), the authors ofGillessen et al. (2012, 2013); Pfuhl et al. (2015) claimedthat the object will get disrupted during or after its pe-riapse passage. Later on, Plewa et al. (2017) stated thatthe density of the ambient medium of Sgr A* is too lowto cause a disruptive event. Even more, they excludedthe possibility of a drag force acting on the DSO. Incontrast, Gillessen et al. (2019) reported a drag forcethat influenced the observed Doppler shifted Br γ lineshape. This underlines the ongoing confusion about thenature of the source. However, in Peißker et al. (2020b)we present a spectral energy distribution (SED) derivedfrom the H-, K-, and L (cid:48) -band data of NACO and SIN-FONI. This SED consists of a dusty and stellar com-ponent and shows that the DSO is more likely a YoungStellar Object instead of a coreless ∼ × M ⊕ cloud thatmoves on a Keplerian orbit around a 4 . × M (cid:12) supermassive black hole.Cl´enet et al. (2003) and Cl´enet et al. (2005) reportedfor the first time two comet-shaped sources, namely X3and X7. These dusty objects can be found in the mid-infrared (MIR) but also show a NIR counterpart. Be-cause of its close projected distance to X7, another lineemitting source is located that we call X7.1 (G5 in Ciurloet al. 2020). Since the nature of this source is better represented by the nameDSO, we will use this throughout the manuscript.
The identification of these objects is still challenging,which is manifested in Fig. 1 in Peißker et al. (2020b).The potentially temporary distance of X7 and X7.1/G5can lead to confusion about the identification withoutspectroscopic analysis. It is, for instance, not clear whythe dusty object X7.1/G5 with an approximate L-bandmagnitude of 14.11 mag ( ∼ .
57 mJy) can neither beobserved in the NACO ( L (cid:48) -band) data presented in thiswork nor in the shown 3 . µm continuum data in Ciurloet al. (2020) (see extended data Fig. 2 in the relatedpublication). A dust-enshrouded source with a stellarcounterpart should be detectable in the L (cid:48) -band as pre-sented in Peißker et al. (2020b). A reliable approachis the spectroscopic analysis in combination with mul-tiwavelength observations. This underlines the need forbroad observation programs. Following the example ofthe DSO and X7.1, we emphasize a multiwavelengthanalysis of these (potentially) dust-enshrouded stars.With the observational coverage of different bands incombination with spectroscopy, the confusion about thenature of these objects can be minimized (see Zajaˇceket al. 2017).However, Muˇzi´c et al. (2010) analysed the X7 sourcein detail and showed the connection to a possible nuclearwind that arises at the position of Sgr A*. This windtis also mentioned in several observational and theoreti-cal publications (Muˇzi´c et al. 2007; Zajaˇcek et al. 2016;Yusef-Zadeh et al. 2017b; Peißker et al. 2020b,c; Yusef-Zadeh et al. 2020). In this regard, Peißker et al. (2019)reported a new bow shock source in the central arcsec-ond that the authors call X8 (G6 in Ciurlo et al. 2020)because of its close projected distance to X7. These twoobjects are the closest bow shock sources that could beused to determine the properties of a possible wind thatarises at the position of Sgr A*.In this work, we will update the analysis of X7 doneby Muˇzi´c et al. (2007, 2010) with the help of SINFONIintegral field spectroscopy and NACO continuum datathat cover almost 16 years. Additionally, we use L (cid:48) -bandcontinuum COMIC/ADONIS+RASOIR data of 1999 toextend the analysis of X7 to about 20 years. This workis part of a broader investigation that is split up in twopublications. Here, we emphasize the observational re-sults and give an outlook on the second part where wetheoretically investigate the observed source X7. In thesecond part of this survey, we will apply two models todescribe an open and closed bow shock based on thework of Wilkin (1996, 2000) and Christie et al. (2016).The spectroscopic capabilities of SINFONI give us anaccess to investigate the velocity along the bow shocksource that could help to describe the nuclear and thestellar wind interaction as well as prominent Doppler- nteraction of an S-star with the environment of Sgr A* DATA & ANALYSISIn this section, we will give a brief overview about theused instruments, the data reduction, and the appliedanalysis tools. 2.1.
SINFONI & NACO
The Spectrograph for Integral Field Observations inthe Near Infrared (SINFONI) was mounted on theVLT and undergoes an upgrade (for further informa-tion about the upgrade, see Kuntschner et al. 2014;Marchetti et al. 2014; Pearson et al. 2016). SIN-FONI operates in the NIR and provides observationsin the J- (1 . − . µm ), H- (1 . − . µm ), K-(1 . − . µm ), and H+K-band (1 . − . µm ). Theoutput files of the ESO pipeline are in the shape of a 3dimensional data cube. This data cube consists of 2 spa-tial dimensions and 1 spectral dimension. The compo-nents of the data cubes are described in spaxels (pixelscontaining a spectrum, see H¨ortner et al. 2012) ratherthan pixels. With SINFONI, we are able to isolate singleemission lines in the H+K-band to create channel (line)maps. In comparison, the NACO instrument works alsoin the J, L (cid:48) , and M (cid:48) -band (Lenzen et al. 2003; Roussetet al. 2003). Since dust can be traced in higher wave-lengths, the L (cid:48) -band setup of NACO is favored for thesearch of the dusty bow shock source.In both cases, we apply the usual data reduction stepslike, e.g., dark- and flat-field corrections. We also ap-ply the mandatory sky correction to the adaptive optics(AO) corrected data. Additional correction steps aredescribed in detail in Peißker et al. (2019, 2020a,b,c,d)where the here analyzed data is also used. Please con- Nasmyth Adaptive Optics System (NAOS) & Near-Infrared Im-ager and Spectrograph (CONICA) = NACO sider also the Appendix E for a detailed overview aboutthe used data.We also note that a part of this data was used in Parsaet al. (2017). The authors describe the Schwarzschildprecision of S2, which was independently confirmed byGravity Collaboration et al. (2020). The collaborationused GRAVITY, an interferometric instrument with aresolution almost one magnitude better than NACO .This underlines the robustness and validity of the NACOdata. 2.2. COMIC/ADONIS+RASOIR
The NIR camera COMIC was installed in LaSilla/Chile at the 3.6 m telescope and used the AO sys-tem ADONIS+RASOIR (Beuzit et al. 1994; Lacombeet al. 1998). It operated in the J-, H-, K-, K (cid:48) -, L (cid:48) -, andM-band with two different plate scales (35 mas/pixeland 100 mas/pixel). It was optimized for L- and M-bandobservations and decommissioned in 2001 (Pasquini &Weilenmann 1996). For the here presented data, the ex-posure time was set to 10 seconds. The observationalpattern was chosen to be s-o-s (sky-object-sky) followedby flat and dark exposures. For combining the data, weuse the shift and add algorithm to maximize the signal-to-noise (S/N) ratio. This is followed by rebining thedata to smooth sharp edges caused by the resolution.The COMIC/ADONIS+RASOIR data analyzed in thiswork was first published in Cl´enet et al. (2001).2.3. High-pass filter
Depending on the scientific goal, a suitable frequencypass filter can improve the amount of accessible imageinformation. In the case of an elongated source like X7,using the Lucy-Richardson algorithm (Lucy 1974) is notthe most satisfying option for the L (cid:48) -band NACO data.However, using a high-pass filter like the smooth sub-tract algorithm can reveal the stellar component of thebow shock source in the K-band SINFONI data if theobject is confused with nearby S-stars. For that, we aresubtracting a smoothed version of the input image file.The size of the Gaussian that is used for the smoothingshould be of the order of the related image point spreadfunction (PSF). The resulting smooth subtracted imageshould then be resmoothed with a Gaussian PSF thatcan be 10 −
20% smaller than the image PSF. With thistechnique, the influence of overlapping PSF-wings canbe minimized. RESULTS Gravity Collaboration et al. (2020) state 3 mas compared to 27mas of the L (cid:48) -band setting of NACO. Pei β ker et al. This section shows the results of the survey of theX7/S50-system between 2002 and 2018. We presentthe line map and continuum detection of the bowshock source X7 and show the ongoing implied decou-pling of the shell from its central star, S50. Further-more, we compare the observations with the publishedCOMIC/ADONIS+RASOIR data of 1999 and apply aphotometric analysis to the NACO images.3.1.
Line map and velocity gradient detection of X7
Throughout the SINFONI data between 2005 and2018, the source X7 can be at least partially observed.A key parameter is the FOV. Hence, the SINFONI datain 2006, 2008, 2014, 2015, and 2018 can be used for adetailed analysis. By analyzing continuum subtractedline maps, we find the length from the tip to the tail ofthe detected Doppler-shifted Br γ emission to be around0.23” in 2006. Furthermore, we measure the length ofthe bow shock of about 0.35” in 2018.Because of the high S/N ratio of the SINFONI datain 2018 (see Appendix E) at the spatial position of theDoppler-shifted Br γ -emission of X7, we use this set toinvestigate the velocity gradient of the bow shock source.For this purpose, we fit a Gaussian to the blue-shiftedBr γ -line in the related spectral range (2 . ± . µm ).Afterwards, the related spaxel carrying the velocity in-formation is copied to the same position in a new arraythat is as big as the input file. We manually mask theclose-by source X7.1/G5 (see Ciurlo et al. 2020; Peißkeret al. 2020b) and non-linear pixel.In Fig. 1, the resulting velocity gradient is shown. Wefind a difference from the tip to the tail along the pro-jected bow shock structure of ≈ ±
20 km/s. Consid-ering a spatial pixel scale of 12.5 mas in the H+K-bandin the highest plate-scale setting of SINFONI and themeasured projected bow shock length of 349 mas, weget a linear gradient of ≈ . ± . emission triplet can be found(Appendix B, Fig. 10). Due to crowding and therein theresulting possibility of confusion, we limit the analysisof the H emission triplet to the data of 2018.3.2. Continuum detection of X7 L (cid:48) -band observation of the bow shock source X7 in theclose distance of the S-cluster shows that the object isalways one of the most prominent sources in the closevicinity of the SMBH (see Fig. 2). The L (cid:48) -band bright-ness and elongated shape of X7 underlines the uniquecharacter of the object.After 2002, X7 becomes increasingly brighter than most of its nearby stars like, e.g., S1, S2, S61, and S71. Thebow shock shape is clearly noticeable in the NACO L (cid:48) -band (green circles indicate its position in Fig. 2). After2010, the source shows a more elongated shape with anapproximate projected length of 333 mas in 2016. Thisis almost three times as much as the L (cid:48) -band dust emis-sion detected with NACO in 2002 (112 mas). Comparedwith the line emission area of the SINFONI data in 2006,2008, 2009, 2013, 2014, 2015, and 2018, we find match-ing values for the gaseous emission (for a detailed list,see Table 2). Hence, the size of the projected area ofthe ionized gas is coinciding with the L (cid:48) continuum dustemission of X7.Since we observe a clear increasing projected sizeof X7 between 2002 and 2018, we investigate the L (cid:48) -band data of 1999 to see if this trend is also observ-able in data before 2002. For this purpose, we use theinvestigated COMIC/ADONIS+RASOIR L (cid:48) -band datain 1999 by Cl´enet et al. (2001). We apply a high-passfilter to reduce the influence of overlapping PSF. Af-terwards, we use a Gaussian that is about 50% in sizeof the initial smoothing kernel (Appendix D, Fig. 12)on the resulting high-pass filtered image. In additionto some prominent members of the S-cluster, we iden-tify at the expected position of S50 a spherical L (cid:48) -bandemission several magnitudes above the noise level. Bycomparing the closest NACO L (cid:48) -band data to verify theCOMIC/ADONIS+RASOIR identifications of 1999, wefind matching positions for almost all stars/features.3.3. S50
Muˇzi´c et al. (2010) reported that the stellar counter-part of X7 could be associated with the S-cluster starS50. In Fig. 12 (right side), we present the orbit plots ofS50 based on the analysis presented in Ali et al. (2020).Throughout the available data covering the related spa-tial area, we find without confusion that the bow shocksource X7 is moving along with S50 (see Fig. 3 andAppendix, Fig. 9) till 2009. S2 (K-band) and S65 (L-band) as the two brightest and therefore most prominentmembers of the S-cluster can always be observed in thesame FOV as S50. Hence, we are using these two S-stars for a photometric analysis to investigate the mag-nitude of S50 and X7 in various bands (see Table 3). Incombination with the published SHARP data (Sch¨odelet al. 2002), we find a constant K-band magnitude ofS50 of m K ≈
16 mag. We find a similar magnitudewith NACO (VLT) data of 2007 and SINFONI (VLT)data of 2019. Based on the data that covers almost 20years, we conclude that the S-cluster member S50 doesnot show a variable K-band emission. However, this isnot the case for the L (cid:48) -band continuum emission that nteraction of an S-star with the environment of Sgr A* Figure 1.
Bow shock source X7 in 2018. The upper left plot shows the K-band continuum with SINFONI of the S-clusterwhere the black × marks the position of Sgr A*. The marked position of the SMBH coincides with the S-cluster star S2 in 2018because of its pericenter passage. We adapt the line map contours of X7 from the Br γ -emission detection at 2 . µm (uppermiddle image) and include them in the continuum image. The upper right panel shows a zoomed-in map of the Br γ line mapwith a spatial pixel size of 12.5 mas. We present the velocity in this panel based along the line map detection of X7 in theSINFONI cube of 2018. For that, we fit a Gaussian to the spectrum of every spaxel in order to create a confusion free velocitymap. In the lower panel, the spectrum of X7 can be seen where we mark prominent lines. The related spectrum is integratedover all pixel shown in the top right panel (’Velocity map’). The telluric emission between 1 . − . µm is clipped. The mostprominent blue-shifted emission lines are Br δ @ 1 . µm , HeI @ 2 . µm , Br γ @ 2 . µm , [FeIII] G − H @ 2 . µm ,and [FeIII] G − H @ 2 . µm . Next to the blue-shifted HeI and Br γ line, we observe a red-shifted emission that is relatedto X7.1/G5. This source is in projection spatially close to X7 (Peißker et al. 2020b). seems to vary between 2008-2018. We will elaborate onthis point in detail in Sec. 3.5.3.4. Decoupling of X7 from S50?
Based on the L (cid:48) -band observations, we find a notice-able elongation of the source X7 that becomes increas-ingly prominent after 2009 (please see Fig. 2). Compar-ing the NACO L (cid:48) -band images with the SINFONI linemaps, we find that the symmetric distribution of gas anddust cannot be observed after 2009. Compared to theSINFONI data between 2006-2008 and 2010-2018, thedata shows a rather compact gas emission in 2009 (seeFig. 3). Whereas the data of 2006-2008 shows a sym-metrical gas-to-dust distribution with respect to S50 andX7, we find that this symmetry of the S50-X7 system is broken for the observations between 2010-2018. Fur-thermore, we observe that the distance of the gaseousfront of X7 (i.e., head) is increasing year-by-year withrespect to S50 (Fig. 4). In contrast, the back (or tail)of the Br γ gas emission does not show a comparable be-havior compared to the head after 2009. As previouslydescribed, this leads to an asymmetric distribution ofthe gas around the central stellar source S50. This bro-ken symmetry between the shell and the star can alsobe observed in the NACO L (cid:48) -band data (see Fig. 5).Hence, the data implies that the gas and dust shell startsto detach in projection after 2010. This process can betracked throughout the available NACO and SINFONIdata beginning in 2009 and is indicated in Fig. 4. Fur-thermore, we find that the intensity maximum of the Pei β ker et al. Figure 2. L (cid:48) images of the GC observed with NACO between 2002 and 2018. The size of every panel is 1 . × . × and locked in every panel. The green circleindicates the position of the bow shock source X7. In the upper left panel, we show the position of the S-star S65 with a whitecircle. The related measured projected on-sky size and the position angle of X7 of every year are listed in Table 2. nteraction of an S-star with the environment of Sgr A* Spectral line (@rest wavelength [ µ m]) transition central wavelength [ µ m] Velocity [km/s]Br10 @1.7366 µ m n=10-4 1.7335 ± δ @1.9450 µ m n=8-4 1.9414 ± µ m 2 p P − s S ± γ @2.1661 µ m n=7-4 2.1619 ± F eIII ]@2.1451 µ m G − H ± F eIII ]@2.2178 µ m G − H ± F eIII ]@2.2420 µ m G − H ± F eIII ]@2.3479 µ m G − H ± @2.4065 µ m v=1-0 Q(1) 2.4045 ± @2.4134 µ m v=1-0 Q(2) 2.4130 ± @2.4237 µ m v=1-0 Q(3) 2.420 ± Table 1.
Observed emission and absorption lines of X7/S50 in 2018. All emission lines are related to Fig. 1 whereas theH absorption lines are shown for better visibility in Appendix B, Fig. 10. The typical uncertainty of the measured centralwavelength (peak intensity) indicates the standard deviation to 2 . × − . Hence, the uncertainty of the derived Doppler-shiftedvelocity is about ±
35 km/s. Year L (cid:48) size (continuum) Br γ size (line) Position angle (projected)in [yr] in [mas] in [mas] in [ ◦ ]2002 112 - 422003 148 - 442004 162 - 452005 180 - 452006 200 230 452007 206 - 452008 229 230 452009 274 192 452010 212 - 502011 262 - 512012 272 - 512013 314 246 522014 - 311 -2015 - 321 -2016 333 - 552017 348 - 572018 388 349 60*2019 - - - Table 2.
Projected length of the bow shock source X7. The line emission length is extracted from the SINFONI data cubethat shows the required FOV. The related line map represents the Doppler-shifted Br γ emission line of the bow shock. Fromthe NACO data, we derive the length of the bow shock from the L (cid:48) -band continuum emission. Please note that the observationof X7 in 2009 can be distinguished in a pre- (NACO, 2009.26) and post-event (SINFONI, 2009.47). We indicate the time of thepre- and post-event (that shows a discontinuous behavior of the increasing elongation of the X7/S50 system) with the horizontallines before and after 2009 and 2010 respectively. To cover statistical variations, reading errors, background effects, and detectorirregularities, we determine a spatial uncertainty of ± ± ◦ is given. The asterisk of the position angle measurement of 2018 indicates 60 ◦ as a lower limit. Thislower limit is justified because X7 is not aligned towards Sgr A* in 2018. Pei β ker et al. Figure 3.
Doppler-shifted Br γ line maps observed withSINFONI in 2009. East is to the left, north is up. The xmarks the position of Sgr A* which is derived by the off-set of the well known orbit of S2. The filled contour line isrelated to the position of S50 and S33 (see the included leg-end). From the same data cube, we extract a K-band image(2 . µm -2 . µm ) and isolate in the same wavelength windowthe Doppler-shift Br γ line at around 2 . µm . dust is located at a distance of less than 13 mas to theposition of S50 (Fig. 2). As a result, the tail of X7 getsincreasingly brighter when comparing the data between2002 and 2018.3.5. Photometric analysis of X7
The photometry was done in the H-, K-, L (cid:48) -, and M (cid:48) -band. As shown in Fig. 2, Fig. 5, Fig. 12, and Fig.4 the dusty bow shock of X7 gets elongated between1999 and 2018. After 2007, the projected elongated sizeof the L (cid:48) -band emission exceeds a spatial coverage oftwo PSF ( ≈ . L (cid:48) -band head magnitude is notfree of confusion. For the photometric analysis, we useS65 because of its well-known stable magnitude of about10 .
96 mag (Hosseini et al. 2020). For the magnitudeof X7, we use the peak emission of the L (cid:48) -band dustemission (see Fig. 2). The magnitude of X7 is derivedfrom the peak intensity and can be related to the tailof the source after 2008. For every dataset, a one-pixelaperture is used. No background subtraction is appliedbecause of the high S/N ratio that exceeds several ordersof magnitude the intensity of the surroundings.The fit presented in Fig. 6 can be categorized in twodifferent results:1. A constant magnitude of X7 before 2007, 2. A variable magnitude of the tail after 2007.Regarding point 1, the COMIC/ADONIS+RASOIRand NACO L (cid:48) -band data between 1999 and 2006 doesnot show a magnitude variation. Additionally, point 2underlines a slightly variable L (cid:48) -band tail magnitude ofthe bow shock at the K-band position of S50.These variations of the L (cid:48) -band magnitude of X7 coin-cide with the discontinuous shape evolution that is ob-served in the Br γ line maps (see Fig. 3 and Fig. 5).By investigating several datasets of the GC that coverindividual bands, we find an increasing flux towards Band Central wavelength mag S mag S /X flux S /X in [ µm ] in [mJy]H 1.65 16.00 19.65 0.0861K 2.20 14.13 16.00 0.2459 L (cid:48) M (cid:48) Table 3.
Magnitude and flux of the bow shock source X7.We use the band related ESO filter for the zero magnitudeflux. The dereddened H-, K-, and L (cid:48) -band values are relatedto the SINFONI and NACO data of 2016. The M (cid:48) data-point is determined from the NACO data of 2012 where weapplied a flux conserving smooth-subtract Gaussian (PSF-sized kernel). higher bands (from H- to M-band, see Table 3) for X7.Using the magnitude values, we derive the SED with atwo-component fit for the emission of S50 (H and K) andX7 ( L (cid:48) and M (cid:48) ). This indicates a dust-dominated emis-sion source with a multiwavelength appearance. Sincethe commonly observed dust temperature in the GC isabout 200 K (Cotera et al. 1999), the derived envelopetemperature of 450 K must be heated up by the internalstellar source S50. DISCUSSION AND CONCLUSIONIn this section, we will discuss the results and the im-plications for future observations of the X7/S50 system.We will also speculate about some possible interpreta-tions regarding the increasing position angle and the im-plied decoupling of X7 and S50.4.1.
The shape of X7
From the survey of X7 over two decades with all pub-licly available SINFONI and NACO data, we have shownthat the shape of the bow shock does change over timeon a significant level. Even when we consider differentweather and background scenarios, the here presentedfindings underline a dynamical star-envelope setup. As nteraction of an S-star with the environment of Sgr A* Figure 4.
Distance of the head and tail of X7 in relation to the position of S50 and Sgr A*. On the left, the distance of thehead related to the position of S50 is plotted. In combination with Fig. 3, we distinguish between two responsible processes forthe evolution of the dust shell X7 which is reflected in the two fits. The overall trend is indicated with a blue transparent fit.On the right, the head (red), the tail (green), and S50 (blue) is shown with their position with respect to Sgr A*. Again, thetrend shows that the head is moving towards Sgr A* and further away from S50. Typical uncertainties of about 1 px are notincluded to preserve the better readability of the plots. One pixel [px] corresponds to 12.5 mas. shown in Table 2 and Fig. 3, the shape of X7 undergoesa transition: we find an almost constant position angleand magnitude with a linear increasing bow shock sizeboth in gas and dust till 2009. Based on Muˇzi´c et al.(2010), this setup for X7 is expected because S50 as thestellar counterpart is located close to the front tip ofthe bow shock X7. As theoretically described by Wilkin(1996, 2000) and observed by Muˇzi´c et al. (2010), wecan confirm that the S-star S50 is located always at theposition of the maximum peak intensity of the observed L (cid:48) -band emission of the bow shock X7. This L (cid:48) -band in-tensity peak can be found close to the apex of the bowshock at a distance of R = (cid:113) ˙ m w v w Ω ρ a v ≈ . × cm(Muˇzi´c et al. 2010) till 2009. Here, ˙ m w describes themass-loss rate of the star, v w is the stellar wind velocity, Ω a dimensionless parameter to control the shape of thebow shock (Ω = 4 π for an isotropic stellar wind), ρ a isthe density of the ambient medium, and v a the relativestellar velocity in a non-stationary medium.Between 2009.47 and 2010.49, we observe a discontin-uous process since the Br γ and L (cid:48) -band size is decreasedby almost 30% compared to the observation in 2009.26(NACO). After 2010, not only is the Br γ and L (cid:48) -bandcontinuum size expanding, but also the position of S50seems to change with respect to the shell. Hence, R is not a fixed value anymore and seems to change yearby year. Because the stellar position with respect toits dusty envelope does not follow any simple stationarymodel, we will speculate about some possible interpre-tations.0 Pei β ker et al. Figure 5.
NACO L (cid:48) -band continuum images (upper row) and SINFONI Doppler-shifted Br γ line maps (lower row) displayingthe immediate environment of Sgr A*. Here we compare the appearance of the dust ( L (cid:48) -band) and the ionized gas (Br γ ) inrelation to the K-band of S50 which is indicated by the green dot. The green filled contour lines are extracted from the relatedK-band image of the same data (SINFONI) or year (NACO). Since NACO was decommissioned in 2014/2015, we use the L (cid:48) -and K-band observations of early 2016 which are just 0.6 yr later than the displayed SINFONI line map of 2015. In every image,the colored × marks the position of Sgr A* which is derived with the well observed S2 orbit. The pixel scale is identical in eachrow. Figure 6. L (cid:48) magnitude of X7 between 1999 and 2018with a typical uncertainty of ± .
02 mag (see also Hos-seini et al. 2020). The data before 2002 was observedwith COMIC/ADONIS+RASOIR and presented partially inCl´enet et al. (2001). The red data-points shows the magni-tude of X7 till 2007. After 2007, the main peak emission canbe found in the back of the emission source and is thereforerelated to the tail of X7. In this figure, a lower magnitudevalue is brighter.
The authors of Henney & Arthur (2019) discuss dust-and bow-waves as a possibility for asymmetric shapes.Considering a possible ‘rip-point’ (where the shell gets
Figure 7.
Spectral energy distribution of the X7/S50 sys-tem that indicates a dust-embedded stellar source. detached from the star) harbors the problem that theseprocesses (including the trajectories of the dust grains)take up to several 1000 years as proposed by Henney& Arthur (2019). We have shown that the gas distribu-tion is coinciding with the dust emission (see Table 2 andFig. 5). In 2008, we find a matching size of the emissionof about 230 mas. The NACO data of 2009.26 seemsto follow the linear evolution of the observed emissionsize in 2008. For the SINFONI data of 2009.47, we ob-serve a source size that is unexpected. Because of thesetimescales, we see a reduced chance for the possibility nteraction of an S-star with the environment of Sgr A* − to a fewpercent for a consecutive observation of 3 years. Theprobability for the outer region of the S-cluster shouldtherefore be in a comparable range since we observe S50along with X7 between 2002-2009 (NACO) and 1999with COMIC/ADONIS+RASOIR (Appendix, Fig. 12).As shown in Fig. 2 and Fig. 5, the shifted L (cid:48) -bandintensity maximum towards the tail is followed by theprojected position of S50. Based on the derived L (cid:48) -bandmagnitude year-by-year, the temperature of X7 is al-ways well above 200K which can only be achieved byan internal heating source. Hence, we conclude that thetail of X7 gets heated up by S50. Alternatively, a windthat originates south-west of the position of Sgr A*could be responsible for the increased tail emission in2018. However, this does not explain the Wilkinoide(Wilkin 1996) bow shock between 2002 and 2009 that isobserved throughout the NACO and SINFONI data. Incombination with the continuum and line emission dataof 2006 and 2008 (see Fig. 5), we will not discuss thepossibility of another wind coming from south-east anyfurther, especially considering the observed footprintof a wind that originates at the position of Sgr A* orIRS16 in the mini-cavity (see, e.g., Lutz et al. 1993).A more suitable explanation of the observed gas anddust emission of X7 is forward scattering explained bythe Mie-theory. This scatter mechanism describes dustgrains as an emitter with the mentioned forwarded scat-tering. Single and multiscattering events occur where,e.g., dust emits and transmits stellar light, which isreemitted by close-by grains. As long as S50 is embed-ded in the dusty shell X7, the ionized and blue-shiftedBr γ -emission is symmetrically distributed following thealigned dust grains. After 2009, the peak emission of the L (cid:48) -band emission can be observed closer to the tailof X7 whereas the gaseous tip gets more prominent .Overall, we conclude that a projection scenario thatdescribes a random encounter between S50 and X7 ishighly unlikely but not excluded.4.2. Two observed processes: the change of theposition angle between X7 and Sgr A*
Besides the observed decreased projected source sizein 2009-2010, we find that the position angle (with re-spect to Sgr A*) is increasing faster as the shell of S50is aligned towards the SMBH (Table 2). Even though achange of the position angle is expected since the propermotion of the X7/S50-system is directed towards thenorth (Muˇzi´c et al. 2010), the gas and dust shell ispointing/aligned to a position 0 .
45” north of the SMBH(see Fig. 2, 5) in 2018. Comparing the position angleof 2006 and 2018 shows a growth of about 40%. If S50would be located close to the position of the tip of thebow shock at a distance R , a growth by around 12%would be expected in 2018. However, assuming thechance of reading uncertainties, the position angle of60 ◦ in 2018 between Sgr A* and X7 marks a lower limit.The observations and the measured properties suggestto distinguish the description of X7 in pre 2009.26 andpost 2009.46 since the object shows a discontinuous de-velopment as a function of time.Summing up the observational results leads to two as-sumptions: either X7 is a tidally stretched object where the head is on its way towards Sgr A* (A), orthe dust- and gas-shell seems to be ripped apart by anunknown interaction (B).A) The trajectory of the head, as shown in Fig. 4,shows a clear trend towards Sgr A*. The dis-tance between the SMBH and the gaseous headof X7 decreased by around 20% over almost twodecades. Taking into account the proper motion ofthe S50/X7 system, this is expected. Even thougha clear trend can be observed, projection effectscould also play a role because of the orbit of S50(see Appendix, Fig. 12). Studying the projectedpositions of the head, tail, and S50 with respectto Sgr A* (Fig. 4) implies that the R.A. distanceof the head stays almost constant. If the headwould be attracted by Sgr A*, we would not ob- We advise the interested reader to compare the Br γ emission of2008 and 2018 presented in Fig. 5. Discussed by Randy Campbell et al., UCLA, at GCWS 2019(proceedings in prep.). Pei β ker et al. serve a preserved dusty shell of X7 because thefront would simply accelerate towards the SMBHwith respect to S50 and the tail. Hence, the shapeof the Br γ -emission in 2018 might be explainedby the forward (and backward) single- and mul-tiscattered stellar light of S50. If upcoming ob-servations can confirm the observed decoupling ofthe head from S50 and its tail, it might triggerthe flaring activity of Sgr A* above the statisticallevel (Witzel et al. 2012). Please consider also theAppendix (Fig. 11) for a possible outlook.B) As discussed before, the Br γ line map of 2009 (Fig.3) but also the size of the L (cid:48) -band continuum de-tection (Table 2 and Fig. 2) marks a noticeablestep in the discontinuous evolution of X7. Addingthe growth of the position angle of X7, the in-creasing distance between the head and S50, andthe relative position of the shell and the S-star tothe calculation creates the assumption that we ob-serve a dissolving event. Since the overall shape ofthe dust shell as observed with NACO seems to bepreserved even though a clearly increased elonga-tion can be observed, it is safe to assume that theshell stays intact. Hence, clear evidence for thescenario of a destroyed shell cannot be given.Considering the here discussed observational resultsleads to the problem of the ongoing spatial misplacementof S50 with respect to X7 and the growing position angle.We will elaborate on this in the following subsections.4.3. Unexpected event around 2010
Recently, Vorobyov et al. (2020) modeled the behav-ior of gas and dust features of protoplanetary diskswhich move with a supersonic motion in a dense am-bient medium. Considering the Br γ emission in Fig. 3in 2009 in combination with the related L (cid:48) -band emis-sion size (Table 2), we conclude that there might be aprominent decoupling of gas and dust as discussed byHenney & Arthur (2019). As discussed, the time scalesof the cited work does not fit the observation. Hence,the observations suggest the presence of a disturbingevent. We speculate that this event has been caused bythe close fly-by (in projection) of S33, which would atleast partially explain the almost compact Br γ line mapemission in 2009 and the discontinuous evolution of theprojected L (cid:48) -band size of X7 (see Table 2). A critical pa-rameter of this speculative scenario is the 3-dimensionaldistance and therefore the position of S50/X7 and S33with respect to each other.For giving an estimate on the 3-dimensional distancebetween S33 and S50, we use the related proper mo-tion ( v t ) and line-of-sight velocity ( v r ). For v r , we use a lower limit of around 500 km/s (Muˇzi´c et al. 2010).For deriving a LOS velocity, an averaged value of theobserved H Q(1) and H Q(3) absorption line is used.Hence, for v t of S50 we derive a value of around 350km/s in 2018 (see Appendix, Fig. 10 and Table 1). Thisvelocity estimate results in a approximate 3-dimensionalvelocity of ( v r + v t ) − / ≈ km/s . This results inan approximate distance d towards Sgr A* of d S ≈ . pc ≈ . . .
01” or 120 AU .Considering the derived 3-dimensional distance betweenS33 and S50, the modeled interaction between an in-truder and the host star with an envelope as presented inVorobyov et al. (2020) could be a possibility. A detailedmodel should answer the question about the stellar-windinteraction with the ambient wind (Yusef-Zadeh et al.2020) but exceeds the scope of this work.Furthermore, it should be mentioned that O’Gormanet al. (2015) and Wallstr¨om et al. (2017) presentedALMA observations which do not show a symmetricaldust/gas distribution of the envelope related to the hoststar (which happens to be in both cases a giant). Wall-str¨om et al. (2017) observed a so-called ’Spur’ whichdescribes an asymmetric gas feature related to the hoststar. This ’Spur’ could be compared to the dust and gasshell X7 of S50. Wallstr¨om et al. (2017) argue that this’Spur’ might be created by a sporadic eruption event ofthe host star. Nevertheless, Zajaˇcek et al. (2020) mod-eled recently the depletion of red giants and showed thatthe detached and shocked envelope of the host star cansuffer from the interaction with Sgr A*. Even thoughSchartmann et al. (2018) used stellar winds to model theS2 peri-center passage, it is shown that the presence ofa SMBH results in an asymmetric mass distribution. Ifthe gas/dust shell got detached and its length scale in-creased beyond the stellar Hill radius, the gravitationalinfluence of Sgr A* would dominate the evolution of X7as was described by Eckart et al. (2013) and numericallymodelled by Zajaˇcek et al. (2014).4.4. The nature of the source X7/S50
From the multiwavelength analysis with NACO andSINFONI in the H-,K-,L, M-band, and the modeledSED, we find that the X7/S50 system consists of a stel- Transition v=1-0 Q(1) Transition v=1-0 Q(3) nteraction of an S-star with the environment of Sgr A* γ -line map of 2006 and 2018with the NACO L (cid:48) -band continuum observations showsthe gas- to dust-component ratio is around 1:2-1:3 whichare typical values for HAe/Be or T-Tauri stars (Man-nings & Sargent 2000). The weak H -absorption lines(Appendix, Fig. 10) underline the possibility for observ-ing a YSO as discussed in Muˇzi´c et al. (2010). The the-oretical modeling of the dust and gas of X7 strengthenthe possibility of a YSO.Additionally, Rivinius et al. (1997) reported wind vari-ations for early-B hypergiants with mass-loss rates ofseveral 10 − M (cid:12) yr − . This variations are also investi-gated by Muratorio et al. (2002). In both cases, theP-Cygni profile of highly excited [FeIII] multiplets/linesare indicators for a complex wind interaction with thestellar source. Even if we do not find a prominent P-Cygni profile in the spectrum, a nondetection can beexplained by the high sky emission line variations whichleads to over/undersubraction effects as shown by Davies(2007). Finding a P-Cygni feature would increase thecomplexity of the X7 system since there would be wind-wind-accretion processes that should be a part of thementioned model. The wind launched at the position ofSgr A* would be accompanied by stellar winds of S50.Therefore, the S50 dust and gas accretion would be in-fluenced by the aforesaid wind-wind process.Furthermore, the origin of the excited [FeIII] lines isstill not clear (Peißker et al. 2019, 2020b) even thoughwe speculate the detection could be linked to the areaand the Br γ -bar (Sch¨odel et al. 2011; Peißker et al.2020c). However, Wolf & Stahl (1985) mention thathigher excited [FeIII] lines could have been pumpedby HeI lines. In the spectrum of X7, we find a strongblue-shifted HeI line at 2 . µm with a matching LOSvelocity. Hence, we consider the pumping of the for-bidden Fe-lines as a possible explanation. For the sakeof completeness, we note that every of the four mostprominent emission lines in the present K-band spec-trum in Fig. 1 is accompanied by a less intense linewhich is related to the source X7.1/G5. In addition,we do find a red-shifted H line (about 650 km/s ) at2 . µm (transition v=1-0 S(0)). Because of the direc-tion of the Doppler-shifted H line, this emission mightprobably be related to another species.From the here shown results and the discussed scenar-ios, we conclude that the stellar source of X7 can beassociated without any doubt with the S-cluster star Transition 2 p P − s S S50, which confirms the analysis of Muˇzi´c et al. (2010).As implied by the H absorption lines, the LOS velocityof the star is blue-shifted. Hence, the Doppler-shifteddirection of the stellar LOS-velocity matches the emis-sion lines of the surrounding envelope, which also showsa blue-shifted motion.The shape of the bow shock in 2002 is almostspherical and Wilkinoide. With the presentedCOMIC/ADONIS+RASOIR data of 1999, we find evi-dence that earlier L (cid:48) -band data than 2002 confirm thetrend of a ‘growing’ dusty envelope.The two distinct observed processes, the LOS-velocity,and the star/envelope evolution underline the promi-nent dynamical process that highlights the uniquenessof the X7/S50 system.Along the X7/S50 source, we observe a strong andprominent velocity gradient in 2018. Considering theexistence of a formed wind at the position of Sgr A* orIRS16, we assume this might be the origin of the gra-dient. In 2009, it seems the envelope starts to interactwith the nearby S-cluster star S33 since we trace indica-tions of this possible interaction in the same year (Fig.3). The L (cid:48) NACO data shows that the tail of X7 getsbrighter between 2010 and 2018. We predict that thisgain of brightness will likely continue in the future. Wealso speculate that the ongoing interaction of S33 andSgr A* with the shell of S50 could lead to the partialdestruction of the bow shock.4.5.
Sporadic or stellar winds?
As we have observed and presented in Fig. 2 butalso listed in Table 2, the shell of S50 is pointing inprojection above Sgr A*. As proposed by Wardle &Yusef-Zadeh (1992), strong stellar winds arising fromthe IRS16 complex are responsible for the creation of themini-cavity. The authors discuss an observed 2 . µm emission line at the position of the mini-cavity (see alsoLutz et al. 1993) which can most likely be related to the[FeIII] multiplet observed in several dusty sources westof Sgr A* (Ciurlo et al. 2020; Peißker et al. 2020b). Theionized iron multiplet can also be observed for X7/S50as shown in Fig. 1. If we exclude the possibility of awind arising at the position of Sgr A*, the excitationof iron as well as the position angle (Table 2) could belinked to stellar winds from IRS16. The supermassiveblack hole would be responsible for refocusing the wind(Fig. 8) and sources that are leaving the ‘slip-streamof Sgr A*’ would suffer from this interaction. Thisdynamical evolution of the gaseous and dusty shell ofthe X7/S50 system underlines the need for a constantsurvey of the GC region in various bands.4 Pei β ker et al. Figure 8.
Sketch adapted from Wardle & Yusef-Zadeh(1992). The [FeIII] emission is also observed by Lutz et al.(1993). The position of X7 and the observed position angleof 2018 is implied with the red object. Sgr A* is located atthe black dot.
If a wind responsible for the alignment and evolutionof the X7/S50 system is indeed arising at the positionof Sgr A*, the apparent change of the position anglewith respect to Sgr A* is unexpected. Since we clearlyobserve the evolution of the elongation of the X7/S50system, it may be explained by a temporarily activewind phase of Sgr A* as indicated by Morris & Ser-abyn (1996). Speculatively, this could contribute to the‘Paradox of youth’ (Ghez et al. 2003) where star forma-tion is ‘allowed’ for a short period of time. Nevertheless,in combination with the X7 proper motion (Muˇzi´c et al.2010) directed towards the north, the alignment angleof X7/S50 may have been induced to the system before2009. After 2009, the wind activity may have beendecreased while the position angle increased (Table 2)because of the proper motion of the X7/S50 system.4.6.
Future observations with the Extremely LargeTelescope and the James Webb Space Telescope
Near- and mid-infrared instruments will play a keyrole in investigating the evolution of the X7/S50 sys-tem. The prominent detection of X7 in the L (cid:48) - and M (cid:48) -band promises successful observations with MIRI(James Webb Space Telescope, see Bouchet et al. 2015;Rieke et al. 2015; Ressler et al. 2015), METIS (Ex-tremely Large Telescope, see Brandl et al. 2018), andMICADO (Extremely Large Telescope, see Trippe et al. 2010). MIRI and METIS will be able to finalize the in-vestigation about the possible clumpiness of X7 whichcould be used for theoretical models (e.g., the filling fac-tor, see Peißker et al. 2020c). With a more accurate re-sult, we will be able to precisely determine the densityand therefore the mass of the dusty shell. Furthermore,we are able to search for more complex emission lines inthe local line of sight ISM like, for example, N H . Addi-tionally, gas emission lines like, e.g., CO and HCN , canprovide a more detailed description about the natureof the X7/S50 system. These gas- and ice-absorptionlines can also be used as an additional probe for a stel-lar disk and a possible YSO. Moultaka et al. (2006) andMoultaka et al. (2009) showed that these lines are use-ful to determine local extinction values for the interstel-lar medium (see also Sch¨odel et al. 2010; Peißker et al.2020c).Even if we have shown S50 can be associated with thestellar counterpart of X7, a hidden star at a distance of R from the apex of the bow shock should be detectablewith MICADO (see the simulated view of the GC withMICADO in Davies & Genzel 2010).As we have presented in Fig. 2, investigating the GCwith a wider FOV in the mentioned bands should alsoreveal more (elongated) sources that might be sufferingfrom the wind that is formed at the position of Sgr A*or at IRS16. We conclude that the upcoming observa-tions of the GC with the ELT will be able to manifestthe dynamical influence of the nuclear wind. We cansafely assume the X7/S50 system will not be the onlysource in the GC which is undergoing a dynamical in-fluence. Yusef-Zadeh et al. (2017a) already showed thatYSOs with bipolar outflows can be observed in the en-vironment of the SMBH. Even though we cannot finallyanswer the question about the nature of the X7/S50system, we see some weak traces that point towards itsYSO nature. If the theoretical models reveal matchingparameters of the X7/S50 system with a YSO, the originof these sources is still not clear. However, the impli-cation of a population of YSOs promises an importantcornerstone in the investigation of the direct vicinity ofthe nearest SMBH that resides in our Galaxy. nteraction of an S-star with the environment of Sgr A* Ali, B., Paul, D., Eckart, A., et al. 2020, ApJ, 896, 100,doi: 10.3847/1538-4357/ab93aeArulanantham, N. A., Herbst, W., Gilmore, M. S., Cauley,P. W., & Leggett, S. K. 2017, ApJ, 834, 119,doi: 10.3847/1538-4357/834/2/119Balick, B., & Brown, R. L. 1974, ApJ, 194, 265,doi: 10.1086/153242Beuzit, J.-L., Hubin, N., Gendron, E., et al. 1994, inSociety of Photo-Optical Instrumentation Engineers(SPIE) Conference Series, Vol. 2201, Adaptive Optics inAstronomy, ed. M. A. Ealey & F. Merkle, 955–961,doi: 10.1117/12.176129Bouchet, P., Garc´ıa-Mar´ın, M., Lagage, P.-O., et al. 2015,Publications of the Astronomical Society of the Pacific,127, 612, doi: 10.1086/682254 Brandl, B. R., Absil, O., Ag´ocs, T., et al. 2018, in Societyof Photo-Optical Instrumentation Engineers (SPIE)Conference Series, Vol. 10702, Ground-based andAirborne Instrumentation for Astronomy VII, ed. C. J.Evans, L. Simard, & H. Takami, 107021U,doi: 10.1117/12.2311492Christie, I. M., Petropoulou, M., Mimica, P., & Giannios,D. 2016, MNRAS, 459, 2420, doi: 10.1093/mnras/stw749Ciurlo, A., Campbell, R. D., Morris, M. R., et al. 2020,Nature, 577, 337, doi: 10.1038/s41586-019-1883-yCl´enet, Y., Rouan, D., Gendron, E., et al. 2001, A&A, 376,124, doi: 10.1051/0004-6361:20010931Cl´enet, Y., Rouan, D., Gratadour, D., Gendron, E., &Lacombe, F. 2003, in SF2A-2003: Semaine del’Astrophysique Francaise, ed. F. Combes, D. Barret,T. Contini, & L. Pagani, 163Cl´enet, Y., Rouan, D., Gratadour, D., Gendron, E., &Lacombe, F. 2005, in Science with Adaptive Optics, ed.W. Brandner & M. E. Kasper (Berlin, Heidelberg:Springer Berlin Heidelberg), 286–290 Pei β ker et al. Cotera, A., Morris, M., Ghez, A. M., et al. 1999, inAstronomical Society of the Pacific Conference Series,Vol. 186, The Central Parsecs of the Galaxy, ed.H. Falcke, A. Cotera, W. J. Duschl, F. Melia, & M. J.Rieke, 240Davies, R., & Genzel, R. 2010, The Messenger, 140, 32Davies, R. I. 2007, MNRAS, 375, 1099Do, T., Witzel, G., Gautam, A. K., et al. 2019, ApJL, 882,L27, doi: 10.3847/2041-8213/ab38c3Eckart, A., & Genzel, R. 1996, Nature, 383, 415,doi: 10.1038/383415a0Eckart, A., Genzel, R., Ott, T., & Sch¨odel, R. 2002,MNRAS, 331, 917, doi: 10.1046/j.1365-8711.2002.05237.xEckart, A., Britzen, S., Horrobin, M., et al. 2013, ArXive-prints. https://arxiv.org/abs/1311.2743Eckart, A., H¨uttemann, A., Kiefer, C., et al. 2017,Foundations of Physics, 47, 553,doi: 10.1007/s10701-017-0079-2Eckart, A., Muzi´c, K., Yazici, S., et al. 2013, A&A, 551,A18, doi: 10.1051/0004-6361/201219994Genzel, R., Eisenhauer, F., & Gillessen, S. 2010, Reviews ofModern Physics, 82, 3121,doi: 10.1103/RevModPhys.82.3121Genzel, R., Pichon, C., Eckart, A., Gerhard, O. E., & Ott,T. 2000, MNRAS, 317, 348,doi: 10.1046/j.1365-8711.2000.03582.xGhez, A. M., Duchene, G., Morris, M., et al. 2002, inAmerican Astronomical Society Meeting Abstracts, Vol.201, 68.04Ghez, A. M., Duchˆene, G., Matthews, K., et al. 2003,ApJL, 586, L127, doi: 10.1086/374804Gillessen, S., Eisenhauer, F., Trippe, S., et al. 2009, ApJ,692, 1075, doi: 10.1088/0004-637X/692/2/1075Gillessen, S., Genzel, R., Fritz, T. K., et al. 2012, Nature,481, 51, doi: 10.1038/nature10652—. 2013, ApJ, 763, 78, doi: 10.1088/0004-637X/763/2/78Gillessen, S., Plewa, P. M., Widmann, F., et al. 2019, ApJ,871, 126, doi: 10.3847/1538-4357/aaf4f8Gravity Collaboration, Abuter, R., Amorim, A., et al. 2018,A&A, 615, L15, doi: 10.1051/0004-6361/201833718—. 2020, A&A, 636, L5, doi: 10.1051/0004-6361/202037813Henney, W. J., & Arthur, S. J. 2019, MNRAS, 486, 4423,doi: 10.1093/mnras/stz1130Hoadley, K., France, K., Arulanantham, N., Loyd, R. O. P.,& Kruczek, N. 2017, ApJ, 846, 6,doi: 10.3847/1538-4357/aa7fc1Hosseini, S. E., Zajaˇcek, M., Eckart, A., Sabha, N. B., &Labadie, L. 2020, A&A, 644, A105,doi: 10.1051/0004-6361/202037724 H¨ortner, H., Gardiner, M., Haring, R., Lindinger, C., &Berger, F. 2012, in Proceedings of the InternationalConference on Signal Processing and MultimediaApplications and Wireless Information Networks andSystems - Volume 1: SIGMAP, (ICETE 2012), INSTICC(SciTePress), 19–24, doi: 10.5220/0004126400190024Kuntschner, H., Jochum, L., Amico, P., et al. 2014, inSociety of Photo-Optical Instrumentation Engineers(SPIE) Conference Series, Vol. 9147, Ground-based andAirborne Instrumentation for Astronomy V, 91471U,doi: 10.1117/12.2055140Lacombe, F., Marco, O., Geoffray, H., et al. 1998, PASP,110, 1087, doi: 10.1086/316231Lenzen, R., Hartung, M., Brandner, W., et al. 2003, inProc. SPIE, Vol. 4841, Instrument Design andPerformance for Optical/Infrared Ground-basedTelescopes, ed. M. Iye & A. F. M. Moorwood, 944–952,doi: 10.1117/12.460044Lucy, L. B. 1974, AJ, 79, 745, doi: 10.1086/111605Lutz, D., Krabbe, A., & Genzel, R. 1993, ApJ, 418, 244,doi: 10.1086/173386Lynden-Bell, D., & Rees, M. J. 1971, mnras, 152, 461Mannings, V., & Sargent, A. I. 2000, ApJ, 529, 391,doi: 10.1086/308253Marchetti, E., Fedrigo, E., Le Louarn, M., et al. 2014, inSociety of Photo-Optical Instrumentation Engineers(SPIE) Conference Series, Vol. 9148, Adaptive OpticsSystems IV, 914826, doi: 10.1117/12.2055155Morris, M., & Serabyn, E. 1996, ARA&A, 34, 645,doi: 10.1146/annurev.astro.34.1.645Moultaka, J., Eckart, A., & Sch¨odel, R. 2009, ApJ, 703,1635, doi: 10.1088/0004-637X/703/2/1635Moultaka, J., Eckart, A., Viehmann, T., & Sch¨odel, R.2006, in Journal of Physics Conference Series, Vol. 54,Journal of Physics Conference Series, ed. R. Sch¨odel,G. C. Bower, M. P. Muno, S. Nayakshin, & T. Ott,57–61, doi: 10.1088/1742-6596/54/1/010Muratorio, G., Markova, N., Friedjung, M., & Israelian, G.2002, A&A, 390, 213, doi: 10.1051/0004-6361:20020708Muˇzi´c, K., Eckart, A., Sch¨odel, R., et al. 2010, A&A, 521,A13, doi: 10.1051/0004-6361/200913087Muˇzi´c, K., Eckart, A., Sch¨odel, R., Meyer, L., & Zensus, A.2007, A&A, 469, 993, doi: 10.1051/0004-6361:20066265O’Gorman, E., Vlemmings, W., Richards, A. M. S., et al.2015, A&A, 573, L1, doi: 10.1051/0004-6361/201425101Parsa, M., Eckart, A., Shahzamanian, B., et al. 2017, ApJ,845, 22, doi: 10.3847/1538-4357/aa7bf0Pasquini, L., & Weilenmann, U. 1996, The Messenger, 85, 9 nteraction of an S-star with the environment of Sgr A* Pearson, D., Taylor, W., Davies, R., et al. 2016, in Societyof Photo-Optical Instrumentation Engineers (SPIE)Conference Series, Vol. 9908, Ground-based and AirborneInstrumentation for Astronomy VI, 99083F,doi: 10.1117/12.2234074Peißker, F., Eckart, A., & Parsa, M. 2020a, ApJ, 889, 61,doi: 10.3847/1538-4357/ab5afdPeißker, F., Eckart, A., Sabha, N. B., Zajaˇcek, M., & Bhat,H. 2020b, ApJ, 897, 28, doi: 10.3847/1538-4357/ab9826Peißker, F., Eckart, A., Zajaˇcek, M., Ali, B., & Parsa, M.2020c, The Astrophysical Journal, 899, 50,doi: 10.3847/1538-4357/ab9c1cPeißker, F., Hosseini, S. E., Zajaˇcek, M., et al. 2020d,A&A, 634, A35, doi: 10.1051/0004-6361/201935953Peißker, F., Zajaˇcek, M., Eckart, A., et al. 2019, A&A, 624,A97, doi: 10.1051/0004-6361/201834947Pfuhl, O., Gillessen, S., Eisenhauer, F., et al. 2015, ApJ,798, 111, doi: 10.1088/0004-637X/798/2/111Plewa, P. M., Gillessen, S., Pfuhl, O., et al. 2017, ApJ, 840,50, doi: 10.3847/1538-4357/aa6e00Ressler, M. E., Sukhatme, K. G., Franklin, B. R., et al.2015, Publications of the Astronomical Society of thePacific, 127, 675, doi: 10.1086/682258Rieke, G. H., Wright, G. S., B¨oker, T., et al. 2015,Publications of the Astronomical Society of the Pacific,127, 584, doi: 10.1086/682252Rivinius, T., Stahl, O., Wolf, B., et al. 1997, A&A, 318, 819Rousset, G., Lacombe, F., Puget, P., et al. 2003, inProc. SPIE, Vol. 4839, Adaptive Optical SystemTechnologies II, ed. P. L. Wizinowich & D. Bonaccini,140–149, doi: 10.1117/12.459332Sabha, N., Eckart, A., Merritt, D., et al. 2012, A&A, 545,A70, doi: 10.1051/0004-6361/201219203Schartmann, M., Burkert, A., & Ballone, A. 2018, A&A,616, L8, doi: 10.1051/0004-6361/201833156Sch¨odel, R., Morris, M. R., Muzic, K., et al. 2011, A&A,532, A83, doi: 10.1051/0004-6361/201116994 Sch¨odel, R., Najarro, F., Muzic, K., & Eckart, A. 2010,A&A, 511, A18, doi: 10.1051/0004-6361/200913183Sch¨odel, R., Ott, T., Genzel, R., et al. 2002, Nature, 419,694, doi: 10.1038/nature01121Shahzamanian, B., Zajaˇcek, M., Valencia-S., M., et al.2017, 322, 233, doi: 10.1017/S1743921316011819Shahzamanian, B., Eckart, A., Zajaˇcek, M., et al. 2016,A&A, 593, A131, doi: 10.1051/0004-6361/201628994Trippe, S., Davies, R., Eisenhauer, F., et al. 2010, MNRAS,402, 1126, doi: 10.1111/j.1365-2966.2009.15940.xValencia-S., M., Eckart, A., Zajaˇcek, M., et al. 2015, ApJ,800, 125, doi: 10.1088/0004-637X/800/2/125Vorobyov, E. I., Skliarevskii, A. M., Elbakyan, V. G., et al.2020, A&A, 635, A196,doi: 10.1051/0004-6361/201936990Wallstr¨om, S. H. J., Lagadec, E., Muller, S., et al. 2017,A&A, 597, A99, doi: 10.1051/0004-6361/201628416Wardle, M., & Yusef-Zadeh, F. 1992, Nature, 357, 308,doi: 10.1038/357308a0Wilkin, F. P. 1996, ApJL, 459, L31, doi: 10.1086/309939—. 2000, ApJ, 532, 400, doi: 10.1086/308576Witzel, G., Eckart, A., Bremer, M., et al. 2012, ApJS, 203,18, doi: 10.1088/0067-0049/203/2/18Wolf, B., & Stahl, O. 1985, A&A, 148, 412Yusef-Zadeh, F., Royster, M., Wardle, M., et al. 2020,MNRAS, doi: 10.1093/mnras/staa2399Yusef-Zadeh, F., Wardle, M., Kunneriath, D., et al. 2017a,ApJL, 850, L30, doi: 10.3847/2041-8213/aa96a2Yusef-Zadeh, F., Sch¨odel, R., Wardle, M., et al. 2017b,MNRAS, 470, 4209, doi: 10.1093/mnras/stx1439Zajaˇcek, M., Eckart, A., Karas, V., et al. 2016, MNRAS,455, 1257, doi: 10.1093/mnras/stv2357Zajaˇcek, M., Britzen, S., Eckart, A., et al. 2017, A&A, 602,A121, doi: 10.1051/0004-6361/201730532Zajaˇcek, M., Araudo, A., Karas, V., Czerny, B., & Eckart,A. 2020, ApJ, 903, 140, doi: 10.3847/1538-4357/abbd94Zajaˇcek, M., Karas, V., & Eckart, A. 2014, A&A, 565, A17,doi: 10.1051/0004-6361/201322713 Pei β ker et al. APPENDIX A. K-BAND POSITION OF S50 IN RELATION TO THE L (cid:48) -BAND EMISSION OF X7Here we are showing the relation between the K-band detection of S50 and the L (cid:48) -band emission of X7 (Fig. 9)observed with NACO. To compare the projected on-sky distances, we are rebinning the L (cid:48) -band data to the same pixelscale as the K-band data, i.e., two pixels correspond to 27 mas. By using the stellar position of S50 in the K-band, Figure 9.
Galactic center observed with NACO in the L- and K-band in 2002. In the upper left and right panel, Sgr A* isindicated with a green × , the white arrow points towards the position of X7 (L-band) and S50 (K-band). As in Fig. 12, S65 canbe used as a reference source for the identification. With the combination of the L (cid:48) - and K-band data, we derive the position ofthe stellar source S50 with respect to X7 (lower panel, see the green dot inside the dusty emission). For the interested reader,we note that the K-band image also demonstrates the high asymmetrical stellar distribution of the S-cluster in projection. we pinpoint the stellar location in the L (cid:48) -band (see Fig. 9). This procedure is similar to the steps for the SINFONIdetection with the difference that we are using data cubes. In the final mosaic data cube of a related year, we selectthe 2 . − . µm range to extract the related K-band image. Then, we compare the position of S50 in the extractedK-band image with the continuum subtracted Br γ line maps that are constructed from the related data cube (Fig. 5). nteraction of an S-star with the environment of Sgr A* B. H EMISSION OF S50For investigating the spectrum of S50, two main cornerstones have to be fulfilled:1. A maximized data quality,2. An individual detection of S50.Regarding point 1, a high number ( >
20) of single exposures with a satisfying quality (FWHM < . Figure 10. H triplet measured at the K-band position of S50 with SINFONI. use a PSF sized aperture. Furthermore, we fit a Gaussian to the detected H triplet with a measured uncertainty ofabout ±
35 km/s. As pointed out by, e.g., Arulanantham et al. (2017) and Hoadley et al. (2017), H lines can be usedas a tracer for protoplanetary disks of YSOs. Considering the analysis of Muˇzi´c et al. (2010) and the proposed natureof S50 as a T-Tauri or Ae/Be Herbig star seems to be a reasonable connection. However, we would like to point outthat future observations in combination with theoretical models will confirm or reject this claim. C. X7, A TIDALLY STRETCHED FEATUREAs a rather speculative scenario, we shortly discuss the possibility that X7 is a tidally stretched gas and dust feature(as proposed by Randy Campbell, UCLA, at GCWS 2019; proceedings in prep.). Isolating the observation of theX7/S50 observation in 2018 could lead indeed to the assumption that the source is a tidally stretched gas and dustfeature. Even though this scenario promises a wide range of useful scientific implications, observations of comparableobjects have shown that a tidally stretched object is rather unlikely (Gillessen et al. 2012; Eckart, A. et al. 2013;Valencia-S. et al. 2015). Considering Fig. 4 (left side), we do find an increasing distance of the head from S50.However, the overall trend of the X7/S50 system seems to be not affected by Sgr A* (Fig. 4, right side). Even withthe observed and detected asymmetry regarding the stellar position with respect to its gaseous and dusty shell X7,the system is following the proper motion as found by Muˇzi´c et al. (2010). As pointed out several times, a long-timesurvey of the evolution of X7/S50 is required. D. COMIC/ADONIS+RASOIR DATA OF 1999In Fig. 12, we present the results of the long-time survey of X7 in the L (cid:48) -band with COMIC/ADONIS+RASOIR(1999) in combination with the NACO data (2002, 2003 - 2018 is shown in Fig. 2). For the image presented inFig. 12 which is observed with COMIC/ADONIS+RASOIR, we use a high pass filter to highlight features of the0 Pei β ker et al. Figure 11.
Possible evolution of the X7/S50 system. The sketch is based on the line map detection of X7 in 2018 at about2 . µm shown in Fig. 5. The green filled contour represents the K-band position of S50. The white curved line along X7corresponds to the speculative scenario where the head of the system gets detached and attracted by Sgr A* (light-blue x). Thearrow indicates the direction of the proper motion of X7 and S50 as derived by Gillessen et al. (2009) and Muˇzi´c et al. (2010). S-cluster. In both images, we clearly detect the structure of the S-cluster (Fig. 12). Even though the resultingCOMIC/ADONIS+RASOIR image of 1999 suffers from a decreased magnitude sensitivity, we are still able to identifyseveral (isolated) sources including the spherical shaped bow shock source X7 at the position of S50. As indicated bythe orbital plots presented on the right-handed side of Fig. 12, we identify the nearby S-cluster stars S33, S71/S72, S65,and S87 and mark them accordingly. Moreover, we include the K-band based orbit of S50 (red dot) in the presentedCOMIC/ADONIS+RASOIR data of 1999 (red ellipse). E. DATAHere, we list the NACO and SINFONI data. Parts of this data were analysed in various publications like Muˇzi´c et al.(2010), Witzel et al. (2012), Eckart et al. (2013), Zajaˇcek et al. (2014), Valencia-S. et al. (2015), Shahzamanian et al.(2016), Parsa et al. (2017), and Peißker et al. (2019, 2020a,b,c,d). These listed publications underline the robustnessof the used data. For the sake of completeness, it should be noted that Parsa et al. (2017) derived with the hereused data the gravitational redshift of S2 caused by the SMBH. This was later independently confirmed by GravityCollaboration et al. (2018) and indicates the quality of the data reduction process applied to the data. nteraction of an S-star with the environment of Sgr A* Figure 12.
Galactic center in the L (cid:48) -band observed with COMIC/ADONIS+RASOIR and NACO in 1999 and 2002 respectively.The green × marks the approximate position of Sgr A*. In 1999 and 2002, the position of S2 and Sgr A* are confused becauseof its close proximity to each other. Some re-identified S-stars are marked with a light green circle. In 1999, the orbital spatialposition of the S-cluster stars S71 and S72 coincide which results in the bright spot marked with a light green circle. The righthanded side shows orbits of the S-stars S33 (marked), S50, S71/S72 (marked), and S87 (marked). The position of S65 can beused for orientation in these plots (please see Fig. 2 for comparison). The orbit of S50 is highlighted in red. The empty circleof S33 in 2002 corresponds to the position of the star in the high-pass filtered image. Pei β ker et al. Date Observation ID Amount of on source exposures Exp. TimeTotal Medium High(YYYY:MM:DD) (s)2005.06.16 075.B-0547(B) 20 12 8 3002005.06.18 075.B-0547(B) 21 2 19 602006.03.17 076.B-0259(B) 5 0 3 6002006.03.20 076.B-0259(B) 1 1 0 6002006.03.21 076.B-0259(B) 2 2 0 6002006.04.22 077.B-0503(B) 1 0 0 6002006.08.17 077.B-0503(C) 1 0 1 6002006.08.18 077.B-0503(C) 5 0 5 6002006.09.15 077.B-0503(C) 3 0 3 6002007.03.26 078.B-0520(A) 8 1 2 6002007.04.22 179.B-0261(F) 7 2 1 6002007.04.23 179.B-0261(F) 10 0 0 6002007.07.22 179.B-0261(F) 3 0 2 6002007.07.24 179.B-0261(Z) 7 0 7 6002007.09.03 179.B-0261(K) 11 1 5 6002007.09.04 179.B-0261(K) 9 0 0 6002008.04.06 081.B-0568(A) 16 0 15 6002008.04.07 081.B-0568(A) 4 0 4 6002009.05.21 183.B-0100(B) 7 0 7 6002009.05.22 183.B-0100(B) 4 0 4 4002009.05.23 183.B-0100(B) 2 0 2 4002009.05.24 183.B-0100(B) 3 0 3 600
Table 4.
SINFONI data of 2005, 2006, 2007, 2008, and 2009. The total amount of data is listed. nteraction of an S-star with the environment of Sgr A* Date Observation ID Amount of on source exposures Exp. TimeTotal Medium High(YYYY:MM:DD) (s)2010.05.10 183.B-0100(O) 3 0 3 6002010.05.11 183.B-0100(O) 5 0 5 6002010.05.12 183.B-0100(O) 13 0 13 6002011.04.11 087.B-0117(I) 3 0 3 6002011.04.27 087.B-0117(I) 10 1 9 6002011.05.02 087.B-0117(I) 6 0 6 6002011.05.14 087.B-0117(I) 2 0 2 6002011.07.27 087.B-0117(J)/087.A-0081(B) 2 1 1 6002012.03.18 288.B-5040(A) 2 0 2 6002012.05.05 087.B-0117(J) 3 0 3 6002012.05.20 087.B-0117(J) 1 0 1 6002012.06.30 288.B-5040(A) 12 0 10 6002012.07.01 288.B-5040(A) 4 0 4 6002012.07.08 288.B-5040(A)/089.B-0162(I) 13 3 8 6002012.09.08 087.B-0117(J) 2 1 1 6002012.09.14 087.B-0117(J) 2 0 2 6002013.04.05 091.B-0088(A) 2 0 2 6002013.04.06 091.B-0088(A) 8 0 8 6002013.04.07 091.B-0088(A) 3 0 3 6002013.04.08 091.B-0088(A) 9 0 6 6002013.04.09 091.B-0088(A) 8 1 7 6002013.04.10 091.B-0088(A) 3 0 3 6002013.08.28 091.B-0088(B) 10 1 6 6002013.08.29 091.B-0088(B) 7 2 4 6002013.08.30 091.B-0088(B) 4 2 0 6002013.08.31 091.B-0088(B) 6 0 4 6002013.09.23 091.B-0086(A) 6 0 0 6002013.09.25 091.B-0086(A) 2 1 0 6002013.09.26 091.B-0086(A) 3 1 1 600
Table 5.
SINFONI data of 2010, 2011, 2012, and 2013. Pei β ker et al. Date Observation ID Amount of on source exposures Exp. TimeTotal Medium High(YYYY:MM:DD) (s)2014.02.27 092.B-0920(A) 4 1 3 6002014.02.28 091.B-0183(H) 7 3 1 4002014.03.01 091.B-0183(H) 11 2 4 4002014.03.02 091.B-0183(H) 3 0 0 4002014.03.11 092.B-0920(A) 11 2 9 4002014.03.12 092.B-0920(A) 13 8 5 4002014.03.26 092.B-0009(C) 9 3 5 4002014.03.27 092.B-0009(C) 18 7 5 4002014.04.02 093.B-0932(A) 18 6 1 4002014.04.03 093.B-0932(A) 18 1 17 4002014.04.04 093.B-0932(B) 21 1 20 4002014.04.06 093.B-0092(A) 5 2 3 4002014.04.08 093.B-0218(A) 5 1 0 6002014.04.09 093.B-0218(A) 6 0 6 6002014.04.10 093.B-0218(A) 14 4 10 6002014.05.08 093.B-0217(F) 14 0 14 6002014.05.09 093.B-0218(D) 18 3 13 6002014.06.09 093.B-0092(E) 14 3 0 4002014.06.10 092.B-0398(A)/093.B-0092(E) 5 4 0 400/6002014.07.08 092.B-0398(A) 6 1 3 6002014.07.13 092.B-0398(A) 4 0 2 6002014.07.18 092.B-0398(A)/093.B-0218(D) 1 0 0 6002014.08.18 093.B-0218(D) 2 0 1 6002014.08.26 093.B-0092(G) 4 3 0 4002014.08.31 093.B-0218(B) 6 3 1 6002014.09.07 093.B-0092(F) 2 0 0 4002015.04.12 095.B-0036(A) 18 2 0 4002015.04.13 095.B-0036(A) 13 7 0 4002015.04.14 095.B-0036(A) 5 1 0 4002015.04.15 095.B-0036(A) 23 13 10 4002015.08.01 095.B-0036(C) 23 7 8 4002015.09.05 095.B-0036(D) 17 11 4 400
Table 6.
SINFONI data of 2014 and 2015. nteraction of an S-star with the environment of Sgr A* Date Observation ID Amount of on source exposures Exp. TimeTotal Medium High(YYYY:MM:DD) (s)2017.03.15 598.B-0043(D) 5 2 0 6002017.03.19 598.B-0043(D) 11 0 5 6002017.03.20 598.B-0043(D) 15 4 11 6002017.03.21 598.B-0043(D) 1 0 0 6002017.05.20 0101.B-0195(B) 8 2 6 6002017.06.01 598.B-0043(E) 5 0 3 6002017.06.02 598.B-0043(E) 8 0 8 6002017.06.29 598.B-0043(E) 4 2 17 6002017.07.20 0101.B-0195(C) 8 5 0 6002017.07.28 0101.B-0195(C) 6 0 0 6002017.07.29 0101.B-0195(D) 9 0 0 6002017.08.01 0101.B-0195(E) 4 0 0 6002017.08.19 598.B-0043(F) 8 0 2 6002017.09.13 598.B-0043(F) 8 0 0 6002017.09.15 598.B-0043(F) 10 1 1 6002017.09.29 598.B-0043(F) 2 0 0 6002017.10.15 0101.B-0195(F) 2 0 0 6002017.10.17 0101.B-0195(F) 4 0 0 6002017.10.23 598.B-0043(G) 3 0 0 600
Table 7.
SINFONI data of 2017. Pei β ker et al. Date Observation ID Amount of on source exposures Exp. TimeTotal Medium High(YYYY:MM:DD) (s)2018.02.13 299.B-5056(B) 3 0 0 6002018.02.14 299.B-5056(B) 5 0 0 6002018.02.15 299.B-5056(B) 5 0 0 6002018.02.16 299.B-5056(B) 5 0 0 6002018.03.23 598.B-0043(D) 8 0 8 6002018.03.24 598.B-0043(D) 7 0 0 6002018.03.25 598.B-0043(D) 9 0 1 6002018.03.26 598.B-0043(D) 12 1 9 6002018.04.09 0101.B-0195(B) 8 0 4 6002018.04.28 598.B-0043(E) 10 1 1 6002018.04.30 598.B-0043(E) 11 1 4 6002018.05.04 598.B-0043(E) 17 0 17 6002018.05.15 0101.B-0195(C) 8 0 0 6002018.05.17 0101.B-0195(C) 8 0 4 6002018.05.20 0101.B-0195(D) 8 0 4 6002018.05.28 0101.B-0195(E) 8 3 1 6002018.05.28 598.B-0043(F) 4 0 4 6002018.05.30 598.B-0043(F) 8 5 3 6002018.06.03 598.B-0043(F) 8 0 8 6002018.06.07 598.B-0043(F) 14 1 7 6002018.06.14 0101.B-0195(F) 4 0 0 6002018.06.23 0101.B-0195(F) 8 1 1 6002018.06.23 598.B-0043(G) 7 2 1 6002018.06.25 598.B-0043(G) 22 5 7 6002018.07.02 598.B-0043(G) 3 0 0 6002018.07.03 598.B-0043(G) 22 12 10 6002018.07.09 0101.B-0195(G) 8 3 1 6002018.07.24 598.B-0043(H) 3 0 0 6002018.07.28 598.B-0043(H) 8 0 3 6002018.08.03 598.B-0043(H) 8 0 1 6002018.08.06 598.B-0043(H) 8 1 1 6002018.08.19 598.B-0043(I) 12 2 10 6002018.08.20 598.B-0043(I) 12 0 12 6002018.09.03 598.B-0043(I) 1 0 0 6002018.09.27 598.B-0043(J) 10 0 0 6002018.09.28 598.B-0043(J) 10 0 0 6002018.09.29 598.B-0043(J) 8 0 0 6002018.10.16 2102.B-5003(A) 3 0 0 600
Table 8.
SINFONI data of 2018. nteraction of an S-star with the environment of Sgr A* NACODate Observation ID numberofexposures Totalexposuretime(s) λ Table 9.
K-band data observed with NACO between 2002 and 2018. Pei β ker et al. NACODate Observation ID numberofexposures λ L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) L (cid:48) Table 10. L (cid:48)(cid:48)