P. Koubsky

The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst - II. The circumstellar environment and the aftermath

Context. The nova outburst of V407 Cyg in 2010 Mar. 10 was the first observed for this star but its close resemblance to the well known symbiotic-like recurrent nova RS Oph suggests that it is also a member of this rare type of Galactic novae. The nova was the first detected at γ-ray energies and is the first known nova explosion for this system. The extensive multiwavelength coverage of this outburst makes it an ideal comparison with the few other outbursts known for similar systems. Aims. We extend our previous analysis of the Mira and the expanding shock from the explosion to detail the time development of the photoionized Mira wind, circumstellar medium, and shocked circumstellar environment to derive their physical parameters and how they relate to large scale structure of the environment, extending the previous coverage to more than 500 days after outburst. Methods. We use optical spectra obtained at high resolution with the Nordic Optical Telescope (NOT) (R ≈ 45 000 to 65 000) and medium resolution Ondy Observatory (R ≈ 12 000) data and compare the line variations with publicly available archival measurements at 30 GHz OVNR and at X-rays with Swift during the first four months of the outburst, through the end of the epoch of strong XR emission. We use nebular diagnostics and high resolution profile variations to derive the densities and locations of the extended emission. Results. We find that the higher the ionization and/or the higher the excitation energy, the more closely the profiles resemble the He II/Ca V-type high velocity shock profile discussed in Paper I. This also accounts for the comparative development of the [N II] and [O III] isoelectronic transitions: the [O III] 4363 A profile does not show the low velocity peaks while the excited [N II] 5754 A does. If nitrogen is mainly N +3 or higher in the shock, the upper state of the [N II] nebular lines will contribute but if the oxygen is O +2 then this line is formed by recombination, masking the nebular contributor, and the lower states are collisionally quenched but emit from the low density surroundings. Absorption lines of Fe-peak ions formed in the Mira wind were visible as P Cyg profiles at low velocity before Day 69, around the time of the X-ray peak and we identified many absorption transitions without accompanying emission for metal lines. The H Balmer lines showed strong P Cyg absorption troughs that weakened during the 2010 observing period, through Day 128. The Fe-peak line profiles and flux variations were different for permitted and forbidden transitions: the E1 transitions were not visible after Day 128 but had shown a narrow peak superimposed on an extended (200 km s −1 ) blue wing, while the M1 and E2 transitions persisted to Day 529, the last observation, and showed extended redshifted wings up of the same velocity. We distinguish the components from the shock, the photoionized environment, and the chromosphere and inner Mira wind using spectra taken more than one year after outburst. The multiple shells and radiative excitation phenomenology are similar to those recently cited for GRBs and SNIa.

Gaia Data Release 2: Summary of the variability processing and analysis results

Context. The Gaia Data Release 2 (DR2) contains more than half a million sources that are identified as variable stars. Aims: We summarise the processing and results of the identification of variable source candidates of RR Lyrae stars, Cepheids, long-period variables (LPVs), rotation modulation (BY Dra-type) stars, δ Scuti and SX Phoenicis stars, and short-timescale variables. In this release we aim to provide useful but not necessarily complete samples of candidates. Methods: The processed Gaia data consist of the G, GBP, and GRP photometry during the first 22 months of operations as well as positions and parallaxes. Various methods from classical statistics, data mining, and time-series analysis were applied and tailored to the specific properties of Gaia data, as were various visualisation tools to interpret the data. Results: The DR2 variability release contains 228 904 RR Lyrae stars, 11 438 Cepheids, 151 761 LPVs, 147 535 stars with rotation modulation, 8882 δ Scuti and SX Phoenicis stars, and 3018 short-timescale variables. These results are distributed over a classification and various Specific Object Studies tables in the Gaia archive, along with the three-band time series and associated statistics for the underlying 550 737 unique sources. We estimate that about half of them are newly identified variables. The variability type completeness varies strongly as a function of sky position as a result of the non-uniform sky coverage and intermediate calibration level of these data. The probabilistic and automated nature of this work implies certain completeness and contamination rates that are quantified so that users can anticipate their effects. Thismeans that even well-known variable sources can be missed or misidentified in the published data. Conclusions: The DR2 variability release only represents a small subset of the processed data. Future releases will include more variable sources and data products; however, DR2 shows the (already) very high quality of the data and great promise for variability studies.

Properties and Nature of Be Stars: 28. Implications of Systematic Observations for the Nature of the Multiple System with the Be Star o Cassiopeae and its Circumstellar Environment

Abstract : The analysis of radial velocities of the Be star o Cas from spectra taken between 1992 and 2008 at the Ondrejov Observatory and the Dominion Astrophysical Observatory allowed us to reconfirm the binary nature of this object, first suggested by Abt and Levy in 1978, but later refuted by several authors. The orbital parameters of this SB1 system imply a very high mass function of about one solar mass. This in turn leads to a very high mass of the secondary, possibly higher than that of the primary. In order to look for such a massive secondary, o Cas was observed with the Navy Prototype Optical Interferometer, which allowed the binary components to be spatially resolved for the first time. The interferometric observations lead to the detection of a secondary, about 3 mag fainter than the primary. The possible properties of this peculiar binary system and the reasons why the massive secondary does not dominate the optical spectrum are discussed.

The spectroscopic evolution of the symbiotic star AG Draconis I. The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008

Context. AG Dra is one of a small group of low metallicity S-type symbiotic binaries with K-type giants that undergoes occasional short-term outbursts of unknown origin. Aims. Our aim is to study the behavior of the white dwarf during an outburst using the optical Raman lines and other emission features in the red giant wind. The goal is to determine changes in the envelope and the wind of the gainer in this system during a major outburst event and to study the coupling between the UV and optical during a major outburst. Methods. Using medium and high resolution groundbased optical spectra and comparisons with archival FUSE and HST/STZS spectra, we study the evolution of the Raman O VI features and the Balmer, He I, and He II lines during the outburst from 2006 Sep. through 2007 May and include more recent observations (2009) to study the subsequent evolution of the source. Results. The O VI Raman features disappeared completely at the peak of the major outburst and the subsequent variation differs substantially from that reported during the previous decade. The He I and He II lines, and the Balmer lines, vary in phase with the Raman features but there is a double-valuedness to the He I 6678, 7065 relative to the O VI Raman 6825 A variations in the period between 2006-2008 that has not been previously reported. Conclusions. The variations in the Raman feature ratio through the outburst interval are consistent with the disappearance of the O VI FUV resonance wind lines from the white dwarf and of the surrounding O +5 ionized region within the red giant wind provoked by the expansion and cooling of the white dwarf photosphere.

Properties and nature of Be stars ? 30. Reliable physical properties of a semi-detached B9.5e+G8III binary BR CMi = HD 61273 compared to those of other well studied semi-detached emission-line binaries

Reliable determination of the basic physical properties of hot emission-line binaries with Roche-lobe filling secondaries is important for developing the theory of mass exchange in binaries. It is a very hard task, however, which is complicated by the presence of circumstellar matter in these systems. So far, only a small number of systems with accurate values of component masses, radii, and other properties are known. Here, we report the first detailed study of a new representative of this class of binaries, BR CMi, based on the analysis of radial velocities and multichannel photometry from several observatories, and compare its physical properties with those for other well-studied systems. BR CMi is an ellipsoidal variable seen under an intermediate orbital inclination of ~51 degrees, and it has an orbital period of 12.919059(15) d and a circular orbit. We used the disentangled component spectra to estimate the effective temperatures 9500(200) K and 4655(50) K by comparing them with model spectra. They correspond to spectral types B9.5e and G8III. We also used the disentangled spectra of both binary components as templates for the 2-D cross-correlation to obtain accurate RVs and a reliable orbital solution. Some evidence of a secular period increase at a rate of 1.1+/-0.5 s per year was found. This, together with a very low mass ratio of 0.06 and a normal mass and radius of the mass gaining component, indicates that BR CMi is in a slow phase of the mass exchange after the mass-ratio reversal. It thus belongs to a still poorly populated subgroup of Be stars for which the origin of Balmer emission lines is safely explained as a consequence of mass transfer between the binary components.

The new orbital elements and properties of epsilon Persei

A detailed analysis of a large collection of electronic spectra from three observatories, together with radial velocities published earlier, were used to derive a new ephemeris and improved orbital elements for the epsilo Per binary. Observations covering a time interval of about 37 000 days (101.3 years) can be reconciled with a constant orbital period of 14.06916 � � 0.00004�. The high orbital eccentricity of 0.555 � 0.009 was also confirmed. New spectral observations confirm that there is a periodic variation of the systemic velocity. Together with new evidence from astrometric observations (also analyzed here), they confirm the existence of a third body in the system with an orbital period of about 9600 days (26.3 years), rather than 4156 days, as reported earlier. Application of the disentangling technique to the Halpha spectra with good S/N ratios did not allow detection of spectral lines of either the secondary or tertiary components. For plausible inclinations between 30� and 90�, the observed mass function implies a mass of the secondary M_2=0.85-1.77 M o , if a primary mass is adopted of 13.5 � 2.0 M o . Attempts to detect the third body via interferometric observations should continue in spite of this first negative result.

The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst

Context. V407 Cyg was, before 2010 Mar., known only as a D-type symbiotic binary system in which the Mira variable has a pulsation period of approximately 750 days, one of the longest known. On 2010 Mar. 10, it was discovered in outburst, eventually reaching V < 8. This is the first recorded nova event for this system, but it closely resembles the spectroscopic development of RS Oph, the prototypical symbiotic-like recurrent nova. It was also detected by Fermi above 100 MeV and displayed strong, likely nonthermal centimeter wavelength radio emission. Aims. Unlike classical novae occurring in compact cataclysmic binary systems, for which the ejecta undergo free ballistic expansion, this explosion occurred within the dense, complex wind of a Mira variable companion. This paper concentrates on the development of the shock and its passage through the Mira wind. We also present some constraints on the binary system properties. Methods. Using medium and high resolution ground-based optical spectra, visual and Swift UV photometry, and Swift X-ray spectrophotometry, we describe the behavior of the high-velocity profile evolution for this nova during its first three months. Results. Using the diffuse interstellar bands visible in the high-resolution optical spectra, we obtain an extinction E(B - V) ≈ 0.45 ± 0.05. The spectral type of the red giant during this period, when the star was at R minimum, was no earlier than M7 III. The peak of the X-ray emission occurred at about day 40 with a broad maximum and decline after day 50. The main changes in the optical spectrum began at around that time. The He II 4686 A line first appeared between days 7 and 14 and initially displayed a broad, symmetric profile that is characteristic of all species before day 60. The profile development thereafter depended on ionization state. Low-excitation lines remained comparatively narrow, with v rad,max of order 200-400 km s -1 . They were systematically more symmetric than lines such as [Ca V], [Fe VII], [Fe X], and He II, all of which showed a sequence of profile changes going from symmetric to a blue wing similar to that of the low ionization species but with a red wing extended to as high as 600 km s -1 . The [O I] 6300, 6364 doublet showed a narrow wind-emission component near the rest velocity of the system and a broad component, 200-300 km s -1 , whose relative intensity increased in time. Forbidden lines of N II and O III had two separate contributors to the profiles, a broad line that increased in strength and velocity width, exceeding 200 km s -1 , and narrow components from a surrounding ionized region at higher velocity than the Mira wind. The Na I D doublet developed a broad component with similar velocity width to the other low-ionization species. The O VI Raman features observed in recent outbursts of RS Oph were not detected. We interpret these variations as aspherical expansion of the ejecta within the Mira wind. The blue side is from the shock penetrating into the wind while the red wing is from the low-density periphery. The maximum radial velocities obey power laws, v max ~ t -n with n ≈ 1/3 for red wing and ≈0.8 for the blue.

The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst: I. the shock and its evolution

Context. V407 Cyg was, before 2010 Mar., known only as a D-type symbiotic binary system in which the Mira variable has a pulsation period of approximately 750 days, one of the longest known. On 2010 Mar. 10, it was discovered in outburst, eventually reaching V < 8. This is the first recorded nova event for this system, but it closely resembles the spectroscopic development of RS Oph, the prototypical symbiotic-like recurrent nova. It was also detected by Fermi above 100 MeV and displayed strong, likely nonthermal centimeter wavelength radio emission. Aims. Unlike classical novae occurring in compact cataclysmic binary systems, for which the ejecta undergo free ballistic expansion, this explosion occurred within the dense, complex wind of a Mira variable companion. This paper concentrates on the development of the shock and its passage through the Mira wind. We also present some constraints on the binary system properties. Methods. Using medium and high resolution ground-based optical spectra, visual and Swift UV photometry, and Swift X-ray spectrophotometry, we describe the behavior of the high-velocity profile evolution for this nova during its first three months. Results. Using the diffuse interstellar bands visible in the high-resolution optical spectra, we obtain an extinction E(B - V) ≈ 0.45 ± 0.05. The spectral type of the red giant during this period, when the star was at R minimum, was no earlier than M7 III. The peak of the X-ray emission occurred at about day 40 with a broad maximum and decline after day 50. The main changes in the optical spectrum began at around that time. The He II 4686 A line first appeared between days 7 and 14 and initially displayed a broad, symmetric profile that is characteristic of all species before day 60. The profile development thereafter depended on ionization state. Low-excitation lines remained comparatively narrow, with v rad,max of order 200-400 km s -1 . They were systematically more symmetric than lines such as [Ca V], [Fe VII], [Fe X], and He II, all of which showed a sequence of profile changes going from symmetric to a blue wing similar to that of the low ionization species but with a red wing extended to as high as 600 km s -1 . The [O I] 6300, 6364 doublet showed a narrow wind-emission component near the rest velocity of the system and a broad component, 200-300 km s -1 , whose relative intensity increased in time. Forbidden lines of N II and O III had two separate contributors to the profiles, a broad line that increased in strength and velocity width, exceeding 200 km s -1 , and narrow components from a surrounding ionized region at higher velocity than the Mira wind. The Na I D doublet developed a broad component with similar velocity width to the other low-ionization species. The O VI Raman features observed in recent outbursts of RS Oph were not detected. We interpret these variations as aspherical expansion of the ejecta within the Mira wind. The blue side is from the shock penetrating into the wind while the red wing is from the low-density periphery. The maximum radial velocities obey power laws, v max ~ t -n with n ≈ 1/3 for red wing and ≈0.8 for the blue.

The spectroscopic evolution of the symbiotic-like recurrent nova V407 Cygni during its 2010 outburst I. The shock and its evolution

Context. V407 Cyg was, before 2010 Mar., known only as a D-type symbiotic binary system in which the Mira variable has a pulsation period of approximately 750 days, one of the longest known. On 2010 Mar. 10, it was discovered in outburst, eventually reaching V < 8. This is the first recorded nova event for this system, but it closely resembles the spectroscopic development of RS Oph, the prototypical symbiotic-like recurrent nova. It was also detected by Fermi above 100 MeV and displayed strong, likely nonthermal centimeter wavelength radio emission. Aims. Unlike classical novae occurring in compact cataclysmic binary systems, for which the ejecta undergo free ballistic expansion, this explosion occurred within the dense, complex wind of a Mira variable companion. This paper concentrates on the development of the shock and its passage through the Mira wind. We also present some constraints on the binary system properties. Methods. Using medium and high resolution ground-based optical spectra, visual and Swift UV photometry, and Swift X-ray spectrophotometry, we describe the behavior of the high-velocity profile evolution for this nova during its first three months. Results. Using the diffuse interstellar bands visible in the high-resolution optical spectra, we obtain an extinction E(B - V) ≈ 0.45 ± 0.05. The spectral type of the red giant during this period, when the star was at R minimum, was no earlier than M7 III. The peak of the X-ray emission occurred at about day 40 with a broad maximum and decline after day 50. The main changes in the optical spectrum began at around that time. The He II 4686 A line first appeared between days 7 and 14 and initially displayed a broad, symmetric profile that is characteristic of all species before day 60. The profile development thereafter depended on ionization state. Low-excitation lines remained comparatively narrow, with v rad,max of order 200-400 km s -1 . They were systematically more symmetric than lines such as [Ca V], [Fe VII], [Fe X], and He II, all of which showed a sequence of profile changes going from symmetric to a blue wing similar to that of the low ionization species but with a red wing extended to as high as 600 km s -1 . The [O I] 6300, 6364 doublet showed a narrow wind-emission component near the rest velocity of the system and a broad component, 200-300 km s -1 , whose relative intensity increased in time. Forbidden lines of N II and O III had two separate contributors to the profiles, a broad line that increased in strength and velocity width, exceeding 200 km s -1 , and narrow components from a surrounding ionized region at higher velocity than the Mira wind. The Na I D doublet developed a broad component with similar velocity width to the other low-ionization species. The O VI Raman features observed in recent outbursts of RS Oph were not detected. We interpret these variations as aspherical expansion of the ejecta within the Mira wind. The blue side is from the shock penetrating into the wind while the red wing is from the low-density periphery. The maximum radial velocities obey power laws, v max ~ t -n with n ≈ 1/3 for red wing and ≈0.8 for the blue.

VEGA: A Visible Spectrograph and Polarimeter for the VLTI

The ESO/VLTI has now clearly a position of world leader in the domain of ground-based optical interferometry. With four 8.2 m telescopes and two (four) 1.8 m telescopes, the Paranal Observatory is without any doubt the best optical interferometric facility in the world. Since many years, it has attracted the major part of the European interferometric community and with the opening of MIDI and AMBER, the astronomers have now access to ’general user’ interferometric instruments in the thermal and near infrared. This paper describes a project for a second generation focal instrument of the VLTI, named VEGAfor Visible spEctroGraph and polArimeter. The goal is to give access to the visible wavelength region, with spectroscopic and polarimetric capabilities, taking advantage of the coherent field of view of the VLTI. It is a unique scientific field for the VLTI. For example, a 200m interferometer operating in the visible will be able to resolve structures of the order of 0.5 mas or 0.1 AU at the distance of the Ophiuchus cloud.