MASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31: Discovery, Light Curve, Hydrodynamics, Evolution
V. M. Lipunov, S.Blinnikov, E.Gorbovskoy, A.Tutukov, P.Baklanov, V.Krushinski, N. Tiurina, P. Balanutsa, A. Kuznetsov, V. Kornilov, I. Gorbunov, V.Shumkov, V.Vladimirov, O. Gress, N. M. Budnev, K. Ivanov, A. Tlatov, I.Zalozhnykh, Yu. Sergienko, A. Gabovich, V. Yurkov
aa r X i v : . [ a s t r o - ph . H E ] A p r MNRAS , 1–15 (2016) Preprint April 27, 2017 Compiled using MNRAS L A TEX style file v3.0
MASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31: Discovery, LightCurve, Hydrodynamics, Evolution
V. M. Lipunov , ⋆ ,S.Blinnikov , , E.Gorbovskoy , , A.Tutukov , P.Baklanov , , , V.Krushinski , N. Tiurina ,P. Balanutsa , A. Kuznetsov , V. Kornilov , , I. Gorbunov , V.Shumkov , V.Vladimirov , O. Gress , N. M. Budnev , K. Ivanov ,A. Tlatov , I.Zalozhnykh , Yu. Sergienko , A. Gabovich , V. Yurkov M.V.Lomonosov Moscow State University, Faculty of Physics, Leninskie gory, GSP-1, Moscow, 119991, Russia M.V.Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetsky pr., 13, Moscow, 119234, Russia Alikhanov Institute for Theoretical and Experimental Physics B. Cheremushkinskaya, 25, Moscow, 117218 Russia,Kavli IPMU (WPI), Kashiwa, Japan, Institute of Astronomy of Russian Academy of Science Pyatnitskaya str., 48, Moscow 119017 Russia Novosibirsk State University, Novosibirsk 630090, Russia National Research Nuclear University (MEPhI), 115409 Moscow, Russia Kourovka Astronomical Observatory, Ural Federal University, Lenin ave. 51, Ekaterinburg 620000, Russia Applied Physics Institute, Irkutsk State University, 20, Gagarin blvd,664003, Irkutsk, Russia Kislovodsk Solar Station of the Main (Pulkovo) Observatory RAS, P.O.Box 45, ul. Gagarina 100, Kislovodsk 357700, Russia Blagoveschensk State Pedagogical University, Lenin str., 104, Amur Region, Blagoveschensk 675000, Russia
Accepted 2017 XXX. Received 2017 Apr; in original form 2016 Feb
ABSTRACT
We report the discovery and multicolor (VRIW) photometry of a rare explosive star MASTER OTJ004207.99+405501.1 - a luminous red nova - in the Andromeda galaxy M31N2015-01a. We useour original light curve acquired with identical MASTER Global Robotic Net telescopes in onephotometric system: VRI during first 30 days and W (unfiltered) during 70 days. Also we addedpublishied multicolor photometry data to estimate the mass and energy of the ejected shell, anddiscuss the likely formation scenarios of outbursts of this type. We propose the interpretation of theexplosion, that is consistent with the evolutionary scenario where star merger is a natural stage of theevolution of close-mass stars and may serve as an extra channel for the formation of nova outbursts.
Key words: stars: novae, stars: individual: MASTEROTJ004207.99+405501.1, stars: individual:ultraluminous red nova
The optical transient MASTER OT J004207.99+405501.1 (Shumkov et al. 2015a) discovered by the MASTER global robotictelescope network (Lipunov et al. 2010) was found to belong to a rare type of luminous red novae (LRNe, Kurtenkov et al.2015a,b; Williams et al. 2015) whose history began with the discovery of the outburst of M31-RV by Rich et al. (1989).However, the canonical prototype of this class of events is now considered to be the outburst of the star V838 Monocerotis(Munari et al. 2002b), which reached an absolute magnitude of -10 at maximum light (Munari et al. 2002a). Luminous rednovae differ from common members of this class primarily by the apparent lack of any thermonuclear processes, their largeemitted energy, a characteristic plateau on the light curve (Ivanova et al. 2013), and very strong reddening that varies withtime. The plateau phase indicates that compared to common novae, LRNe have more massive and dense envelopes where astationary recombination front forms that has approximately constant luminosity like that which occur during the explosionsof type IIP supernovae (MacLeod et al. 2017). The observation of the progenitor of V1309 Sco by Tylenda et al. (2011), whofound it to be a contact binary with a period of 1.4 days, provided strong support for the merging mechanism of red novaoutbursts.All these results made the object extremely popular among observers operating on all sorts of instruments - from one-metertelescopes to the Spitzer infrared space telescope and SWIFT gamma-ray laboratory (Bersier et al. 2015; Dong et al. 2015;Fabrika et al. 2015; Harmanen et al. 2015; Hodgkin et al. 2015; Adams et al. 2015a,b; Kurtenkov et al. 2015a,b; Ovcharov et al.2015; Pessev et al. 2015a,b,c,d; Geier & Pessev 2015; Shumkov et al. 2015b; Srivastava et al. 2015; Steele et al. 2015; Rich et al. ⋆ E-mail: lipunov gmail.com c (cid:13) V. M. Lipunov et al.
Figure 1.
The discovery MASTER image of MASTER OT J004207.99+405501.1/ M31LRN . The third right one is the referenceMASTER-Kislovodsk image without transient / M31N2015-01A
MASTER OT J004207.99+405501.1 / M31N2015-01a was discovered by the MASTER auto-detection system (Lipunov et al.2010) during the survey performed by MASTER-Kislovodsk observatory on 2015-01-13.63235 UT (Shumkov et al. 2015a).A total of four images containing this optical transient were acquired with the unfiltered limiting magnitudes of m OT =19 . . . All MASTER telescopes have iden-tical optical schemes and are equipped with identical sets of polarization and BVRI filters (Kornilov et al. 2012; Pruzhinskaya et al.2014).The main advantages of MASTER instruments are the following: (1) wide 8 square degree (twin 2 . ◦ × . ◦ ) field ofview of the main MASTER-II optical channel (with a limiting unfiltered magnitude of up to 20-21 per 60-180s exposition)¡and an even bigger 800 square degree (twin 16 x ◦ ) field of view of Very Wide Field cameras, i.e. MASTER-VWFC (with alimiting magnitude of up to 11-12m and 13.5-15m for 1-s and coadded images, respectively); (2) twin tubes that can be pointedto different fields (allowing wide FERMI error-boxes to be observed almost in real-time) and used to observe the frame indifferent polarizations and in BVRI filters (Lipunov et al. 2010; Kornilov et al. 2012; Lipunov et al. 2007; Gorbovskoy et al.2013).The main goal of MASTER network is to detect prompt GRB emission by providing rapid response to GRB-alerts .MASTER has a very fast positioning system that makes it very suitable for follow-up programs such as prompt opticalobservations of GRB neutrinos and GW alerts etc. When not engaged in alert-triggered observations MASTER carries outsky survey programs including the Andromeda survey in order to discover optical transients of different nature (more than10 types) and to investigate all most important problems of the modern astrophysics.A unique key feature of MASTER is our software that provides full information about all optical sources detected onevery image one to two minutes after the CCD readout. This information includes the full classification of all sources foundin the image, the data from previous MASTER-Net archived images for every source, full information from VIZIER databaseand from all open sources (e.g., Minor planet mpchecker center), computed orbital elements for moving objects, etc. In searchtasks a real astrophysical source cannot occupy only 1, 2 or 4 pixels, because such objects can never be proved to be real http://observ.pereplet.ru MNRAS , 1–15 (2016)
ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 rather than artifacts. A real transient must occupy more than 10 pixels and exhibit a specific profile to be distinguished froma clump of several hot-pixels .MASTER own software discovers optical transients not just by analyzing the difference between the previous and currentimages, but also by fully identifying of every source at every image. This MASTER software allowed us to discover more then1200 (up to September 2016) optical transients in a fully automatic mode . We also faced a challenging task of discovering allsources seen against the Andromeda disc structure, especially during the rising stage. We solved this problem before January2015 and started our nova search survey in the Andromeda galaxy. At the end of 2014 the global MASTER network of twinrobotic telescopes (Lipunov et al. 2010) started automatic search for optical transients in the Andromeda galaxy.MASTER has been observing the Andromeda galaxy every night, weather permitting, resulting in thousands of framesavailable for accurate photometry. Monitoring has been carried out with MASTER network telescopes for 72 days after our discovery of this LRN. We acquireda total of about 400 white-light frames and 130 frames with V, R, and I-band filters with 180-s exposures (see Tables 1,2,3with VRIW-photometry). All observations passed in automatic mode. Thereby, some of the frames were acquired throughlight clouds.For calibration we used the dark frames, acquired on the evening before observations, and twilight flats. Calibration, frameclipping, and astrometric reduction was performed automatically on each observatory of the network. For our photometry weused the 15 ×
15 arcmin frame area centered on the object with about 60 comparison stars from magnitude 13 to 17 in theV band.We used IRAF/apphot package to perform photometry with an optimal aperture for each frame (Tody 1993). Theresulting instrumental magnitudes were corrected using the Astrokit tool to minimize the standard deviation for the ensembleof comparison stars (Burdanov et al. 2014).For transformation of the instrumental magnitudes to a standard system, we used 56 nearby stars from UCAC4 catalog(Zacharias et al. 2013). R and I magnitudes calculated from UCAC4 r- and i-bands by the following equation from Lupton(2005): I = r − . · ( r − i ) − . R = r − . · ( r − i ) − . W = 0 . · B + 0 . · R Then, we cleared our data from the points with big error and deviation. Visual inspection of appropriate frames showedthat they were obtained through the light clouds, and in two cases the problem was caused by cosmic ray particles. Finally,we binned data points of each night by calculation of mean. Error for binned point calculated as standard deviation.We converted our apparent magnitudes to absolute magnitudes with the adopted distance modulus of 24.43 (Feedman,Madore 1990).Complete binned by night light curve of this Nova obtained with MASTER Global Network (MASTER-Kislovodsk,MASTER-Tunka, and MASTER-Ural) is presented at Figure 2. The data are given in the Appendix (Tables 2,3,4,5).M31 has a distance modulus of ( m − M ) = 24 . ± .
06. Given the adopted foreground reddening of E ( B − V ) = 0 . E ( B − V ) = 0 .
18 (Montalto et al. 2009), weconservatively assume that M31LRN was subject to the reddening of E ( B − V ) = 0 . ± .
06, implying an absolute peakmagnitude of M V = − . ± . At present, there is no sure answer to the question: “What is the mechanism responsible for the energy release in LRNe?”. Itmay be:(i) stellar mergers (Soker & Tylenda 2003; Tylenda et al. 2011)(ii) an unusual SN mechanism (Lovegrove & Woosley 2013)(iii) a classical nova mechanism (Shara et al. 2010) http://observ.pereplet.ru/MASTER OT.html MNRAS , 1–15 (2016)
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Figure 2.
Complete light curve of the M31LRN Luminous Red Nova (MASTER OT J004207.99+405501.1) obtained with MASTER-Kislovodsk and MASTER-Tunka(the same instuments, i.e. the same photometry system). The adopted distance modulus is 24.43(Freedman & Madore 1990). The left-hand axis gives the apparent magnitude scale. The data are given in the Tables 2,3,4.
Table 1.
Parameters of the model runs
Name M total M heat R initial E exp t heat M ⊙ M ⊙ R ⊙ ergs s R10M3ht3t3E3 R10M3ht02t3E4 3 0.2 10 4 10 R1.6M2E008 2 2 1.6 8 10 R5 M3 E003 3 3 5 3 10 R20 M3 E003 3 3 20 3 10 R10 M2 E003 2 2 10 3 10 R10 M5 E003 5 3 10 3 10 R10 M3 E001 3 3 10 1 10 R10 M3 E008 3 3 10 8 10 (iv) giant planet capture (Retter & Marom 2003)(v) extreme AGB stars (Thompson et al. 2009).In our study of M31LRN hundreds of models have been tested for simulating nova explosions in a close binary systemwith a common envelope with various initial parameters (in spherically symmetric approximation). The parameters of themost suitable models used for the analysis of processes in the LRN, are shown in Table 1. For modelling M31LRN we haveadapted the code Stella (Blinnikov et al. 2006),which is widely used for computing supernova explosions (Woosley et al.2007; Baklanov et al. 2015; Tolstov et al. 2015).
Stella code is a set of programs for multi-group radiative hydrodynamicsthat can be used to compute the light curves of supernovae of various types in the spherically symmetric approximationwith the thermodynamics of stellar plasma treated in LTE approximation. The code can also be used to compute novaexplosions, although in this case certain adjustments are needed because of the lower velocity gradients in novae compared tosupernovae and because emission in lines has in some cases to be computed beyond the framework of Sobolev approximation.We constructed the initial models in the same way as described in (Baklanov et al. 2005).The nature of LRNs is different from that of collapsing supernovae in many aspects, that is why we do not aim to
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ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Figure 3.
Light curves of the broadband photometry for the model run
R10 M3Mht02t3 E004 with fast heating in central layers. Thesecondary maximum occurs when the ejecta become transparent and the central hot remnant of the merged binary is visible. The lowerpanel shows the velocity on the level of photosphere for this model. reproduce all the details of observed light curves for the whole period of observations using the
Stella code. This task wouldrequire developing of a new code and we leave this for future. More modest problem is being solved in the current investigation:we try to elucidate the physics of LRN emission on the plateau phase of the light curve, when it behaves in a similar way toSN IIP. It is the longest stage in the evolution of LRN with a characteristic behaviour of the light curves, determined by thepassage of cooling and recombination waves through the expanding envelope.The initial system we considered consists of two components: the inner core and and the outer shell. Details of the innercore are not taken into account in our simulations, and the core is treated as a hard sphere of a given mass. The outer shellprior to the explosion is built as a model of a polytropic star, similar to the one described in the article (Baklanov et al. 2005).It is assumed that active dynamic processes in the binary and the formation of the common envelope lead to a strong mixingof matter in the shell. Therefore, the chemical composition in our simulations is uniform with solar abundances at each point.In this paper we are not going into the details of the mechanism. We explored different ways of energy release: from thefast release of all energy through the explosion near the centre within the mass of 0 . − . M ⊙ to a long warm-up of the wholebody of the star.Version with the fast central heating with a time-scale of energy release t heat ∼ s is shown in Fig. 3, it demonstratescommon features of such a heating. The local release of energy in the central core of M = 0 . M ⊙ produces a shock wavereaching the outer edge of envelope in ∼ h . The shock wave propels all matter in the envelope with velocity higher thanthe parabolic one. This leads to the expansion of the envelope like in a supernova IIP. In comparison with our best-fit model(see below) a significant fraction of the energy goes into kinetic energy, which leads to a weaker heating of matter and a dimlight on the plateau stage. After t ∼ d the envelope becomes transparent and the heated core shines through it, giving thesecond maximum on the light curves. The second maximum is not observed for M31LRN, but occurs in similar objects, so itis visible from LRN V838 Mon (Tylenda 2005).It should be noted that the light curves are sensitive to changes in the initial masses and radii of envelopes (Litvinova & Nadezhin1985). See results for three models in FigsBy varying R , M and E one can achieve satisfactory matches of the model and observed light curves at the maximum MNRAS , 1–15 (2016)
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Figure 4.
Light curves of the broadband photometry for the model runs lrnm31 e00* in various bands for variable energy. light, see 7 For example, increasing the energy of the explosion to the E = 8 × erg leads to a higher speed of the envelopeexpansion. Light curves rise to the maximum faster, and the stage of CRW is shorter. It can be seen that the model does notsatisfactorily describe the observations since light curves do not match the observations after the maximum. In addition, thephysics of the light curve near the dome is not explained by a wave recombination (MacLeod et al. 2017). Best-fit model
The best fit to M31LRN observations is obtained with the model
R10M3ht3t3E3 , whose light curves are shown in Figure 8.The model has a total mass of M tot = 3 M ⊙ and the envelope radius R = 10 R ⊙ . The initial configuration was the same as theabove-mentioned “fast” model. The main difference between the two models is in the mode of energy release during initiationof LRN explosion.Thermal energy E = 3 × erg is released throughout the whole mass M tot during a longer time t heat ∼ s. MNRAS000
R10M3ht3t3E3 , whose light curves are shown in Figure 8.The model has a total mass of M tot = 3 M ⊙ and the envelope radius R = 10 R ⊙ . The initial configuration was the same as theabove-mentioned “fast” model. The main difference between the two models is in the mode of energy release during initiationof LRN explosion.Thermal energy E = 3 × erg is released throughout the whole mass M tot during a longer time t heat ∼ s. MNRAS000 , 1–15 (2016)
ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Figure 5.
Light curves of the broadband photometry for the model run lrnm31 m* in various bands for variable mass.
It is evident that at the stage of the plateau, this model is in much better with observations. The deviation in the bandI, is apparently due to the insufficiently precise description of opacity in the infrared region. When calculating the opacity inthe lines we use a list of 150 thousand atomic transitions. The main emphasis in the formation of lines in this list has beenmade on the ultraviolet and visible range of the spectrum (which is important for supernovae), while in the infrared regionthere is some shortage of lines which is planned to fill out in future calculations.
The dynamics of the expansion and the accompanying processes are illustrated in a series of snapshots shown in Figure 9. Bythe end of the first day of the shock has heated up the envelope and accelerated the matter at the level of the photosphereto the velocity v ∼
900 km/s. Later, the inner layers lose their momentum pushing the overlying layers, as well as due to the
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Figure 6.
Light curves of the broadband photometry for the model run lrnm31 r* in various bands for variable radius. attraction of the underlying matter. On day 10 the system has stabilized: about M ∼ M ⊙ halts and stays in a bound state,and about M ej ∼ M ⊙ is ejected and enteres the phase of free expansion.The behavior of the light curves can be monitored on the Rosseland opacity curve (Tau) in Figure 9. It is worth noting thatTau has been specially designed for those plots in order to allow the qualitative monitoring the location of the photosphere.Code Stella solves transport equations for the frequency grid from 1 ˚A up to 5 · ˚A, without imposing any restrictionson the shape of the distribution intensity and opacity in the cells of the frequency grid.One can clearly see that the investigated plateau stage, which is determined by the passage of a Cooling and RecombinationWave (Grassberg et al. 1971, CRW), begins already in the first days after the explosion. In the right column of Figure 9 theX-axis shows the Lagrangian coordinate M ( R ). It is evident that the CRW runs inside along the mass coordinate, reaching theinner stalled core at t ∼ d . According to the radial Eulerian coordinate (left column of Figure 9) the CRW is permanentlycarried on by the expanding matter. Therefore, the photospheric radius grows initially, providing a maximum of the lightcurve at ∼ d , and then decreases slowly, reproducing the slow decline in the observed M31LRN bands. MNRAS000
Light curves of the broadband photometry for the model run lrnm31 r* in various bands for variable radius. attraction of the underlying matter. On day 10 the system has stabilized: about M ∼ M ⊙ halts and stays in a bound state,and about M ej ∼ M ⊙ is ejected and enteres the phase of free expansion.The behavior of the light curves can be monitored on the Rosseland opacity curve (Tau) in Figure 9. It is worth noting thatTau has been specially designed for those plots in order to allow the qualitative monitoring the location of the photosphere.Code Stella solves transport equations for the frequency grid from 1 ˚A up to 5 · ˚A, without imposing any restrictionson the shape of the distribution intensity and opacity in the cells of the frequency grid.One can clearly see that the investigated plateau stage, which is determined by the passage of a Cooling and RecombinationWave (Grassberg et al. 1971, CRW), begins already in the first days after the explosion. In the right column of Figure 9 theX-axis shows the Lagrangian coordinate M ( R ). It is evident that the CRW runs inside along the mass coordinate, reaching theinner stalled core at t ∼ d . According to the radial Eulerian coordinate (left column of Figure 9) the CRW is permanentlycarried on by the expanding matter. Therefore, the photospheric radius grows initially, providing a maximum of the lightcurve at ∼ d , and then decreases slowly, reproducing the slow decline in the observed M31LRN bands. MNRAS000 , 1–15 (2016)
ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Figure 7.
Light curves of broadband photometry for the model run demonstrating the absence of degeneracy in R and M It is important for the model not only to be consistent with photometric data but also to have hydrodynamic prop-erties similar to those actually observed. Figure 8 shows the computed mass flow velocity at the photosphere level for thebest-fit model
R10M3ht3t3E3 . We have no detailed spectroscopic observations to superimpose onto our model computations.(Williams et al. 2015) report Hα data (FWHM = 900 ± km/s ), which provide an upper constraint for the photosphericvelocity because the strong Hα line forms above the photosphere, where the mass expansion velocity is higher than thephotospheric velocity. The photospheric velocity is better to estimate by weak lines. In this case the value inferred from theNaI D line (FWHM = 600 ± km/s ) agrees well with the model computations at the time of maximum light (fig. 8).Our computations show that the overall behavior of broad-band light curves (Fig. 8) can be reproduced fairly well bycodenamed model R10M3ht3t3E3 .We performed our computations for a spherically symmetric configuration consisting of an envelope and an inner corewhere the components of the system merge. In this formulation the component merger is treated as a source of thermalenergy without taking into account the actual physics of the process (Soker & Tylenda 2003). Without performing a fullmultidimensional computation we cannot claim that our inferred total mass of M tot = 3 M ⊙ characterizes the mass of thebinary before the merger. It is possible that in the case of a multidimensional computation the ejected mass and kinetic energyof the ejecta could be obtained with a less massive binary.Williams et al. report the absolute magnitude of M V = − . M ⊙ . However, this estimate is not very reliable because it is unlikely that bothmerging objects are main-sequence stars. They are more probably red giants whose masses cannot be determined solely fromtheir luminosity. One of the key evolutionary stages of binary stars is the specific state when the sizes of stars become comparable to that of theentire binary system (Snezhko 1968; Paczy´nski 1966; van den Heuvel 1970; Svechnikov & Snezhko 1974; Masevich & Tutukov1981)
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Figure 8.
Light curves of broadband photometry for the model run
R10M3ht3t3E3 . The lower panel shows the speed at photospherelevel in this model. This is the best model for the plateau stage.
It is a key stage because at that time violent mass exchange begins in the binary, resulting in dramatic and fast changeof its parameters due to the exchange (and even loss) of the angular momentum and mass contained in the stars before thecontact. The catastrophic change of binary parameters may result in complete merger of its component stars or in the abruptdecrease of the size of the binary semiaxis, and have a crucial effect on subsequent evolution stages that end with the formationof close binaries with degenerate components - neutron stars and white dwarfs. This is how white-dwarf close binaries formwhose mergers may produce type Ia supernovas and, in the case of systems consisting of two neutron stars, short gamma-raybursts. Hence mergers of two classical main-sequence stars or subgiants may contribute to the study and understanding ofsuch important astrophysical phenomena as dark energy and gamma-ray bursts.In the paradigm of synchronously rotating stars with a high mass ratio moving in circular orbits the filling of the Rochelobe is followed by violent mass transfer by the primary to the secondary and the formation of a common envelope. On theother hand, an equal-mass binary may evolve into a fully contact system of two stars both of which simultaneously fill their
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ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Figure 9.
LRN shell structure and its evolution as calculated in the model
R10M3ht3t3E3 at 1, 10, 20, 50, 90 days. The color codesthe graph of a physical quantity dependence on the radial variable: density – black [logarithmic scale, in units of g/cm ] bolometricluminosity – orange [in units of 10 erg/s], temperature – red [logarithmic scale, K], velocity of matter – blue [in units of 10 cm/s],Rosseland opacity – green [cm /g]. The difference between the left and right columns is the radial variable, plotted along the axis X. Inthe left column in the X-axis indicates a radius in units of R sun , and in the right hand column on the X axis using Lagrangean coordinate M – mass of the shell at a given radius.MNRAS , 1–15 (2016) V. M. Lipunov et al.
Roche lobes. In the limiting case violent mass transfer may occur on the hydrodynamic time scale with the amount of releasedenergy on the order of the thermal energy of the component stars ∼ GM /a ∼ · erg/s · m ( a/R ⊙ ), where M tot is thetotal mass of colliding stars, and a is the semimajor axis of the binary.From this point of view it is very important to obtain observational evidence for such processes in binary systems and todetermine the corresponding physical properties - the released energy, ejected mass, and angular momentum. Ultra-luminousred novae may be observational manifestations of violent mass transfer in the binary (Blagorodnova et al. 2017).We already pointed out that the observation of the progenitor of V1309 Sco in the form of a contact binary with aperiod of 1.7 days (Tylenda et al. 2011) provides a strong evidence for the merger model of LRNe. This conclusion is alsocorroborated by the approximate occurrence rate of such events – one event in 20-40 years per galaxy like Milky Way orM31. To show this, let us use the distribution of binary semimajor axes a (Masevich & Tutukov 1981). This distributionhas the form dN ∼ . d log( a/R ⊙ ). Systems with semi-axes 6 . a/R ⊙ .
12 merge during the Hubble time. However, novaluminosities depend essentially on the mass of the ejected envelope, and the occurrence rate of LRNe may be several timeslower, which is consistent with observations of the M31 galaxy, where the last such nova was observed in 1989.Or in another way, if all stars are close binaries then the maximum merger rate of systems with a total mass of 6 solarmasses is equal to the birth rate of 3 − M ⊙ stars, which in the case of the Salpeter mass function is equal to 1/10 year.Given that close binaries make up for about 20-30 percent of all stars, we obtain an estimate of 1 / − /
50 year. The lastred nova in the Andromeda galaxy exploded 20 years ago, which is consistent with theoretical expectations
In this paper we described the technique of the discovery of the nova M31LRN and long-term observations of its light curvewith MASTER network of robotic telescopes. It is important that the entire observational part of the study was performed onidentical telescopes equipped with identical photometers. The resulting light curve agrees fairly well with the independent lightcurve published by (Kurtenkov et al. 2015b). However, our interpretation led us to infer a relatively higher total progenitormass. The rather long plateau ( 50 days) requires a higher merged stellar mass ( 3 solar masses). The corresponding explosionenergy should be lower 2 . · erg , whereas the total kinetic energy of the ejected envelope is lower by three orders ofmagnitude. The proposed interpretation of the explosion is consistent with the proposed evolutionary scenario where starmerger is a natural stage of the evolution of close-mass stars and may serve as an extra channel for the formation of novaoutbursts. ACKNOWLEDGMENTS
MASTER Global Robotic Net is supported in part by the Development Programm of Lomonosov Moscow State University.This work was also supported in part by the RFBR grant 15-02-07875 (discovery and observations), by Russian ScienceFoundation grant 16-12-00085 (interpretation and data analysis) and grant 16-12-10519 (theoretical modelling of the Novadone by P.B). Grant no. IZ73Z0-152485 SCOPES Swiss National Science Foundation supports work of S.B.
References
Adams S., Kochanek C. S., Dong S., Wagner R. M., 2015a, The Astronomer’s Telegram, 7468Adams S., Kochanek C. S., Dong S., Wagner R. M., 2015b, The Astronomer’s Telegram, 7485Baklanov P. V., Blinnikov S. I., Pavlyuk N. N., 2005, Astronomy Letters, 31, 429Baklanov P. V., Sorokina E. I., Blinnikov S. I., 2015, Astronomy Letters, 41, 95Bersier D., Kochanek C. S., Wagner R. M., Adams S., Dong S., 2015, The Astronomer’s Telegram, 7537Blagorodnova N., et al., 2017, ApJ, 834, 107Blinnikov S. I., R¨opke F. K., Sorokina E. I., Gieseler M., Reinecke M., Travaglio C., Hillebrandt W., Stritzinger M., 2006, A&A, 453, 229Burdanov A. Y., Krushinsky V. V., Popov A. A., 2014, Astrophysical Bulletin, 69, 368Dong S., Kochanek C. S., Adams S., Prieto J.-L., 2015, The Astronomer’s Telegram, 7173Fabrika S., et al., 2015, The Astronomer’s Telegram, 6985Freedman W. L., Madore B. F., 1990, The Astrophysical Journal, 365, 186Geier S., Pessev P., 2015, The Astronomer’s Telegram, 8220Gorbovskoy E. S., et al., 2013, Astronomy Reports, 57, 233Grassberg E. K., Imshennik V. S., Nadyozhin D. K., 1971, Astrophysics and Space Science, 10, 28Harmanen J., McCollum B., Laine S., Rottler L., Bruhweiler F. C., 2015, The Astronomer’s Telegram, 7595Hodgkin S. T., et al., 2015, The Astronomer’s Telegram, 6952Ivanova N., Justham S., Nandez J. A., Lombardi J. C., 2013, Science, 339, 433Kornilov V. G., et al., 2012, Experimental Astronomy, 33, 173Kurtenkov A., Ovcharov E., Nedialkov P., Kostov A., Bachev R., Dimitrova R. V. M., Popov V., Valcheva A., 2015a, The Astronomer’sTelegram, 6941 MNRAS000
Adams S., Kochanek C. S., Dong S., Wagner R. M., 2015a, The Astronomer’s Telegram, 7468Adams S., Kochanek C. S., Dong S., Wagner R. M., 2015b, The Astronomer’s Telegram, 7485Baklanov P. V., Blinnikov S. I., Pavlyuk N. N., 2005, Astronomy Letters, 31, 429Baklanov P. V., Sorokina E. I., Blinnikov S. I., 2015, Astronomy Letters, 41, 95Bersier D., Kochanek C. S., Wagner R. M., Adams S., Dong S., 2015, The Astronomer’s Telegram, 7537Blagorodnova N., et al., 2017, ApJ, 834, 107Blinnikov S. I., R¨opke F. K., Sorokina E. I., Gieseler M., Reinecke M., Travaglio C., Hillebrandt W., Stritzinger M., 2006, A&A, 453, 229Burdanov A. Y., Krushinsky V. V., Popov A. A., 2014, Astrophysical Bulletin, 69, 368Dong S., Kochanek C. S., Adams S., Prieto J.-L., 2015, The Astronomer’s Telegram, 7173Fabrika S., et al., 2015, The Astronomer’s Telegram, 6985Freedman W. L., Madore B. F., 1990, The Astrophysical Journal, 365, 186Geier S., Pessev P., 2015, The Astronomer’s Telegram, 8220Gorbovskoy E. S., et al., 2013, Astronomy Reports, 57, 233Grassberg E. K., Imshennik V. S., Nadyozhin D. K., 1971, Astrophysics and Space Science, 10, 28Harmanen J., McCollum B., Laine S., Rottler L., Bruhweiler F. C., 2015, The Astronomer’s Telegram, 7595Hodgkin S. T., et al., 2015, The Astronomer’s Telegram, 6952Ivanova N., Justham S., Nandez J. A., Lombardi J. C., 2013, Science, 339, 433Kornilov V. G., et al., 2012, Experimental Astronomy, 33, 173Kurtenkov A., Ovcharov E., Nedialkov P., Kostov A., Bachev R., Dimitrova R. V. M., Popov V., Valcheva A., 2015a, The Astronomer’sTelegram, 6941 MNRAS000 , 1–15 (2016)
ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Table 2.
The R-band MASTER photometry of M31 2015 from MASTER-Kislovodsk and MASTER-Tunka observatoriesThe Data, MJD R, mag R error , 1–15 (2016) V. M. Lipunov et al.
Table 3.
The V-band MASTER photometry of M31 2015 from MASTER-Kislovodsk and MASTER-Tunka observatoriesThe Data, MJD R, mag R error http://classic.sdss.org/dr4/algorithms/sdssUBVRITransform.html MacLeod M., Macias P., Ramirez-Ruiz E., Grindlay J., Batta A., Montes G., 2017, ApJ, 835, 282Masevich A. G., Tutukov A. V., 1981, Fizika i ehvolyutsiya zvezd (Physics and evolution of stars). VINITI, Moskva, USSRMasevich A. G., Tutukov A. V., 1988, Ehvolyutsiya zvezd: teoriya i nablyudeniya (Evolution of stars: theory and observations).. Glavnayaredaktsiya fiziko-matematicheskoj literatury, Nauka, Moskva, USSRMassey P., Olsen K. A. G., Hodge P. W., Strong S. B., Jacoby G. H., Schlingman W., Smith R. C., 2006, AJ, 131, 2478Montalto M., Seitz S., Riffeser A., Hopp U., Lee C.-H., Sch¨onrich R., 2009, Astronomy & Astrophysics, 507, 283Munari U., et al., 2002a, A&A, 389, L51Munari U., Desidera S., Henden A., 2002b, IAU Circ., 8005Ovcharov E., Kurtenkov A., Valcheva A., Nedialkov P., 2015, The Astronomer’s Telegram, 6924Paczy´nski B., 1966, Acta Astron., 16, 231Pessev P., Geier S., Kurtenkov A., Nielsen L. D., Tomov T., 2015a, The Astronomer’s Telegram, 7272Pessev P., Geier S., Kurtenkov A., Nielsen L. D., Slumstrup D., Tomov T., 2015b, The Astronomer’s Telegram, 7572Pessev P., Geier S., Stritzinger M., Kurtenkov A., Tomov T., 2015c, The Astronomer’s Telegram, 7624Pessev P., Geier S., Stritzinger M., Kurtenkov A., Tomov T., 2015d, The Astronomer’s Telegram, 8059Pruzhinskaya M. V., et al., 2014, New Astron., 29, 65Retter A., Marom A., 2003, Monthly Notices of the Royal Astronomical Society, 345, L25Rich R. M., Mould J., Picard A., Frogel J. A., Davies R., 1989, ApJ, 341, L51Schlegel D. J., Finkbeiner D. P., Davis M., 1998, The Astrophysical Journal, 500, 525Shara M. M., Yaron O., Prialnik D., Kovetz A., Zurek D., 2010, The Astrophysical Journal, 725, 831Shumkov V., et al., 2015a, The Astronomer’s Telegram, 6911Shumkov V., et al., 2015b, The Astronomer’s Telegram, 6951Snezhko L. I., 1968, Soviet Ast., 12, 199Soker N., Tylenda R., 2003, The Astrophysical Journal, 582, L105Srivastava M., Ashok N. M., Banerjee D. P. K., Venkataraman V., 2015, The Astronomer’s Telegram, 7236Steele I. A., Williams S. C., Darnley M. J., Bode M. F., Barnsley R. M., Smith R. J., Jermak H. E., 2015, The Astronomer’s Telegram,7555Svechnikov M. A., Snezhko L. I., 1974, in Boyarchuk A. A., Efremov Y. N., eds, Non-stationary Stars and Methods of their Investigation.Phenomena of Non-stationarity and Stellar Evolution. pp 181–230Thompson T. A., Prieto J. L., Stanek K. Z., Kistler M. D., Beacom J. F., Kochanek C. S., 2009, The Astrophysical Journal, 705, 1364Tody D., 1993, in Hanisch R. J., Brissenden R. J. V., Barnes J., eds, Astronomical Society of the Pacific Conference Series Vol. 52,Astronomical Data Analysis Software and Systems II. p. 173 MNRAS , 1–15 (2016)
ASTER OT J004207.99+405501.1/M31LRN 2015 Luminous Red Nova in M31 Table 4.
The I-band MASTER photometry of M31 2015 from MASTER-Kislovodsk and MASTER-Tunka observatoriesThe Data, MJD R, mag R error A TEX file prepared by the author.MNRAS , 1–15 (2016) V. M. Lipunov et al.
Table 5.
MASTER unfiltered (W) photometry of M31 2015 from MASTER-Kislovodsk and MASTER-Tunka observatoriesThe Data, MJD W, mag W error000