Optical Study of Type I Supernovae Progenitor Candidate Recurrent Nova RS Ophiuchi.

1. Optical Study of Type I Supernovae ProgenitorCandidate Recurrent Nova RS Ophiuchi. by Irina Voloshina Sternberg Astronomical Institute, Moscow State university, Moscow, Russia Abstract. Recurrent nova RS Oph is the long period (~ 455 days) binary system consisting of a hot white dwarf with mass close to Chandrasekhar limit and a giant secondary. Here we present the results of analysis of photometric observations of this recurrent nova which were performed during last years after 2006 outburst. The photometry was carried out on three small telescopes (38-cm, 50-cm and 60-cm) coupled with CCD cameras at Crimean Station of Sternberg Astronomical Institute. We discuss the long-term light curve behavior of RS Oph and results of a search for periodicities in the optical light curves of this recurrent nova. • Recurrent nova RS Oph is a wide binary system (a = 316.5 Ro) • optical star (a red giant M2III) + white dwarf • Mass of white dwarf is very close to the Chandresekhar limit: 1.3 Mo • Porb=455d.73, i ~33o, • the accretion mass rate is ~1x10-7 Mo/year, d ~ 1.7 kpc • was discovered in 1898, fast nova • nova-likes outbursts were detected in 1933, 1958, 1967, 1985 and 2006 • The outburst of RS Oph in 1958 was most extensively observed in the past, the outburst in 1985 is characterized by the width of spectral range of simultaneous observations, - beside ground optical observations it was observed from space. • during outbursts the brightness of RS Oph changes from 12m.5 to 4m.5 • photometric behavior of this object during the different periods of his history was investigated by different authors. The most well-known detailed studies were done by Walker (1957) Walker (1977) and Bruch (1980, 1986, 1992). • The rapid light variations with amplitude about 0m.3 were found in this nova. Dorzycka et al. (1996). RS Oph has been detected also at radio waves and X-rays. Recurrent Nova represent the small group of cataclysmic variables(10 members and 1 suspected). Properties: more than one outburst, recurrence period ~ decades, outburst luminosity Mv≤ -5.5 accretion rate ~ 10-8 – 10 -7 M yr -1 They subdivide in two groups (paper ofAnupama): - long period binaries (simular to symbiotic stars) hot white dwarf (primary) + giant (secondary) Members: T СrB,RSOph, V3800 Sgr and V745 Sco - short period binaries (simular to classical novae) or U Sco class white dwarf (primary) + evolved main sequence star (secondary) Members: U Sco, V394 CrA, LMC 1990 n.2, T Pyx, CI Aql, IM Nor V1017 Sge suspected to be recurrent nova . Vicinity of RS Oph on one of one of the frames obtained in April 2007 in R band. Examples of RS Oph observations obtained with different telescopes : in 2007 (left) in 2008 (right) CCD observations of RS Oph were made with the aim to study short time variability on the scale of minutes to hours with differenttelescopes and CCD devices in Crimea: 38-cm telescope of Crimean Astrophysical Observatory, SBIG ST7 CCD detector (765 x 510 pixels), R band the field of view - 4 x 6 arcmin, 2x2 binning mode, duration of observational sets about 4-5 h. 70-cm telescope of Crimean Astrophysical Observatory, SBIG ST7 CCD detector (382 x 255 pixels), duration of observations sets about 1.5-2.0 h 50-cm telescope of Sternberg Astronomical Institute (SAI), Pictor 416 CCD detector, the field of view8.5 x12 arcmin,V band, duration of observational sets 3.5 h 60-cm telescope of Sternberg Astronomical Institute, Ap 47 CCD detector ( 1024 x 1024 pixels), R ban The field of view - 6 x 6 arcmin, 2x2 binning mode, duration of observational set 4 -5 h Fig.1a Power spectrum of brightness variations by data for April 2008 Fig.2c Fig.1a. R light curve of RS Oph obtained with the 38-cm telescope Fig.1c. R light curves of RS Oph obtained with the 60 cm telescope on April 9, 2008 Fig.1b. R light curve of RS Oph obtained withthe 70-cm telescope Fig.1d. R light curve obtained with the 60-cm telescope on April 13, 2008. Fig.3a. Fig 5 The mean light curves of RS Oph folded with folded with periods obtained in 2008 Fig.2 Observational light curves of RS Oph obtained on the same night with two telescopes: small and large. This figure demonstrates the good agreement of RS Oph data received with different telescopes Fig.1f. Observational V light curve obtained with the 50-cm telescope on April 25, 2008 Fig.3 Power spectra of brightness variations of RS Oph obtained by observations in R band in April 2007. Fig 5 The mean light curves of RS Ophfolded with periods obtained in 2007 Fig. 3 Daily light curves of RS Oph obtained in 2009. References 1. Anupama, G.C. , 2008, ASP Conf. Ser., submitted 2.Dobrzycka, D., Kenyon, S.J. 1996, AJ, 108, 2259 3. Bruch, A., 1980, IBVS, 1805 4. Bruch, A. 1986. Astron.Astrophys., 167, 91 5. Bruch, A., 1992, Astron. Astrophys., 266, 237 6. Walker, M.F. 1957, in IAU Sym. № 3, “Non-StableStars”, ed. G.Herbig, CambridgeUniversity Press, p.46 7. Walker, A.R. 1977, MNRAS, 179, 587 Acknowledgments The author thanks Org. Committee for partial financial support and Dr. Sementsov for kind help with presentation. This work was supported by RFBR grant 02-09-0225. Results Analyzing all observational data of RS OPh obtained in 2007-2008- 2009 we come to conclusion that the following types of variability are existed in the daily light curves of RS Oph. They are: • Flickering,- aperiodic brightness variations with an amplitude up to 0m.15−0m.20 on the time scale minutes,- flares and dips. • Rapid semi-coherent variations with period ~31-32 min (~ 0d.021 – 0d.022) and significant amplitudes which presented in all observational nights in 2007 • Rapid semi-coherent variations with periods 49.5 min (with semi-amplitude 0.090), 34.5 min (with semi-amplitude 0.057) and 26.8 min (with semi-amplitude 0.042) and significant amplitudes which presented in observational light curves of RS Oph in April 2008. •We suggest to interpret these variations as quasi-periodic oscillations. • The unusual features (like minimums) with dept up to 0m.30 are seen in the daily light curve of RS Oph obtained on April 25, 2008. They are quite different from the other light curves obtained early on April 9 and 13, 2008 (see fig.1c, d, and f) XXVI-th IAP Annual Coloquium “Progenitors and environments of stellar explosions“ June 28 to July 2, 2010, Paris, France

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