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Title: An accreting white dwarf near the Chandrasekhar limit in the Andromeda galaxy

The intermediate Palomar Transient Factory (iPTF) detection of the most recent outburst of the recurrent nova (RN) system RX J0045.4+4154 in the Andromeda galaxy has enabled the unprecedented study of a massive (M > 1.3 M {sub ☉}) accreting white dwarf (WD). We detected this nova as part of the near-daily iPTF monitoring of M31 to a depth of R ≈ 21 mag and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of M{sub R} = –6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast nova. It shows optical emission lines of He/N and expansion velocities of 1900-2600 km s{sup –1} 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with kT {sub eff} ≈ 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is an RN with a time between outbursts of approximately 1 yr, the shortest known. Recurrent X-ray emission from this binary was detected by ROSAT in 1992 and 1993,more » and the source was well characterized as a M > 1.3 M {sub ☉} WD SSS. Based on the observed recurrence time between different outbursts, the duration and effective temperature of the SS phase, MESA models of accreting WDs allow us to constrain the accretion rate to M-dot >1.7×10{sup −7} M{sub ⊙} yr{sup −1} and WD mass >1.30 M {sub ☉}. If the WD keeps 30% of the accreted material, it will take less than a Myr to reach core densities high enough for carbon ignition (if made of C/O) or electron capture (if made of O/Ne) to end the binary evolution.« less
Authors:
;  [1] ;  [2] ; ;  [3] ; ; ; ;  [4] ;  [5] ;  [6] ;  [7] ; ;  [8] ;  [9] ;  [10]
  1. Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)
  2. Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
  3. Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)
  4. Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)
  5. Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States)
  6. Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel)
  7. The Observatories, Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
  8. Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States)
  9. Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
  10. Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22356994
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 786; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; APPROXIMATIONS; CARBON; DECAY; DENSITY; DETECTION; ELECTRON CAPTURE; EMISSION; EVOLUTION; EXPANSION; GALAXIES; MASS; NOVAE; PHOTOMETRY; SOFT X RADIATION; SPECTROSCOPY; SUPERNOVAE; VELOCITY; WHITE DWARF STARS