A model for the quiescent phase of the recurrent nova U Scorpii

Izumi Hachisu, Mariko Kato, Taichi Kato, Katsura Matsumoto, Ken'ichi Nomoto

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Abstract

A theoretical light curve is constructed for the quiescent phase of the recurrent nova U Scorpii in order to resolve the existing distance discrepancy between the outbursts (d ∼ 6 kpc) and the quiescences (d ∼ 14 kpc). Our U Sco model consists of a very massive white dwarf (WD), an accretion disk (ACDK) with a flaring-up rim, and a lobe-filling, slightly evolved, main-sequence star (MS). The model properly includes an accretion luminosity of the WD, a viscous luminosity of the ACDK, and a reflection effect of the MS and the ACDK irradiated by the WD photosphere. The B light curve is well reproduced by a model of 1.37 M WD + 1.5 M MS (0.8-2.0 M MS is acceptable) with an ACDK having a flaring-up rim and the inclination angle of the orbit i ∼ 80°. The calculated color is rather blue (B-V ∼ 0.0) for a suggested mass accretion rate of 2.5 × 10-7 M yr-1, thus indicating a large color excess of E(B-V) ∼ 0.56 with the observational color of B-V = 0.56 in quiescence. Such a large color excess corresponds to an absorption of Av ∼ 1.8 and AB11 ∼ 2.3, which reduces the distance to 6-8 kpc. This is in good agreement with the distance estimation of 4-6 kpc for the latest outburst. Such a large intrinsic absorption is very consistent with the recently detected period change of U Sco, which is indicating a mass outflow of ∼3 × 10-7 M yr-1 through the outer Lagrangian points in quiescence.

Original languageEnglish
Pages (from-to)L189-L192
JournalAstrophysical Journal
Volume534
Issue number2 PART 2
Publication statusPublished - 2000 May 10

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Keywords

  • Accretion, accretion disks
  • Binaries: close
  • Novae, cataclysmic variables
  • Stars: individual (U scorpii)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Hachisu, I., Kato, M., Kato, T., Matsumoto, K., & Nomoto, K. (2000). A model for the quiescent phase of the recurrent nova U Scorpii. Astrophysical Journal, 534(2 PART 2), L189-L192.