Common Envelope Ejection for a Luminous Red Nova in M101

N. Blagorodnova, R. Kotak, J. Polshaw, Mansi M. Kasliwal, Y Cao, Ann Marie Cody, G. B. Doran, N. Elias-Rosa, M. Fraser, C. Fremling, C. Gonzalez-Fernandez, J. Harmanen, J. Jencson, E. Kankare, R.P. Kudritzki, Shrinivas R. Kulkarni, E. A. Magnier, I. Manulis, F. J. Masci, S. MattilaP. Nugent, Paolo Ochner, A. Pastorello, T. Reynolds, K. Smith, J. Sollerman, F. Taddia, G. Terreran, Lina Tomasella, M. Turatto, P.M. Vreeswijk, P. Wozniak, S. Zaggia

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Abstract

We present the results of optical, near-infrared, and mid-infrared observations of M101 OT2015-1 (PSN J14021678+5426205), a luminous red transient in the Pinwheel galaxy (M101), spanning a total of 16 years. The light curve showed two distinct peaks with absolute magnitudes {M}r≤slant -12.4 and {M}r≃ -12, on 2014 November 11 and 2015 February 17, respectively. The spectral energy distributions during the second maximum show a cool outburst temperature of ≈ 3700 K and low expansion velocities (≈ -300 km s-1) for the H i, Ca ii, Ba ii, and K i lines. From archival data spanning 15-8 years before the outburst, we find a single source consistent with the optically discovered transient, which we attribute to being the progenitor; it has properties consistent with being an F-type yellow supergiant with L ˜ 8.7 × {10}4 L⊙, {T}{eff}≈ 7000 K, and an estimated mass of {{M}}1=18+/- 1 M⊙. This star has likely just finished the H-burning phase in the core, started expanding, and is now crossing the Hertzsprung gap. Based on the combination of observed properties, we argue that the progenitor is a binary system, with the more evolved system overfilling the Roche lobe. Comparison with binary evolution models suggests that the outburst was an extremely rare phenomenon, likely associated with the ejection of the common envelope of a massive star. The initial mass of the primary fills the gap between the merger candidates V838 Mon (5-10 M⊙) and NGC 4490-OT (30 M⊙).
Original languageEnglish
Article number107
Number of pages15
JournalThe Astrophysical Journal
Volume834
Issue number2
DOIs
Publication statusPublished - 06 Jan 2017

Keywords

  • binaries: close
  • novae
  • cataclysmic variables
  • stars: individual: M101 OT2015-1
  • PSN J14021678+5426205
  • stars: massive
  • stars: winds
  • outflows

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