We present observations of M31LRN 2015 (MASTER OT J004207.99+405501.1), discovered in M31 in 2015 January, and identified as a rare and enigmatic luminous red nova (LRN). Spectroscopic and photometric observations obtained by the Liverpool Telescope showed the LRN becoming extremely red as it faded from its M(V) = -9.4 +/- 0.2 peak. Early spectra showed strong Halpha emission that weakened over time as a number of absorption features appeared, including Na I D and Ba II. At later times strong TiO absorption bands were also seen. A search of archival Hubble Space Telescope data revealed a luminous red source to be the likely progenitor system, with pre-outburst Halpha emission also detected in ground-based data. The outburst of M31LRN 2015 shows many similarities, both spectroscopically and photometrically, with that of V838 Mon, the best studied LRN. We finally discuss the possible progenitor scenarios.
@article{arxiv.1504.07747,
title = {A Luminous Red Nova in M31 and its Progenitor System},
author = {S. C. Williams and M. J. Darnley and M. F. Bode and I. A. Steele},
journal= {arXiv preprint arXiv:1504.07747},
year = {2015}
}
Comments
5 pages, 3 figures, 1 table, accepted for publication in the Astrophysical Journal Letters. Some minor changes, clarification, and additional references following feedback and the typesetting stage of publication