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Discovery of a red supergiant donor star in SN2010da/NGC 300 ULX-1

Heida, M. and Lau, R. M. and Davies, B. and Brightman, M. and Fürst, F. and Grefenstette, B. W. and Kennea, J. A. and Tramper, F. and Walton, D. J. and Harrison, F. A. (2019) Discovery of a red supergiant donor star in SN2010da/NGC 300 ULX-1. Astrophysical Journal Letters, 883 (2). Art. No. L34. ISSN 2041-8213. doi:10.3847/2041-8213/ab4139.

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SN2010da/NGC 300 ULX-1 was first detected as a supernova impostor in 2010 May and was recently discovered to be a pulsating ultraluminous X-ray source. In this Letter, we present Very Large Telescope/X-shooter spectra of this source obtained in 2018 October, covering the wavelength range 350–2300 nm. The J- and H-bands clearly show the presence of a red supergiant (RSG) donor star that is best matched by a MARCS stellar atmosphere with T_(eff) = 3650–3900 K and log(L_(bol)/L⊙) = 4.25 ± 0.10, which yields a stellar radius R = 310 ± 70R ⊙. To fit the full spectrum, two additional components are required: a blue excess that can be fitted either by a hot blackbody (T ≳ 20,000 K) or a power law (spectral index α ≈ 4) and is likely due to X-ray emission reprocessed in the outer accretion disk or the donor star; and a red excess that is well fitted by a blackbody with a temperature of ~1100 K, and is likely due to warm dust in the vicinity of SN2010da. The presence of an RSG in this system implies an orbital period of at least 0.8–2.1 yr, assuming Roche-lobe overflow. Given the large donor-to-compact object mass ratio, orbital modulations of the radial velocity of the RSG are likely undetectable. However, the radial velocity amplitude of the neutron star is large enough (up to 40–60 km s^(−1)) to potentially be measured in the future, unless the system is viewed at a very unfavorable inclination.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Heida, M.0000-0002-1082-7496
Brightman, M.0000-0002-8147-2602
Fürst, F.0000-0003-0388-0560
Grefenstette, B. W.0000-0002-1984-2932
Kennea, J. A.0000-0002-6745-4790
Walton, D. J.0000-0001-5819-3552
Harrison, F. A.0000-0003-2992-8024
Additional Information:© 2019 The American Astronomical Society. Received 2019 August 1; revised 2019 August 27; accepted 2019 September 4; published 2019 September 25. M.H. would like to thank M. Bachetti, E. Levesque, G. Vasilopoulos, I. el Mellah, S. Guillot, and E. Quatart for useful discussions. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) 102.D-0535(A). Facility: VLT(X-shooter). - Software: Astropy (Astropy Collaboration et al. 2013), Reflex (Freudling et al. 2013), Molecfit (Kausch et al. 2015; Smette et al. 2015), TURBOSPECTRUM (Plez 2012).
Group:Space Radiation Laboratory, Astronomy Department
Subject Keywords:High-mass X-ray binary stars, Late-type supergiant stars; Neutron stars
Issue or Number:2
Classification Code:High mass X-ray binary stars (733); Late-type supergiant stars (910); Neutron stars (1108)
Record Number:CaltechAUTHORS:20190917-093523828
Persistent URL:
Official Citation:M. Heida et al 2019 ApJL 883 L34
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98670
Deposited By: Tony Diaz
Deposited On:17 Sep 2019 17:57
Last Modified:16 Nov 2021 17:40

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