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Optical and infrared observations of SGR 1806-20

Kulkarni, S. R. and Matthews, K. and Neugebauer, G. and Reid, I. N. and van Kerkwijk, M. H. and Vasisht, G. (1995) Optical and infrared observations of SGR 1806-20. Astrophysical Journal, 440 (2). L61-L64. ISSN 0004-637X. doi:10.1086/187761.

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The soft gamma-ray repeater (SGR) 1806-20 is associated with the center-brightened nonthermal nebula Gl0.0-0.3, thought to be a plerion. As in other plerions, a steady X-ray source, AX 1805.7-2025, has been detected coincident with the peak of the nebular radio emission. Vasisht et al. have shown that the radio peak has a core-jet appearance and argue that the core marks the true position of the SGR. At optical wavelengths, we detect three objects in the vicinity of the radio core. Only for the star closest to the core, barely visible in the optical but bright in the infrared (K = 8.4 mag), the reddening is consistent with the high extinction (A_v≃30 mag) that has been inferred for AX 1805.7-2025. From the absence of CO band absorption, we infer that the spectral type of this star is earlier than late-G/early-K. The large extinction probably arises in a molecular cloud located at a distance of 6 kpc, which means that the star, just like AX 1805. 7 - 2025, is in or behind this cloud. This implies that the star is a supergiant. Since supergiants are rare, a chance coincidence with the compact radio core is very unlikely. To our knowledge, there are only three other examples of luminous stars embedded in nonthermal radio nebulae: SS 433, Cir X-1, and G70.7+1.2. Given this and the low coincidence probability, we suggest that the bright star is physically associated with SGR 1806- 20, making it the first stellar identification of a high-energy transient.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Kulkarni, S. R.0000-0001-5390-8563
Vasisht, G.0000-0002-1871-6264
Additional Information:© 1995 American Astronomical Society. Received 1994 October 7; accepted 1994 December 7. We thank D. Frail for advance information of the radio data and T. Nakajima for help with evaluating the chance coincidence probabilities. We gratefully acknowledge discussions with D. Frail and T. Murakami, and the referee, B. Margon, for suggestions which resulted in a better flow of logic. Some of the optical observations were made at the Palomar 60 inch telescope which is jointly owned by the California Institute of Technology and the Carnegie Institute of Washington. S. R. K.'s research is supported by the US NSF, NASA, and the Packard Foundation. M. H. v. K. is supported by a NASA Hubble Fellowship. Infrared astrophysics at Caltech is supported by grant from the NSF.
Group:Infrared Processing and Analysis Center (IPAC), Division of Geological and Planetary Sciences
Funding AgencyGrant Number
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:gamma rays: bursts - stars: individual (SGR 1806-20) - stars: neutron - X-rays: stars
Issue or Number:2
Record Number:CaltechAUTHORS:20170214-142325352
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Official Citation:Optical and infrared observations of SGR 1806-20 Kulkarni, S. R.; Matthews, K.; Neugebauer, G.; Reid, I. N.; van Kerkwijk, M. H.; Vasisht, G. Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 440, no. 2, p. L61-L64
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74302
Deposited By: Ruth Sustaita
Deposited On:15 Feb 2017 05:12
Last Modified:11 Nov 2021 05:26

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