[vsnet-chat 72] Coordinates for LMC X-Ray sources.

[Mati Morel <morel@ozemail.com.au>]

>Date: Fri, 14 Feb 1997 17:15:01
>To: vsnet-chat@kusastro-kyoto-u.ac.jp
>From: Mati Morel <morel@ozemail.com.au>
>Subject: Coordinates for LMC X-Ray sources.
>
>Dear Readers,
>In 1996 I received from Dr. Paul Schmidtke, Arizona State University,
>a number of reprints reporting the results of his work on LMC/SMC
>X-ray sources, especially Supersoft Sources (SSS). Study of these 
>sources is a highly specialized area, involving firstly use of data
>form X-ray detecting satellites such as ROSAT. The identification of
>optical counterparts is a somewhat painstaking process, using large
>telescopes, as the optical ids., are generally faint, at the mag.
>19-20 level.  However, a couple of the LMC SSS's have been studied 
>in some detail at optical wavelengths, such as CAL 87, which is an
>eclipsing binary. It shows short duration, shallow X-Ray eclipses
>which coincide in phase with the primary optical minimum. A paper
>appears in Pub. Ast. Soc. of the Pacific, 105, 863-866, 1993 August.
>A finder chart is given, but no coordinates. The position is
>(1950) 5h47m27.0s  -71 10'11". This star is included in the list of
>known LMC variables in vol. 5 of the GCVS, as star V4382 (page 69).
>
>Not all X-ray sources in the direction of the Magellanic clouds are
>Cloud members. Some are local foreground stars, while some are even
>background objects (AGNs - Active Galaxy Nuclei).
>
>Another reprint summarizes LMC SSS's as follows:
><Three of the supersoft X-ray sources in LMC have been identified
>with disk-dominated, close binaries whose absolute magnitudes range
>between Mv ~ -1.6 and +0.5. We note that the orbital periods for  
>these systems are longer than the ones for typical low-mass X-ray
>binaries. Two of the systems (CAL 83 and RXJ0513.9-6951) show evidence
>of high-velocity outflows or possibly collimated, precessing jets.
>Optical counterparts for three systems have not been found, but they
>must be considerably fainter than those already identified.
>.....(one sentence omitted)..... The nature of the component stars in
>the supersoft sources is not yet resolved, but models include white
>dwarfs, neutron stars, or black holes as the collapsed star. It seems 
>likely that the SSS include several types of systems, and more than
>one model may be needed to understand them.>
>Source: reprint of paper "Supersoft X-ray Sources in the LMC", pp439-444 in
>'Compact Stars in Binaries' (1996, J. van Paradijs et al eds.).
>
>A very useful paper providing positions and finder charts for Magellanic
>Cloud X-ray sources appears in Publ. A.S.P. for January 1997.
>
>Cheers,
>Mati Morel
>
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>Stellar Data & Information Centre
>c/o M. Morel
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>Tel. /fax : 61 49 662078  E-mail: morel @ozemail.com.au
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>

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