Re: GSC 00279 00321

[jg <jg@jgws.freeisp.co.uk>]

Michael Koppelman wrote:


> I no longer think this star is the X-ray source 1RXS J115752.7+062658. It is
> off by 22 arcseconds in the Aladin viewer. That seems too far away but I
> don't know for sure.


The catalogue estimated positional error for this xray source is 26
arcseconds, inclusive of 6 arcsecs "systematic error", latter
instrumentation related no doubt.

The profile of the detection is broad and the xrays are quite "soft"
(soft is actually a technical term to do with intensity, I think, hard
xrays are more usually from more energetic sources than soft ones.  Soft
ones are more likely to be from a relatively simple thermal origin,
whilst hard ones may be from something more interesting like cyclotron
type mechanisms, or material crashing on to dense objects in strong
gravitational fields).

An informal, and rather loose, check of ROSAT faint sources against
variables I did a while ago, and a more in depth cross ID look-see
Taichi Kato did about the same time (ie when the RASS FSC cat came out,
and posted to vsnet-id-rosat probably) tended to turn up variables like
semiregulars, eclipsers, RS CVn stars and the like as faint xray
sources.  Nothing conclusive, it's just that those are just the sort of
objects that cropped up. It seems fairly reasonable for stars with some
chromospheric and/or coronal activity to be faint xray sources.
Professionals can comment if thinking too loose here.

This Galactic longitude is not too overly populated with stars, so it
could be said that the association of this xray source with this star is
possible, but not positively confirmed.  There don't appear to be any
galaxies, quasars, pulsars or other esoteric objects in the background
at this location.


This would be harder if it was a Milky Way field where the sheer density
of stars, variables, xrays sources and what have you leads to quite a
high frequency of happenstance association in the field of view.


Cheers

John G