[vsnet-chat 81] Draco C-1 and the SSXS

[munari@astras.pd.astro.it (FAX +39 424 600023, TEL. 600033)]

A few additional words about Draco C-1 for those interested to have a look
at it:

        RA (2000.) =  17 19 57.5 
        DEC        = +57 50 05

An I-band excellent finding chart is published by Aaronson et al. (1982)
ApJ 254, 507. Inside 4 arcmin from C-1 there are also C-2 and C-3, the only
other known carbon stars is the Draco dwarf galaxy (satellite of our own 
Galaxy). They all shine around V=17 and I=15 mag.
The ROSAT observations on the Super-Soft X-ray Source nature of
Draco C-1 have been discussed at the June 1996 Colloquium on Symbiotic 
Stars (the proceedings due to appear in press in these weeks).

The ultraviolet properties as inferred from IUE observations have been 
discussed by Munari & Buson (1994, Astron.Astrophys. 287, 87).
The WD in C-1 is so hot and luminous that no better explanation exists
that it is stably burning the accreted material from the carbon giant
companion. A bright outburst (no one so far recorded) could onset any 
moment. From application of standard mass-luminosity relations
it appears that the WD in Draco C-1 is closing on the Chadrasekhar mass,
opening bright prospects for a SN Ia display. 
Because the distance module and reddening of the Draco galaxy is 
                    
                         m - M = 19.6         E(B-V)= 0.03       mag

a SN Ia exploding there could rival in apparent magnitude with Vega !

A last word about finding charts of ROSAT sources. Apart from those in
the Grainer et al. (ed) proceedings, finding charts for 384 and 169
respectively extreme ultraviolet sources (EUV) observed by ROSAT
can be found in:

    Shara et al. (1993) PASP 105, 387

    Mason et al. (1995) MNRAS 274, 1194

Regards

              Ulisse Munari
              Padova-Asiago Astronomical Observatories

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