[vsnet-alert 10110] Re: outburst of HD 74771?

[Howard E. Bond]

arne wrote:
> 
> Howard E. Bond wrote:
> > The 8th-mag southern star HD 74771 is a possible very bright cataclysmic
> > variable, pointed out by S. Otero in vsnet-alert 8817.
> >
> > It appears that it may currently be in outburst:
> >
> > http://www.astrouw.edu.pl/cgi-asas/asas_variable/084434-3757.9,asas3,0,0,1000,0
> >
> > so it would be very important to obtain photometry and spectroscopy over at
> > least the next several days.
> >
> > J2000 coordinates are: 08 44 34.0 -37 57 52
> >
> The light curve looks CV-like except for the amplitude.
> My guess is that HD 74771 is not the CV, but that there is some
> background object that is outbursting.  About the only way you
> can tell is either a good seeing image, or else an astrometric
> measure in outburst and quiescence.  Perhaps this is already
> available through Hipparcos.
> Arne

Dr. Henden's suggestion (also made in an e-mail to me from Brian Skiff, who
pointed out that HD 74771 is a cataloged visual binary) turns out to be correct.

Images obtained by J. Espinoza through clouds with the SMARTS 1.3m telescope at
Cerro Tololo on 2008 Apr 25.064 show that HD 74771 has a blue (B-V ~ 0)
companion at V ~ 11, located 6".8 WNW of the 8th-mag HD star. The cataloged
brightness of the companion is much fainter, about 15th mag.  

This companion is very probably the cataclysmic variable and X-ray source,
rather than the HD star itself. The system could be physical, or possibly just a
chance alignment.

Howard E. Bond
Space Telescope Science Institute