[vsnet-alert 10395] Re: New CV from 1RXS catalog

[Denis Denisenko]

Taichi Kato wrote:

> Is this really a polar?

Well, in the text of ATel I have written more cautiously: "Judging from 
the orbital period and variations of the light curve we _suppose_ the 
object to be a cataclysmic variable of AM Her type - that is, a polar 
variable".  And also, from the rather high X-ray to optical flux ratio 
similar to that of eclipsing polar J0209+2832 (16.0-17.0 mag out of 
eclipse and 0.0543 counts/s in ROSAT data).  However, I was also 
surprised by the eclipse almost disappearing in a high state.  Is the 
growing accretion disc the only possible explanation?  Could it be due 
to the "grazing" eclipse and accretion column growing in length in a 
bright state?

I could have well mistaken - I still don't posess enough experience and 
have a lot and lot to learn!  If J1808+1010 is an UGSU instead, that 
makes this object even more interesting, meaning it can produce bright 
outbursts in future!

> The ROSAT hardness ratio also looks slightly too hard.
>
> It seems to me that this object still has a possibility of an
> X-ray bright dwarf nova-type object with low/high states in quiescence
> similar to IR Com and HT Cas

Indeed, the infrared and X-ray parameters of J1808+1010 are very similar 
to those of peculiar UGSU dwarf nova IR Com, except for the orbital 
period (0.087039d for the latter):

-------------------------------------------------------------
Object     J       H      K      X-flux   HR1 +/-    HR2 +/-
-------------------------------------------------------------
IR Com   15.032  14.611  14.582  0.0605  1.00 0.20  0.44 0.20
J1808+10 14.930  14.651  14.329  0.0530  1.00 0.22  0.40 0.24
-------------------------------------------------------------

X-flux here is ROSAT countrate (ct/s), and HR1 and HR2 are hardness 
ratios of (0.5-2.0) to (0.1-0.4) keV and (0.9-2.0) to (0.5-0.9) keV 
bands normalized to [-1, 1] range.  Coincidence between two objects is 
amazing!  For comparison, the above mentioned J0209+2832 has 
HR1=0.54+/-0.29 and HR2=-0.22+/-0.33 - definitely softer than these two.

Taichi Kato wrote:

> A spectroscopic observation would distinguish these possibilities.

I have "insider's" information that the spectroscopy was already 
performed last night, immediately after posting the ATel.  Probably 
another telegram will be published later, maybe even today.

Denis