[vsnet-alert 9179] (fwd) V838 Mon engulfs its companion

[Taichi Kato]

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The Astronomer's Telegram                   http://www.astronomerstelegram.org 
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Posted: Fri Dec 15 01:30:01 EST 2006 -- Tue Dec 19 01:30:01 EST 2006
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ATEL #966							     ATEL #966

Title:		V838 Mon engulfs its companion
Author:	Howard E. Bond (STScI)
Queries:	bond at stsci.edu
Posted:	18 Dec 2006;  17:54  UT
Subjects:	Optical, Request for Observations, Binaries, Cataclysmic
		Variables, Novae, Transients, Variables, Stars

In ATel #964 Goranskij reported a sudden fading at blue wavelengths  
of the peculiar variable star V838 Mon. We report that the fading is  
confirmed by CCD frames obtained with the Andicam camera on the   SMARTS
Consortium 1.3m telescope at Cerro Tololo (observers: J.   Espinoza & D.
Gonzalez). Observations during 2006 are as follows (UT   dates are for
the B observations; the V magnitudes were obtained   within 1-2 days of
those at B). We also list the observations   reported by Goranskij in ATel
#964.      

<table>   <tr><td>  Date   </td><td> B	 </td><td> V	 </td><td>		      
</td></tr>   <tr><td>  ------ </td><td> ----- </td><td> ----- </td><td>		
</td>   </tr>   <tr><td>  Jan 11 </td><td> 16.63 </td><td> 15.40
</td><td>		       </td>   </tr>   <tr><td>  Jan 21 </td><td> 16.62 </td><td>
15.40 </td><td>		       </td>   </tr>   <tr><td>  Feb  7 </td><td> 16.62
</td><td> 15.39 </td><td>		       </td>   </tr>   <tr><td>  Feb 18 </td><td>
16.61 </td><td> 15.38 </td><td>		       </td>   </tr>   <tr><td>  Mar 26
</td><td> 16.61 </td><td> 15.36 </td><td>		       </td>   </tr>   <tr><td>
Apr 19 </td><td> 16.60 </td><td> 15.35 </td><td>		       </td>   </tr>
<tr><td>  May 18 </td><td> 16.62 </td><td> 15.36 </td><td>		       </td>
</tr>   <tr><td>  Sep 21 </td><td> 16.54 </td><td> 15.33 </td><td>		
</td>   </tr>   <tr><td>  Oct 21 </td><td> 16.47 </td><td> 15.27
</td><td>		       </td>   </tr>   <tr><td>  Oct 26 </td><td> 16.42 </td><td>
15.36 </td><td>  Goranskij ATel 964 </td></tr>   <tr><td>  Nov 22 </td><td>
17.14:</td><td> 15.70 </td><td>		       </td>   </tr>   <tr><td>  Dec 
2 </td><td> 17.33 </td><td> 15.75 </td><td>  Goranskij ATel 964 </td></tr>
<tr><td>  Dec 10 </td><td> 17.52 </td><td> 15.76 </td><td>  Goranskij
ATel 964 </td></tr>      </table>      

V838 Mon was nearly constant during most of the first half of   2006, with
perhaps a slight brightening in V. After emerging from   behind the Sun,
it appeared to brighten by ~0.1 mag in V and ~0.2   mag in B through the
end of October. The sudden decline had its   onset sometime in November.

Spectroscopic observations with the SMARTS 1.5m telescope   (observers:
C. Aguilera & A. Pasten) also show dramatic changes. The   blue emission
lines of [Fe II] reported in 2006 May by Barsukova et   al. (ATel #803)
continue to be strong, while the blue continuum due   to the B3 companion
is fading. A very strong H-alpha emission line   was detected in a spectrogram
on 2006 Oct 12 and again on Nov 29 and   Dec 13, whereas no H-alpha emission
was seen on 2006 May 14.      

These findings suggest that ejecta from the V838 Mon outburst   have now
reached the vicinity of the B3 V companion and are   beginning to engulf
the star. Continued monitoring is encouraged.  

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Password Certification:  Howard E. Bond (bond at stsci.edu)
http://www.astronomerstelegram.org/?read=966
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