[vsnet-campaign 1058] (fwd) Microquasar candidate J1628-41: Call for observations

[Taichi Kato <tkato>]

(fwd) Microquasar candidate J1628-41: Call for observations

(Comment by T. Kato): The object has the following identifications:
GSC7861.1088 162847.30 -415239.0 (2000.0) 13.14 6
USNO0450.24415462 162847.294 -415238.76 (2000.0) 10.9 15.6
162848.0 -415240 (2000.0) 1RXS_J162848.1-415241 0.119 1.00 0.60

Date: Sat, 4 Aug 2001 01:24:54 +0400 (EEST)
From: "Gregory S. Tsarevsky" <tsar@gamma.asc.rssi.ru>
Subject: [vsnet-alert 6183] Microquasar candidate J1628-41: Call for observations 

Dear colleagues,

As you know microquasars are a very rare class of the X-ray binaries (XRB)
showing relativistic radio jets closely resembling misterius jets from
the extragalactic quasars/AGNs. Only a half of a dozen microquasars have
been discovered up-to-date from the ~300 XRBs known (see comprehensive
review by Mirabel and Rodriguez in Annual Review of Astronomy and
Astrophysics, vol. 37, p. 409, 1999).

In the course of systematic search for new microquasars in the whole
Galactic Plane, we have found a few tens of promising objects. 
One of them is a relatively bright microquasar candidate J1628-41a 
as follows:
-1) It is a bright ROSAT source in the Galactic Plane with a hard spectrum
    characteristic for the X-ray binaries (XRB).
-2) It was detected by the Australia Telescope Compact Array (ATCA) as 
    a 7 mJy flat spectrum radio source with an unresolved core and some
    evidence of the jet. 
-3) With precision radio coordinates, it was identified with a star-like
    object, which has the following USNO data:
     ===========================================================
      Name       RA_2000       DEC_2000    r-o"  Bmag  Rmag   
     -----------------------------------------------------------
      J1628-41a  16 28 47.267 -41 52 38.6  0.4   15.5  11.4
     ===========================================================
      (r-o" - the difference in the radio and optical positions)
 Note: 
 Apparent color-index B-R=4.1 may suggest a possible strong source
 variability or/and large absorption in the source direction.

-4) Preliminary low resolution spectroscopy with the Anglo-Australian 
    4-m Telescope showed J1628-41a as a K5 spectrum object with a strong
    and variable H-alpha emission, i.e. possible low mass XRB (LMXRB).

We very much need help of the Southern VSNET community to start a
multicolor photometry of our best microquasar candidate J1628-41a,
to reveal its possible 
 - disc driven flare activity,
and 
 - eclipsing behavior with orbital period in a wide range say 0.1-20 d.

I would be happy to send a detailed description of the project to those
VSNET colleagues who would like to participate in the observations
requested. 

Dr Elena Pavlenko from the Crimean Astroph. Observatory will report this
in The Physics of Cataclismic Variables and Related Objects Conference
to be held in Goetingen just next week, see
        http://vsnet.uni-sw.gwdg.de/CVConference/

A finding chart will be send by request.

On behalf of the international team of the project
A Search for New Microquasars in X-ray, Radio and Optics,

Dr Gregory S. Tsarevsky  
 _____________________________________________________
 Australia Telescope National Facility, Sydney    ,    
 and Astro Space Centre, Moscow   	      ,--_|\   
                                             /      \   
 Tel: +612 9372 4260   Fax: +612 9372 4176   \_,--._#  
 http://vsnet.atnf.csiro.au/people/gtsarevs/         v   
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