Web Publications

Extending Request to Observe HMXBs in Support of Radial Velocity Observations
August 13, 2007

AAVSO Alert Notice 348 (issued April 6, 2007) included the request from Dr.
Gordon Sarty, University of Saskatchewan, for AAVSO assistance in observing
four (4) High Mass X-ray Binaries (HMXBs) in support of his spectroscopic
observations with the Dominion Astrophysical Observatory (DAO) 1.85-m
Plaskett telescope, in Victoria, BC, Canada. Dr. Sarty has obtained additional
observing time on these objects and is requesting our continued assistance
over the next several weeks.

Dr. Sarty asks our observers to obtain IVBR photometry (in that order of
preference) from now through September 2007. Observations with the DAO
Plaskett telescope will be made August 20 to September 3 and will be measured
to find the radial velocities. "The object is to determine the orbital
periods of the HMXBs. Optical photometry will also reveal other periods and
variation due to mass transfer, pulsations, and other effects. The availability
of photometry will be very valuable for interpreting the spectroscopic data.

"HMXBs consist of an exotic neutron star or black hole in orbit around a more
massive ordinary (O or B type) star. Mass is transferred from the ordinary
star to the exotic star through a variety of mechanisms, including accretion
disks (to the exotic star), decretion disks (from a rapidly spinning ordinary
star), and high stellar winds. These mass transfer processes cause many HMXBs
to be variable stars. The true distribution of HMXB orbital periods is not
yet known because the orbital periods of many are years in length. Thus
amateur observations of HMXBs will be very valuable for finding the true
distribution. More information about HMXBs will be published in an article in
JAAVSO Vol. 35, No. 2." A preprint of that article may be found at

http://www.aavso.org/publications/ejaavso/ej56.shtml

The table below lists the four target HMXBs for this observing campaign:

Desig.     AAVSO Name   Name          R.A.(2000)  Dec.(2000)   Mag  LPH no.

1930+53    1936+541     1936+541      19:32:52.3  +53:52:45.5  9.8  115
2027+47    J2030.5+47   J2030.5+4751  20:30:30.9  +47:51:50.7  9.3  123
2157+49    2202+501     2202+501      22:01:38.2  +50:10:04.6  8.8  127
2204+54    2206+543     2206+543      22:07:57.1  +54:31:05.8  9.9  128

[Note that 2204+54 2206+543 was formerly in the AAVSO validation file as
2204+53 2204+54CEP; the designation and name have been changed as shown
in the above list.]

The LPH number is a cross-reference to the HMXB listing in the JAAVSO
paper and the HMXB chart web page which may be found at:

http://www.usask.ca/psychology/sarty/AAVSO_HMXB_Charts.html

As mentioned in Alert Notice 348, please follow the observing instructions
given on the chart web page and on the charts and submit your results directly
to the AAVSO International Database. Also as before, Dr. Sarty says that
contributors of useful data will be offered authorship on the publications
resulting from this observing campaign, and he asks that any questions about
this observing campaign be sent to him at  .

Your observations of these bright HMXBs are extremely important both to the
success of this research and to increasing the fundamental knowledge of this
class of objects. Many thanks for your efforts and your astronomical
contributions.

Good observing!

Elizabeth O. Waagen

Senior Technical Assistant

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