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Alert Notice 551: GDS_J1701281-430612 monitoring for HST observations

Note added September 27, 2016: Dr. Reynolds adds the following: "Visual observations would be useful in setting a baseline and understanding how variable the source is in a relative sense at the time of our HST observation."

September 20, 2016: Dr. Mark Reynolds (University of Michigan) and colleagues have requested AAVSO assistance in monitoring the cataclysmic variable GDS_J1701281-430612 in support of HST/COS observations scheduled for early October.

Dr. Reynolds writes: "[GDS_J1701281-430612] is a cataclysmic variable binary system. X-ray observations with XMM-Newton have revealed a 15 min pulsation period, and an X-ray spectrum consistent with that expected from channeled accretion onto a magnetic white dwarf. The goal of this HST observation is to study the inner accretion flow from the truncated accretion disk onto the white dwarf."

Beginning now and continuing through late October, V, R, and I photometry of GDS_J1701281-430612 is requested; the extinction in blue makes B photometry less valuable and is not recommended. The HST observing window is October 3-9. Until October 1, nightly snapshots in VRI are requested to establish a baseline and follow   the target's behavior. From October 1, observations a few times per night are requested, then more frequently during the HST observations themselves at a cadence that allows for a good S/N. Following the HST observations, nightly snapshots are requested for about two weeks to provide context.

When the exact date/time of the HST observations is known, observers will be notified via an AAVSO Special Notice. If you don't already subscribe to this publication, you may do so at no charge from your AAVSO web account page.

GDS_J1701281-430612 ranges between about 15.2 R and 16.2 R. Although V measurements have not been made of this object, according to Dr. Reynolds optical spectra indicate that V-R should be about zero. GDS_J1701281-430612 is also known as 2MASS J17012815-4306123.

Coordinates (2000.0):  R.A. 17 01 28.14  Dec. -43 06 12.3

Charts with a comparison star sequence for GDS_J1701281-430612 may be created using the AAVSO Variable Star Plotter (VSP). Be sure to include the underscore in the name. Observers should create an 'e' scale chart to see the sequence.

Please submit observations to the AAVSO International Database using the name GDS_J1701281-430612 exactly as written here.

This campaign is being followed on the AAVSO Observing Campaigns webpage. A thread has been created on the Campaigns and Observation Reports forum at (


This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.


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