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C C D V I E W S #337
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May 26, 2005

** This is a special edition of CCD Views **

Table of Contents
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1. Monitor LS Peg for XMM Newton Observations

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1. MONITOR LS PEG FOR XMM NEWTON OBSERVATIONS

Dr. Darren Baskill (University of Leicester) has requested optical observations of LS Peg (currently suspected as being a DQ Her nova-like) to coincide with upcoming observations by the XMM Newton X-Ray observatory.

Observations in are requested from now until July 8. Intensive, time series observations are requested 12 hours before and also during the actual XMM observation which is scheduled for June 6, 2005 from 08:55 - 21:34 (UT). So we need time series coverage from:

20:55 June 7 (UT) to 21:34 June 8 (UT)

Use an Ic filter if you have one and a V filter if not. Set your exposure time for maximum precision. This is a bright system (V~12) so it should be easy to get an SNR of 100. The latest ASAS-3 observation is:

May 13.4185 V=12.324 +/- 0.097

A new AAVSO f-scale chart has been prepared and is here: http://www.aavso.org/cgi-bin/searchcharts3.pl?name=ls%20peg

Arne Henden has calibrated the field this week in BVRI so we will be adding R and Ic magnitudes to the chart in a couple of weeks.

Specifics science goals from Dr. Baskill:

"A possible 30.9 minute period was detected in the ASCA observation of LS Peg, with an amplitude of 32%. Rodriguez-Gil et al (2001) independently report a detection of a period at 29.6 min in the circular polarisation of LS Peg. This coincidence suggests that the modulation in X-rays and circular polarisation may have a common physical origin which warrants further investigation.

XMM-Newton is currently scheduled to observe LS Peg for 10 hours on the 8th of June, 2005. Optically, LS Peg can usually be found around 12th magnitude.

In looking deeper for a weaker period with XMM-Newton, we will validate the method of identifying magnetic accretors from their spectra alone, a method which works even at low signal-to-noise. This will establish X-ray spectroscopy as a method for identifying & investigating magnetic accreting systems. The extra signal-to-noise will also allow us to search for periods in different energy bands, just like Patterson et al. (1998). While XMM-Newton observes the heated gas at the white dwarf in X-rays, and the inner disk at UV (with the XMM-Newton optical/UV monitor), we would also like simultaneous high time resolution optical observations to track the movement of gas from the outer disk. We would like this optical data from 12 hours before the XMM-Newton observation, right through the observation itself. In addition, in order to see more general changes in the outer disk and what state the outer disk is in during the XMM-Newton observation, we would like optical observations spanning several weeks either side of the XMM-Newton observation."

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Good observing!

Aaron Price, AAVSO Technical Assistant (PAH)
Gary Walker, Chairman of the AAVSO CCD Committee (WGR)

Copyright 2005, American Association of Variable Star Observers

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