July 14, 2005
SUBJECT:
1. MULTICOLOR CCD CAMPAIGN FOR AM HER TO SUPPORT XMM NEWTON OBSERVATIONS
2. BP HYI ECLIPSING BINARY CAMPAIGN
1. MULTICOLOR CCD CAMPAIGN FOR AM HER TO SUPPORT XMM NEWTON OBSERVATIONS
Summary
The polar AM Her is going to be observed with the XMM Newton satellite observatory later this month. We have been asked to coordinate multicolor CCD ground based photometry during the observing periods.
AM Her is at R.A. = 18:16:13.3 Dec. = +49:52:05 (2000).
Background
AM Her (AAVSO designation 1813+49) is member of the class of magnetic cataclysmic variables a.k.a. "polars". In a polar, the magnetic field of the white dwarf primary completely dominates the accretion flow of the system. Variability is mostly caused by diamagnetic blobs of material which fall ballistically along a stream to a magnetic pole. There it impacts the surface of the white dwarf directly and at high speeds. There is no accretion disc in polars.
Dr. Boris Gaensicke (University of Warwick) is a member of a team that will be observing AM Her with the XMM Newton X-Ray satellite. He has requested observations in BVR. The R observations will show potential cyclotron activity and the BV observations will show any flickering activity.
More information on AM Her and polars can be found in our June 2001 Variable Star of the Month:
http://www.aavso.org/vstar/vsots/0601.shtml [obsolete link; see article at http://www.aavso.org/vsots_archive ]
Observations
From now until July 28 please observe AM Her once per night in BVR. If you do not have a complete BVR filter set then please observe in whatever filters you do have.
Please begin time series observations for as long as possible during the following days and times. These are the scheduled observing periods for XMM Newton with an extra hour added to the beginning and end. This data is requested in case any anomalous behavior is detected during the X-Ray observations.
All times are UT.
2005-07-19 15:31:41 - 2005-07-19 20:28:21
2005-07-21 15:28:20 - 2005-07-21 20:25:00
2005-07-23 15:15:58 - 2005-07-23 20:12:38
2005-07-25 15:09:17 - 2005-07-25 20:05:57
2005-07-27 14:59:53 - 2005-07-27 19:56:33
Please set your exposure times for maximum precision and an SNR>100. Latest observations from the AAVSO International Database:
JUL 14.1928 15.1 JM CCDV Err: N/A
JUL 12.9250 <14.0 OJR Visual
JUL 12.2194 15.31 WDZ CCDV Err: 0.05
JUL 12.2088 15.24 KKQ CCDV Err: 0.02
JM Robert James Las Cruces, NM
OJR Jose Ripero Madrid, Spain
WDZ Don Wells Missouri City, TX
KKQ Kevin Kessler Ellicott City, MD
Note that AM Her can increase in brightness by a magnitude or so in just a few hours. So be careful to monitor your exposures and not to saturate. Take a look at the AAVSO Quick Look data for examples of recent activity:
http://www.aavso.org/cgi-bin/quickquick.pl?star=am%20her [obsolete link; review data using light curve generator at http://www.aavso.org/lcg ]
The existing AAVSO f-scale chart for AM Her has been edited to include a table of CCD BVR magnitudes. It can be downloaded at this URL:
http://www.aavso.org/cgi-bin/searchcharts3.pl?name=am%20her [obsolete link; create charts using VSP at http://www.aavso.org/vsp ]
This campaign will be coordinated by Aaron Price (aaronp@aavso.org).
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2. BP HYI ECLIPSING BINARY CAMPAIGN
Summary
BP Hyi is a little studied variable star in the direction of the Small Magellanic Cloud (SMC). It is cataloged as an eclipsing binary but the data that classification is based on is very sparse. Also, its color implies that it could be a realtively unique type of eclipsing binary. We request nightly observations until we build enough of a light curve to determine its classification.
Background
BP Hyi is listed as an EA type eclipsing binary in the GCVS. This designation stems from an article in the Bulletin of the Harvard College Observatory written by Harlow Shapley and Virginia McKibben in 1942. Vital statistics according to the GCVS and the article are as follows:
BP Hyi is at R.A. = 02:07:45.6 Decl. = -73:29:46 (2000)Period: 2.65d
Range 15.3 - 16.2 (photographic)
AAVSO Designation: 0206-73
According to the Bulletin, it is an A class luminous star in the direction of the SMC. There are not many highly luminous blue eclipsing binaries with such high amplitudes. It's color indices also do not preclude it from being a nearby CV. In summary, not much is known is about this star and there is the potential that it could be very interesting.
Observations
CCD observations of this system are requested until we get enough data to determine its light curve. Please observe it in V for as long as possible and for as many contiguous days as possible. Only through combining *many long* observing runs can we build a suitable light curve to determine its type.
This is a faint system. Luckily for us the period is long so time resolution is not as important. Take your time and stack exposures if neccessary to get an SNR > 100. If possible, spread your observing times around so your observations are not made at the same time each night. This will help minimize 1 day aliases in the power spectrum.
While it is towards the SMC, this particular region is not relatively crowded. But you still must take careful note of the aperture you use in the photometry and use the same aperture across all your frames and observing runs. Consistency is the better part of valor! Stay consistent and precise and your data will be useful.
A chart for this object is available at:
http://www.aavso.org/cgi-bin/searchcharts3.pl?name=bp%20hyi [obsolete link; create charts using VSP at http://www.aavso.org/vsp ]
If we are successful, we will submit an IBVS paper on this object and everyone who submits a long series of useful observations will be included as a coauthor. Also, we will keep anyone who submits useful data updated via e-mail as to the progress of the project.
This campaign will be coordinated by Aaron Price (aaronp@aavso.org).
Many thanks for your valuable astronomical contributions and your efforts.
Good observing!
This Alert Notice was prepared by Aaron Price.
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