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By Elizabeth O. Waagen, AAVSO Headquarters
The dwarf nova cataclysmic variable U Geminorum, prototype of its class, has been in the AAVSO observing program since 1908, and has always been a popular observing target. The first observation was made by Miss Ida Whiteside, a professor at Vassar College in Poughkeepsie, New York, on January 30, 1908.
The most recent observation added to the AAVSO International Database was
made on November 30, 2005, by Glenn Chaple of Townsend, Massachusetts.
From Ida's through Glenn's observation, 94,745 observations of U Gem have
been contributed to the AAVSO International Database by 1,298 observers!
Some observers seem to be particularly fond of U Gem - 12 observers have made over 1,000 observations of U Gem during their observing careers. Radha Chandra, Giovanni Lacchini, Leslie Peltier, David Rosebrugh, Ernst Mayer, Gerry Dyck, Ken Medway, John Bortle, Cyrus Fernald, Carolyn Hurless, Lasse Teist Jensen, and Robert James have collectively contributed 30,784 observations (to date, that is)!
A long-term light curve of one-day means of U Gem covering the interval 1910-2005 accompanies this note.
A long-term light curve of individual observations from U Gem's discovery in 1855 to 1964, and more detailed light curves
from 1964 through 2000 may be seen in AAVSO Monograph 2, U Geminorum Light Curves 1855-1985, and its three supplements, U
Gem Light Curves 1986-1990, 1991-1995, and 1996-2000. Of course, the individual observations from 1908 to date may also be
seen (and downloaded) via the AAVSO website, specifically the Light Curve Generator.
AAVSO Light Curve Generator
An AAVSO Variable Star of the Month article was written on U Gem in February 1999 by Aaron Price.
The AAVSO has participated in many observing campaigns on U Gem over the decades, in support of ground-based, satellite,
and even space shuttle observations. Thanks to observers' efforts worldwide, a number of significant results have been obtained
and understanding of these very complex systems has been advanced.
To illustrate how AAVSO observers affect U Gem research and U Gem research can affect observers, I would like to quote
from two Annual Reports of the late Janet A. Mattei, AAVSO Director for 30 years.
First, from Janet's 1990-1991 report:
"When U Gem had an outburst in November 1990, we informed ROSAT astronomers. They were able to schedule multi-wavelength
satellite and ground-based observations. A few days later, one afternoon, Dr. Christopher Mauche called saying he was able
to obtain IUE time to observe U Gem that night if it was still up. Since the European observers are 6-7 hours ahead of us
and could provide that information, we called several of them but they were all clouded out. So I then called our observer
Haldun Menali in Istanbul, Turkey, at 11:30 pm his time and asked him, if it was clear, please to check how bright U Gem was
that night and inform Dr. Mauche. Haldun was able to observe U Gem and it was indeed still bright. Dr. Mauche was able to
obtain an impressive IUE spectrum, for which he was very appreciative. Haldun was so excited to receive a call from the USA
and to provide this crucial information for a satellite that he was inspired to write a fascinating article of his experience
in a Turkish paper. In it he explained how, upon the receipt of my phone call, he bundled up and rushed out into the cold
with his telescope, how he had to fight the clouds, how he had to convince a policeman who had become suspicious of his telescope
and his observing attire that his activities were legitimate, and how he finally accomplished making that crucial observation
of U Gem at outburst."
Second, from Janet's 1997-1998 report:
"Our colleagues Drs. Christopher Mauche at Livermore National Laboratory and Peter Wheatley in the Netherlands were granted
Target-of-Opportunity (TOO) observing time on the Extreme Ultraviolet Explorer (IUE) and the Rossi X-Ray Timing Explorer (RXTE)
to observe U Gem while it was in outburst. We alerted our observers to keep a close eye on U Gem. Here the drama begins --
"Janet Mattei wrote to Chris Mauche on Nov. 7, 1977, at 5:10 am PST: '
The following observation indicates U Gem is in outburst: U Gem Nov. 7.269 UT 9.7 HSG (G. Hanson) This is the only observation
reported from last night, but Gene is a very good observer and he...reported U Gem at magnitude 13.4 the night before. I just
gave the observation above to Peter Wheatley over the phone. He said that he requested the RXTE team to start the observations
yesterday after he saw our News Flash on U Gem.'
"Chris to Bryce (of EUVE) at 5:27 am PST, Nov. 7:
'Wake up, man! U Gem is in outburst! Start the EUVE TOO as soon as humanly possible! Pete Wheatley just called to say that
XTE is going to be on source by 17:00 hrs UT. Are you going to let them beat you to the source?'
"Chris to Pete and Janet: 'FYI, Bryce is working on it, and will try to beat XTE to the source, but he can't promise anything
yet. I'm going back to bed for another 3 hours.'
"Janet wondered how Chris could act so fast so early in the morning, and asked what kind of an alarm system he had to wake
him up at the alert of an outburst. Chris replied: 'My alarm system is Pete Wheatley: I left him to follow up with you in
the AM and told him not to call me unless it was a go. Pete called me, I called Bryce after sending him e-mail - hence sleep
was lost by everyone, at least on this coast. Bryce tells me he will be on source at 18:19 UT. I hope that is soon enough
to catch the rise to outburst. Thanks for your most excellent assistance.'
"As a result of this successful collaboration between our observers and professional colleagues, excellent sets of data
on U Gem have been obtained in the x-ray, extreme ultraviolet, and optical wavelengths which will help to answer some of the
questions about the accretion disc, the boundary layer near the white dwarf, and the white dwarf itself in this compact binary
system."
There are many other examples of how U Gem has played a starring role in the AAVSO's involvement in variable star astronomy
research, and there will certainly be many more in the future. Today, the other variables step back and give U Gem center
stage so we may all say:
"Happy Birthday, U Gem!"
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