by Roger Pickard, Director BAA VSS

Although discovered in 1855, and the prototype of this class of eruptive
variable star the first positive observation of U Gem in the current
BAAVSS database does not appear until 1925. This was made by W M Lindley
on January 15th at approximately 10:15pm when he recorded it at magnitude
12.2. His next positive observation was 13th February when it was even
fainter at 13.7 and he had to wait until 24th April before he recorded it
in full outburst at 9.6.

However, Lindley had made 9 observations of U Gem in 1924 but they were
all negative. But if you take the first of these as the first true
observation in the VSS database then the date for this first observation
is 1924 October 24 at 2:06 am.

Lindley was the only observer of U Gem, with some 90 observations, until
1932 when such greats as W H Steavenson and F M Holborn, to mention but
two, contributed observations.

There are a total of 20913 observations of U Gem in the VSS database of
which 8768 are positive estimates. Not surprisingly, the early war years
of 1941 and 1942 recorded the lowest numbers of observations with 41 and
42 respectively. Interestingly, the full year before the war of 1938
recorded the second highest total with 660. (1988 recorded the very most
with just 7 more at 667 and also the most positive estimates at 333).

Three observers have made over 1000 observations of U Gem, F M Holborn,
1440; W M Lindley, 1010 and, coming right up to date, with 1199 and still
counting, Mike Gainsford.

Lindley was to become Director of the VSS in 1939, a post he held until
1958 making him the longest serving Director, beating De Roy by two years.

The VSS always prides itself on being one of the oldest variable star
sections in the world, but I thought it would be interesting to see when
the first observation appeared in the AAVSO database. I was quite
surprised to find that they have observations of U Gem going back to
January 31, 1908.

Regarding features of the light curve to be gleaned from the VSS data I
can do no better than to quote, in part, two paragraphs from John Toone's
notes in the BAA Handbook for 2000 where, under Variable Star of the Year,
he wrote:-

Visually, U Gem is normally around magnitude 14.0 to 14.5 at minimum but,
when in eclipse, the star can drop below magnitude 15.0. The outbursts
occur on average every 100 days but the time between them has been seen to
fluctuate between extremes of 33 and 256 days. When in outburst the star
often peaks at around magnitude 9.0.

Two distinct types of outbursts are normally observed and are termed
"longs" and "shorts", lasting on average 16 and 10 days respectively.
"Longs" and "shorts" normally alternate but 7 successive "longs" and 4
successive "shorts" were observed during the period 1928 to 1979. Then in
1985 an outburst lasting 42 days occurred which was twice as extended as
the longest "long" on record. This was followed by the shortest "short" on
record lasting just 6 days. There then followed two more successive
"shorts" (unless a "long" was missed during the summer of 1986) which
completed a unique spell of activity for this star.
The rise to maximum is usually at a rate in excess of 3 magnitudes per day
and is often fully accomplished within 30 hours.

And there the situation rested until I sent off the above note to Mike
with a copy to John Toone.

John immediately telephoned me (this was too important to rely on email!)
to say that my records must be wrong because he had observations from old
BAA Journals of observation of U Gem going back to 1908 and would send me
photocopies of the relevant pages.

So, I added the following.

In the Variable Star Section Interim Report No. 26, for 1908 the Director,
Colonel E. E. Markwick, reported that two maxima of U Gem had been
observed, the first on Feb 9 at mag 9. But he didn't report the first,
even if negative, observation.

But things didn't stop there!

By this time, and via a different route, I'd become aware that there were
probably more observation out there waiting to be entered into machine
readable form. Storm Dunlop provided me with a list of potential
articles containing VS observations from the Monthly Notices of the RAS
which go back to 1827.

The following is a quote from MNRAS LXVII [67], No.2, p.119 [Dec. 1906] by
Prof H H Turner, on Joseph Baxendell's observations.

"It is scarcely possible to hand it to anyone who is not familiar with
variable star records . . . . I take this opportunity of saying that I
should be very glad of skilled volunteer assistance, at any rate in
dealing with the copied ledgers for different stars, and perhaps with
these early records also. If any variable star observer has leisure for
work of the kind and would communicate with me, 1 should gratefully accept
assistance in making this mass of valuable material ready for publication
as soon as possible. Unaided my work at it must necessarily be slow."

It's interesting, that after almost 100 years, I'm still struggling to
find volunteers to complete the task of entering old observations into the
database!

But what of the observations of J Baxendell?

Turner explains at some length the notes Baxendell made about the
comparisons used and from this it can be seen that his first observation
may have been on 1858 February 1 at mag 14, although this is not definite.

(For those not fortunate enough to attend the BAA VSS Meeting at Alston
Hall last year, where, incidentally, Mike Simonsen was one of the invited
speakers, they would have missed John Toone's talk on Baxendell).

But there are also observations by Pogson in the MNRAS also edited by
Turner.
Pogson began to look for U Gem soon after Hind's discovery and his first
positive observation was dated 1856 March 26 when he made the following
remarkable note:-

"The variable subject to strange fluctuations at intervals of 6 to 15
seconds, and quite to the extent of 4 mags. The neighbouring small stars
were very steady, not at all twitching like the variable. The phenomenon
(which was quite new to me) was watched for above half-an-hour. At times
it quite vanished, and then surpassed the comparison star a. (Note: Star
a was given as magnitude 8.8 which we now know to be 8.6 and he was using
the 7.2 inch (18cm) refractor at the Radcliffe Observatory).

On the next night Pogson notes "Far from steady, but the pulsations much
less marked than last night". And on later nights he reported: "U
certainly less steady than the neighbouring stars."

U Gem was around maximum at this time.

As we know, U Gem has been seen to exhibit flickering when at minimum, but
at maximum?

However, prior to these observations, Pogson had looked for U Gem but
without success and the first observation likely to be entered into the
database is one of 1856 Jan 2 when he recorded it as less than 12.

And finally, a big thank you to Mike for asking me to write a note about
this star, for indirectly, it's lead to the discovery of lots more VS
observations out there that still need to be entered into the database.

Roger Pickard
Director BAA VSS