Non-Periodic Phenomena in Variable Stars
IAU Colloquium, Budapest, 1968
ECLIPSES OF U GEMINORUM
MARGARET W. MAYALL
A. A. V. S. O., Cambridge, USA
During the last 4 observing seasons, 1964-65 to 1967-68, the AAVSO has
received many visual observations of the eclipses of U Geminorum. Some
are too fragmentary to use in a preliminary analysis, but we have 97
eclipses which were observed over a long enough period of time to give a
value of the width of the eclipse curve.
Most of these 97 eclipses were observed by 4 very careful and
experienced observes, and 75% were by Leslie Peltier with his 12-inch
Clark refractor. About 1/4 of these were made in collaboration with
Carolyn Hurless. The two observers made alternate estimates about one
minute or less apart.
The other 25% were made by Clinton B. Ford, Carolyn Hurless and Thomas
Cragg, with a few by Vicki Schmitz and Diane Lucas.
Visual observers find it too difficult to make rapid accurate estimates
of one star for more than about one hour at a time. Consequently, it is
often impossible to determine the time of eclipse by the method used by
Dr. Krzeminski, although the observations do confirm the change in
period found by the photoelectric observers.
In this preliminary discussion I have used the width of the eclipse curve
at magnitudes 14.2 and 14.6. The normal minimum magnitude of U Geminorum
between eruptions is 13.8 to 14.0. At times the eclipses reach 15th magnitude
and at other times they barely reach 14.2.
One of our observers, Ron Thomas (AAVSO Abstracts, 1968 June) arranged
the eclipse curves into different types, and attempted to find a correlation
between type of curve and the time elapsed since an eruption. In a modified
form, the types are:
Type I - similar to the schematic curve used by photoelectric observers
(Krzeminski Ap. J. 142, 1053, 1965) to determine the time of minimum,
with an increase before the sharp drop to minimum, followed by a rapid
rise 3/4 of the way to normal magnitude.
Type II - steep decrease and slow rise.
Type III - slow decrease and rise.
Type IV - slow shallow decrease, followed by an interval of nearly
constant brightness.
Type V - erratic variations of a few tenths to three-quarters of a
magnitude before and after predicted time of minimum.
Table I lists the eruptions of U Geminorum which were observed during
1964-1968. The numbering is a continuation of the systems started by
Leon Campbell. The data for Epochs 1 to 3 is published in JRASC Vol 51,
2, March 1957.
Table I
Eclipses of U Geminorum
J. D. Type Min. Mag. Width Observer Days from
2,430,000+ eruption
14.2 14.6
8799 II 14.9 .009 .004 CR +15
8802 V 14.9 - .027 CR +18
8810 IV 14.9 .010 .007 CR +27
8811 I 14.8 .013 .008 CR, BM +27
8812 ? 14.7 ? .002 P +28
8818 I 14.6 .011 .003 CR +34
8820 III - .012 - P +36
8842 II 14.4 .010 - FD +58
8847 II 14.5 .011 - CR +63
8851 III 14.7 .016 .005 FD +67, -38
8853 III 14.6 >.015 .003 P +69, -36
8855 I 14.75 .019 .007 FD +71, -34
8856 I 14.7 .016 .004 FD +72, -33
8870 I 14.6 .012 .001 P +86, -19
8873 I 14.8 .013 .003 P, HR +89, -16
8878 II 14.8 .011 .004 P, HR +94, -11
8879 I 14.75 >.027 .005 P +95, -10
8881 III 14.8 >.035 .007 P, HR +97, -8
8884 I 14.8 >.018 .007 P, HR +100, -5
8897 II 14.7 .016 .004 CR +8
9024 II 14.7 .013 .002 P +25
9033 II 14.75 .019 .008 P +34
9035 II 14.7 .014 .003 P +36
9036 III 14.5 .016 - P +37
9038 II 14.7 .015 .003 P +39
9058 III 14.8 >.017 .006 P +59
9059 III 14.5 .016? - CR +60
9060 III 14.7 .014 .007 FD +61
9062.7 I 15.0 .016 .007 FD +63
9062.9 III 14.8 >.022 .006 P +63
9063 III 14.7 >.024 .007 P +64
9064 III 14.7 >.022 .006 P +65, -45
9065 II 14.75 >.018 .008 P +66, -44
9069 II 14.6 .011 .001 FD +70, -40
9084 I 14.8 >.014 .005 P +85, -25
9087 I 14.4 .007 - P +88, -22
9094 I 14.3 .002 - FD +95, -15
9095 III 14.4 .008 - P +96, -14
9113 IV 12.2 - - F, BM +4
9120 II 14.4 .010 - P +11
9123 III 14.5 .016 - P +14
9129 IV 14.4 .019 - P +20
9137 IV 14.5 .014 - P +28
9139 II 14.8 .012 .003 CR +30
9140 I 14.8 .017 .007 FD +31
9141 III 14.5 .015 - P +32
9143 I 14.5 .012 - P +34
9144 II 14.6 .015 .002 P, HR +35
9150 III 14.5 .008 - FD +41
9154 III 14.9 .016 .009 FD +45
9168.5 - 14.65 >.020 .008 P +59
9168.7 - 14.55 >.012 .001 P +59
9170 IV 15.0 >.032 .030 CR +61
9173 III 14.6? .019 .003 LS +64
9174.5 ? 14.8: ? ? P +65, -40
9174.7 I 15.0 .018 .007 FD +65, -40
9176 IV 14.6 >.020 .001 P +67, -38
9177 III 14.8 .018 .003 P, LS +68, -37
9178 III 14.6 .018 .001 P, HR +69, -36
9179 III 14.75 .018 .007 P, HR +70, -35
9198 III 14.8 .019 .007 P +89, -16
9200 I 14.9 >.020 .010 P +81, -14
9201 I 14.75 >.026 .006 P, LS +92, -13
9202 I 14.9 .017 .010 P, HR +93, -12
9207 ? 14.6 .018 .001 P, HR +98, -7
9229 III 14.3 .008 - P, HR +15
9238 III 14.4 .014 - P, HR +24
9240 I 14.2 .006 - FD +26
9241 III 14.5 .011 - P, HR +27
9256 III 14.6 .017 .001 P, HR +42
9262 IV 14.5 .013? - P, HR +48
9264 III 14.5 .015? - P, HR +50
9452 II 14.6 .019? .003 P +69, -17
9453 II 14.9 >.015 .007 P +71, -16
9478 III 14.6 .017 .002 P +9
9493 III 14.9 .026 .013 P +24
9500 III 14.7 ? .006 P, HR +31
9503 III 14.8 .031 .008 P +34
9506 IV 14.7 >.038 .014 P +37
9508 II 14.8 >.021 .007 P +39
9524 II 14.8 >.017 .009 P +55
9531 III 14.9 >.026 .007 P +62
9533 III 14.9 >.031 .010 P, HR, SV +64
9535 III 14.9 >.106 .007 P +66, -47
9558 III 14.8 >.022 .002 P +89, -24
9559 II 14.9 >.017 .008 P, HR +90, -23
9567 III 14.85 >.021 .010 P, HR +98, -15
9596 III 14.5 .016 - P +14
9940 IV 14.8 >.021 .010? P, HR, SV +43
9941 IV 14.7 >.021 .013? P +44
9944 II 14.9 >.014 .008 P +47
9945 II 14.8 >.023 .008 P +48
9946 III 14.8 >.035 .007 P +49
9948 III 14.8 >.046 .008 P, HR +51
9972 IV 14.8 >.015 .002 P +75
BM = Baldwin HR = Hurless
BOR = Bornhurst LS = Lucas
CR = Cragg P = Peltier
FD = Ford SV = Schmitz
Table II gives the data for the eclipses used in this discussion.
Table II
U Geminorum Eruptions
No. Class J. D. Diff. J. D. Mag Diff. J. D. Diff.
11.0I Max 11.0D
388 n 8467 108 8468 9.0 106 8472 99
391 w 8781 314 8784 8.8 316 8792 320
392 n 8888 107 8889 9.5 105 8891 99
394 n 9108 220 9109 9.5 220 9112 221
395 w 9212 104 9214 9.3 105 9223 111
397 w 9377 165 9382 9.2 168 9387 164
398 n 9468 91 9469 9.8 87 9472 85
399 w 9579 111 9582 8.9 113 9591 119
401 w 9768 189 9771 8.6 189 9776 185
402 n 9893 125 9897 9.5 126 9898 122
The diagram shows the time before or after an eruption when various
types of eclipse light curves were observed. I find no correlation
between the number of days from an eruption and the type of light curve,
depth of minimum, or width of the curve at magnitude 14.2 or 14.6.
Fig. 1.
Type of Minimum vs. Days from Eruption
I have great confidence in these visual light curves, and feel sure that
a large number of minimum observations give good evidence that U Geminorum
eclipses are irregular in shape and there is no difference in the shape before
or after the outburst.