(cba:news) the times they are a-changin
Joe Patterson
jop at astro.columbia.edu
Tue Feb 11 04:54:14 EST 1997
Dear CBAers, 2/11/97
Whew, in two days I leave for nine weeks in South Africa. Lotta
stuff to do. Wanted to get some current info in your hands.
EG Cnc has grown mighty faint (17.2) and the mini-eruptions have
paused for a while, but it still sports a wave in the light curve at
something like the old superhump period. Dave Harvey and Bob Fried
have managed to track it reasonably well in dark skies with 14-
and 16-inchers. Never before have we gotten the chance to test the
staying power of superhumps 5 mag below maximum light! So I earnestly
implore you to try to follow this wonderful star. Only a few of you
will be able to follow the short-period modulation, but snapshot
magnitudes are of much interest too. We'll do spectroscopy of the
star, trying to find Porb, during Feb 16-24; and will also I hope get
photometric coverage from Israel during Feb 19-22. So assign it an
extra high priority for the next 2 weeks (deep, deep apologies for the
rampaging Moon towards the end).
The other evening star these days is BH Lyn. We've been doing
well on this star for 6 weeks now, with coverage from practically
everyone. So I'm inclined to stay on it about four more weeks. We
can't go any longer because, to be candid, once you start observing DW
UMa you're likely to be hooked for the rest of its season! BH Lyn is
rewarding, but DW UMa is the Mother Lode of permanent-superhump
delights.
So now let's talk about the UMa guy. This is definitely the best
morning-sky target this month. Maybe any month. In addition to the
strong negative superhumps and eclipses, the star may show something
else of great interest. Plot out the light curve at the end of this
letter, a long run which Tonny Vanmunster got a few days ago. In
successive orbits, the star trends up, then down, then up again - as if
there were a signal at about *half* the orbital frequency.
I've been mystified at similar things appearing in the power
spectra of other superhumpers. Only once did I really emphasize it in
print (the 1995 V1159 Ori paper), but I have repeatedly seen signals at
about half the main superhump frequency. Because this is a pretty low
frequency and our data routinely leaves the more subtle extinction
effects uncorrected, I've been unsure as to whether it's real. (Also
because it really violates my intuition - I just can't understand how
2xPorb is a natural timescale in the binary!) I really wanted some
bright star to come along and show the effect at large amplitude,
taking it out of the realm of doubt. It seems possible that Mister DW
is doing just that.
So DW UMa is surely the morning-sky target of choice. Tonny's
data is with a 10-inch, so there are no great demands on equipment
here. He used the comp star 5 arcmin SW from the variable, designated
as C1 ("primary comp") on Jonathan's official CBA charts. This star is
otherwise known as GSC 3822 72, and has an official GSC magnitude of
12.5. If you might saturate on this comp, try instead Mister GSC 3822
1157 (5 arcmin WNW from the variable); it has GSC mag = 14.4 and is our
"check star", labelled C2 on the CBA charts.
EG, BH, and DW are the entrees through the end of February.
Now SW Sex itself, the prototype of the class, is rolling into
position and sits near the equator (1012-03), giving views from all
over our planet. It would be great if our southern friends would start
the year's coverage. Then, depending on the results, we can adjust its
priority for March/April observing all over the world. I believe it
will be a friendly star, with eclipses, little flickering, and a
probable superhump.
Again I stress that we can use snapshots too. Especially for CR
Boo, HS Vir, PG1510+234 = Ser 1, V803 Cen, and EG Cnc. Each of these
stars shows very rapid photometric activity, so a high density of
observation (e.g. more than one/night) is highly warranted.
Buena suerte, I dunno how to say good luck yet in Afrikaans.
joe
Tonny's light curve, JD versus delta mag (V-C1):
9.6 hr and pretty nifty
486.3829 3.15
486.3838 3.35
486.3903 3.02
486.3921 2.62
486.394 2.42
486.3949 2.34
486.3958 2.23
486.3968 2.22
486.3977 2.1
486.3986 2.12
486.3995 2.02
486.4005 2.01
486.4014 1.98
486.4023 2.05
486.4033 2.07
486.4042 1.9
486.406 2.02
486.407 1.97
486.4088 1.94
486.4097 2.03
486.4107 1.95
486.4116 2.03
486.4134 1.93
486.4144 2.06
486.4153 2.05
486.419 2.07
486.4199 2.06
486.4208 2
486.4218 1.95
486.4227 1.96
486.4236 1.95
486.4245 2.03
486.4255 1.98
486.4273 1.92
486.4282 1.93
486.4301 1.82
486.431 1.81
486.4329 2.06
486.4338 1.97
486.4347 1.96
486.4356 1.96
486.4375 1.98
486.4394 1.97
486.4412 2
486.4421 2.07
486.4431 2.05
486.444 2.05
486.4449 1.98
486.4458 1.99
486.4467 2.01
486.4477 1.95
486.4486 2.02
486.4495 1.96
486.4505 1.99
486.4514 2.04
486.4523 2.04
486.4532 1.94
486.4551 1.96
486.456 1.93
486.4569 1.99
486.4579 1.98
486.4588 1.95
486.4597 1.88
486.4606 2.02
486.4625 1.93
486.4634 1.82
486.4643 1.83
486.4653 1.89
486.4662 1.85
486.468 1.77
486.469 1.74
486.4708 1.72
486.4727 1.65
486.4745 1.71
486.4755 1.65
486.4764 1.65
486.4773 1.62
486.4782 1.68
486.4791 1.65
486.4801 1.69
486.481 1.8
486.4819 1.77
486.4856 1.65
486.4866 1.69
486.4875 1.73
486.4884 1.73
486.4893 1.72
486.4921 1.64
486.493 1.59
486.494 1.55
486.4949 1.57
486.4958 1.62
486.4977 1.67
486.4994 1.64
486.5003 1.59
486.5012 1.67
486.5029 1.69
486.5038 1.68
486.5056 1.68
486.5073 1.81
486.5082 1.75
486.5091 1.75
486.5108 1.87
486.5127 1.94
486.5173 2.44
486.5182 2.68
486.5191 2.85
486.5287 2.45
486.5296 2.27
486.5306 2.12
486.5315 2.11
486.5324 2.09
486.5333 2
486.5343 2.02
486.5352 1.97
486.5361 1.94
486.537 1.93
486.538 1.89
486.5389 1.89
486.5398 1.88
486.5408 1.88
486.5417 1.87
486.5426 1.93
486.5435 1.97
486.5445 1.97
486.5454 1.94
486.5463 1.89
486.5472 1.89
486.5482 1.85
486.5491 1.89
486.55 1.92
486.5509 1.92
486.5519 1.9
486.5528 1.91
486.5537 1.89
486.5546 1.88
486.5556 1.91
486.5565 1.88
486.5574 1.87
486.5583 1.89
486.5593 1.92
486.5602 1.91
486.5611 1.9
486.562 1.85
486.563 1.86
486.5639 1.8
486.5648 1.87
486.5657 1.88
486.5667 1.92
486.5676 1.89
486.5685 1.94
486.5694 1.9
486.5704 1.9
486.5713 1.92
486.5722 1.97
486.5731 1.91
486.5741 1.9
486.575 1.94
486.5759 1.88
486.5769 1.88
486.5778 1.88
486.5787 1.91
486.5796 1.89
486.5806 1.92
486.5815 1.98
486.5824 2.04
486.5833 2.01
486.5843 1.97
486.5852 1.97
486.5861 1.94
486.587 1.97
486.588 2.01
486.5889 2
486.5898 1.99
486.5907 1.96
486.5917 1.95
486.5926 1.99
486.5935 1.93
486.5944 1.93
486.5954 1.97
486.5963 1.96
486.5972 1.93
486.5981 1.89
486.5991 1.97
486.6 1.99
486.6009 1.99
486.6018 2
486.6028 2.03
486.6037 2.02
486.6046 1.98
486.6055 1.94
486.6065 1.97
486.6074 1.93
486.6083 1.97
486.6092 1.99
486.6102 1.98
486.6111 1.97
486.612 1.97
486.613 1.94
486.6139 1.98
486.6148 2.02
486.6157 2.05
486.6167 2.03
486.6176 2.03
486.6185 2.02
486.6194 2.03
486.6203 2.1
486.6213 2.05
486.6222 2.03
486.6231 2.07
486.6241 2.07
486.625 2.09
486.6259 2.02
486.6268 2.06
486.6278 2.01
486.6287 1.99
486.6296 2.09
486.6305 2.1
486.6315 2.1
486.6324 2.05
486.6333 2.06
486.6342 2.08
486.6352 2.1
486.6361 2.09
486.637 2.07
486.6379 2.05
486.6389 1.99
486.6398 2.01
486.6407 2.09
486.6416 2.13
486.6426 2.06
486.6435 2.16
486.6444 2.16
486.6453 2.18
486.6463 2.23
486.6472 2.23
486.6481 2.28
486.6491 2.25
486.65 2.36
486.6509 2.33
486.6518 2.35
486.6527 2.44
486.6537 2.61
486.6546 2.93
486.6555 3.05
486.6564 3.3
486.6574 3.48
486.6611 3.99
486.6639 3.43
486.6648 3.24
486.6657 2.96
486.6666 2.85
486.6676 2.72
486.6685 2.6
486.6694 2.56
486.6703 2.48
486.6713 2.39
486.6722 2.35
486.6731 2.4
486.674 2.41
486.675 2.4
486.6759 2.38
486.6768 2.35
486.6777 2.38
486.6787 2.37
486.6796 2.38
486.6805 2.42
486.6814 2.52
486.6824 2.44
486.6833 2.49
486.6842 2.56
486.6851 2.55
486.6861 2.55
486.687 2.49
486.6879 2.5
486.6888 2.5
486.6898 2.25
486.6907 2.26
486.6916 2.34
486.6925 2.28
486.6935 2.28
486.6944 2.2
486.6953 2.22
486.6962 2.13
486.6972 2.19
486.6981 2.17
486.699 2.25
486.7 2.23
486.7009 2.22
486.7018 2.26
486.7027 2.19
486.7037 2.17
486.7046 2.21
486.7055 2.2
486.7064 2.32
486.7074 2.32
486.7083 2.33
486.7092 2.38
486.7101 2.38
486.7111 2.4
486.712 2.35
486.7129 2.34
486.7138 2.35
486.7148 2.33
486.7157 2.37
486.7166 2.32
486.7175 2.35
486.7185 2.29
486.7194 2.37
486.7203 2.33
486.7212 2.36
486.7222 2.28
486.7231 2.3
486.724 2.29
486.7249 2.23
486.7259 2.22
486.7268 2.22
486.7277 2.16
486.7286 2.2
486.7296 2.18
486.7305 2.24
486.7314 2.3
486.7323 2.3
486.7333 2.34
486.7342 2.3
486.7351 2.26
486.7361 2.22
486.737 2.16
486.7379 2.19
486.7388 2.12
486.7398 2.16
486.7407 2.13
486.7416 2.17
486.7425 2.15
486.7435 2.15
486.7444 2.13
486.7453 2.09
486.7462 2.16
486.7472 2.12
486.7481 2.11
486.749 2.13
486.7499 2.05
486.7509 2.07
486.7518 2.05
486.7527 2.04
486.7536 2.07
486.7546 2.04
486.7555 2.05
486.7564 1.99
486.7573 1.97
486.7583 1.96
486.7592 1.95
486.7601 2.01
486.761 1.95
486.762 2.01
486.7629 1.95
486.7638 1.99
486.7647 1.95
486.7657 1.96
486.7666 1.98
486.7675 2.05
486.7684 1.97
486.7694 1.95
486.7703 1.94
486.7712 1.97
486.7722 1.96
486.7731 2
486.774 2.03
486.7749 2.04
486.7759 2.07
486.7768 2.06
486.7777 1.95
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