(cba:news) stars of september
jop at astro.columbia.edu
Mon Sep 18 06:19:45 EDT 2006
Sep 18, 2006.
Time for moving on to new targets.
The second of this year's campaigns on V1223 Sgr has been quite good, with
coverage from Bob Rea, Berto Monard, and Bruce Dickson. The behavior of
the pulse timings over the season is certainly the best-documented ever
for this neglected star. The issue of a superhump signal still awaits
further analysis, in particular an allowance for differential extinction
over the night (which I usually neglect or treat only roughly - but here
it's important, because the observations are fairly late in the season).
Anyway, the season has run out and it's time to move on.
Also time to close the books on V Sge. Great coverage by Pierre de
Ponthierre, Bob Koff, and Tonny! But we have a very precise orbital
light curve, which was the goal - so let's sweep it off the stage.
Likewise for the other stars on the prime list. V1830 Sgr never got much
attention, though probably enough to track the pulse. Now clobbered by
twilight. V1494 Aql coverage was adequate to specify the orbital waveform,
thanks to Bob Koff and Jerry Foote... that's good enough, let's quit.
Thus do all the primary targets vanish. The secondaries are eroded too.
Oph, Her, and V419 Lyr are now out of season, and CI Aql was too faint
for most CBAers. Out with all of 'em. Remaining are the pulse-timing
stars: mainly AO Psc and FO Aqr. These are always attractive targets when
you have only 1-3 hours, because their periods are very short (14 and 21
min) and continued coverage is always needed to track the slowly evolving
The best northern star for these Sep/Oct nights is certainly RX0022+61,
or 1RXS J002258+6141 if you're a stickler. We found the periods in this
star very late last season, so they're defined only over a very short
baseline. Let's wring out its secrets this year! An intensive campaign
over the next 6 weeks will do the job nicely, and with that handy
declination you could perhaps get this star all night long (which *really*
helps with differential-extinction issues). BTW ignore the Downes et al.
"V=18" - the star is much brighter, and the pulse/orbit signals are very
healthy. Unless the star has faded a lot from last season, you can
definitely get good data from this star.
The best southern star is certainly EF Tuc = RX0001-67 = EC2359-67. We
obtained a lot of data three years ago, which showed strong periodic
signals. Let's get another season's worth and go to press!
Now for some others - mostly northern, but some southern. Some of these
are equally if not more interesting, but I demote 'em slightly for the
simple reason that they're tough targets for small scopes. But they're
not equally tough for everybody. So if you have a good night and good
telescope at hand, take a crack at 'em!
WZ Sge stars. Our favorite! Unfortunately these stars have never gone
into outburst, so they are still denied the banner headlines that CVs
crave. But we press on with our covert photometric studies... and are
readying papers on these two bookended north & south guys. These are
HS 2331+39 ("And") and BW Scl. They're pretty challenging at 16-16.5,
but their orbital light curves have a decent amplitude and can be well
specified by good-quality observations from relatively small scopes.
We definitely need another season to whip these stars into shape.
MN Dra (2023+64). There is some strange data out there on the periods in
this star. We can only observe in outburst, and we've never caught one.
Can you keep an eye on this star, and sing out when it erupts?
Cep 1 = GD 552 (2250+63). Same story there, but an eruption is very,
very unlikely. None have been seen in history. Generally at 16.5.
HS0417+7445. An SU UMa star for which the period is still unknown.
Presently in (super?)outburst, so probably a very fine target for the next
I think I've been a little unfair to the south here: just two stars, plus
two equatorial. Berto or Grant or some other australite might want to
make a comment or suggestion...
As usual, it's generally a good idea to keep after a particular star, not
jump around a lot. The reason is that our enterprise is designed for
period-finding, and that works better when we have fewer issues of
calibration between observatories. If you get ten nights of data on one
star with a fixed comparison star, that really simplifies calibration
issues. On the other hand, it isn't a fixed rule! Noisy and flat light
curves are no prizes either. So use your judgment re that.
I recently received a draft of a paper on the dwarf nova V1316 Cygni from
David Boyd, reporting CBA coverage of the summer 2006 eruption. The paper
is of professional quality and needing very little revision to be journal-
ready. Now I don't know David - maybe he's a closet professional scientist
(like Berto and Dave Skillman). But it reminds me that CBA really ought
to operate with the data more widely shared among observers, and CBA
observers should be encouraged to do analysis of entire data sets on
particular stars. This would really streamline the reporting of data!
Our data sets are typically very large, by far the best in the CV world
for time-series studies... and you would find scientific writing not
difficult once you get the hang of that strange "just the facts ma'am"
writing style. If you're a CBA observer, this data is available right
now - just ask! Me and Jonathan, that is. It's possible that I can steer
it to you in a slightly editted form, and Jonathan can get the original
submission to you right away. (In a few months we hope to install a
system whereby you can get it automatically, but we have to design and
password-protect that system.)
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