(cba:news) july stars
jop at astro.columbia.edu
Thu Jul 5 06:54:29 EDT 2007
Time for a major overhaul of targets. GW Lib has been center stage, and
has continued to flash superhumps to the present, even 3 months after
outburst. But the data are getting ratty and the signal isn't changing
much - so the returns are diminishing. Those of you who have been
observing it a lot might want to keep visiting it for another month or
so... but I'm going to demote it to secondary.
No dwarf nova cries out for immediate attention, so we pass to novae and
We have a long baseline of data on V1494 Aql. I dunno how bright it is
now (17?), but it would be *great* to see what has happened to its 3.4
hr orbital signal. The latter is powered by the white dwarf's
underlying supersoft X-ray emission, which is not directly observable -
but can still be probed by a proxy signal (the reflected light in the
orbital signal). This would give us an 8-year baseline for supersoft
study - by far the best available. The star sits on the celestial
equator and transits near midnight. Very, very tempting target, if you
can handle the faintness.
Another equatorial target that has been good to us is V1432 Aql. This
is an asynchronous AM Her star, in which rotation has been slightly
de-synched from orbit, possibly from the effect of a (putative) nova
eruption. We've been tracking it for some years, but missed the last
two. Time to re-establish the rotation ephemeris (another 3.4 hr wave).
Lotta DQ Her stars on the menu too. These are perhaps more suitable if
you don't do much observing - on the grounds that observations yield
mainly a pulse timing (mean pulse arrival time of the rapid signal), and
scattered pulse timings usually suffice to establish a yearly
ephemeris. For most of our program stars, though (as you well know if
you've been reading these missives!!), we need many long runs on
Anyway, the relevant and easy DQ Hers are AO Psc and V1223 Sgr. Others
that are not so easy are DQ Her and RX1730-05 (=Oph); these require
pretty fast photometry (time resolution better than 20 s for sure) to
resolve the fast pulses. And another tough one is RX1803+40, mainly
because it's pretty faint.
DQ Hers haven't been so popular among CBAers, but you might want to
adopt one of these stars and try it out.
Two key northern stars this month are MV Lyr and V533 Her. The former
is in a low state and possibly invisible to CBAers; but if you can see
it, it's a great target to study for a possible orbital signal (which
would constrain the existence of an underlying undetectable supersoft
source). It's mighty faint though (18?), so might need special
techniques. V533 Her is plenty bright at ~15, and we want to study it
for orbital/superhump signals (your job) and for rapid pulsations (my job).
We start an observing run on Kitt Peak on July 12, and some quick
re-arranging of priorities may occur around then. Plus of course for
the latest greatest star that pops off up there...
btw this replaces all the stars on our page-one, which has been getting
mighty brown around the edges...
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