(cba:news) early may stellar menu

Joe Patterson jop at astro.columbia.edu
Tue May 6 22:12:59 EDT 2014


Dear CBAers,

     The month of AY Sex has come to an end.  The HST spectroscopic 
observation (basically a time-resolved 1100-3000 A spectrum) was 
beautiful and a humdinger - looked practically like a quasar spectrum 
(numerous very broad and generally high-excitation lines... and a few 
weak mystery lines).  Thanks for all the coverage!

     Also time to ring the curtain down on DW UMa and OT1759+25.  It 
would, however, be good to continue observations of T Pyx, HP Lib, and 
perhaps AM CVn.  These are not quite ripe yet in their 2014 coverage.

    May-June-July is high season for classical novae, and let's go get 
'em.  I've become ever more fascinated by their orbital light curves 
over the few decades after eruption.  Early in the decay, the light 
curves look like classic reflection effects, as if the secondary is 
merely reflecting the incident light from the hot white dwarf ("heating
effect").  Then it can acts as a bolometer for the white dwarf, long 
after the supersoft X-ray source has disappeared.  We've tested this out 
for one nova, and managed to follow T_wd down to 120,000 K. That was a 
thrill for me; the X-ray telescopes can't detect anything south of 
300,000 K.  Later on, it seems to get more complex... but anyway, the 
point is to obtain orbital light curves season by season.  Within the 
first 5-10 years, the changes are most obvious - presumably since the 
white dwarf cools faster then.  We've started similar programs on NR 
TrA, V1494 Aql, V339 Del, V959 Mon, V2491 Cyg, V382 Vel, V2362 Cyg, and 
V1500 Cyg.  Some of these are off-season, but bear 'em in mind.  Also, 
smapshot estimates of magnitude will be very helpful too.  These stars 
are pretty neglected years after outburst... so we often don't know 
whether they're feasible targets (until you look).

    Also, the most recent novae (2013-4) are of great interest too - 
we'd like to know exactly when the orbital wave first appears.  This is 
probably the exact time the ejected shell goes transparent - out first 
look at the underlying hot white dwarf.  By comparing that to the time 
the soft X-rays first appear, as seen by the SWIFT satellite, we'll get 
our theory tested.

    While we're on the subject of heating, there's *dwarf* novae to 
think about too.  V355 UMa and GW Lib are both WZ Sge - type dwarf novae 
which had recent outbursts, and both contain pulsating white dwarfs as 
well.  Still well placed in the sky, but somewhat challenging for 
brightness.

     For very lengthy runs on northern stars, my #1 recommendation is HS 
1813+6122 (J2000: 18 14 29.83 +61 23 34.3) = "Dra" in Downes catalog. 
Decently bright star, very very likely to show superhumps.  And it's 
time also to do a campaign on UX UMa, which we have criminally avoided 
all these years.  Perfectly placed in the night sky.

    Scrambling to get my SAS/AAVSO paper in.  It's wonderful that so 
many of you are coming this year.

joe
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