From jop at astro.columbia.edu Tue Feb 13 10:38:48 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 13 Feb 2007 10:38:48 -0500 Subject: (cba:news) Stars for February Message-ID: Dear CBAers, U Gem has dropped to quiescence now, there to remain, presumably, for another 80 days or so. I hope you can keep up occasional coverage for the duration. We'd like to study the hump eclipse and eclipse structure throughout the inter-outburst cycle. Because U Gem presents a uniquely favorable geometry for studying the mass-transfer bright spot (spot eclipsed but not the white dwarf and inner disk), this star can yield detailed information on variations in hot-spot brightness and location. If you do try to keep vigil on U Gem, try to keep the integrations pretty short (30 s?) to cleanly resolve ingress and egress... and I recommend white light to raise signal-to-noise. It's vital to use the same comparison star always; but if you used one in eruption and it's now too bright, then select another - making sure that you tell me. We do not, however, need nightly coverage on U Gem. Just keep hammering away a couple times a week... and then we'll increase the frequency when we can smell the next outburst. In the south, Bob Rea has been keeping a solitary vigil on WX Pyx. This is 17th mag but still a fine target for a 14", since it's a large- amplitude DQ Her star. We have a good ephemeris for 2007... and can now wait about 60 days before obtaining a little late-season coverage to jump the cycle count back to 2006 (and thereby secure it for a decade). We can also back off RR Pic - Grant Christie got some data which will secure its cycle count. The two top southern objects now are T Pyx - we only need a 2-3 week observation, but it needs to be dense (a dozen long-duration time series would be great!) - and Swift 0732-13 ("Pup"). Remember the latter? We had a very extensive campaign last year, and proved it's yet another DQ Her star. The light curve looks very flat, but this is caused by a very nearby reddish star diluting the light of the CV. This doesn't much harm the rapid pulsation we seek to study, though. In the north, I recommend three of the new targets for this year: Aur = RX0636+35 Gem = RX0704+26 Lyn = SDSS0804+51 All DQ Her stars which we've been endeavoring to follow closely during the season. The U Gem eruption forced a hiatus - but let's get back on track. They're all pretty close to 16th mag and have large-amplitude fast pulsations. Olde Whiteface has wheeled out of the way again, Venus has reappeared with gusto, and even Mercury popped up to say hello last week. (Us borealites haven't seen it much in the last decade; all the good elongations are southern.) Great time to be observing! joe