From jop at astro.columbia.edu Sat May 11 19:12:42 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 11 May 2002 19:12:42 -0400 (EDT) Subject: (cba:news) Warning: IY UMa virus Message-ID: Sorry ... cheap trick. I'm sure it's actually perfectly safe to observe IY UMa. But despite all the pleasure and science this star brought us in the spring of 2000, I thought we should pass it up this time around. Basically because I can't imagine our getting better coverage than last time around, and because "the night is very large and full of wonders". Prime northern target remains RX1643+48. Any help from European longitudes on this guy? It's quite bright and would help tame those infuriating May twilights. The coverage so far suggests an intricate network of finely spaced periods... great grist for our mill if we get coverage sufficiently extensive. Contributions from all longitudes eagerly sought! If you have a longitude, we'd love your data. We're not doing well with GP Com... it's a little too faint and too inactive to be popular with CBAers. So off the stage it goes. The best first target is our old friend CR Boo. Down south, V803 Cen seems to have gotten too faint to keep observer interest up. But it's worth keeping a close eye on. We started this year's campaign with a superoutburst, and should keep the faith till the next super, so we can basically cover one full cycle. In the evening, I'd say CR Boo and V803 Cen are the best targets. In the southern morning sky, it might (or might not) be worth keeping up the watch on V2051 Oph. Berto, Bob Rea, and Jerry Foote have been visiting this star, so we have good round-the-world coverage. I guess my comment is: if it's still bright enough to get a good signal on, then continue... and otherwise not. (It has jumped around a bit, and I'm a bit puzzled by its eruption state.) Sorry I've been so quiet lately. End of semester. Final exam Tuesday, graduation the week after. Just ahead lies freedom. joe From jop at astro.columbia.edu Mon May 13 08:45:12 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 13 May 2002 08:45:12 -0400 (EDT) Subject: (cba:news) V2051 Oph Message-ID: A new batch of data from Berto clarifies the state of this star. It remains in an extended outburst state, and the light curves continue to show deep eclipses and big superhumps. Definitely a CBA green-light special, and the southern star of choice in the midnight and morning skies. It would be great to get some coverage from the Americas too, to complement Bob and Berto. Jerry, can you keep the faith on this guy? Greg and Neil, what about Australian honor? joe From jop at astro.columbia.edu Wed May 22 07:57:14 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 22 May 2002 07:57:14 -0400 (EDT) Subject: (cba:news) stars for may-june In-Reply-To: Message-ID: Hi Berto (and CBAers), It's too early for me to figure out much from that stretch of light curve... but the object sure looks interesting enough to follow! So we have kind of a crisis in the southern morning sky these days. V2051 Oph is still in outburst and still producing great humps and eclipses... we have a lot invested and it would be awfully nice to keep going. It will surely teach us a lot about the timescale for superhump demise (which has become a potent constraint on theories - last year's flavor said "they die when the superoutburst dies", but one popular flavor this year says "they last forever"). That V4641 Sgr is interesting needs no explanation. Then there are round-the-world campaigns we want to trigger soon on V603 Aql and especially V1494 Aql. Oh, how we love these equatorial stars! Finally there's V803 Cen, still well placed and having not yet completed a full supercycle. That's what we seek - coverage of a full supercycle. I imagine we're around 70% of the way through it - but we dunno without keeping the vigil. Anyway I think it's *really* important to get occasional potshots (few a night maybe - that's Stan Walker's pace) at its present low light level - before resuming some normal time series early in the next super. That would be a good time to say goodbye. If for example we could cover it enough to know what the outburst repitition time is at 17th mag (i.e. the 17->14 burps), that would be outstanding - the only dwarf nova in the sky where we can measure recurrence time at two different brightness levels (17 and 14.5 - what a grand experiment)! Anyway since V4641 Sgr is bright now and the lure of the unknown is great, I guess we should work pretty hard on it for now. Early evening is still good for V803, and we can keep the Aquila boys at bay for a few weeks. So that's good. V2051 Oph will definitely suffer, and I just hope you australites can find a way to keep its suffering minimal. Maybe a couple of you (Bob Rea maybe?) can keep the faith on Oph... Looking forward to meeting many of you at Photometry 2002 in NZ in September! It's simpler in the north. The campaign on RX1643+34 is wonderful beyond words. I'll try though. Captain Bob and Ed Beshore (CBA-Colorado) have come roaring back into action, and Dave Skillman, Brian Martin, and Tonny Vanmunster have kept up a withering barrage. We've identified the orbital period, the (negative) superhump period, and the wobble period (3.9 days). All very nice. But the most interesting thing is the 1000 s QPOs, which everyone observing the star gets drawn to - they're very strong, very distinct, and sometimes look pretty damn coherent. With 42 nights of coverage (now up to ~55), the mean power spectrum shows the basic story I think. The main signal is a broad QPO covering 60-110 c/day. That's responsible for the obvious large-amplitude flickering. But in that broad signal appears to be a stable peak at 82 c/day, a feature that may enable precise timing over the 2-month campaign (jury still out on that one). The bottom line I think is to go for ~1-2 more weeks on RX1643, when I'll reevaluate. It would be nice if one of the borealites would start up the campaign on V795 Her though... another bright novalike with powerful and relatively stable superhumps (which have just returned to action after a 10-year vacation). joe From jop at astro.columbia.edu Thu May 23 13:54:01 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 23 May 2002 13:54:01 -0400 (EDT) Subject: (cba:news) change in the north! Message-ID: Dear CBAers, I think it's time to end the campaign on RX1643+34. The star has flashed some nice (negative) superhumps at us, and we know the orbital period to better than one part in a thousand. Plus some other nice results on flickering and QPOs. Nice star, but we'll retire it. Staying in the same constellation (and brightness), let's shift to V795 Her. This star has much bigger superhumps, recently reactivated after 14 years of vacation. Great target for May and June. Some people might wish to do a fainter star; V849 Her would be a nice choice. It's kind of a mystery to us. Two nights last year showed little variability, yet ten years ago there were very strong waves in the light curve. I think those are the best northern targets these days. joe