From jk at cbastro.org Sat Dec 4 19:06:44 1999 From: jk at cbastro.org (Jonathan Kemp) Date: Sat, 4 Dec 1999 17:06:44 -0700 (MST) Subject: (cba:news) data archive Message-ID: This is just a quick note to let you know that a list of data sets submitted by CBAers (to cba-data at cbastro.org) will now begin to appear at our web site approximately monthly. Just follow the 'data' link on the navigation bar... Jonathan CBA Oracle From jop at astro.columbia.edu Wed Dec 8 17:40:05 1999 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 8 Dec 1999 15:40:05 -0700 (MST) Subject: (cba:news) New Stars for December Message-ID: OK, it seems that no one particularly wanted to revive AO Psc or V709 Cas for encore performances. I give up, let's move on. Just heard a report that DV UMa erupted - now that's a very happy thing! DV UMa is an eclipsing dwarf nova, so the eclipses enable mapping of the origin of the accretion disk light (i.e. its precise location in the disk). Definitely the top priority for us. We got fair coverage of the last outburst in 1997, but just enough to whet the appetite. The other main star for coverage is Tau 2, suitable before DV UMa rises. Early coverage suggests a superhump, always nice to find (because they're illegal) in these long-period systems. I promise not to crave anything else, if we can only get coverage of these two stars (both around 14.8 I think; moon's outa the way, so should be fairly easy). But for southerners, CN Ori season has started. That's the best target for long runs these days from the south. My parole hearing comes up in 12 days. Trying to stay on my best behavior. joe From jop at astro.columbia.edu Fri Dec 10 15:17:22 1999 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 10 Dec 1999 13:17:22 -0700 (MST) Subject: (cba:news) Vacillation, except for DV UMa Message-ID: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ He has sounded forth the trumpet that shall never blow retreat, He is sifting through the stars and tells the chaff from the wheat. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Well that's supposed to be so, but don't count on it. Last message, a fickle wind blew in and swept away AO Psc and V709 Cas. Now I'm having severe doubts about Tau2, which is throwing some very disagreeable noise at us, and no obvious periodicities. Therefore, at the risk of incurring your wrath and exasperation, I'm taking Tau2 off the menu. I hope that CBA eyes will devoutly turn to DV UMa! Haven't received any data yet, but am very hopeful. We got some data from superoutburst in April 1997, but really need another for a proper study in that state. (The light curve is on the homepage, by the way.) Then there's FS Aur. I won't be fickle on this star! It has a fascinating light curve at a period completely discrepant from its spectroscopic period, which is 0.0595 d. That would be a great first object of the night. V405 Aur = RX0558+5353 is pretty good competition in the same part of the sky. And CN Ori is the best southern star du jour. As soon as our australite friends get going, I'll start bugging the borealites so we can get extended longitude coverage. Any luminosity state is just fine (true for all the others too). It has finally turned cloudy (in fact stormy) in Arizona. So we are really desperate for DV UMa! joe From jk at cbastro.org Mon Dec 13 12:44:18 1999 From: jk at cbastro.org (Jonathan Kemp) Date: Mon, 13 Dec 1999 10:44:18 -0700 (MST) Subject: (cba:news) cba preprint - v803 cen Message-ID: A new CBA Preprint on V803 Centauri can now be found on the publications page of the CBA web site. www.cbastro.org/publications Regards, Jonathan ----- V803 Centauri, A Helium-Rich Dwarf Nova Joseph Patterson, Stan Walker, Jonathan Kemp, Darragh O'Donoghue, and Marc Bos Publications of the Astronomical Society of the Pacific (submitted, December 1999) We report 1992-1999 photometry of the helium-rich cataclysmic variable V803 Centauri. In its high-brightness state at V=13, the star shows a strong periodic signal with P=1618 s; this resembles the superhumps associated with many dwarf novae. However, it is unusual because the superhump endures through all brightness states, including the very faint state at V=17. The star also becomes occasionally stuck in a "cycling state", in which the brightness varies in the range 13.4-14.5, with a period of 0.98 d. This appears to be the recurrence pattern of "normal" dwarf-nova outbursts. Thus the underlying physics is probably that of a dwarf nova, but with an accretion disk dominated by helium. Reckoned as a dwarf nova, V803 Cen presents an interesting test for accretion disk theory, because it appears to display two timescales for eruption recurrence: 0.94 d at V=14.5, and ~5 d at V=17.2. This is roughly consistent with the general idea that recurrence time scales inversely with accretion rate. From jop at astro.columbia.edu Tue Dec 21 14:07:32 1999 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 21 Dec 1999 12:07:32 -0700 (MST) Subject: (cba:news) DV UMa and V405 Aur Message-ID: Dear CBAers, DV UMa has faded a lot and the Moon is nearly full, so that campaign is now over. Poor weather made our coverage a bit scattered, so it was much less successful than I hoped. Although we definitely have enough to determine the superhump period with good precision, we don't get that much information out of our sparsely covered eclipses. We do have very good coverage at *minimum* light (about 18.8) earlier in the year, plus fair coverage from the 1997 superoutburst. So here's what I suggest. Send me whatever bits you have left from the 1999 coverage. This will help fill out the in-progress DV UMa study. But the people at Ouda (Uemura and Kato) have asked several of you for data to accompany and fill out their time series, and my guess is that they've done a very good job with coverage of this outburst - that the scientific return is maximized by making your data available to them. So I recommend doing that. Who knows, maybe it will even lead eventually to erasing through collaboration our one zone of ignorance on the planet (Asia-Pacific in the north) - which we've been hoping for for years. I'd use the data too but at a much lower level, probably just to measure the period and compare with 97. On another subject, we've started an intensive campaign on RX0558+5353 = V405 Aur. This star should survive moonlight quite well, so now's the time to hit it with your full fury. 7-10 days of coverage should do the trick. Onrushing twilight has probably clobbered IP Peg, but U Gem season is just starting and we have a nice collection of orbital light curves. We should try to document how all these change in the weeks leading to and following outburst. Very rewarding star to observe! Parole board met and grudgingly authorized me to leave. But I'm still here and having trouble getting outa here. A lingering aftereffect of Life in the Little House. joe