From jop at astro.columbia.edu Thu May 3 10:19:16 2001 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 3 May 2001 10:19:16 -0400 (EDT) Subject: (cba:news) A Plea for CR Boo Message-ID: Dear CBAers, May 3, 2001. You norteamericanos know that a high-pressure dome has settled over the Northeast, and we're (Dave Skillman, John Stull, Dave Toot) getting lots of great data on a very cooperative CR Boo. Any prospect of help from other longitudes? Even the western US would help a lot, and observations from AU/NZ/Europe/Oceania/Asia would be precious! CR Boo appears to be *triply* periodic - like AM CVn - near the orbital period of ~1480 s. The exact identity of Porb is unclear, though. The 1471 s signal found by the Whole Earth Telescope is obvious in the data, but since there are two other periodic signals at slightly longer period, it's not clear which should be called Porb. Anyway with such a cornucopia of signals tightly nestled in there, we really REALLY need to beat aliasing problems into submission. Not the easiest of fields, and the Moon will be ravaging it soon, but let's try to nail this sucker as soon as possible! Presently cycling in the range 13.7-14.7 with a cycle time of about 16 hours (weird huh?). joe From jop at astro.columbia.edu Wed May 9 15:25:14 2001 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 9 May 2001 15:25:14 -0400 (EDT) Subject: (cba:news) Helium stars for May nights Message-ID: Dear CBAers, May 9, 2001. Still lusting here in the Big Apple for data on CR Boo. Dieter Husar reports that it has gone into a low state at 16.5. That plus the bright moon may explain the paucity of CBA data over the last 10 days or so. Many of you will strain to get decent signal-to-noise at this light level, but there is so little coverage in the low state that your data are likely to be quite useful even if it's pretty noisy. It's also time to start our campaign on HP Lib. This one is magnitude 13.5, and reasonably equatorial (-14 degress), so available to all. Rated G, suitable for all audiences. The period we're trying to track is near 19 minutes, so keep the exposures short. Fire away on both stars. I'm just grading my final exam today, so my correspondence and data analysis will suddenly become much more prompt! joe From jop at astro.columbia.edu Sun May 20 12:27:53 2001 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 20 May 2001 12:27:53 -0400 (EDT) Subject: (cba:news) AL Com and competitors Message-ID: Dear CBAers, 5/20/01 AL Com's recent jump into superoutburst made me ponder the issue of whether to start a campaign. Tonny's note made me realize that I should not just ponder it but say something about it. So here goes. At 13th mag and as a member of a select and interesting family (the WZ Sge stars, the most reluctant of the SU UMas), AL Com is certainly a tempting target. And it may well turn out that observations over the next 3 weeks will provide important new information about this class and its superhumps. You never know till you try. Nevertheless, with some uncertainty I'm going to recommend not. Here's why. (1) We got very good coverage of the 1995 eruption, and I'm doubtful we can improve on it now. This is especially true since some of our most established observers in the USA have been off the air for some time now, meaning that we'll have to rely a lot on Europe where we have mainly small telescopes and short nights. (2) It would mean curtailing the CR Boo campaign, which I dearly hope can continue at least until the next full moon in 2 weeks. The continuity of coverage is important. (3) It would delay the other campaigns on May targets, namely HP Lib and V849 Her. (4) The Ouda group appears to be pouncing on the star and will probably do a good job with it. Of course it would be best to collaborate with them and thereby have the basis for a better study; but until that happy day arrives, it seems generally sensible not to compete on every interesting CV that pops off up there. (5) Finally - I guess this is a variant on (1) - I have some disinclination to reobserve a dwarf nova that has once been extensively observed in the same luminosity state. True all the more in this case since I expect this year's observations would be less extensive, but also because of an astrophysical reason: that the most subtle effects in superhumps -- especially the displaced "quasi-harmonics" -- tend to occur in novalike variables, not dwarf novae. Why? Well, possibly because dwarf-nova disks rapidly evolve, not remaining stable long enough to permit our period-search efforts to reach high sensitivity. In the fullness of time, I guess we'll learn what are the smarter strategies; at present, just chalk it up as a prejudice. By the way, I certainly don't apply this to the enterprise of accurate measurement of principal superhump periods! I think that's really important; newly discovered superhumps are golden! So the bottom line is that I'd like to keep the focus on CR Boo and HP Lib, with a new campaign starting up as soon as practical on V849 Her. But re AL Com, I'm still a very interested spectator! joe By the way, I should report that the 2001 RZ LMi campaign, led and somewhat dominated by Jeff Robertson and Tut Campbell, was extremely successful. It certainly appears to prove that the superhumps really do linger throughout the interregnum between superoutbursts, contrary to folk wisdom (and to my above dissing of dwarf novae). Still not clear if the superhumps actually maintain *phase* between adjacent supermaxima, though. From jk at cbastro.org Thu May 31 22:39:34 2001 From: jk at cbastro.org (Jonathan Kemp) Date: Thu, 31 May 2001 16:39:34 -1000 (HST) Subject: (cba:news) notes from cba hilo Message-ID: Hi CBAers, 31 May 2001 I just wanted to pass along some notes on data submission and a few other topics, especially for some of our newer members. We generally prefer data in a two-column (julian date vs var-comp delta mag) format. Occasionally, CBAers will contribute a third column such as airmass or check-comp delta mag, which is occasionally helpful. Usually, most other columns aren't overwhelmingly useful and, given our familiarity with the stars and our receipt of data from various stations with different instrument compliments, we are able to evaluate things such as noise level and measurement error without a slew of extra columns devoted to all the field stars or a set of error bar measurements. And, when dealing with various sorts of data, the simplicity makes our lives easier! For those wondering about heliocentric corrections, we slightly prefer to add them in ourselves. However, most important is that you are consistent and that submissions to the data archive are labeled as JD (or as HJD, in those rare cases). And, we generally adhere to specifying the *middle* of the integration in our timings. Also, for those of you unaware, we highly recommend sending data directly to the data archive (data at cbastro.org). The advantages of this include the file getting automatically archived and sorted before being forward on to Joe and I, and, when it comes time to compiling observing logs and checking to make sure we have all data sets, this is quite useful. [If you have data files you've already submitted to Joe and would like to send them to the archive, please send them to data-old at cbastro.org.] More information on data format and submission can be found at https://cbastro.org/data/. And, to continually keep track of data sets submitted to the archive and provide recognition to those who contribute, the listing of data sets submitted to the archive is posted monthly at https://cbastro.org/archive/. At some point in the near future, I would like to start including reviews of some sort on our web site. These might include review of those pieces of reduction software, types of CCD imagers, or models of telescopes that are either common or useful to members of the CBA. If you consider yourself fairly familiar with something on which you would like to contribute a short piece, please let us know! For those who might have missed it, the Catalog and Atlas of CVs is now online at http://icarus.stsci.edu/~downes/cvcat/. This is the one by Downs et al. that had several hardcopy iterations and now lives in cyberspace with frequent updates. Also, we will soon be revising the network pages to include some of our newer members. If you haven't noticed the link before, please feel free to visit https://cbastro.org/forms/station.html to let us know more about your station and setup. You can also find this link at the bottom of every network page. If you've submitted before and merely need to update an entry or two, you needn't worry about the other fields. And, as we hope to issue a new CBA newsletter following my upcoming New York visit, please let us know if we don't have your postal address or if your postal address that we have has changed. Lastly, I just wanted to let you know that we have essentially fully phased out the last remnants of our operation on the old cbastro.org server, so please be sure to use web and e-mail addresses for cbastro.org! Anyway, that's about all from CBA Hilo. I'll be in New York in a few weeks to meet with Joe about various CBA issues. And, oh yeah, I got married a fortnight ago! :-) Jonathan CBA Hilo