From jop at astro.columbia.edu Fri Jan 4 17:31:14 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 4 Jan 2002 17:31:14 -0500 (EST) Subject: (cba:news) HV Vir jumps into superoutburst, probably Message-ID: Dear CBAers, Patrick Schmeer just found another very lazy dwarf nova in eruption, around mag 12.5 or so. It's HV Vir, last glimpsed by small telescopes in 1992. It's likely that the present outburst is a super, in which case we'll definitely want to train some telescope power on it. The only drawback is the RA - Virgo isn't ideal this time of year. On the other hand, it erupts only once every decade or so, so we can't be too finicky... and with good longitude distribution for equatorial stars, we can hope to track it fairly well even though no one observer can get really long runs. It's a classic CBA target, calling for long time series in (predominantly) unfiltered light... patch some different longitudes together, and we'll get very good coverage. Definitely the prime after-midnight target out there. Likely to display a rich superhump structure like WZ Sge - which flashed 17 noncommensurate periods! For southerners, TX Col is priority one now; Fred and Jennie kicked off the season with a great run on January 2. Bob, it's time to bring the BW Scl campaign to a close. The other object I wanted to put forward now is T Pyx: we've been timing the orbital hump now for 6 years, and are on the verge of being able to nail down the orbital ephemeris over a 15-year baseline. The results suggest, but do not conclusively prove, that the period is increasing on a timescale of ~5x10**5 years. This would require a powerful mechanism for self-destruction in the binary. But first we need to know sure: is it really blowing itself apart that fast? For northerners I'd recommend FS Aur and/or BK Lyn as the early targets of choice, followed by HV Vir. It's presumably the last call for HV this decade, and the data should be quite gorgeous... what's a little winter chill compared to that? joe all targets on "charts" page of website. From jop at astro.columbia.edu Sun Jan 6 13:52:08 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 6 Jan 2002 13:52:08 -0500 (EST) Subject: (cba:news) HV Vir Message-ID: Well, it's definitely a super, and I hope you folks can capture those precious photons before they fade. Arne Henden sent me some good comp stars - quite a few, but I picked out a couple for special recommendation (not too red, and suitably bright, and probably on everybody's chip). Namely, a V=14.10 star 2.0' W and 1.35' S from HV Vir (the bright star at the lower right of the Downes et al. chart - the one at the CBA website), and a V=16.24 star 3.6'E and 1.2' S from HV Vir (off the Downes et al. chart). The first star is best - it will serve you for most of the eruption, quite possibly all of the eruption. A great comp star. But with the larger telescopes, you might saturate this star late in the eruption, and might want to shift to the second star (or some other fainter star in the field, as long as you tell me which it is). Ooooo, another wz sagittae star erupts, that's exciting. I'm not sure that the southerners, with those short nights, can get it... but borealites should have a lot of fun with this star! joe From jop at astro.columbia.edu Thu Jan 17 13:24:02 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 17 Jan 2002 13:24:02 -0500 (EST) Subject: (cba:news) stars for jan-feb Message-ID: Dear CBAers, Time for a revisit of targets... It's a good time to take TT Ari off the rolls. The star appeared to flash its negative superhump throughout the season; the latter appeared for the first time in 1997, and has presumably been going strong ever since. This long baseline will furnish the data for a nice study of period stability. I had hoped that the positive superhump would accompany, which would then give us the opportunity to study *simultaneous* period changes in both types - this would be a very valuable discriminator among candidate models. It'll take close analysis to be sure; but so far it appears that the positive SH was too bashful. V603 Aql is I guess the ideal star for this experiment - but then becomes mostly a project for australites, since the short summer nights hamper sensitivity in period studies (in Aquila) for us northerners. We'll fire that project up in May. So exit TT Ari. Now let's talk FS Aur. The coverage has been really great, led by Major Tom and Captain Bob. I have a moderately long-term ephemeris - 4 years - describing this mysterious 3.4 hour photometric wave (mysterious since the binary period is 1.4 hours). To my surprise, no other signals appear in the time series - CVs are usually pretty sassy in all the hard-to-understand structure in the power spectrum they shake at you. Anyway, I think the best strategy is to take it off the menu NOW, then fire it up again for a brief reprise in March/April - the extra 60 days of baseline will establish the period sufficiently well to bridge to next season, and quite possibly backwards to encompass all known light curves. So exit FS Aur too. The star I'd like to promote for northern coverage during the next month is BZ CAM. This star tortured us in 1994, with its 3.2 hour waves which were not quite periodic yet not quite nonperiodic either. It's an all-night target for all northerners, and at magnitude 12.7 is suitably bright for everybody. I hope we can get very long light curves for a few weeks, which should be sufficient to decode even a fairly complex spectrum of periodic signals. I'm really counting on our friends in Europe, since I know from experience that this star does not readily yield its secrets to fixed longitudes! Late in the night, for all hemispheres, HV Vir is the star of choice. We're getting decent coverage, but limited by the season of course since Virgo doesn't rise high enough till ~2 am. Definitely a great target as long as it remains decently bright - since it only outbursts once a decade or so. TX Col remains the best evening object for southerners. Some very nice data coming from Fred and Jennie, and also Greg Bolt from Perth (of TU Crt fame... but in CBA quiescence for about 4 years). Dave Buckley and his crowd are doing photometry and spectroscopy from SAAO this week, so this is absolute prime time to fill out the campaign with worldwide data. Finally there's BH Lyn. We tried this one 5 years ago, and got some beautiful data but too limited in longitude to measure periods without ambiguity (except for the eclipse period, which is obvious!). Nicely placed for northerners at 0822+51, and decently bright (14.5 out of eclipse). Bob Fried has gotten a few nights to kick off the campaign - let's keep it going! As for the other stars, let's: (1) keep BK Lyn on the menu as secondary (good last target of the night once HV Vir gets too faint) (2) kick RZ LMi temporarily off (people are having too much trouble with it) (3) keep EC0511-79 on, in the hope that someone will actually observe it! Good luck! joe From jop at astro.columbia.edu Sat Jan 19 14:03:34 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 19 Jan 2002 14:03:34 -0500 (EST) Subject: (cba:news) BZ Cam... begone! Message-ID: Oh gracious, what a dismal performer BZ Cam appears to be! Two long nights from Bob Fried and Tom Krajci give really good light curves with no evidence whatever for periodic signals. Very different from its appearance circa 1994-5, when it was always flashing something big around 3 hours, and the issue was sorting it out. I worry that in its present (bright) state it'll be a big fat nothing. Naturally we report such things, but we don't have to be *interested* in them! So I say unto you, cast it back into the darkness, lest it bring weeping and gnashing of teeth. And go with BH Lyn and BK Lyn. A bit fainter but these guys will deliver! Rah, rah, New England. joe From jk at cbastro.org Wed Jan 30 05:08:40 2002 From: jk at cbastro.org (Jonathan Kemp) Date: Wed, 30 Jan 2002 00:08:40 -1000 (HST) Subject: (cba:news) News and notes Message-ID: Hi CBAers, Just a few additional notes of possible interest... A brief paper on RX 2329+06 has just been accepted for publication in ApJL. The abstract is included below and a link to the astro-ph preprint (0201487) appears at the CBA web site in our publications section. Please note that a more thorough treatment of the CBA photometry is in the works and will appear soon! Errata: Apologies to Elena Pavlenko for omitting her in the list of WZ authors and thanks to Alon Retter for noting that an extra paragraph from the HP Lib abstract got mysteriously appended to the end of the WZ Sge abstract in my last note. Perhaps both signs that I need just a bit more sleep. Lastly, Joe and I have had some discussions on authorship lately and I thought I'd pass along some of his comments on the issue: >>> The great bulk of the WZ Sge data motivated us to follow a more-or-less mathematical rule re authorship. It's a one-percent rule. The idea is that, like most observational papers, the work is about half data and half analysis/writing. The data was about 1200 hours, so there's about 2400 hours of "effective data" in the effort. So we set about 24 hours (1%) as the threshold for authorship - awarding some extra points for nice longitudes, big glass, and great-quality data. Some people logged vastly more (up to about 200) hours, so various co-observers (if any) rode in on their coat-tails. Other people got - I hope! - warm acknowledgments and - surely! - some great karma awarded in that Great Scorebook in the Sky. This is pretty close to our standard practice. I never really thought about it numerically before, but I think we've been applying a similar three-percent rule all along. That would be *ruthless* for WZ Sge, though. Anyway I don't guarantee 100% accuracy in our accounting (some guy named Arthur Anderson did the accounting, anybody ever heard of him?) - so I'll be happy to correct any mistakes that I or Anderson made. <<< Cheers, Jonathan -- 1RXS J232953.9+062814: A Dwarf Nova with a 64-minute Orbital Period and a Conspicuous Secondary Star J. Thorstensen, W. Fenton, J. Patterson, J. Kemp, T. Krajci, & I. Baraffe Astrophysical Journal, Letters (accepter, January 2002) We present spectroscopy and time-series photometry of the newly discovered dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a superhump with a period of 66.06(6) minutes. The low state spectrum shows Balmer and HeI emission on a blue continuum, and in addition shows a rich absorption spectrum of type K4+-2. The absorption velocity is modulated sinusoidally at P_orb=64.176(5) min, with semi-amplitude K=348(4) km s^-1. The low-state light curve is double-humped at this period, and phased as expected for ellipsoidal variations. The absorption strength does not vary appreciably around the orbit. The orbital period is shorter than any other cataclysmic variable save for a handful of helium-star systems and V485 Centauri (59 minutes). The secondary is much hotter than main sequence stars of similar mass, but is well-matched by helium-enriched models, indicating that the secondary evolved from a more massive progenitor. A preliminary calculation in which a 1.2 M_solar star begins mass transfer near the end of H burning matches this system's characteristics remarkably well. ----