From jop at astro.columbia.edu Sun Sep 6 09:51:21 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 06 Sep 2009 09:51:21 -0400 Subject: (cba:news) stars for spetember Message-ID: <4AA3BE59.4050603@astro.columbia.edu> Dear CBAers, Those pesky dwarf novae are taking a little rest (apparently V713 Cep didn't have real serious intentions), the bright Moon is soon to leave us, and it's a good time to ramp up observing a bit. In particular, it's vital that we now get a couple of September weeks on V4743 Sgr, a star we tracked extensively in June and July. By adding September coverage, we accumulate a total of ~120 days of seasonal coverage - this gives us enough baseline to count cycles uniquely all the way back to 2003, and thus establish a precise ephemeris for both the orbital and the (presumed) rotational clocks. That's the really high priority for southern observers. BW Scl is, too. We have about two uninterrupted weeks now, due to Berto and Bob Rea. Around one more should yield a power-spectrum sensitivity almost as good as we could ever theoretically obtain. So let's keep the faith a little longer. Aside from these two, the other southern star I recommend is VZ Scl. We've never done a serious campaign on it, and with the star decently bright at 15.6, it's time to train some telescopes on it. I suspect this maybe be a long-term target. Northern observers have been a little quiet lately. Maybe the beach has been too tempting. But when you get back from the beach, V455 And awaits. That's my number one recommendation - very long runs on this well-placed star. Shorter runs on RX0022+61 = IGR0023+61, RX1803+40, and RX1703-05 would also be good. Finally, an excellent beginner star is V Sge. Plenty bright, and with deep eclipses which show a period change still not understood (and not so securely measured). Also, it's pretty easy for me to evaluate data quality for this star. Same goes for AO Psc and FO Aqr; these don't need any new coverage until December, but they're easy to observe and will help me evaluate data-quality issues. Happy observing! joe From jop at astro.columbia.edu Mon Sep 14 12:51:40 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 14 Sep 2009 12:51:40 -0400 Subject: (cba:news) VX For in outburst - at last! Message-ID: <4AAE749C.3000200@astro.columbia.edu> Dear CBAers, Wow, I've lived to see the day! This star zoomed to 12.6 from about 20.5 in 1990, and stayed bright for many weeks (declining at ~0.1 mag/day). The spectra made it pretty clear it was an erupting dwarf nova, and even in 1990 it seemed very, very likely that the star would flash superhumps. But I studied it for 7 straight nights at Cerro Tololo, and found only small and apparently aperiodic wiggles in the light curve. Basically a very high-quality nothing. Then my run ended... and I've always wondered what this star is. Now it's 2009, and we know a lot more about the WZ Sge syndrome among dwarf novae. The most extreme of these stars generally take quite a long time to sprout actual superhumps; WZ Sge itself takes 10 days. So that's a pretty good conjecture - that it's quite extreme even among the WZ Sge class... and that had I taken over that 0.9 m telescope and refused to leave, I would eventually have seen those telltale superhumps. We don't yet know much about this eruption, but if it's a super (odds are decent), then this is the glamor object of the year for dwarf novae. We also don't yet know when it erupted. This one's only for southerners... but I'll definitely be thrilled to see any data you can get on it! The basic info is all in the Downes catalog. And the good early-night southern target continues to be V4743 Sgr. So far, our late-season coverage of this star is just a few short runs from Bob Rea - it would be nice to see that firmed up. A good star to sacrifice, in order to get substantial time on these two targets, is BW Scl. We can definitely suspend the latter campaign for a while - maybe for the season. joe -------- Original Message -------- Subject: [vsnet-alert 11471] VX For outburst Date: Tue, 15 Sep 2009 02:13:48 +1000 From: Rod Stubbings To: CC: cvnet-outburst at yahoogroups.com The probable dwarf nova VX For appears to be in outburst. I have never seen this star in outburst before and the only information on it is from IAUC 5127, 1990 on the discovery. FORVX 090914.636 130 Stu.RASNZ Regards, Rod Stubbings. From jop at astro.columbia.edu Wed Sep 16 06:37:12 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 16 Sep 2009 06:37:12 -0400 Subject: (cba:news) VX For superhumps Message-ID: <4AB0BFD8.9080500@astro.columbia.edu> Rod's great discovery a few days ago was followed by Berto's first night of photometry last night... which showed obvious humps, quite likely to be superhumps (meaning with a period slightly longer than the precise Porb). I'm attaching Berto's announcement. So it's an SU UMa, case closed. That's pretty significant too; in the star's only historical outburst (1990) the star was first suspected to be a supernova, mostly because of its presence in Fornax, where galaxies are numerous and eruptive variables are rare. The spectrum showing zero-redshift features proved it was galactic, but my failure to find periodic humps with quite good data over 1 week was puzzling. And it's still puzzling, unless Rod caught it well after the outburst started. If any of you have information or an educated opinion - or even an uneducated opinion - as to when the present outburst really began, I'd love to hear it. I think it's very likely to be a full-bore, certifiable, card-carrying WZ Sge star. Every piece of evidence suggests that, except this latest (so far weak) indication that superhumps appeared practically at the start of outburst. (That's why estimating the true start is quite important.) Anyway, this should be a great, great target for time-series photometry as long as it stays bright - which I expect to be two weeks or more. joe -------- Original Message -------- Subject: [vsnet-alert 11476] VX For Date: Wed, 16 Sep 2009 11:23:20 +0200 From: Berto Monard To: cba-news at cbastro.org CC: Vsnet-Alert at Ooruri.Kusastro.Kyoto-U.Ac.Jp Timeseries photometry with unfiltered CCD of VX For at CBA Pretoria on the night 15-16 Sep 2009 show modulations with amplitude around 0.2 and period around 1.5h. The mean magnitude was 12.9CR. Astrometry vs UCAC2 determines VX For at position 03 26 45.72 -34 26 24.6 (2000) This is exactly the same value as in the 2006 D&S catalogue. For photometric comparison I have used a star at position 03 26 57.8049 -34 28 00.090 with a derived R magnitude 13.2 . This star is an easy target for southern observers. Regards, Berto Monard / CBA Pretoria