From jop at astro.columbia.edu Tue Mar 1 08:58:34 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 1 Mar 2016 08:58:34 -0500 Subject: (cba:news) March stars Message-ID: <56D5A00A.9040607@astro.columbia.edu> Dear CBAers, The new month brings retirements. BH Lyn. Done for the year. Great orbital light curve, but the superhumps have vanished. HZ Puppis. Done for the month. A few nights in April would be nice, to nail down the year-to-year cycle count. T Pyx. Paper finally submitted to MNRAS. Should be on astro-ph today. Whew! A 10-year effort... slowed by laziness, greed, and the 2011 eruption. V902 Mon. A really strange star. Catalogued as an eclipsing DQ Her star, and we have some fine light curves. But by my reckoning, the fast signals are *exactly* at the 6th and 13rd harmonics of the orbital frequency - and at no other harmonic. Now *that's* a doozy! We'll pick it up next year, and get a sharper test of just how exact this weird coincidence is. And some other stars which very much need coverage now: Swift J0503.7-2819. It's magnitude 18.4 and out of season, so won't be popular. But a week of coverage now would be mighty nice! Swift J0939.7-3224. A long-Porb DQ Her star, at 17.3 not so unreasonable to cover. But the long period (>8 hours) requires long runs AND well-separated longitudes, and so far we have only Gordon in eastern Australia. Definitely a fine target for other longitudes! Swift J0820.6-2805. Don't know much about this one yet. Only Gordon has tried it so far. Still hoping we can learn something about this guy, but it's 18.4. AM CVn. Recent coverage has been good - keep it up, as *dense* coverage is ideal for disentangling the complex period structure. Now some of the older DQs: WX Pyx. Definitely! One of the most mysterious, and practically no published data on it. V647 Aur, V667 Pup, MU Cam, and especially DW Cnc. All needing coverage to establish long-term period evolution. No actual dwarf novae in this message, and I'm also skipping a few novalikes only because I haven't studied the data. Perhaps Enrique will supplement this message with some of the stars I've missed (AT Cnc?) joe The last message also contains some useful info (esp. the Halpern-Thorstensen paper) https://cbastro.org/pipermail/cba-public/2016-February/000982.html ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Mon Mar 14 16:46:17 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 14 Mar 2016 16:46:17 -0400 Subject: (cba:news) MU Cam and DW Cnc Message-ID: <56E72319.4060409@astro.columbia.edu> Dear CBAers, I'm trying to use this break from classes to catch up on, among other things, the DQ Her stars. 1. David Cejudo has accumulated a nice streak of long runs, from Spain, on MU Cam. For the last 1.5 months the star has had a mean brightness near 15.15... and episodes of near-constant mean brightness *really* help the sensitivity of period search. So this would be an ideal time for long runs from the USA. The main signals are pretty much known, but long runs can reveal the subtler signals that are usually present - sidebands/harmonics. A week's worth of long runs from USA longitudes would be great. 2. DW Cnc. Pretty much the same comment - except that the Spanish perpetrator is Enrique, and this star is especially tricky with a complicated triply-periodic structure. A week or more of USA runs might allow us to cash in these suspected, but not proven, signals. These late-winter targets are ideal to do now, since the Sun will be snatching them away soon. WX Pyx is another hard-to-figure-out guy too... the only reason I'm not mentioning that one is that we've *never* had enough data to really prove its stability. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Mar 25 04:53:11 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 25 Mar 2016 04:53:11 -0400 Subject: (cba:news) RZ LMi, mostly... and some other March-April targets In-Reply-To: References: Message-ID: <56F4FC77.1000307@astro.columbia.edu> Dear CBAers, It's time for us to get back to RZ LMi, one of our common Feb-Apr targets of 5-10 years ago. It's the most frequently outbursting of the most frantic dwarf-nova class of them all, the ER UMa stars. No one has ever managed to learn its precise orbital period, since spectral features are extremely weak and not necessarily stable... and since it spends so little time at anything resembling "quiescence". This and other recent vsnet posts about this star do not necessarily indicate anything unusual - we've been misled and foiled by this star several times before! But it *might* turn out to be a true and long-lived standstill, and that would finally give BK Lyn a much-needed cousin in the sky (as presently the only such short-period star). It's definitely worth another try. Decently well-placed in the evening sky. And I'd say the same for V803 Cen, too, though with less confidence that its present behavior is anything unusual. Let's jump back on this star for at least 2 weeks or so. IM Nor is wrapped up for the year. The eclipses are stable and verify the huge Pdot we found in last year's study. A true counterpart to T Pyx! The AM CVn coverage has been really good - magnificent! The main goal, studying the weak orbital wave for its precise timing, has been met. So on general principles, it's probably time to quit. Maybe Enrique can comment on AT Cnc. It has a persistent short period, but so far, my analysis suggests that it's a quasi-periodic oscillation ("QPO") rather than the *stable* short-period signal that we always treasure greatly. Hard to be sure. If it is a QPO, it's the most stable of the QPOers - but even that would be millions or billions of times less stable than a true DQ Her star! I'm tempted to say that AT Cnc season is over... Enrique, whaddayathink? DQ Her (intermediate polar) observations are always valued, and Koji Mukai's webpage is always the best source for thius class: http://asd.gsfc.nasa.gov/Koji.Mukai/iphome/iphome.html More in a day or two. joe p -------- Forwarded Message -------- Return-Path: RZ LMi: still in superoutburst Kiyota-san, Geoff Stone have reported new time-resolved observations. Enrique de Miguel has supplied snapshot observations. The object is still in superoutburst (at least on Mar. 24). The mean magnitude has been almost constant since Mar. 13 and the light curve even looks like a standstill. Superhumps are still present. Let's see what happens next! ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/