From jop at astro.columbia.edu Sat Aug 3 12:43:46 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 03 Aug 2013 12:43:46 -0400 Subject: (cba:news) v1101 aquilae! Message-ID: <51FD3342.40409@astro.columbia.edu> Hi CBAers, I've finished my preliminary look at the V1101 Aql data, over the first 18 days. Superb... and in ways that we probably don't yet understand. This star is occasionally classified as a Z Cam star; it has some ups, downs, and long in-betweens... so it comes by that label honestly. It's also sometimes compared to RZ LMi, the most frantic of the ER UMa stars; that's warranted too, because there's a 20ish-day cycle (between high and low states)that recurs. That's the first oddity - because these labels belong to different sides of the period gap. It's a Greek among the Trojans. And it gets much stranger, because the star also appears to show *four* other periods: at 3.90 hr, 4.13 hr, 4.73 hr, and 3.0 d. At least the first two are very stable. For those of you who followed last year's adventures, that was the pattern of BK Lyn, the nova-turned-novalike-turned-dwarf-nova. A virtually identical pattern in a star longward of the period gap is a really big surprise. The star ranges from ~15.7 to 14.2 in a 20-day cycle, and shows big waves ("negative superehumps" in the jargon of the day) near minimum. The variations near maximum are harder to trace, because it looks like negative and positive superhumps then superpose. Another complicating factor is that the negative and positive superhumps appear to differ in frequency by ~1.10 c/day - creating problems in disentangling 'em. So far, most of the water is being carried by Joe U and David Cejudo. It would be great if more CBAers made this their regular target... and if we could remedy our "Pacific gap". Jim Jones to Jennie McCormick tro Bob Rea to Greg Bolt - those would be good handoffs which span the entire Pacific (presently our main zone of ignorance). The daily alias issues are especially important near maximum light in the 20-day cycle, when the two superhumps seem to wrestle for control of the light. As a comparison we're mainly using the AAVSO 13.6 star, which has V=13.603. I recommend that one. Another possibility is the AAVSO 14.9 star, which has V=14.866. Most people are using clear filters, with cycle times around 1-1.5 min. The periods are longer... but other than that, this star produces some of the most beautiful light curves in our arsenal! joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Aug 16 14:33:34 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 16 Aug 2013 14:33:34 -0400 Subject: (cba:news) Musings on Nova Del 2013, and some other novae, actual and imagined In-Reply-To: <00ef01ce9aa2$c41ff050$4c5fd0f0$@netnet.net> References: <00ef01ce9aa2$c41ff050$4c5fd0f0$@netnet.net> Message-ID: <520E707E.4000902@astro.columbia.edu> Hi Tony et al., It's kind of a celebrity object right now, and too bright for our CCDs. Plus it's quite unlikely now to show rapid variability, because the "photosphere" is thousands of WD-radii in size (the expanding shell is a big opaque envelope many times bigger than the entire underlying binary). So I'd rather lie low until the shell goes transparent - that's when we can first see down to the inner binary. Roughly speaking, that's when the soft X-rays first appear, or *very* roughly when the nova falls about 5 mag. Others will study this object pretty well, now that it has hit the headlines. That's all premised on the assumption that it's "just another nova". I haven't seen any evidence yet that it's something different... but the sky is full of surprises! The stars that I'd mainly like to promote this month are V1101 Aql and GD 552 ("Cep 1") in the north... BW Scl in the far south... and V1432 Aql and V1494 Aql (Nova Aquilae 1999 - now *that* was a sight to see!) for any conceivable hemisphere. Oh yes, one more, speaking of novae: HR Del. A nice bright star that has been strangely neglected (by us, too) in time-series photometry. There are some hints of multiple periodicities in the historical record. Porb is around 5 hours, so this star does need quite long nightly runs. But it's mighty bright, and for small scopers could be a great, great target. joe On 8/16/2013 1:05 PM, Anthony J. Kroes wrote: > Are we interested in this object? One of my astronomy club members sent me > the link below and also a picture he took early this morning - a wide field > shot with a DSLR camera which easily caught the Nova at about magnitude 5. > > > > http://www.universetoday.com/104103/bright-new-nova-in-delphinus-you-can-see > -it-tonight-with-binoculars/#more-104103 > > > > Tony Kroes > > ____________________________________________________________ > Center for Backyard Astrophysics (CBA) mailing lists > https://cbastro.org/communications/mailing-lists/ > ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Aug 22 17:57:30 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 22 Aug 2013 17:57:30 -0400 Subject: (cba:news) NR TrA, sound the drums Message-ID: <5216894A.2090402@astro.columbia.edu> Dear CBAers, The CBA coverage of NR TrA, while excellent this year, ended >2 months ago. That seemed enough at the time, since it seemed that the period (presumed orbital in origin) was stable. However, Fred Walter (Mr. MR TrA, and on the verge of being Mr. Nova) tells me now that he suspects, based partly on our earlier data, that the period wanders slightly. That's a whole different ballgame! (Sorry for the slang, foreigners, but you get the idea.) So we have enormous need for NR TrA time-series now. The period (orbital, or whatever it is) is long and the season is late, but with our strategically placed southern observers - S Africa/Chile/NZ/AU - we have a fighting chance of battling all that southern ocean and accurately defining the star's present period and waveform. At least the declination is favorable. Josch, I'd nominate this one for evening coverage. The variations are relatively slow, and V1432 Aql can wait a few weeks (plus get northern help, unlike TrA). And Gordon, it's good for eastern AU, or for that matter any AU, as well. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Aug 28 21:38:51 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 28 Aug 2013 21:38:51 -0400 Subject: (cba:news) V1101 Aql mostly Message-ID: <521EA62B.1030205@astro.columbia.edu> Dear CBAers, V1101 Aql continues to amaze, with its startlingly coherent 3.9 hour and 16 day periodicities... and at such high amplitude! The smart money (sorry, gambler's slang) still says this is a negative superhump, but there's a not-small chance that it's something more exotic. Maybe unprecedented. I don't know any star like this. And CBAers have really been working overtime: Joe U, Enrique, David Cejudo, Jim Jones, Doug Slauson, Richard Sabo, Mike Potter, George Roberts, Tut Campbell, Ken Menzies, Michael Cook, Marlin Costello, Greg Bolt, Gordon Myers. Wow! And we now have a beautiful 44-day light curve, sufficiently regular to specify all the main periods (though not necessarily with enough wisdom to *interpret* them). So let's experiment a little. The star is bright enough, and the signals strong enough, to survive filtration. If you have broadband filters (1000 A-ish, like the Johnson filters), then consider taking the time series in filtered light. You could choose a single-filter time series, e.g. V or I, or interleave them (V, I, V, I, etc.) While the strategy is basically exploratory, what I'm wondering is whether the alleged "superhump" is really a signature of a strongly magnetic WD, which are also commonly signified by a *very* red color (redder than any thermal process could reasonably produce). I don't think *most* people should do this. Maintaining our beautiful 44-day light curve for a few more weeks is mighty important. But if some people observe in filtered light, there would be new information, and a test of my hypothesis (or at least the version of it invoking cyclotron radiation). Meanwhile, keep the faith on the star. BTW watch out for the nearby intruder stars, in this somewhat crowded field. They could *really* louse up colors. In the far south, the campaigns on BW Scl, NR TrA, and CD Ind continue, an the stars are definitely cooperating. Details in the next 1-2 days. And I still *crave* light curves of V1494 Aql! Kind of an orphan in recent years. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Aug 29 10:11:21 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 29 Aug 2013 10:11:21 -0400 Subject: (cba:news) ASAS-SN 2013/08/29 Transients Update: Bright CV Candidate ASASSN-13ck In-Reply-To: References: Message-ID: <521F5689.90201@astro.columbia.edu> Detection form ASAS and Kris Stanek. This is an 8-magnitude range, decently bright (therefore likely nearby, around 400 pc)... and it *just* erupted. So it certainly looks like a tempting target. Great sky position up there in Pisces, available to all hemispheres and practically all hours of the night. Fire away, with the usual CBA weaponry. BTW... For the last few years I've been lukewarm to discoveries of new dwarf novae in eruption. The reason is that we already have decent information on ~150 of them... and thus to make a strong impact on current knowledge, we might expect to need ~150 more. (That's a commonly cited rule of thumb.) Nevertheless, there are a couple of reasons why this ho-hum reaction might be inappropriate: 1. We might be wrong. Science's golden rule: eschew hubris! 2. The extreme dwarf novae, more or less the "WZ Sge class" with a magnitude range >7 mag, are very poorly understood and very hard to get data on, since they erupt very seldom and become very faint in quiescence. And they're *probably* the most common type of CV, even though few are known (because they're so extremely bashful). So we need to study every one that jumps up and says boo. joe -------- Original Message -- Received: from astronomy.mps.ohio-state.edu (astronomy.mps.ohio-state.edu [140.254.78.200]) by ooruri.kusastro.kyoto-u.ac.jp (Postfix) with ESMTP id C63781FC074 for ; Thu, 29 Aug 2013 22:31:41 +0900 (JST) Received: from milkyway.astronomy.osu.edu (milkyway.astronomy.osu.edu Object RA (J2000) DEC (J2000) Disc. Date V mag ---------------------------------------------------------------------------- ASASSN-13ck 0:11:33.71 4:51:23 2013-08-29.47 12.93 ----------------------------------------------------------------------------- Bright CV candidate, matches to a blue g=20.8 SDSS star; nothing there on 2013/08/27; ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/