From jop at astro.columbia.edu Thu Oct 1 16:19:37 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 01 Oct 2009 16:19:37 -0400 Subject: (cba:news) V368 Peg in superoutburst Message-ID: <4AC50ED9.2000604@astro.columbia.edu> Hi CBAers, V368 Peg is now in very bright outburst, and flashing some great superhumps. This is a perfect target now, especially with the growing moonlight. We've never managed to get good coverage of this star - now's the time! (replacing V455 And in the evening sky). joe From jop at astro.columbia.edu Sun Oct 11 07:14:38 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 11 Oct 2009 07:14:38 -0400 Subject: (cba:news) TT Ari, V368 Peg, VX For Message-ID: <4AD1BE1E.9070407@astro.columbia.edu> Dear CBAers, As some of you know, TT Ari - one of the brightest of all CVs at V~10.9 (normally) - has fallen off the table in the last few weeks. It's now down around V=13.3 and dropping. This is the first deep drop in many years, and will give us an opportunity to track the light curve photometrically before (somewhat), during, and after its minimum. It's not a *sure* bet to be photometrically interesting, as the disk gets kinda faint... but we won't know till we look, and its beautiful placement in the October midnight sky couldn't be more cooperative. Mainly a northern target, but I hope that we'll get some NZ-AU coverage too, since we have quite a vast Pacific-and-Asia longitude gap for northern targets. Meanwhile, VX For continues to tantalize in the southern sky. It's reeling off some echo outbursts, and we're now getting good coverage from AU (mainly Arto and Chris Stockdale), NZ (Bob Rea), and ZA (Berto). As for superhumps... whew, I think the answer is no, but the analysis is tricky when the nightly light curves show these strong ramps. That's the general expectation: after the main outburst is over, superhumps in dwarf novae tend to die, get weak, get sloppy... or some undecipherable combination. The long-lived echoes support the idea that this is a very old dwarf nova, with a puny secondary; but only the actual mass ratio, still unknown, will severely test this idea. Anyway, the star is worth following as long as it keep flashing the echoes (3 so far I think). V368 Peg is staging a great show - some really handsome superhumps. I'm just starting my analysis, but it seems likely this will be a showpiece object. It's time to end our long campaign on V455 And. EXCEPT during Nov. 9-17. We have a Kitt Peak run on those dates, and will be able to time the very fast signals. Supporting CBA photometry will be quite good then. BW Scl continues to be a very good target - a gold mine of periodic signals. Our paper on this star is "mostly written", and has remained in that status for 5 years, even though I work a lot on it every year. I learn too much new every year. So, realistically, I guess if you never send me any more data, I'll send the paper off quite soon. And if you keep torturing me with new things, the paper will fatten up, improve... and stay imprisoned in my computer. Which is better? Happy observing! joe From jop at astro.columbia.edu Tue Oct 13 07:48:52 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 13 Oct 2009 07:48:52 -0400 Subject: (cba:news) echo outbursts, and missed outbursts Message-ID: <4AD46924.9030705@astro.columbia.edu> Dear CBAers, Just a few musings/speculations this time. Some of you know that EG Cnc jumped into outburst a few days ago, and is now (or was yesterday) declining rapidly. Definitely one of our favorite stars! It's pretty early in the Cancer observing season, so we have only a weak constraint on when that outburst started. It could be the very beginning of a super, or the end (one of the infamous "echo outbursts"). Or it could be merely a normal outburst; I believe two such events have been seen in EG Cnc, and they are generally documented in WZ Sge stars, other than grand old WZ itself. The next week will probably tell us which of these is true, or perhaps yet another possibility. The most interesting would be the beginning of a super... although the poor seasonal timing (Cancer in mid-October) probably means that we can't expect to get as much coverage as we did in the 1996 outburst. The latter was one of the best-observed DN eruptions in history. VX For is likely a similar binary, a very old guy with a puny secondary. Accordingly the star is busily executing echo outbursts now - a poorly understood phenomenon but one that appears to characterize the WZ Sge stars. Superhumps have become very weak and hard to follow, maybe even gone altogether. The smart money says they're not likely to come back. But the echoes might go on for a while, and documenting those is mighty important, since this is essentially the first observed outburst in history (that of 1990 really didn't produce anything, aside from many puzzled conversations in Chile). The era of handsome light curves is probably over, but the star's behavior over the next two weeks is likely to be scientifically rewarding. In case it's not obvious, I'm really excited by this return of a mysterious old friend! A big and very uncertain question for all these normally faint stars which rarely erupt is: just how common are non-supers? (Often called "normal" outbursts, but it's an odd term, since they are presumed to happen very rarely or even never.) Of course we can simply count the ones in the documentary record... but how many do we miss? I don't have any suggestions about this, but thought I'd raise it in case anyone else does. V368 Peg is probably an "ordinary" SU UMa star, with supers roughly once a year. As Arto remarked and as his light curve proved, the star has declined from plateau, yet kept its superhumps going strong. This could be interesting to track; we know that generally speaking, superhumps tend to outlast the superoutbursts which create them... but there has never been a star (or at least not a hydrogen-rich star) which illustrated this in sufficient detail to yield some nice numerical estimates of this. Olde Whiteface is finally falling out of the sky, so you might be able to get some good data on these stars, now pretty faint. joe From jop at astro.columbia.edu Thu Oct 15 06:08:02 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 15 Oct 2009 06:08:02 -0400 Subject: (cba:news) getting greedy on TT Ari Message-ID: <4AD6F482.5070302@astro.columbia.edu> Dear CBAers, TT Ari is continuing to decline towards its historical V=15.5 low state, and in fact might be already there. Some data has trickled in - just a little, but enough to make me awfully greedy for more. As usual, being a CBAer deep in my heart, I'm most desirous of long nightly time series - which, after being spliced together around the globe, will yield a superb record of periodic signals in the light curve. Naturally that'll take a while to assemble. But I'm already surprised to see the very strong flickering/QPOs that continues in the light curve. It's not obvious where this flickering arises. The accretion rate must be much lower now, but the hot WD should still be plenty luminous - it'll take months/years/decades for the WD, heated by centuries (at least) of accretion, to cool off. So why doesn't the WD now (presumably a more or less constant source) dominate the faded disk? This question will perhaps be best addressed by spectrophotometry, which can parse the secondary+disk+WD components. However, multicolor photometry can probe it also. It would be very nice to know the color of the flickering light. Very few (or perhaps none) of you are equipped to obtain rapid multicolor photometry - spinning the filter wheel fast enough to time-resolve the ten-minute flickering - but many of you have blue or infrared filters, and long time series in one filter (say B or I, something like that) could convey a lot of information. But don't neglect the white-light ("pink") that we usually revere! It's just that in this particular case, since the competing light sources are very red (secondary) and very blue (hot WD), filtered data has a good chance of supplying important extra information. You always have to balance that against the statistical quality of your data, though - and I fear that at V=15.5, the star might be a touch too faint for the filtered time series (which must have good time resolution, remember). So think about that. We (actually Koji Mukai) will be getting a Swift observation in X-rays and ultraviolet in the next few days. So this is REALLY a good time to get thee to a telescope... and squeeze off some beautiful time-series of the star! joe From jop at astro.columbia.edu Thu Oct 15 11:59:08 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 15 Oct 2009 11:59:08 -0400 Subject: (cba:news) TT Ari X-ray observation Message-ID: <4AD746CC.2060105@astro.columbia.edu> ...by Swift will take place October 16 from 1:26 UT to 9:15 UT. Nicely timed for Europe and the Americas, except that it's MIGHTY SOON. That's Thursday night, in USA-speak. Truly simultaneous observation would be just great - and should probably be white light, since statistical accuracy is of paramount importance in analyzing for correlations. But anything within a few days is close enough to be "contemporaneous", and has heightened value also. Good luck! The star's brightness seems to be jumping around in the last few days; the snapshot magnitudes are kind of confusing. If you have clear skies and a V filter, be sure to get a (decently, not fanatically) calibrated V magnitude in there somewhere, so our time series don't have a large zero-point uncertainty. Koji Mukai secured this time, and points out that a new gamma-ray burst would bump us off the schedule. May our skies be quiet and clear. joe From jop at astro.columbia.edu Sun Oct 18 11:08:13 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 18 Oct 2009 11:08:13 -0400 Subject: (cba:news) OT 2102+02, and ASAS2243+08; also TT Ari and ES Cet Message-ID: <4ADB2F5D.9050906@astro.columbia.edu> Dear CBAers, I saw this vsnet note, and thought we might jump to it. 2102+02 only permits brief runs in late October, but it's equatorial, so maybe we can stitch together good multi-longitude light curves. Greg, can you supply any other info on this star? 0.3 mag superhumps... whew, that sounds pretty interesting, and 2 hours could also be. We're doing moderately well on ASAS2243+08, but it has started a rapid fade. Still a good target for up to a few nights. OT J210205.7+025834: new SU UMa-type dwarf nova Greg Bolt has reported observations clearly showing 0.3-mag superhumps. The period is around 2 hours. Further observations are strongly encouraged to determine the superhump period. TT Ari campaign is going great... let's give this brazen star a long run in Oct-Nov 2009! And oh, I forgot to mention ES Cet, now transiting near midnight, and available to everyone, though slightly favoring southerners. We've been tracking its 10-minute period, and I wanted to get one more solid season of timing it before publishing the Pdot or upper limit (it's an important constraint on the mass transfer rate, and hence evolution). joe From jop at astro.columbia.edu Fri Oct 23 08:41:48 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 23 Oct 2009 08:41:48 -0400 Subject: (cba:news) VX For down, and TT Ari ever so up Message-ID: <4AE1A48C.7010808@astro.columbia.edu> Dear CBAers, I think VX For has about finished its show. Maybe it has one more echo ahead of it, but it'll be a big-scope target from now on. As some of you know, TT Ari has been sensational, flashing an entirely unexpected periodic or quasiperiodic signal of enormous amplitude (1.4 mag), and P~0.38 d. This is certainly something new to the world of (human knowledge of) TT Ari, and quite possibly to CVs generally. We can track it - the star's bright enough, equatorial enough (sort of), and sufficiently well-placed in the sky to permit a really close watch. I'll send the merged light curve so far to campaigners, and say more tomorrow about observing styles (although continuous V - preferably - or clear monitoring is OK). We have an Asia-Pacific gap for northern targets, as usual, and it would be really good if AU/NZ observers helped us fill this gap. Photometric precision and length of run is not so important when you're mainly filling a gap. More tomorrow, or tonight. joe From jop at astro.columbia.edu Fri Oct 23 17:39:17 2009 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 23 Oct 2009 17:39:17 -0400 Subject: (cba:news) TT Ari, take 1... and filter selection Message-ID: <4AE22285.2090805@astro.columbia.edu> Or at least publicly take one. We decided to jump out with a quick "what we learned on the first day" note, and here it is: http://www.astronomerstelegram.org/?read=2254 I limited the author list to those with light curves coincident with the X-ray observation. However, there are some really beautiful light curves rolling in now, and such beauties are hard to keep cooped up in a computer for long. We'll figure out some way to get 'em out in the light of day pretty soon. At this early stage, the ~0.38 day waves are the most interesting aspect of the light curve, and this timescale forces us to worry about how we take our data. In particular, our longest/best light curves last 8-9 hours, and this is practically the same as the signals we wish to measure. Thus uncorrected extinction effects will certainly contaminate our data. It's *differential* extinction that matters, and this can be pretty large for clear-filter data, since the effective wavelength for TT Ari will be much bluer than that for an average field star (about 0.10 mag/airmass). I can satisfactorily correct your data if you supply the airmass - and the need is minimal if you observe in a decently narrow band (like V). So one of those strategies would be helpful. But if software/hardware limitations mean that you're a clear-filter guy, that's all right. I learn a lot about how to make these corrections from experience. It remains desirable, IN PRINCIPLE, to get B and I - or some similar well-spaced blue and infrared - light curves. But we already know roughly that the light curves are similar - as is true for practically every CV. So no quick riches for this approach. Nevertheless, really extensive coverage like this would probably teach us a lot; I don't recommend it, but a very extensive set of B/I light curves would make a liar out of me. Whew, tomorrow I promise to cover the rest of the CV goodies in the October sky. joe