From jop at astro.columbia.edu Tue Sep 4 16:32:17 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 04 Sep 2007 16:32:17 -0400 Subject: (cba:news) HS2331+3905, the big one! Message-ID: <46DDC0D1.30003@astro.columbia.edu> Dear CBAers, HS2331+3905 has just erupted! This is the first eruption ever, AND it is surely one of the strangest and most important CVs in the sky. Plus it's 13th mag at least, and transiting near local midnight. I'll be sending out many notices soon about this star. I've learned a lot about it in our past two years of coverage, but certainly didn't think I was going to see an eruption any time soon! It's THE TOP PRIORITY for all northern observers. Great will be your pangs of conscience if you don't get to a telescope mighty soon! joe Downes et al. have it as "And", and a very good paper is by Araujo-Betancor et al. (I think 2005). From jop at astro.columbia.edu Wed Sep 5 08:52:15 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 05 Sep 2007 08:52:15 -0400 Subject: (cba:news) HS2331 on the warpath Message-ID: <46DEA67F.1040806@astro.columbia.edu> Dear CBAers, HS2331 brightened through the night, reaching 8.8 around 12:00 UT. I know that Bob Koff obtained at least a few hours on it, but otherwise am still unaware of what our coverage was. We had a night on a 2.4 m telescope - and couldn't cope with the brightness. We might substitute a dense filter, but most likely will leave this to CBA scopes. The event is likely to last a month or more (or even much more), but will go through stages with different characteristics. WZ Sge in 2001 was a cornucopia of riches, but this one is likely to be even better, because of all the odd periods the star presents. We've been observing HS2331 heavily for two years, and in fact obtained two nights of data the week before outburst... so we'll actually know *phases* as well as periods just before outburst, and can compare with post-outburst results. Delete MN Dra and V1006 Cyg, by the way. I'll work up a full observing list in the next day... but take advantage of this historic opportunity! Bob and Donn, since you were fastest off the blocks, do you have any comp star advice? We basically need good comp stars when bright, when faint, and when intermediate. I'll work on this between crises today (it's the start of school)... but any advice would be very welcome. joe From jop at astro.columbia.edu Wed Sep 19 08:12:23 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 19 Sep 2007 08:12:23 -0400 Subject: (cba:news) V455 And and CD Ind... Message-ID: <46F11227.3050802@astro.columbia.edu> Dear , Pardon me for the brevity. The start of the school year has set me back! Still, I have been analyzing all the data coming in... and here's my report/suggestions. V455 And = HS2331, as you all know, is having an outburst for the ages. The coverage is almost as good as that of WZ Sge in 2001, and vastly better than any other dwarf nova in history. It's great to have bright eruptions from stars transiting near local midnight, and in this case with many periodic clocks to study the effects of outburst. A few of you are obtaining multicolor data; except possibly for the very beginning of outburst, there appear to be no significant color effects in the star. It's basically a big blue light bulb, and the main reasons for observing it filtered are these: (1) Archival. With V data, it's possible to say meaningfully "how bright it is". (2) (Differential) extinction. Through a very wide or no filter, a CV's extinction always exceeds that of the comparison star, introducing unwanted waves in long light curves. (2) is an item of some consequence, and worth doing if you can afford the roughly 6x loss of photons (in which case V is probably the best choice). But I tend to be skeptical about (1). CVs are forever variable anyway, and there is likely no significance to their exact brightness. *Someone* needs to do V measurements; and everyone - even unfiltered diehards - needs to make an estimate of the brightness level. But the sensitivity of time series to periodic signals is greatly improved by a healthy count rate. So for our purposes, unfiltered generally wins. Exceptions are a very bright star (like V455 And the last 2 weeks!) and an interest in timescales natural to extinction (say 6-24 hours). There's another very specialized reason that applies to this star. It has strong 68 and 34 second signals at quiescence. Their origin is still unclear, but we FERVENTLY would like to measure how they are affected by the outburst. So we need quite short integrations. To resolve both, you need a cycle time (integration + dead time) of <17 s, or let's say 13 s to be more comfortable. Can you do that? I think for most of you the answer is no; if that's true, try for ~20 s, which will fail to resolve the harmonic properly, but do a decent job on the fundamental. Avoid, however, cycle times very close to 17 s and 34 s; when the period is an exact multiple of the sampling time, terrible things happen! (Like trying to measure the Earth's rotation period with brightness measures at noon and midnight every day!) For the moment, V455 And is certainly the best northern object. To say the least. In the south, it's time to quit on V1432 Aql. We've covered 1.2 cycles of its 50-day supercycle, done very well (primarily due to Berto), and the data clarify the ephemerides and timescale for synchronization. It's also time to quit on EC2117 ("Ind"). This is a great eclipsing binary, with hardly anything yet published on it; we have excellent data, and one or more of you southerners might want to write something up - I'll be happy to send you all the data and a preliminary analysis. Apart from its faintness, CD Ind is a great, great target this month and next. This too is an "asynchronous polar", and our data (mainly Bob Rea's) show many effects cycling on the six-day beat between Porb and Prot. They also specify the long-term ephemeris, which has never yet been published. This star may well be the most revealing of this small class of CVs (only five known) - revealing of the magnetic torques present in this "asynchronous" geometry. Try hard for CD Ind! Not so brief... but in a few days, I hope to make up more detailed target suggestions. Please keep up the cba-chat, it's working very well I think! joe From jop at astro.columbia.edu Thu Sep 20 06:37:37 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 20 Sep 2007 06:37:37 -0400 Subject: (cba:news) V455 And, HV Aur, and fall AAVSO Message-ID: <46F24D71.4070300@astro.columbia.edu> Dear CBAers, Data continuing to pour in on V455 And. With 8 hour runs from Europe and North America, we could hardly ask for better coverage! OK, technically we could. We've had an Asia/Pacific gap for northern stars ever since Tom moved back to New Mexico (from Uzbekistan). But the Japanese receive data from Europe and North America, and have plenty from Japan... so they'll manage to cover the daily gaps. To the extent that 15 hours/day is not enough, they'll get that base covered. In general, my experience is that aliasing issues disappear around 10 hours/day... so I'm mighty thrilled with our data right now! And the attention to shorter timescales is also a plus, though perhaps unfeasible after another 1-1.5 mag of fading. I will try to beg a few time series from generous astronomers at bigger telescopes here and there. Everyone contributing to this campaign is welcome to have all the data, and use for any purpose you like (except sending to terrorists). We don't now have any easy and proper way to do this, but you can try any of the following: 1. Bug Jonathan to set up a proper system of access. 2. Bug Jonathan to let YOU set up a proper system of access. 3. Ask me or Jonathan to send you any not-too-huge subset of data received (which you can identify by clicking on "recent" or "archive". 4. Ask me for all of it, in the form that I reduce it to: daily merged files with mean (and trend if significant) removed. Eventually we hope to figure out a way to deposit it with the AAVSO, which will increase its usefulness further. And speaking of that, I hope a few of you will be at the AAVSO fall meeting in Cambridge. I expect there'll be a rump session on our newly favorite dwarf nova! Finally, two other CVs of high interest seem to have erupted: NSV 1485 and HV Aur. Each would be a really fine target for time series photometry. Tonny, can you summarize again what you've learned about NSV 1485 (and info for prospective observers)? I've long regarded HV Aur as a mystery star; eruptions are very rare and very sparsely covered - it is high time to change that! (Well, the latter, anyway.) Happy observing! joe From jop at astro.columbia.edu Thu Sep 27 15:59:56 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 27 Sep 2007 15:59:56 -0400 Subject: (cba:news) V455 And, CD Ind, BW Scl Message-ID: <46FC0BBC.3020802@astro.columbia.edu> Dear CBAers, Well I've spent a lot of time on the V455 And = HS2331 data now. The (probable) rotation frequency is back - corresponding to 67.618 s and half that. This means that fast integrations are VERY desirable in this star. Most of the power is at 68 s, so cycle-times around 25 s, like many of you are using, are OK. But if you get it down to 15 s, that would be super! I'm now trying to figure out when those oscillations came back. All in the fullness of time. By the way, the eclipses seem to be back too. Yet another reason (a lesser one) to do fast photometry. Give it a try! You might need to switch to unfiltered, though. The CD Ind campaign is well worth continuing. However, it's also BW Scl season again - time to get long nightly runs on this star, the southern counterpart of HS2331 (except that it's in quiescence - and, like HS2331, has never erupted). Maybe we'll hit the daily double this year. More to come. joe From jop at astro.columbia.edu Fri Sep 28 10:07:24 2007 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 28 Sep 2007 10:07:24 -0400 Subject: (cba:news) high-speed timings of V455 And Message-ID: <46FD0A9C.6080203@astro.columbia.edu> Dear CBAers, So it appears that many of us will be doing faster-than-usual photometry in the next few weeks. Here are some things to bear in mind: (1) make the cycle time (integration+dead) less than 0.5 x the shortest period you suspect might be present. For this star, we know of a signal at 34 s (the harmonic of the 68 s fundamental, but with a fine structure that conveys some extra information in itself)... so "under 15 s" would be nice. (2) report times as "mid-integration" - not "mid-cycle", or "start-exposure", or anything else that might seem logical. (3) report times to 5 places (after the decimal). (4) check computer clock against wwv to insure accuracy. we seek accuracy to +-1 second; +-2 is tolerable... above that, well, only if your data are lousy anyway! (5) use JD, not HJD, BJD, MJD, or any other convention. In practice, the short-exposure (i.e. short cycle-time) requirement might prove to be a problem after the star fades some more. MOST of the information is at the 68 s fundamental; so cycle times around 25 s or so, which appear to be convenient for most of you, will be OK. Nevertheless, shorter cycle times always give you a broader net for catching things you didn't expect! joe