From jop at astro.columbia.edu Tue Feb 5 20:39:22 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 5 Feb 2002 20:39:22 -0500 (EST) Subject: (cba:news) february stars Message-ID: -------------- next part -------------- An embedded message was scrubbed... From: Joe Patterson Subject: (cba:news) stars for february Date: Tue, 5 Feb 2002 17:42:51 -0500 (EST) Size: 1564 URL: From jop at astro.columbia.edu Thu Feb 14 15:59:53 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 14 Feb 2002 15:59:53 -0500 (EST) Subject: (cba:news) comparisons 'n stuff Message-ID: Thanks Arne, Dave, Berto - Interesting issues. I don't have anything really *factual* to add to what these 3 have said - but I favor the traditional V-C, K-C approach for a systematic program like ours which will blend observations from different telescopes. If we all use the same comp and the same detector (those Kodak chips were great because there were so many around, and they were sufficiently blue-blind that the blue excess of the CV wasn't too bad), then V-C means something straightforward. With ensemble photometry it's harder to say - everyone uses a different ensemble, etc. Also, I sometimes apply corrections for differential extinction - this will become more important as the enhanced-blue detectors get out into the world, because there will then be a *large* difference in the effective color of CV and comp. With ensemble photometry it's too vague, because the "supercomp" doesn't have any definable color. Perils of white light. Filters help with many of these problems. But then our little faint stars go away... and we get nothing at all. We need all those tainted pink photons! I think a few CBAers do ensemble photometry, and that's OK, but the traditional V, V-C, C-K is just fine. Makes me feel warm all over. By the way, if you want to add another column, consider *airmass*. That would help me for the very bluest of CVs - the AM CVn stars, who clock in about B-V=-0.2 - which show differential extinction effects that can be pretty annoying. (They tend to insert artificial periods of 1, 2, 3, and 4 cycles/day into the time-series). Oh.......... and let's take BH Lyn off the menu! Time to get going BIG-TIME on DW UMa. Nearer the equator, and in the evening, there's BG CMi and PQ Gem. More details tomorrow. joe From jop at astro.columbia.edu Thu Feb 14 18:29:42 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 14 Feb 2002 18:29:42 -0500 (EST) Subject: (cba:news) u gem Message-ID: There's a report that U Gem just went into outburst. If so, it would be a great target for smallscopers to go for - you'll love the data at 10th magnitude. Watch for saturation! Despite its ancient status, U Gem still presents us with puzzling issues in outburst. The timing and amplitude of its eclipse and hump will be very helpful in figuring out the sequence of events up there. But don't be disappointed if they go away! (THat carries information too) joe (But I still think the bigscopers should do PQ Gem and DW UMa and EC0511-79 and T Pyx!) From jop at astro.columbia.edu Fri Feb 15 11:51:45 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 15 Feb 2002 11:51:45 -0500 (EST) Subject: (cba:news) ccds etc. Message-ID: Well, I go along with Arne's reply to Berto, as well as Berto's reply to Dave, and Dave's reply to Berto! (Oh, and please send campaign contributions in cash to General Delivery, NY, NY.) We've done well with a 3 mag difference, as long as you stay away from Saturation Scylla on the one hand, and Low S/N Charybdis on the other. But at 5 mag, your data's probably going to Davy Jones' Locker. But I wanted to make one final comment about comps. My biggest fear is that people won't observe because they can't get the "right comparison star" on the chip, don't have the right filter, etc. The CBA is sort of an like an infantry charge up a well-defended hill. Grab something that looks like a weapon, tone up that ol' blood-curdling scream, and join the charge. Don't wait for the supply sergeant to issue better weapons! Sling lead into the enemy ranks, and keep the pressure up. At the very least, maybe you'll take a bullet which otherwise would have wiped out some really fancy telescope. I think I need some herbal tea now. joe From jop at astro.columbia.edu Fri Feb 15 17:58:01 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 15 Feb 2002 17:58:01 -0500 (EST) Subject: (cba:news) valentine stars Message-ID: Dear CBAers, Well the cast of characters is changing fast. Series of one-act plays goin' on up there. HT Cas fell back to quiesecence. Back to obscurity for it. BH Lyn. She loves me, she loves me not. The star tantalized with some waves and level shifts (0.3 mag very slow variations). We got 26 of 32 nights covered, with a good range of longitude. We'll *probably* pull periods out of this, but it'll take some work - too much work to invest in weak results. The 1997 campaign also gave a tantalizing but not quite decisive result. If the two tantalizers are consistent, then we're in business. Anyway, I don't want to invest any more in this coquettish star, since there are some great performers nearby in the sky. Namely, BK Lyn and DW UMa. We should keep up pressure on these stars for a long time. They're both showing *big* negative superhumps + nodal precession periods of a few days. Since DW UMa eclipses, it provides the opportunity to map the spatial extent of the superhumping light source... a pretty nifty trick. I'm *really* hoping for long European or Asian coverage of these stars, as that will enormously aid in defining the daily light curve. We get 9 hours from North America, but lust for more! Arto, you still out there? How about one bronze medal in X-country skiing for 3 nights on DW UMa? In the far south, there's EC05114-7955. Definitely the one to keep the pressure on... and I'd be grateful for whatever you can get on T Pyx (anyone sentimental about the old-timers?). We're trying to get a seasonal timing of T Pyx, it needs about 30 hours of coverage. Finally there's PQ Gem, making its debut in these pages. It's a DQ Her star, therefore definitely one of our boys. But its 13 minute pulse is *color* dependent, unlike virtually everything else we study. So it's awkward to do in white light - hard to interpret the results. Nevertheless, I'd like to run a campaign on it right now in the evening sky. We're doing it in BLUE light at MDM right now, so your own observations, effectively something like R, will provide "multiwavelength" coverage. Happy observing! joe From jop at astro.columbia.edu Fri Feb 22 09:01:38 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 22 Feb 2002 09:01:38 -0500 (EST) Subject: (cba:news) stars new and old Message-ID: Dear CBAers, Time for an update on campaigns. BK Lyn and DW UMa. These campaigns are going apace, with both stars performing well. BK Lyn is thundering away with a large-amplitude negative superhump, maybe the best such example in the sky. Keep it up! DW UMa, which sported a big negative superhump a few years ago, has turned double-agent and is now fraternizing with the apsidal superhumpers. Also worth continuing for a few more weeks. I recommend you adopt one of these stars and stick with it - it improves the night-to-night calibration, assuming you keep the same comparison star. We got some great data on PQ Gem this past week, and the star is worth observing on into the spring... but mainly for the purpose of pulse timings (requiring just a 2-hour run, though more is admittedly better). Ditto for BG CMi. Finally, up north there's TT Boo. Despite its brightness, we still haven't got good superhump and orbital periods for this star. It's in superoutburst now, and it's a great target in the morning sky. If you can start a run as late as midnight or so, this is the guy to do! Down south, it's still T Pyx and EC0511, for which data are coming in from Bob Rea, Berto Monard, and Fred and Jennie. Happy observing! Don't forget TT Boo! joe From jop at astro.columbia.edu Wed Feb 27 10:25:13 2002 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 27 Feb 2002 10:25:13 -0500 (EST) Subject: (cba:news) changing of the guard Message-ID: Dear CBAers, Some pretty substantial news about campaign stars... Bob Rea and Berto Monard have been plugging away on EC0511-7955, a 15th mag novalike variable described in a recent MNRAS paper by Chen et al. (describing photometry and spectroscopy of CVs from South Africa). Both have struggled with weather, but yesterday I spent half the day studying the spliced light curves over a 20-day baseline. And lo! Some beautiful periods emerged! The orbital period is manifest by a shallow eclipse, of variable depth but recurring with a strict 0.1414 d period. Negative superhumps at 0.1368 and 0.0696 d also occur; these are the wo+N and 2wo+N components, in the terminology that is becoming familiar. Finally the "nodal" signal at 4.2 d also appears to be present. So this star scores a 5.9 for technical merit... but only a 5.3 for presentation, since weather ravages have kept the coverage spotty. Let's make a big push now on Mr. 511, and impress those judges in the finals! In the north, the BK Lyn campaign has come to an end. The star has a very large negative (nodal) superhump, plus the nodal frequency itself (0.393 c/day). We have a 70-day baseline, so that's definitely good enough. Very late in the observing season (May), we'll want a few more timings - so we can explore the prospect of counting cycles *between* observing seasons (not yet achieved for any superhumps). What a beauty. But for now, let's get it off the stage and make room for.... BP Lyn = PG0859+415. Another "SW Sex star" with periodic humps (so far, the only known hump is orbital... but that's where we come in). Nicely positioned in the evening sky for attack by the CBA phalanx. Plus TT Boo, still humping away in superoutburst. Despite its brightness, we've just never managed to get good coverage of this star... badly timed superoutbursts I guess. Let's see if we can get this one covered! Oh, and let's show DW UMa off the stage too. We've got a good season's coverage, with a very fine apsidal superhump. Mission accomplished... make way for youth! So an easy program: EC0511, BP Lyn, TT Boo. joe by the way Jonathan is about to deploy some interesting new pages on the website... right, Jonathan?