From jop at astro.columbia.edu Wed Jul 2 09:04:11 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 2 Jul 2003 09:04:11 -0400 (EDT) Subject: (cba:news) observing campaigns Message-ID: Hey CBAers, Michael's suggestion re same-longititude-same-star observations appears sound to me. I don't think the background chatter on "news" is too high for anyone quite yet. I do have a word of warning, though. We've tried this before, with not so good results. Consider some of the factors which dilute our frequency of observation. (1) Since this is an "amateur" collaboration, no one is technically at work (and nobody ever gets mad about it, or for that matter anything else). No one manages to observe quite as much as they hoped. (And if you do, you need to increase your hopes) (2) Nearly everyone fights against the weather. (3) People have a tendency to defer to the bigger telescopes. Finally, I use overlappped observations to calibrate one observatory against another. I don't need very much overlap to do this... but I do need some strictly simultaneous overlap of good quality. Not to stress the point too much, though! I do think that observer communication is useful for many things, certainly including "when to take a break". By the way, some more discussion re V603 Aql. This is the brightest superhumper in the sky, the most equatorial, and the superhumps appear to be the most permanent. Thus it definitely seems like the best choice to learn more about the fine structure of superhumps. We made a decent start on this in our 1997 paper - but it's time to "take it to the next level" (American sports lingo). We do need contributions from all longitudes to keep the spectral window benign, though. I'm hoping the Kiwis and Aussies will get interested in this, as we rely on them for a huge swath of longitude! joe From jop at astro.columbia.edu Fri Jul 4 22:14:52 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 4 Jul 2003 22:14:52 -0400 (EDT) Subject: (cba:news) those devil dwarf novae... Message-ID: Well, I never feel totally happy about chasing dwarf novae... it has started to feel a little too "mainstream". Still, the lure of freshly erupted *new* dwarf novae, with virgin superhumps, is too much to resist. Thanks to Berto and Major Tom, and to Rod Stubbings of course who operates on another plane of existence, we have freshly formed superhumps now in V699 Oph, NSV09923, and V1141 Aql. The first two are altogether new, while the latter was studied just once before in superoutburst. Thus there is a great deal to be learned here about all three stars. NSV 09923 is far southern, at 17 59 16.52 -42 35 06.8. It's a great target for you southerly folks. The other stars are equatorial. V699 Oph is well-placed in the evening sky at 16 25 14.76 -04 40 25.6 -- fun for citizens of all latitudes and longitudes. V1141 Aql is at 19 37 09.81 +02 36 00.5. I'm definitely inclined to declare "campaigns" on each of these stars, with V699 Oph top priority, followed by NSV 09923, followed by V1141 Aql. But these "priority assignments" basically represent a guess about the scientific utility - don't take 'em too seriously, it's a guess that blows to and fro as the superhumps wave in the wind. How do these stars rate in comparison to the present campaign targets? 1. I'm inclined to *retire* WGA1958+32. Cap'n Bob and MDM coverage have nailed it to the wall. 2. The three pulse-timing stars (FO Aqr, AO Psc, V1223 Sgr) should remain as the pulse-timing project is a really key one, in my opinion. But I've seldom had much luck getting CBAers interested in this. 3. I think V4743 Sgr is less important than the dwarf novae - and can take a break. 4. Finally there's V603 Aql. This is in a class of its own, and it would be good if some of the smallscopers kept up the coverage relentlessly for the next six weeks. The fading dwarf novae and the growing Moon are going to hurt the smallscopers especially. I hope that we can bring home those dwarf novae, and keep V603 Aql well serviced too! Joe (feeling greedy) From jop at astro.columbia.edu Mon Jul 7 09:44:55 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 7 Jul 2003 09:44:55 -0400 (EDT) Subject: (cba:news) Struggling with Olde Whiteface Message-ID: A number of CBAers have been waging a good fight with 15th mag dwarf novae this week. But it has also been very hazy in the eastern USA through the week (actually since March)... and I wanted to toss in some remarks about photometry, in case you find them useful. In theory, clouds equally cover the comparison star, the variable, and the sky annulus. Then the software can do the appropriate subtraction/division to yield a delta-magnitude of reasonable quality. Degraded by extra noise, but still reasonable. We usually don't consider the possibility that clouds systematically prefer the variable to the comp, or vice versa. Too Oliver-Stone-ish for normal science. But sky background, now that's another story. You can basically rely on clouds to extinct stars pretty equally... but the effect of sky background depends very greatly on how lit up the clouds happen to be. Brightly lit clouds *increase* the counts when you're observing a faint star, but *decrease* counts when you're observing a bright star. You might think, "well, doesn't the delta-mag extraction take that into account?" Yes, sort of... in theory it does. But we are afflicted with ambitious hopes and modest scopes - so when moonlit clouds arrive in our data, sometimes the counts are entirely dominated by noise in the rapidly varying sky brightness, and the delta-mag has little to do with the target star. You can expect this scenario to kick in when the stars (either star) are faint and the sky background bright and varying. Proximity to the Moon is additionally deadly, since your general sky inspection may underestimate the perils in the exact pointing direction. This is a pretty good description of V699 Oph in the last week, for many observers. You can evaluate the peril by inspecting individual frames, to see if the stars are actually swamped by sky counts. Or, you can switch to a brighter star. All these problems are much ameliorated when you go to a brighter star. Speaking of which... anyone ever heard of V603 Aquilae? joe From jop at astro.columbia.edu Fri Jul 11 16:47:49 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 11 Jul 2003 16:47:49 -0400 (EDT) Subject: (cba:news) V699 Oph Message-ID: Dear CBAers, Well, despite the unfavorable position with respect to Sun and Moon, we are getting some pow'f'l innerestin' data on Mister V699! The star is showing some very revealing fine structure in the superhumps - but we need some more data to clinch the case (before it fades). This is a tough object and you might want to use a red filter (assuming you want to do it all). I don't recommend it for anyone - it's too tough for mass consumption. But I wanted to sound the alarm right away, since the data's pretty time-critical and so far we just have the three longitudes (Utah, Arizona, Uzbekistan) contributing. joe From jop at astro.columbia.edu Sun Jul 13 08:55:47 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 13 Jul 2003 08:55:47 -0400 (EDT) Subject: (cba:news) V699 Oph, r.i.p. Message-ID: Looks like the sun/moon/star circumstances have acted in concert to shut down useful data on this star... no matter how much I might hope for it. Time to move back to V603 Aql, and conquer the Moon. joe From jop at astro.columbia.edu Sun Jul 20 05:24:38 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 20 Jul 2003 05:24:38 -0400 (EDT) Subject: (cba:news) July stars Message-ID: Dear CBAers, Well, now that the Moon has moved outa the way, we can bring down the curtain on V603 Aql. The intense 40-day campaign is over. Results in a few weeks - there's so much data to analyze! (To a first approximation: our old friend, the apsidal superhump; the nodal superhump wasn't obvious.) The star remains a fairly interesting target, though; additional coverage will track the O-C of the superhump and improve the quality of the search for weaker signals. The two northern targets to focus on now are V533 (about 14.7) and V1974 Cyg (I think about 16, but I really dunno). The latter is particularly interesting, because of fancy press clippings ("Nova of the Century") and more especially because this year's spectroscopy shows that the 1992 nebula has faded now and left a pure nova remnant to study. The only light curve this year shows a nice hump, origin unknown. Great target for all-night coverage from borealites. V533 Her is also plenty interesting - beautiful superhump in Feb-Mar, and now we'd like another month to establish a full 6-month baseline for period studies. Decently bright and well-placed. For CBAers of the other hemispheric persuasion, I recommend V4743 Sgr and V1223 Sgr as main (most-of-the-night) targets, with the pulse-timers AO Psc and FO Aqr as second targets. joe From jop at astro.columbia.edu Mon Jul 28 07:34:42 2003 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 28 Jul 2003 07:34:42 -0400 (EDT) Subject: (cba:news) New stars for July/August Message-ID: Dear CBAers, Well we're just about to push the final version of the "20 dwarf novae" paper out the door. Most dwarf novae turn out to be pretty ordinary (of course), and so we decided to toss our coverage of 20 of 'em into one paper - orbital and superhump periods for each. The world should also reckon this a merciful act. The author list was: Patterson, Thorstensen, Kemp, Skillman, Vanmunster, Harvey, Fried, Jensen, Cook, Rea, Monard, Velthius, McCormick, Walker, Martin, Bolt, Pavlenko, O'Donoghue, Gunn, Novak, Masi, Garradd, Butterworth, Krajci, Foote, and Beshore. To the coauthors, sorry we didn't consult on any of this - it seemed like an impossible task. We'll post the thing on the website as soon as it's accepted, and mail copies out right away. I thought the main conclusion was pretty interesting - that the secondary stars have essentially solar composition, and a radius 18+-6% greater than theoretical "zero-age-main-sequence" stars. Since the theoretical models have likely radius uncertainties of ~10% (or more?), you can roughly say that this certifies the secondaries as "main-sequence stars". Why is that interesting, since it has been so stated for 30 years? Well, because throughout those 30 years, there have been hundreds of allegations to the contrary. Often based on just one star, and not quite appreciating the uncertainties... or on treating the theoretical models as Holy Writ. For years we have been in the business of making these rather precise measures of periods (orbital and superhump), and yet I could never find a way to cash 'em in - use 'em for a tight numerical constraint on physical variables. I think we've learned how to do that now. V4743 Sgr. Whoa, Nellie! What a swell star this has been! An Australite gang has been hard at work on it - Berto Monard, Jennie McCormick, Bob Rea, and Greg Bolt... and Tut Campbell has obtained a few nights from Arkansas to fill in the long gap westward from South Africa to New Zealand. This recent nova has a large sinusoidal signal at 6.69 hours, which I take to be the orbital period, and another signal at 69.53 minutes. Union regulations require interpreting the latter as the spin period of a magnetic white dwarf. We dunno whether this is actually true, of course, but it will be damn fascinating to watch it change as this bright and recent nova declines many magnitudes down to true quiescence. Definitely worth tracking as it fades off into the western sunset. Alon Retter has a good measure of these periods too, which he sent me a few weeks ago. This was obtained earlier, so I imagine we'll merge the datasets to get the best leverage on the star's behavior. Berto has unearthed an interesting new CV from the SDSS collection - namely SDSS J2258-0949. Berto, can you send exact coords and references? Kind of a mystery star, wanders rapidly over a 1.5 mag range. Very nicely positioned for all observers, decently bright (13.5-15 I believe)... and a good target for an all-world campaign starting now! In this dark-moon period, it would be awfully timely to cover V1974 Cyg. Even though it was only "The Nova of the (20th) Century", I hope you won't consider it too old-fashioned to keep tracking its odd little periodic wiggles. At last sight a few years ago, it was nicely endowed with both positive and negative superhumps. A greater target for northern bigscopers (it's about 16th mag I think). Finally a coupla items just off the presses. VW CrB went into superoutburst; I woulda been really happy for good data on this star, but am worried about the bad seasonal timing. Europe still has bright nights, we still have no coverage in east Asia, and CorBor doesn't stay up long. Anyone manage to get some good runs on this star? I noticed that Paul Schmidtke, using Bob Fried's telescope, found LQ Peg in a rare low state. This would be a great target for us - but only for bigscopers. Magnitude 17 (or fainter). Give it a try! In summary for targets: DELETE V1141 Aql and V533 Her. PRIMARY TARGETS are SDSS2258-09, V1974 Cyg, V4743 Sgr, LQ Peg SECONDARY TARGETS are the pulse timers (V1223 Sgr, AO Psc, FO Aqr) and VW CrB As usual, this is just a rough guide. It often happens I get hot and heavy over a star that turns out to be a dud - and miss some great ones as a result. Trust your own instincts on this. But it definitely pays to persist on a particular star! Aesop had it right... slow and steady wins the race. I'm (almost) fully moved back to NYC, I'm managing to play a lot of golf, and the Red Sox have won two straight over the Evil Empire (aka the Yankees). Happy, happy. joe