From jop at astro.columbia.edu Sun Apr 3 09:35:02 2011 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 03 Apr 2011 09:35:02 -0400 Subject: (cba:news) dq her pulse maintenance Message-ID: <4D987786.9040201@astro.columbia.edu> DEar CBAers, The ER UMa campaign is going very, very well: 70 nights of nearly continuous data! But as it gets better and better, the *percentage* improvement of coverage gets less and less. The main goal - understanding how the negative superhump interacts with the various normal and super-outbursts - is likely to be significantly enhanced by more coverage. So *some* coverage of the star, especially near quiescence at V=15, is still quite desirable. But I'm inclined to pull the plug on it now as a major campaign target. Likewise for SDSS1339+48. The super-outburst is long over, and, as is typical of these WZ Sge stars, the superhump lingers for a long time - like a headache after you bump your head. I'd say the law of diminishing returns has knocked this star off our menu. The star at quiescence has white-dwarf (rapid) pulsations, so at some point we want to revisit to see if they have returned. But that's mainly a project for 2012, not now. Sayonara. Finally, YZ Cnc. Another long and successful campaign, with coverage in quiescence, normal outburst, and superoutburst... and 2 months long. I'd be inclined to end this campaign also. However, Arek Olech will be writing this one up, so I'll give him the chance to register an opinion on this. Unless another glamor star fires up, we've got an opportunity to do some serious maintenance work on the ephemerides of DQ Her pulses. Time-series photometry early and late in the observing season is always of extra value since it constrains the cycle count in the typically 8-month gap between seasons. And (northern) spring is ideal since it can service the two main clusters of DQ Hers: in the winter and summer skies. Sorry for the long list, but here are evening stars who can really use the attention: HT Cam, RX0636+35, RX0704+26, Swift0732-13, WX Pyx, DW Cnc (long run only), PQ Gem, MU Cam. Vaguely in order of declining priority, but really, it's not possible to predict which stars will have high potential for high-impact observations, since it depends on the rate of period change - which is unknown, and is the point of observing them! Unlike our usual observing philosophy, these stars don't need particularly long runs (3 hrs is plenty), and you can do a menagerie of stars without concern about diluting your efforts. And here are morning stars, with same comments applying: DQ Her (maximum 20 s cycle time), NY Lup, RX1654-19, V4743 Sgr, RX1730-05, and V1223 Sgr. And two middle-of-night guys: EX Hya and YY Dra. The latter would probably repay observation in *blue* light - and probably would need quite long nightly observations (there's an M dwarf which is annoyingly strong in the spectrum, and needs to be subdued. Finally, there's AM CVn and HP Lib. Very, very good targets, in the prime of their seasons... and if you like the all-night targets, these are the stars for you! joe From jop at astro.columbia.edu Mon Apr 4 07:07:10 2011 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 04 Apr 2011 07:07:10 -0400 Subject: (cba:news) NSV1436, ER UMa, BK Lyn, DW UMa Message-ID: <4D99A65E.7030305@astro.columbia.edu> Dear CBAers, Some comments on other recent and present campaign stars. I wanted to remind that ER UMa does continue to be a good target for coverage at/near quiescence (around 15.0-15.3). We don't need the many-longitude-all-night light curves... but it will be very interesting to study the coherence of the powerful negative superhump over a long interval - and the 60-day baseline already is a great start. The exact origin of negative superhumps is still mysterious, and where the amplitudes are large, that's where we're likely to learn the most. Some of the amplitudes are impressively - even disturbingly! - large. That's true of ER UMa, V503 Cyg, BK Lyn, and DW UMa. And speaking of the latter two... We have only sparse data on DW UMa this year, but it does appear that the negative superhump is having a bad year (not yet visible). So let's drop that one. BK Lyn, on the other hand, is sprouting large negative superhumps, as it did in our long 2000 campaign. So that one is very definitely worth pursuing - and in fact, since it got significantly pushed aside by erupting dwarf novae and other seductions around 9 hr right ascension, increased for the next month or so. Josch Hambsch has been observing it assiduously, but the other coverage has been sparse. Another month would be great! I'm pessimistic about NSV 1436. Perseus looks good to the naked eye during April evenings... but not so much for photometry. We haven't got a definite result out of the light curves so far, and it gets worse each day. I think we should suspend this one. joe From jop at astro.columbia.edu Wed Apr 6 16:07:11 2011 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 06 Apr 2011 16:07:11 -0400 Subject: (cba:news) more on bk lyn... the magnificent Message-ID: <4D9CC7EF.5010507@astro.columbia.edu> Dear CBAers, I wanted to talk a little more about this star, which I'm now writing up after several intensive years of study. It's probably the most interesting of the small family of negative superhumpers. In what was basically the first CBA paper, Skillman & Patterson (1993) found a common superhump: a 0.05 mag signal at a period 5% longer than Porb. In retrospect, no great surprise there - we know now that essentially all stars of sufficiently high Mdot and sufficiently short Porb manufacture such signals. We went back to BK Lyn with 50-day campaigns in 1999 and 2002, and short campaigns in two other years. The two long campaigns showed a complex and fascinating power spectrum: very strong signals at 0.394 and 13.739 c/d, and weaker but definite and sharp signals at 12.760, 13.344 (the radial-velocity frequency), 25.521, and 27.475 c/d. Each with an error of 0.002 c/d. It was confusing at first, since the two superhumps are displaced by ~1.0 c/d - so if you don't have very good frequency resolution, they look like simple daily aliases. In my lexicon (not in general use yet), the signals are at N, wo+N, wo-A, wo, 2(wo-A), and 2(wo+N). And the superhumps are *extremely* stable: basically perfect over the ~50-day baselines. Other than a few mentions in conferences, I still - shamefully - haven't written this stuff up. But I am now! And so it goes this year, too. Because of competition in the evening sky (mainly YZ Cnc and ER UMa), the coverage hasn't been great - except for that of Josch Hambsch. Though the 2011 coverage is sparse compared to previous years, there appears to have been an outburst this year, around March 29. I can't tell for sure since we haven't standardized our comparison stars (and there's not enough overlap to calibrate 'em)... but I think so. This could be of great interest, since it could be a distance calibrator (if it's substantially like a dwarf-nova), and also because it may offer some insight into why the star selects between apsidal and nodal superhumps. I say all this to encourage a few more weeks of work on BK Lyn before saying goodbye for the year. Also, it would be nice to get calibrated broadband colors of the star (which we never have). The stability of the nodal superhump is unprecedented - to the point of being suspicious. We should follow the signal deep into evening twilight in May, and pick it up again in morning twilight in October - to see if it is actually phase-stable over the six months. And if it is, then we can keep stretching the baseline to get a good measure of stability. BK Lyn is a pretty bright star: usually 14.5-15.5 and with beautiful periodic signals. A light curve suitable for framing! In the south, Berto's newly found SU UMa star (OT J132900.9+365859, a Catalina-discovered transient) is a very good target. I'm still confused about DR UMa. Anyone want to chime in? Is this a good target, or not? joe From jop at astro.columbia.edu Wed Apr 13 15:19:59 2011 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 13 Apr 2011 15:19:59 -0400 Subject: (cba:news) Fwd: Fwd: BK Lyn Message-ID: <4DA5F75F.1060108@astro.columbia.edu> -------- Original Message -------- Subject: Fwd: BK Lyn Date: Wed, 13 Apr 2011 21:02:54 +0200 From: Enrique de Miguel To: Joe Patterson Hi Joe, I've sent this message to the cba-chat, but for some reason it doesn't get through. Any problem if you forward it to the distribution list? Two GSC designations in the table included below were wrong in the original message and they have been now corrected. Note that there is non-cataloged variable in the field, which I think is the comp you used in the 93 CBA paper with Skillman. Thanks, Enrique Begin forwarded message: > *From: *Enrique de Miguel > > *Date: *13 April 2011 19:16:08 GMT+02:00 > *To: *cba-chat at cbastro.org > *Subject: **BK Lyn* > > As Joe pointed out, this star is persistently showing negative > superhumps. Currently peak-to-peak variations are ~0.20 mag, > but they used to be as large as ~0.6 mag 20-30 days ago. > Nice target ...... > > I've proceeded to calibrate a number of stars in the field of BK Lyn > in the B and V bands. For BK Lyn followers, appropriate values > and comments are given below, along with a DSS chart. Keep > in mind that I'm not a "calibrator" and these values should be > regarded as a guide. The bluest "bright" target in the field (apart > from BK Lyn) is #4 (GSC 2496-0893), with B-V=0.53. This is the one > I'm using as comp star for BK Lyn. > > Note that star #9 (GSC 2496-0739) seems to be a (non-catalogued) > variable (details below). Incidentally, this seems to have been > used as comp star in Skillman and Patterson A&A 417, 298 (1993). > > Enrique > > > Calibrating BK Lyn field > > #label name V B-V erV erBV > 2 GSC 2496-1004 14.950 0.714 0.004 0.005 > 3 GSC 2496-1453 14.890 0.925 0.004 0.004 > 4 GSC 2496-0893 13.897 0.533 0.003 0.004 > 5 GSC 2496-0769 13.991 0.610 0.003 0.004 > 6 GSC 2496-1173 14.010 0.783 0.001 0.004 > 7 GSC 2496-1374 14.286 0.672 0.007 0.003 > 8 GSC 2496-0907 13.529 0.839 0.002 0.006 > 9 GSC 2496-0739 13.262 0.941 0.006 0.012 > 10 GSC 2496-1579 14.260 0.773 0.005 0.003 > 11 GSC 2496-1060 14.852 0.620 0.009 0.008 > > Comments: > 1. Values based on measurements carried out on 4 nights (8, 9, 10, 12 > April 2011) under excellent conditions. > 2. Errors indicate standard deviations about the mean value > calculated over the 4 nights and do not include errors > associated with the transformation. The latter are less > than 0.012 in B band and less than 0.010 in V band. > 3. Star #12 is NSVS 7454553 (pulsating RRab Lyr). > 4. The bright star in the SE is WASP-13 (star hosting an exoplanet). > 5. Star #9 is a non-catalogued low-amplitude variable star, with peak- > to-peak variations of ~0.06-0.07. The periodicity is still uncertain, > but very likely P=0.741(9) d (if pulsating) or multiples of P if > eclipsing. > 6. Nightly values of B-V for BK Lyn show slight variations. For > the 4 calibration nights these values are: 0.025, -0.048, 0.036, > and 0.059, values which are otherwise expected for a target of > this nature. These are instantaneous values and not nightly > averages. > > > > > > > From jop at astro.columbia.edu Fri Apr 15 08:02:21 2011 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 15 Apr 2011 08:02:21 -0400 Subject: (cba:news) Fwd: T Pyx observing campaign Message-ID: <4DA833CD.9010102@astro.columbia.edu> Dear CBAers, I'm battling a bad flu this week, which explains my silence re T Pyx. But the season is not so bad, and since it has been a 45-year wait, this will be likely be our only chance to study this fascinating star in outburst. Jonathan, could you authorize Brad to use cba-news (and I believe all recipients can use cba-chat). Brad can advise more specifically... but some general wisdom re bright-star photometry is: * use a V filter if you have one, and short exposures; * consider using a soft focus (out of focus) image as this will combat saturation; * trade notes re comparison-star selection (somebody's likely to discover the best choice out there); my guess is that multiple-comparison-star approach - which some of you use - is not a wise choice at all. I'm still not thinking - or typing! - all that well, so your own common sense should trump what I've said. It's an exciting opportunity! joe -------- Original Message -------- Subject: T Pyx observing campaign Date: Thu, 14 Apr 2011 23:52:19 -0500 From: Brad Schaefer To: jop at astro.columbia.edu Hi; With this wonderful opportunity, I would like to have a campaign to observe T Pyx with fast photometry with extensive coverage. The idea would be to repeat our extreme success with U Sco, where our 37,000 magnitudes covered the entire eruption with an average of one magnitude every 2.6 minutes. So I propose to ask CBA people to help by putting out an appeal on the CBA email exploder. But I think it best to ask you for whether this use of your email exploder is OK. Cheers, Brad From jk at cbastro.org Thu Apr 28 14:15:37 2011 From: jk at cbastro.org (Jonathan Kemp) Date: Thu, 28 Apr 2011 08:15:37 -1000 (HST) Subject: (cba:news) status update Message-ID: Hi, Just a quick note to say that we are experiencing upstream network issues with our host institution. We hope to have a solution in place by the weekend to restore core communications services. Cheers, Jonathan CBA Hilo From jk at cbastro.org Thu Apr 28 14:15:37 2011 From: jk at cbastro.org (Jonathan Kemp) Date: Thu, 28 Apr 2011 08:15:37 -1000 (HST) Subject: (cba:news) status update Message-ID: Hi, Just a quick note to say that we are experiencing upstream network issues with our host institution. We hope to have a solution in place by the weekend to restore core communications services. Cheers, Jonathan CBA Hilo