From jop at astro.columbia.edu Tue Aug 16 18:10:03 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 16 Aug 2016 18:10:03 -0400 Subject: (cba:news) FO Aqr, done; AO Psc, let it begin Message-ID: <2c4f8ad3-7198-a442-8528-e24c8f527b4c@astro.columbia.edu> Dear CBAers, Great, great effort on FO Aqr - which has gone slightly faint this year. I've finished with the timing analysis, with the cycle count firmly established all the way back to discovery (1981). Gotta love that amplitude! But it's time to stop... unless the star fades a lot more. In October/November, let's re-visit the star to increase the accuracy of the period. This'll test the question: does the rate of period decrease track the accretion rate? (It should, according to theory.) Because a white dwarf's moment of inertia is so high - compared to a neutron star, anyway - it takes a while for the period change (of order miliseconds) to manifest itself. But it's a great time to get going on AO Psc - transiting pretty close to local midnight, and available to all hemispheres. V2069 Cyg remains good, as does V2306 Cyg (but for the latter,watch out for the field). joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Aug 23 05:27:29 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 23 Aug 2016 05:27:29 -0400 Subject: (cba:news) ES Ceti Message-ID: <5214ec75-6247-f24c-dfd5-f108e8484dd3@astro.columbia.edu> Dear CBAers, Cetus is rolling back into the morning sky, and we need one more season to complete our study of the period changes of ES Ceti. This is the (moderately) famous AM CVn star with a 10-minute orbital period, and a waveform showing an "eclipse" each orbit (anyway, a periodic dip). It's perfect for people with short attention spans but large telescopes. Actually, not all that large (it's 17th magnitude)... and not all that short either, since it takes many cycles to accurately measure the periodic 0.1 mag dip. But it's really a CBA special. And it's an ideal target for period study, because the binary is likely driven by gravitational radiation, which scales as a high power of the orbital frequency. Our study through 2015 shows an obvious period change - we just need to nail the rate down with a very accurate point for 2016. With Porb = 10 min, you don't need a long run, but should have ~10 orbits to give an accurate nightly timing. The waveform varies *slightly* from one orbit to the next, so some averaging is needed. Save the Whales, of course... but not this particular one. joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Aug 24 17:59:12 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 24 Aug 2016 17:59:12 -0400 Subject: (cba:news) Stars for August-September Message-ID: <82ec750b-7b6a-8f13-518c-d2ec44ef0b8e@astro.columbia.edu> Dear CBAers, It's time to pull the plug on a few stars. None have been overcome by onrushing twilight - the usual fate - but the coverage has been so good that the data excellently show the period structure and/or waveforms. These are V1494 Aql, FO Aqr, and V2069 Cyg. Done. A couple of runs in November on the latter two will secure the year-to-year cycle count beyond doubt... but lay off 'em for now. ES Cet is a great target. Slightly off season... but with a rapid payoff, since we only need a few weeks' coverage to nail down the period change. Three new northern stars which I recommend are these: V704 Andromedae. An old friend which we never published... and needing more observation. Preferably a lot more - worth making friends with. V1500 Cyg. 18th magnitude but with a 1 mag modulation. LS Peg and LQ Peg. There are published claims which conflict with our previous study, and with each other Let's find who, if anyone, was right. Nice bright stars, usually; definitely need long runs. I'd rate LQ Peg higher priority, but it's just a guess which will be more productive Enrique will advise on J2133+51 and KIC 9406652. These results are great, but he'll decide when we have enough. In the south, V4743 Sgr is currently my favorite, followed by the two Menfolk (AQ and AH; I think AQ is probably the better choice) But AO Psc and V380 Oph are good targets for all hemispheres! joe p P.S. still meditating on HR Del... ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Aug 24 18:28:45 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 24 Aug 2016 18:28:45 -0400 Subject: (cba:news) AR Sco and V1974 Cyg Message-ID: Oops, I forgot two eminently worthy stars: V1974 Cyg in the north, and AR Sco in the south. Both absolutely first-rate CBA targets! joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Aug 25 06:03:12 2016 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 25 Aug 2016 06:03:12 -0400 Subject: (cba:news) and add HR Lyr to the mix, with gusto Message-ID: <141deb67-f127-3c4c-f39d-2fbc0ff27208@astro.columbia.edu> Dear CBAers, The recent announcement of "HR Lyr gone faint" was awfully interesting to me. While faint excursions of CVs are not particularly rare, they're (a) still mostly unexplained by theory, and (b) particularly rare and mysterious for the remnants of recent novae. HR Lyrae erupted in 1919, the year of the Black Sox scandal - that's "recent" in the lives of classical novae. At mag 16-17, HR Lyrae is accessible to most CBAers. So definitely add it to the current menu! The menu is getting crowded. So among the stars newly added, let me list the ones somewhat more likely to have a payoff soon (because we have papers in preparation): V704 And, ES Cet, and V1974 Cyg. That doesn't count two others in an advanced state of preparation, but which were listed earlier: RX2133+51 and KIC 9406652, which Enrique will advise on. And of course AR Sco, the craziest CV to come down the pike in many years. I dunno what we'll do with that one, but it sure does put on a show! joe p p.s. I hope to see a bunch of you at the AAVSO meeting in November. ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/