From jop at astro.columbia.edu Thu Dec 6 08:11:18 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 6 Dec 2018 08:11:18 -0500 Subject: (cba:news) stars for Dec-Jan 2018/9 Message-ID: Hi CBAers, In the north, long nights. In the south, our juiciest targets. Great time for long time series of CVs. Much of our recent work has been on novae (in particular, "old novae"). The reason is that we're testing the theory that classical novae may have a dominant effect on long-term CV evolution - basically by destabilizing (by heating) their secondaries. Our BK Lyn paper of 2013 explored this, and it needs to be tested by application to other stars. That's why I keep harping on T Pyx and CP Pup, where it's most likely to apply (because their secondaries are *feeble*). These two stars are back in the night sky, and merit close observation. CP Pup merits INTENSE observation - round-the-world if possible. Why? Because its period structure - the key to measuring the mass ratio - appears to contain 2 significant, closely spaced periods. At least one of these periods has low coherence, and is possibly the rarest of superhumps - arising from the 2:1 orbital resonance, rather than the 3:1 as is common for superhumps. Testing that would be a coup! The other well-placed old nova for coverage is V959 Mon. Its 7-hour orbital light curve should change as this 2012 nova fades. Let's find out how! Our many-year campaigns on AM CVn stars are finally yielding dP_orb/dt, which has been the long-term goal. We published the results on ES Cet, which "confirmed" (i.e. were consistent with) the prediction from GR. But having produced a long-term ephemeris, we need to check if the star is now obeying it. (We need not only laws, but also police!) And that brings us to AM CVn itself. Almost every year, I say "just one more year" to nail the long-term ephemeris. And, to my embarrassment, I'm back saying that again. But this time, I PROMISE to publish the long-term ephemeris no matter what. I've been bashful about it because its shape appears to signify negative dP/dt, which is incompatible with the commonly held theory that it's a double white dwarf. This year, I've decided to go with the data no matter what the "commonly held" theories say. But now that Can Ven has rolled around again, let's wrap it up with 2018-9 coverage. Unfiltered coverage *definitely* OK for this one. There's an abundance of DQ Her stars filling the Dec-Jan northern sky. V405 Aur, V418 Gem, DW Cnc, HT Cam, and AO Psc are all CBA program stars which need a season (at least a month, anyway) of coverage. Most are fairly easy targets; but HT Cam is faint... and DW Cnc requires LONG nightly coverage because the spin period is long. And AT Cnc is a promising applicant to this club. Its credentials are still mixed. If you want to do it a favor, select it as your "star for the season". We're JUST about to send the ASASSN-18ey paper off. Can anyone squeeze in a few V-band measures in the evening twilight? Just to nail it shut for the year... and bridge to the early-season observations next March. No time-series needed - just a few points will be fine. As usual, unfiltered light is generally OK, and slightly preferred, for CBA light curves. But if you have a lot of photons, pop in the V filter (better for archival purposes). Another good approach is: unfiltered time series plus a few V-band measures to establish the level of mean light in a calibrated system (V is calibrated, unlike unfiltered*). Happy observing! joe *But watch out if your CCD has good UV response. UV light is mildly terrible, since its extinction coefficient is so high. Not welcome! The best variety of "unfiltered" system uses a glass filter to block the UV. ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Dec 6 08:18:01 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 6 Dec 2018 08:18:01 -0500 Subject: (cba:news) apologies to BW Scl Message-ID: <6d97b48e-0e8e-45b2-6631-06256c0df0fb@astro.columbia.edu> Dear CBAers, Oops, I forgot BW Scl, another fascinating star with a very likely 2:1 resonant superhump in the disk. About one month left in its (southern) observing season. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Dec 18 12:24:05 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 18 Dec 2018 12:24:05 -0500 Subject: (cba:news) stars for the new season Message-ID: <808e85b5-9a47-a494-8e4f-9a27eec630b0@astro.columbia.edu> Hi CBAers, Getting ready for the solstice... Stars ready to retire for the season: RX J2133+51. This is Enrique's guy. I'll give him a chance to veto this... but methinks it's done for the year. BW Scl. We have plenty. The runs are getting short, and the strangest feature seen in this star - the alleged "2:1 superhump" is muted this year. T Pyx, believe it or not. The season is just starting, but the early season coverage from the usual southern stalwarts (Josch, Gordon, Berto, Peter) showed that the star is exactly following its 2011-2017 ephemeris. ES Cet. Same story. keeping to its schedule. ASASSN-18ey. Of course. It's in Aquila. You can't get blood from a turnip. Thanks to those (esp. Joe U) who battled evening twilight to get a few final magnitudes. We seem to have become the world's major supplier of data in two categories: pulse timings of DQ Her stars, and orbital light curves and period changes in novae. These are very much traditions worth continuing, and that goal strongly influences my recommendations for targets in this season. IN THE SOUTH: Mainly the Puppis "gang of three" old novae: CP, HZ, and V598. The second is magnetic, and the third probably is. Time to get another season and get that into print. CP Pup is the most mysterious, and amazingly resistant to surrendering its secrets to time-series photometry. Probably it needs something close to round-the-world coverage. Why? See bottom of this message (technical reason, and not likely interesting to northerners) Plus two DQ Her stars: V667 Pup and WX Pyx. IN THE NORTH: Mostly the DQs (intermediate polars) which have been previous winter targets: DW Cnc, HT Cam, V1062 Tau, V1033 Cas, V418 Gem, V647 Aur. Let's suspend AT Cnc for now. I'll have the analysis done by Jan 1, and we might resume. Plus two northern stars which probably belong to the very exclusive "asynchronous polar" club: BY Cam and "Paloma" (5 24 30.5 +42 44 50) Plus two other stars: the old nova T Aur and the eruptive-and-seemingly-weird star ASASSN-18abl (03 00 55.08 +18 02 29.0) That's it for now! joe p CP Pup arcana. Its orbital frequency is almost certainly 16.32 c/d. It has a photometric (and spectroscopic) signal at that frequency. It also has an occasional big superhump at (I'm almost sure) around 16.05 c/d. That's pretty normal stuff. But in the season of best coverage, the latter signal VERY STRONGLY favored 15.1 c/d, which is sort of a shocker. The only sure way to beat a 24-hour alias is to have continuous observation over >24 hours... and the only way to do that is when the star is near opposition (Jan-Feb). So you might want to keep your powder dry for a while. ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Dec 27 09:50:11 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 27 Dec 2018 09:50:11 -0500 Subject: (cba:news) V598 Puppis - and its deckmates Message-ID: Hi CBAers, This peculiar 2007 nova - sometimes called Nova Pup 2007b - was covered pretty well last year by Gordon and Berto. It showed decent but not decisive evidence for periodic signals at 33 and 21 cycles/day. We just started this season's campaign... but Josch joined the act, and the evidence now looks very, very good - especially the 33. Thus it is probably a new intermediate polar, and should be considered very high priority now. It's confusing, because the other 2007 Puppis nova, V597 Pup, is also probably an intermediate polar (according to Warner and Woudt). Keep 'em straight. V597 Pup also a very tempting target, if you can handle the required short integration time (~1 minute for the 4.5 minute period), near 17th magnitude (or fainter?) This - the DENSE coverage of V598 Puppis over the next ~2 weeks - is now the highest priority among (faint) southern targets. ES Cet and T Pyx are nailed down for the year - well-behaved stars! CP Pup can wait. HZ and V667 complete the traffic jam of CBA stars on the poop deck. joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/