From jop at astro.columbia.edu Tue Jan 7 08:23:52 2020 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 7 Jan 2020 08:23:52 -0500 Subject: (cba:news) HZ Puppis! Message-ID: <9fd2f19b-0b64-2569-c69d-b8d58d83090f@astro.columbia.edu> Dear CBAers, We'd like to make a strong effort to go round-the-world on HZ Pup, the remnant of a 1963 nova. Tim Abbott and Allen Shafter identified it as an intermediate polar in the mid-1990s, and our scattered coverage over the last decade has confirmed. However, the power-spectrum is unusual, with nu-orb and nu-spin... and two other stable signals which are near nu-spin. To separate all these things out and decisively identify them, we need round-the-world coverage. I'm too old for space (I could never take the 8 g's), so let's try to do it CBA-style. January is the perfect month, but the star is fairly southern (-28 deg), so we have THREE big oceans to contend with. So far this season, only Gordon has worked on this star. But Berto could do it in South Africa, and Josch could get slow coverage from Chile (maybe replacing V598 Pup, Josch?). But for fast coverage in the Americas, we're probably relying on observers in Florida, Texas, and California (or for more northerly people who have great southern horizons). To beat the inevitable aliasing, it's not necessary to be contiguous in time, so you don't have to fuss over who is clear where and when. If you're near a big ocean, then you have a special role to play. Here's looking at you, Greg (Bolt) and Jennie (McCormick)! The periodic signals are strong (0.15 mag), but you might not be able to see them, as the three signals beat in and out of phase. Also, the star is magnitude 16.9. Meanwhile, there are other campaigns, on which Enrique has discoursed eloquently. I especially recommend DW Cnc because of the strangely high value of Psin/Porb. HZ Pup 2000.0: 8:03:22.8 and dec -28d 28m 28s. Magnitude 16.9. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Jan 31 15:27:38 2020 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 31 Jan 2020 15:27:38 -0500 Subject: (cba:news) stars for february-march Message-ID: <0540cb29-3dc1-efb2-6bdb-9881e619e16d@astro.columbia.edu> Hi CBAers, Here;s my list of changes in the observing program. These are all cases where we expect to complete observations (i.e., enough to publish) in 2020. There are others, worthy targets but not quite in that almost-done category. I'll list them in a fe days. PLus this list is independent of Enrique's (he is working on different stars). We have enough for V1062 Tau and HZ Pup. Both difficult stars - but we finally battled through to find an ephemeris. Our biggest faves in recent years have been T Pyx and AM CVn. The Sun has finally gotten out of their way, so let's start up our 2020 effort. The prescription for both is basically: as-long-as possible (with <2 airmasses) and as often as possible. The main reason for such greed is simply that - greed. We all long to see power spectra with towering peaks leaping out of the noise! But for AM CVn, there's an extra reason. ings are more complicated. The following is recommended only for true AM CVn devotees. AM CVn's 1028-s orbital signal is quite weak, about 2-5x smaller than the superhump signals which are clear in the light curve, By itself that is no great problem; one could just amass enough data to beat down the noise. Around 3 good-quality and closely-spaced nights would probably reveal the orbital signal very clearly - amplitude and phase. The trouble is that the strong superhump signals are at 1051, 525, and 1011 seconds, plus a few weaker guys... and they're ALL UNSTABLE on a timescale of a few weeks. That instability means that I can't accurately remove these contaminating and fairly strong signals, unless the data are tightly grouped in time. This greatly favors the "long runs on consecutive days" approach. But as these signals slowly drift in and out of phase with each other, there are intervals when the corrupting effects are really maximized. And that might occur in mid-observing -season (Mar-Apr)... so let's pull the trigger now. WE don't need a lengthy campaign. After the 2019 season, I already wrote most of the paper... but pulled it back for reasons that are 90% greed and 10% doubt. One more season will remove that sliver of doubt (re the decades-long change in P_orb). Whew. All that arcana applies only to AM CVn. Everything else, certainly including T Pyx, obeys common sense - the more, the better. One other northern request: QS UMa (H0928+50, as we used to call it). It's a 17th mag guy with an eclipse every 20 hours. Perfectly times for northern observers. And our biggest need is for (brace yourself) V-band photometry. Ideally one orbit in V and one in clear. But the V orbit is mainly to *calibrate* the clear. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/