From jop at astro.columbia.edu Tue Sep 12 01:30:21 2017 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 12 Sep 2017 01:30:21 -0400 Subject: (cba:news) stars for september Message-ID: <96164541-a350-83e7-cfed-16345ba6e6db@astro.columbia.edu> A new menu for the month... -------------- next part -------------- Dear CBAers, The seasonal change looms... time for a new menu of stars. V407 Lup. Our data, from Gordon and Berto, show this recent classical nova to be a 3.3 hour binary (common enough) and a 9.5 minute DQ Her star (very rare for a classical nova). Great... but we started too late in the season to complete the study, and we'll suspend until next April rolls around. WZ Sge. Great coverage this year, especially by Geoff Stone. I've analyzed all the runs until Sept. 7, and was really happy with the accuracy. The eclipses can be timed to an accuracy of +-8 s, although the integration times are typically 25-45 seconds... and despite their shallowness (~0.15 mag, similar to the flickering). This is because of the square walls of the eclipse - and, of course, because we get many eclipses and thus can average them. The campaign was called to check on the surprising result by Han et al. (2017) that the orbital period was decreasing, and pretty fast too. Our data are clearly inconsistent with this conclusion. The timings do show a slow (~25 year?) up-and-down wander of around 25 s, like several other short-period CVs. This result is no stunner, but is worth publishing since WZ Sge is a celebrity star and the alleged period change has attracted a lot of attention. In a few weeks I'll send around a draft to the (numerous) CBA co-authors. Meanwhile, take it off your 2017 menu. I've been working hard on eclipse timings this summer. In principle we can learn the direction and rate of evolution from changes in the orbital period, and we're the best show in town for such data since we have been acauiring lots of time-series data for many years. Here are the seasonally-appropriate stars which probe these matters: QR And (especially! but long runs only, the period is very long) ES Cet - once in a while V617 Sgr - finished for the year; thanks Josch! WX Cen - (long since) finished for the year BW Scl - just a few nights; we'll promote if it looks interesting V Sge - done for the year, thanks for all the great data! Another category in which the world relies on us is: the changing orbital light curve of novae after they erupt (a few years, decades, centuries, and even millennia). These seasonally-appropriate stars are: V Per - getting optimistic here (V=18.5... but we're desperate) T Aur V339 Del V1974 Cyg - David Cejudo has been carrying out a great vigil... but we desperately need a USA observer to complement his Euro coverage V1500 Cyg - unless Enrique says we have enough DQ Her - but here we are quite interested in the fast (71 s) period, as well as the orbit. I recommend you keep your cycle time (integration + read) below 25-30 seconds. The season is getting late, so a good 14.5 mag target now (rather than, say, a month from now). + 2 other bookended stars - north and south - which are tantalizing but so far resisted our efforts to torture their secrets out of them. They are: GD 552 = "Cep 1" in Downes & Shara VZ Scl Let's try harder on these guys! A big menu. Choose a couple of stars and concentrate on them. If any star looks particularly good or unpromising, I'll jump it up in the menu. Enrique will likely follow with comments and suggestions, esp. re the DQ Her stars (intermediate polars). joe -------------- next part -------------- A non-text attachment was scrubbed... Name: cba9917.pdf Type: application/pdf Size: 17897 bytes Desc: not available URL: -------------- next part -------------- ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists http://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Sep 12 03:12:06 2017 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 12 Sep 2017 03:12:06 -0400 Subject: (cba:news) strike V1974 Cyg Message-ID: Hi CBAers, Delete V1974 Cygni from the menu. I finished the analysis of all the data (dominated by David Cejudo's), and there is a very clear detection of the orbital signal. In fact, two, separated by ~90 days (we never had that before, and it's very useful to connect the years). The detection and measurement of the phase of the orbital signal was the goal... and we have it now. Especially nice since the detection is uncontaminated by superhumps; we never had that before, also. Two other things we'd *like* to know are: (1) What is the phase of the radial velocity variation when the light reaches its orbital max? (2) Just how bright is the continuum? The 4000-8000 A region, where we observe the star at "17.12", is probably dominated by the O III emission at 5007 A. That emission from the shell needs to be subtracted to learn how bright the central object is. Only a very motivated spectroscopist could answer (1); so far, none have piped up. (2) is best learned from a single high-quality spectrum; someone might have that. But if you have a filter which excludes that terrible monstrosity at 4959/5007 A, and preferably also H-alpha, you might learn that. Might be worth an effort. You don't necessarily need to detect the periodicity (at 0.08126 days); just measuring the brightness of a clean, line-free continuum would allow us to correct our measurement for all that unwanted and so-far-unmeasured nebular light. Pretty nice result for "the nova of the century"! joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists http://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Sep 15 04:42:16 2017 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 15 Sep 2017 04:42:16 -0400 Subject: (cba:news) v407 Lup, back to the battle! Message-ID: <2697ae84-3c74-7430-7580-cdb708d6d88b@astro.columbia.edu> Hi CBAers, I had planned to wait until next year to present our results on V407 Lup, the 2016 classical nova - namely, the 9-minute and 3.5 hour periods. But a recent ATel (Astronomical Telegram) announces these detections in the X-ray. With much coarser accuracy than our results, of course, since they're based on short-baseline data in the X-ray. So now we should come clean right away! Either in the form of another ATel, or in a very brief published paper. Therefore let's put it back on the menu, for our southern observers, with highest priority. The 9-minute oscillation appears complex - probably not just one stable, constant-frequency-and-amplitude signal. In order to decipher this complexity, it's important that we get as close as possible to 24-hour coverage. 24-hours is impossible since Lupus is way out-of-season, but Berto and Gordon have done well with this 15.5 mag star, and we can probably do well enough to decipher the period structure - unless the period(s?) is/are actually not stable. (If that's so, nothing will save us.) So: back to work on V407 Lup, with gusto! joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists http://cbastro.org/communications/mailing-lists/