From jop at astro.columbia.edu Mon Jul 21 10:57:13 2014 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 21 Jul 2014 10:57:13 -0400 Subject: (cba:news) old novae in the (northern) summer Message-ID: <53CD2A49.40607@astro.columbia.edu> Dear CBAers, Thanks so much for all your kind remarks concerning that asteroid (8794, I think). A cheap way to get into the sky: no risking of life, and you don't have to be a mythological figure or fanatical comet-hunter. The Camp Uraniborg reunion, which generated this, was certainly the high point of my year! (Now that someone else seems to have won the British Open.) It's now 80 years since the discovery of DQ Herculis - the day the music started - and 60 years since Merle Walker's sensational discovery of its 4.6 hr orbital and 71 second spin period. David Cejudo has recently obtained a long string of clear nights on this star, and I see that despite small aperture and long-ish integrations (30 s), his data is of sufficient quality to define all the relevant properties: orbital wave, eclipse shape, precise eclipse timing, presence and precise phase of the 71 s pulse. Wow! I was really surprised how readily the star surrendered these numbers to a CBA scope. Beautifully placed in the July night sky, too. So now's the time to go beyond this and obtain a really comprehensive many-longitude and several-week campaign on this star. Try for long time series - BUT atmospheric extinction is a factor, so the extinction-worry rules apply: (1) Include the airmass if you can; (2) Don't go beyond 2 airmasses (or meridian airmass + 1.0) (3) Consider using a V or V-ish filter (but I don't recommend this for the small scopes, since it will really hurt the measurements of pulse phase and eclipse times). And also a fast-timing pulse rule: choose a cycle time less than half the cycle you're trying to resolve (71/2 = 35.5 s). You can go *slightly* longer, but definitely no longer than 50 s. Around 20 s would be really ideal, if you can count enought photons. You might spot-check your computer clock occasionally: www.time.gov David's comp star appears to be 000-BCB-330, RA=271.84990, DEC=45.82989. David, is that correct? What else is known about this star? Maybe then we can evaluate the possibility that DQ Her was the original inspiration for Superman: http://www.space.com/21949-superman-origin-star-explosion.html And Tyson is another Uraniborger, too. We're piling up a good record studying nova light curves years to decades after maximum light. Snapshot magnitudes are basically the AAVSO business, but I'd be interested too, since it impacts which stars to select for time-series study. For the present season, I'd rate V1974 Cyg, V1500 Cyg, V1494 Aql, HR Del, and V4743 Sgr as top priority - with HR Lyr and V446 Her also probably belonging there, but I don't know much about those (yet). Enrique, could you send in your advice to other observers concerning V446 Her (a fascinating star, but a crowded field, and you have to decide what to do about the contamination)? I'm leaving out V339 Del for the moment, despite my previous mention and my interest in the star, because I'm not sure it yet shows any periodicity. Maybe someone knows differently? I don't list these stars in any order. It usually pays to select one and stick to it for a couple of weeks - after you're reasonably sure that the data look good (some of these targets are pretty faint). We're also getting good coverage of this month's dwarf novae, especially ASASSN-14cv. Keep that one up til it disappears (more from the USA would be very useful). Finally, some of our old friends among the DQ Her stars have come back: AO Psc, V1223 Sgr, FO Aqr, IGR0023+61. Especially the first two, for whom we're finishing our long-term study this year (and probably this summer). Happy observing! joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Jul 29 21:12:46 2014 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 29 Jul 2014 21:12:46 -0400 Subject: (cba:news) Classical novae and DQ Hers for July-August Message-ID: <53D8468E.8060703@astro.columbia.edu> Dear CBAers, This one on classical novae, mostly. Mostly the hardest/faintest targets, but with two advantages: (1) they don't flop up and down, hence are suitable for long and sensitive observing campaigns; (2) they have known outburst dates, hence carry information about how novae decline from max. We've been going strong on V1494 Aql (1999) and DQ Her (1934). Still wish to keep going - in fact accelerate - on both. The former may show a superhump, and the latter may also have a third periodic signal, other than the 4.65 hr eclipse and the 71 s spin period. We probably need just ~2 more weeks on each of them. Strangely, both stars have contaminating neighbors, 1.5 arcsec (V1494) and 4 arcsec (DQ Her) away. You definitely need to include them in your aperture. But in addition, if you get very good seeing, try to measure the brightness and colors of these stars. This will be very hard, and you should use the nova's eclipse to minimize the nova's light (absolutely mandatory for DQ Her, which is normally 3.5 mag brighter than "DQ Her C"). I estimate the unwanted star's V mags as 18.5 (DQ) and 17.8 (V1494). Though measurements in VRI are ideal, a measurement in your instrumental (unfiltered) system is plenty useful too. In fact, "x mag fainter than the nova's average magnitude" would be a quite useful thing to know - we gotta know how deep these eclipses really are! An easy target is HR Del (1967). Good for an intensive study over the next two weeks of bright sky. If we can get good longitude baseline, we can evaluate the published claim of a non-orbital signal. I doubt that this claim is true, but worth checking. Now come the hard ones. V1500 Cyg. Really faint (18.5?), but with a 1.1 mag amplitude periodic signal that probably signifies the white-dwarf rotation. Deserves a several-months long campaign. Enrique, can you send comp-star recommendations? V4743 Sgr (2002). I yearn for this one, with its orbit and spin signals. Berto has started up a campaign - let's keep going! i think it's about 16.5, but possibly some field crowding (I've never actually observed it) V728 Sco and V630 Sgr. Both eclipsers, and faint - probably beyond CBA scopes... but for australites feeling brave, check 'em out! The eclipse offers great diagnostics, if we can only get the data. ************ And now for intermediate polars. V4743 Sgr, definitely, but also CC Scl - our first stab at this fascinating star which spins, dwarf-novas, and superhumps... a lotta work for one little star! In the north, the DQ Hers needing attention are V2306 Cyg and RX2133+51. Finally, there's V1223 Sgr, one of the great intermediate polars. For the first time ever, this year's campaign (mainly Simon Lowther and Peter Nelson) seems to reveal a positive superhump. In principle, the CBA can get great longitude coverage for southern targets (South Africa, Chile, AU/NZ) - so we should be able to nail this down for sure. Lots of rewards to be had in that summer/winter sky. Happy observing! joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/