From jop at astro.columbia.edu Fri Oct 4 06:56:50 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 04 Oct 2013 06:56:50 -0400 Subject: (cba:news) CP Eri in outburst Message-ID: <524E9EF2.1030202@astro.columbia.edu> Dear CBAers, The ASAS-SN survey showed CP Eri in outburst yesterday, at 16.0. We've obbserved one of these about 10 years ago - and it's been a long wait! This is an AM CVn star, a short-period helium CV, and it's (almost) sure to display prominent superhumps. Very likely superoutoutburst, and decently placed at 03h 10m 32.7s -09d 45m 06s. And speaking of super, a super-high-priority target. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Sat Oct 5 05:18:21 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 05 Oct 2013 05:18:21 -0400 Subject: (cba:news) (cba:chat) CP Eri in superoutburst In-Reply-To: References: Message-ID: <524FD95D.9020607@astro.columbia.edu> Hi Bill et al., We haven't observed CP Eri in a long time. But in the past, we used a 15th mag comparison star 60" E and 64" N from CP Eri. Color a tad red, but not unacceptably so. Others are ok too, as usual, if they're appropriately bright. Remember it'll fade a few magnitudes, so the very bright comps won't be suitable. joe We've only caught the superhumps in their full glory on one night. And they're critical - superhumps in AM CVn stars are mighty rare! On 10/5/2013 4:57 AM, Bill Stein wrote: > > Enrique - I am observing CP Eri now, However, I do not see an AAVSO > sequence. Any recommendations? > > Bill > > William L. Stein > Las Cruces, NM > > -----Original Message----- > From: cba-chat-bounces at cbastro.org [mailto:cba-chat-bounces at cbastro.org] On > Behalf Of Enrique de Miguel > Sent: Friday, October 04, 2013 7:44 PM > To: cba-chat at cbastro.org > Subject: (cba:chat) CP Eri in superoutburst > > CP Eri is currently at mean 16.5 mag and showing clear superhumps of > ~0.10-0.12 mag full amplitude. > > Enrique > ____________________________________________________________ > Center for Backyard Astrophysics (CBA) mailing lists > https://cbastro.org/communications/mailing-lists/ > > ____________________________________________________________ > Center for Backyard Astrophysics (CBA) mailing lists > https://cbastro.org/communications/mailing-lists/ > ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Oct 9 20:01:15 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 09 Oct 2013 20:01:15 -0400 Subject: (cba:news) V378 Peg, mainly; also RX2133+51, V1294 Tau, and QR And Message-ID: <5255EE4B.1090307@astro.columbia.edu> Dear CBAers, One big subtraction in the menu. We'll back off of RX2133+51, unless Enrique changes his mind. It has been mighty good to us, and has taught us that negative superhumps are not particularly rare in magnetic systems. Now that we know that, we'll look more vigorously! I'd very much like to promote V378 Peg as a principal northern target for the next month or more. Ringwald and Kozhevnikov have found superhumps in it, and it seems likely from Enrique's first night that they're still rolling through the light curve. Looks like a decent match for V603 Aql, which gave us simultaneous negative and positive superhumps - and enabled precise measurement of both. Large amplitude, decently bright star, well placed in the sky, and never targeted by us. It is high time to fix that latter oversight. QR And is another good northern target. This is a well known supersoft source, one of just a few known in the Milky Way. We basically want to track its eclipse minima in order to measure its rate of period change. The empirical rates in the supersofts generally are impressively high, and indeed I suspect that to be one of the key signatures of a supersoft nature, even when the obvious evidence of its nature (the X-rays themselves) is lacking. That'll take a heap more work to evaluate, though! At 16 hours, the period is kinda long, so you'll need to patient on this guy; but at 12th magnitude, it's friendly to small scopes. Finally (in this note), I did a quick evaluation of the V1294 Tau data. It does appear that the strange periodic structure we saw in 2002 is still there. I do have some doubt about observing it in early October though. As an equatorial target, no one can get really long runs on it. So maybe we should wait for it to get more central in the observing season (a month from now). But on the other hand, maybe you like Taurus. If so, keep the faith on it... and it would be great if some of our australites - commonly loath to turn their scopes north of the equator - pitched in. Especially in AU/NZ, where we otherwise suffer from a big "Pacific gap". Don't forget ES Cet! Very rewarding star for time series: a beautiful light curve you can send home to Mom and Dad! And do it repeatedly, because the error gets smaller with with each observation, unlike typical CVs where flickering always dominate the errors. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Oct 15 05:47:13 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 15 Oct 2013 05:47:13 -0400 Subject: (cba:news) V339 Del and the supersofts Message-ID: <525D0F21.8050903@astro.columbia.edu> Hi CBAers, When novae erupt, they eject a large, thick shell of gas, which is what we see when we look at it from afar. In fact, a nova at maximum light looks pretty much like a normal A-type supergiant (not the big emission lines which make the class famous). Then, as a few weeks or months pass, the shell thins out as it continues to expand. Emission lines appear... and eventually a soft X-ray source signalling a very hot white dwarf, when we can finally see down to the central object. Now soft X-ray telescopes cost about 500 million bucks, which none of us (well, hardly any of us) have. But if we can see down to the white dwarf, then probably the secondary star can also, since it's so much closer. So you might expect a strong "reflection effect" from the heating of one side of the secondary; and as this surface wheels about in its binary motion, a strictly periodic signal at Porb in the optical emission may occur. Properly interpreted and calibrated, the amplitude of this signal in energy units can serve as a *bolometer* for the white dwarf. It's a great experiment to do on every sufficiently bright nova, and if we could do it, we would save about 499.995 million bucks (figuring $5000 for the total cost of all your equipment). It fails when the nova is near max, because the line of sight is so cluttered with absorbing gas... and fails decades later, because the white dwarf has cooled. But for a few years after max, it's sometimes possible to measure this. Kim Page just announced, in ATel 5470, the discovery of the soft ("supersoft" in the current lingo) X-rays in V339 Del, using the Swift X-ray telescope. And I recall in the last couple of days that Arto (Oksanen) announced a *possible* 3-hourish wiggle appearing in the optical light curve. That sets the stage: it's now time to make a strong effort to detect that periodic signal! (Oh yeah, and it's our job.) The star is still very bright at V~8.8, so you'll have to employ some tricks to avoid saturation. Obviously filtering (V or R recommended), and short exposure, and maybe also de-focusing if you've had some experience with that technique and are confident that it won't contaminate your results. Since I'm sitting here in a reclining chair, far from the battlefield, your own practical solutions probably have more value than my advice. See if you can find that signal, and show the US Congress how a proper job is done. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu Oct 24 09:03:49 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 24 Oct 2013 09:03:49 -0400 Subject: (cba:news) V1101 Aql... BK Lyn... and friends? Message-ID: <52691AB5.5030102@astro.columbia.edu> 24 October 2013 Hi CBAers, Grinding away at the write-up of our V1101 Aql campaign, I'm struck with the glaring similarities to BK Lyn. Both have very strong credentials as Z Cam stars, both have negative superhumps, both have what we call "precession" periods (at least until we learn otherwise, which of course might someday come to pass)... and both superhumps are basically characteristics of quiescence rather than outburst. Because they're clearly signatures of quiescence, the superhumps' origin must be drastically different from that of the common superhumps we have come to regard as practically universal among short-Porb CVs in their high states (SU UMas and novalikes). What is that origin? Well, there are some guesses in the literature, but basically we don't know. It's possible that the superhumps are intimately connected to the cause of the Z Cam phenomenon - or vice versa (we've never found superhumps in U Gem stars). Both ideas conflict mightily with today's understanding of what Z Cam stars are - but the superhumps are quite big, and it feels uncomfortable to attribute them to some minor and accidental feature of the binary. So let's see - with a similar global photometry campaign - what relatives of these stars might be out there, waiting to be discovered. Two stars with light curves similar to V1101 Aql, and well-placed in the sky, are IW And (14-17.5) and V513 Cas (15.5-17.5). Both stars spend most of their time near the brighter end of their range, and I think they're great CBA targets. V513 Cas comparison stars were studied by Misselt (1996 AJ), and his stars 5 and 6 appear to be good comparison stars, with sufficiently neutral colors (not particularly red). Let's start the proverbial ball rolling on these stars! Another star interesting in this regard - but more of a long shot since we've tried before and failed - is FY Per. A mysterious hardly-studied bright CV, with two discrepant periods - but the photometric one (1.5 hours?) has never been firmly established or discredited. Perhaps it's transient. It's embarrassing not to know something like that in so bright a CV. A little later in the season, we'll try this with CN Ori. I've long suspected this star as a two-period guy. As many of you know, Mike Simonsen has been cheerleading and leading (he always does both) an AAVSO campaign on Z Cam stars (the "ZCampaign"). In my opinion, this has already greatly expanded what we know about this class, and I suspect will soon lead to wholesale tearing-up of what we thought we knew about these stars. His stuff can be found on the AAVSO website. Fred Ringwald's article on Z Cams also deserves its #1 rating on google: https://sites.google.com/site/thezcamlist/why-observe-z-cam-stars Buena suerte! joe p P.S. When adding stars to our menu, it's only responsible to take some away. In this case, I recommend removing V339 Del and V1294 Tau (as well as V1101 Aql of course). Both V339 and V1294 have given uncertain results; the former won't get better (because the season is getting late, and the variability is small), and the latter can be reinstated later if warranted. I imagine that first looks at the new stars will be more rewarding. I also think a brief break from the DQ Hers (intermediate polars) is fine, although these stars may still be the best choice for *short* time series. ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Fri Oct 25 04:05:53 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 25 Oct 2013 04:05:53 -0400 Subject: (cba:news) Nova Del 2013 = V339 Del = bright super-soft Message-ID: <526A2661.3070606@astro.columbia.edu> Not to exaggerate the might of cba-news... but as soon as I took V339 Del off the menu, ATel #5505 announces the nova's emergence as a STRONG supersoft X-ray source. So now it's time to put it back on the menu! The evening sky is crowded with good targets, and the brevity of Delphinus's appearance in the sky is a problem... but it's an important phase in a nova's life, not to come again for a long time. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Tue Oct 29 17:34:17 2013 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 29 Oct 2013 17:34:17 -0400 Subject: (cba:news) MASTER OT J234843.23+250250.4: a new SU UMa star In-Reply-To: <52701885.70502@bellatrixobservatory.org> References: <52701885.70502@bellatrixobservatory.org> Message-ID: <527029D9.9010002@astro.columbia.edu> Hi CBAers, Announcement from Gianluca - looks mighty interesting! The double-peaked signal, the decent amplitude superhump, the possibly funky period... let's start up a campaign. This should *replace* V378 Peg (in pretty much the same part of the sky). The recent data on V378 Peg brings the campaign to 20 days, with quite excellent density of coverage. It still just shows a single (beautiful, but solitary) periodic signal. joe -------- Original Message -------- Return-Path: Received: from sedna ([unix socket]) by sedna (Cyrus v2.1.18-IPv6- Dear Colleagues, We are performing time resolved photometry on this source, remotely using the robotic 14" unit part of the Virtual Telescope in Italy. The run lasted 4 hours. We detected 0.15mags superhumps: assuming a single peak profile, period is 0.75 hours, maybe it is a double-peak modulation. Data sent to Kyoto for analysis. Regards Gianluca Masi Francesca Nocentini Patrick Schmeer ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/