From jop at astro.columbia.edu Wed Jul 4 06:56:13 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 4 Jul 2018 06:56:13 -0400 Subject: (cba:news) CBA campaigns Message-ID: <4e2dd983-1b7b-74b4-d11a-708798f4c979@astro.columbia.edu> Hi CBAers, Some new, old, and continuing campaigns. 1. Keep up the GREAT work on Maxie = ASASSN-18ey. We're past the hundred-day mark now, and the star is still bright (13) and flashing its very powerful superhumps. We've seen a few superhumps before from the black-hole transients, but never with such longevity, amplitude, and long orbital period (~16 hours). And very amenable to our observing style of long, continuous time series. Truly, truly a Maxie! 2. Time to quit on CR Boo. We have a fair amount of coverage near quiescence (our target), but lots of up-and-down cycles too - the bane of CR Boo campaigns, and presenting analysis problems. Time to sort it in Boo's off-season. 3. As many of you know, the dwarf nova V392 Per seems to have had a classical-nova outburst this year. If true (it *seems* to be true), the star warrants all the attention we can muster. I doubt that anyone can observe it now - but put it on your list when it re-appears (August?) 4. Another star of this type (nova <-> dwarf nova) is V1213 Cen, still available briefly in the evening sky. We've strangely overlooked it - but it's likely to become a touchstone star in understanding the evolution of CVs among the various subtypes (nova/novalike/dwarf-nova/ER UMa). We published a theory about this a few years ago (BK Lyn) - let's find out if it's true. 5. Just emerging in the morning sky is VW Hyi, and the radio astronomers are keen to launch an across-the-spectrum study during its next outburst - preferably starting early in the outburst. Both supers and normals are eligible - and even a *visual* observation is useful (what's wanted is primarily a "trigger" for the multiband campaign). Even a *prediction* of the next outburst is of interest, too. 6. Again on the nova theme, two of our old favorites are back in the sky, asking for attention: V1974 Cyg and V1494 Aql. The big-shot novae of the 1990s. They both have - or had at last glance - fascinating orbital light curves. Very good targets for a July-Aug campaign. Now that I hear of all the CBAers attending the Warwick AAVSO/BAA meeting, I really wish I could go. Lotta personal issues to attend to during the next few weeks. I'll definitely make the November AAVSO meeting in Flagstaff. joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Sat Jul 7 06:02:04 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 7 Jul 2018 06:02:04 -0400 Subject: (cba:news) ASASSN-18ey - the ultimate conspiracy Message-ID: <3e66dd69-aa60-5269-4517-2ef2c089b4f7@astro.columbia.edu> Hi CBAers, It looks like an important X-ray "state transition" (change in the hard-to-soft ratio of X-rays) has just taken place - just as many of our European observers are at the BAA/AAVSO meeting! Didn't this happen in July 2001, when WZ Sge decided to erupt "early", during a previous international meeting in the UK? Is Putin's reach really that powerful? The lack of data in the morning email bodes ill. Walk the puppy, analyze the new data - that has been my morning ritual so far. Not today. The only decent response from us not-in-the-UK observers is to defy the Russian oligarchs and observe ASASSN-18ey with increased zeal. During the previous state transition, about 27 days ago, the powerful 17-hour superhumps were born. What will happen now? Will they die, change to "late superhumps" with a different period or phase, or what? What will be the *timing* of such events? It takes a while for accreting gas to move from the outer disk, where superhumps form, to the inner disk, where the X-rays presumably form. Seems reasonable that would be manifest in the timings... but no one has ever measured such a thing.* The Euros were doing great until now, despite their great latitude disadvantage ("white nights"). It's now time for us moderate-and-southern latitude observers to pick up the slack and wage the campaign with renewed vigor. joe p P.S. For those of you up on your superhump reading, you may recall a rule of thumb: during a high-accretion state, superhumps are basically universal for stars with Porb<3 hours (most dwarf movae), and strictly forbidden for stars with Porb>4 hours. This comes about because superhumps are mass-ratio sensitive, only occurring for M2/M1 < 0.3 - and since M1 (the white dwarf) is always near 1 Mo, it implies M2 < 0.3 Mo. How can that be true in a ~17 hour binary? That's where the black hole comes in. It can be of nearly any mass - 10 Mo for example, which would knock M2/M1 down to a value where superhumps can form. We can do a lot with black holes. Putin also, perhaps... but us as well. *Over the last three months, I've been re-examining the published evidence for superhumps in black-hole binaries. Roughly 5 stars have had such claims published - and as the claims are cited over the years, they acquire extra acceptance ("proof by successive publication"). But IMHO only one star qualifies - GU Mus = Nova Muscae 1991 - and even that one is not beyond doubt. Some of the published "light curves" have less than one point per cycle! (Yes, you read that right; it sounds crazy because it IS crazy. If you have hardly any data, just fold it, and you can sneak it past the tired referees.) ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Jul 11 07:08:25 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 11 Jul 2018 07:08:25 -0400 Subject: (cba:news) Fwd: VW Hyi -- the campaign has begun! In-Reply-To: <1ACF80922713204BA703D6242931D163AD956A24@SRV00048.soton.ac.uk> References: <1ACF80922713204BA703D6242931D163AD956A24@SRV00048.soton.ac.uk> Message-ID: <28251217-2dca-730c-14d4-d5d974d9584f@astro.columbia.edu> Hi CBAers, Here's the key request from Christian for VW Hyi coverage - in particular, to flag the start of the next outburst. We need that as the trigger to send all the other telescopes into action! Even a single *visual* observation could do this, in principle.* Be sure to cc everybody on the below list, because we have to get all the ready-to-start campaigns going in concert. joe p *Just to emphasize: no need for a CBA-type time series here. Just knowing that an outburst has started. -------- Forwarded Message -------- Subject: VW Hyi -- the campaign has begun! Date: Tue, 10 Jul 2018 16:29:01 +0000 From: Knigge C. To: Joe Patterson , Knigge C. , James Miller-Jones , Greg Sivakoff , Deanne Coppejans , Castro Segura N. Hi Joe, This is just a heads-up that our request for a radio trigger on VW Hyi's next outburst (presumably in mid/late July) has been officially approved now! And it looks like we might get Chandra time for the same outburst as well. Perhaps you could send another request for monitoring round to the CBA observer who can see this target? I could also add some more info tomorrow via the cba emails if you think that's helpful. I've cc'd the rest of our team here also, since they're really the ones who will trigger the radio. Could you encourage your observers to contact all of us directly by email, if they believe an outburst has started? It would be important to add all of us to that email, to make sure at least somebody is awake. Thanks! Christian -- =================================================== Professor Christian Knigge Physics & Astronomy University of Southampton Southampton SO17 1BJ ==================================================== ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Wed Jul 18 17:49:26 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 18 Jul 2018 17:49:26 -0400 Subject: (cba:news) VW Hyi Message-ID: Definitely on the rise to a new outburst, and - considering the recent discussion on cba-chat - a ripe target for multi-filter observation. Too late for South Africa I guess, but timed for South America, NZ, AU. Top priority (by far) in the southern morning sky. joe ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jp42 at columbia.edu Wed Jul 18 21:56:42 2018 From: jp42 at columbia.edu (Joe Patterson) Date: Wed, 18 Jul 2018 21:56:42 -0400 Subject: (cba:news) VW Hyi In-Reply-To: References: Message-ID: <8f070cfe-8b6d-b6f5-e8c8-7637f65a810e@columbia.edu> Oops, this is quite false - VW Hyi remains at quiescence.? My quick and erroneous reading of an observation from 10 days ago! Thanks to Arne, Josch, Gordon, Peter Nelson, Stephen Hovell, etc. for pointing it out. joe p On 7/18/2018 5:49 PM, Joe Patterson wrote: > Definitely on the rise to a new outburst, and - considering the recent > discussion on cba-chat - a ripe target? for multi-filter observation. > Too late for South Africa I guess, but timed for South America, NZ, > AU. reporting > Top priority (by far) in the southern morning sky. > > joe > > ____________________________________________________________ > 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/