(cba:news) mostly AM CVn, CR Boo, VZ Sex, and our two Maxies

Joe Patterson jp42 at columbia.edu
Fri Apr 10 09:10:53 EDT 2020

Hi CBAers,

We're managing to stay healthy amid the NYC maelstrom of spring 2020.  
So far, I believe 5 virus deaths among the full students+staff Columbia 
community.  All Columbia buildings locked up.  I've retreated, along 
with my wife Laura and our dog, to a house-in-the-woods in the Catskill 
mountains... and will wait it out til autumn if necessary. I'm certainly 
struggling with video teaching, but with Jonathan's (video) help, have 
managed to steer clear of disaster.  Class prep time has at least 
quadrupled - it reminds me of my first month of teaching, at 21 years old.

CBA attention has suffered too, but that will change after May 7 (end of 
school year, as well as Lusitania sinking).  BTW I'm sure that all 
CBAers have their own accounts of how their life has changed, including 
the astronomy.  We're all bound together by that, and I hope you'll 
share your stories in this forum.

VZ Sex is a very likely intermediate polar which has, for some reason, 
never been on our lists.  (Maybe because of obsession with the 4 
most-famous AM CVn stars, which are all Feb-May targets.)  The 
"outburst" reported below is sufficient reason to remedy that.  IP 
outbursts are pretty lame and disorganized, compared to those of dwarf 
novae.  Practically nothing is known about their origin, frequency, 
amplitude, effect on periodic signals, etc.  This is a good target to 
jump on - decently placed in the sky and available to all hemispheres.

The AM CVn campaign is slowing down, and properly so.  The phase of that 
1028.7322 s orbital signal for 2020 is now well specified, stable, and 
easy to connect with previous years.  It confirms the 60 Myr timescale 
of orbital-period decrease strongly suspected in 2018 and 2019 data.  
Break out the champagne.  But the other target of our study is the 
relative phases of the stronger signals (the positive superhump at 
1051/525 s and the negative at 1011 s).  They're stable on a timescale 
of a few weeks, but always drift on longer timescales.  So to measure 
the sense of that drift (correlated positively or negatively), I've 
found that you need something like a 100-day campaign.  Not necessarily 
long runs, but steady coverage over the next 30 days.

I haven't yet analyzed the CR Boo data, but I will this weekend.  I 
speculate that CR Boo and HP Lib will be very rewarding targets for the 
next two months.  I think V803 Cen should be put aside unless it gets 
very bright (12.5) or very faint (17.5).  And even at 12.5, give it a 
second day to prove it's worthwhile; the "short outbursts" of V803 Cen 
last only a day, and are a dime a dozen (USA saying).

The two Maxies (MAXI J1820+070 and MAXI J0637-430) are at opposite ends 
of the sky, but we have low-intensity campaigns alive for both - 
basically covering the aftermath of the major outbursts.  Snapshot 
magnitudes, whenever you can, would be good; a 10-minute time series, 
say, would be better (these stars might flicker a lot).  Being  near 
quiescence, the stars are likely forgotten by most people - but not by 
us.  Joe U and Josch have led the way on this - but give them some company.

The four-IP paper is in press at ApJ, and I'm near submission on the AM 
CVn and Maxie J1820 papers.  I'll send the latter two around in late 
May, after the video torment ends.

BTW I haven't heard about cancellations/postponements of SAS and AAVSO 
meetings; anyone knowledgeable about those plans?

            joe p

-------- Forwarded Message --------
Subject: 	[vsnet-alert 24155] VZ Sex outburst
Date: 	Fri, 10 Apr 2020 14:02:16 +0900
From: 	Taichi Kato <tkato at kusastro.kyoto-u.ac.jp>
To: 	variable_star_forum at yahoogroups.com, 
vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp, vsnet-alert at yahoogroups.com, 
vsnet-campaign-dn at ooruri.kusastro.kyoto-u.ac.jp, 
vsnet-outburst at ooruri.kusastro.kyoto-u.ac.jp, 
vsnet-outburst at yahoogroups.com

VZ Sex outburst

(IP outburst)

YYYYMMDD(UT) mag observer
20200326.8986 <143 (Eddy Muyllaert)
20200329.9688 <143 (Eddy Muyllaert)
20200331.8951 <143 (Eddy Muyllaert)
20200401.1697 16.455zg (Zwicky Transient Facility Lasair (Masci+ 2019))
20200401.2106 15.049zr (Zwicky Transient Facility Lasair (Masci+ 2019))
20200408.5577 125cG (Yutaka Maeda)
20200408.8701 125 (Eddy Muyllaert)

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