(cba:news) ASASSN-18ey - the ultimate conspiracy

Joe Patterson jop at astro.columbia.edu
Sat Jul 7 06:02:04 EDT 2018

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 

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.)

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