(cba:news) DQ Her, V1223 Sgr, RX1654-19, and the Hercules transient

Joe Patterson jop at astro.columbia.edu
Tue Jun 14 05:37:02 EDT 2016


Hi CBAers,

A few notes concerning stars we're covering.

1. We have the long-term (6-year) spin and orbit ephemerides now for 
RX1654-19.  As usual, Berto has been the powerhouse for this one.  No 
need for further coverage this year,  In future years, we just need 
"maintenance" - a few runs per year.  BTW, it's a spin-up guy - spinning 
up on a timescale (P/Pdot) of 20 million years.

2. Ditto for V1223 Sgr.  We have now an ephemeris over 35 years, and it 
has been rapid spin-down throughout.  This is really puzzling. 
Astrophysical orthodoxy says that DQ Her stars should have episodes of 
spinup and spindown, alternating depending on accretion rate (spinning 
up when Mdot is high, because accretion torques are then high).  The 
alternations might well take centuries or millennia, so it's no shocker 
that we can't test this theory.  BUT by my reckoning, V1223 Sgr is the 
most intrinsically luminous (X-ray-UV-optical) of all the DQs, and it's 
the only one that is certifiably spinning down, not up.  Just the 
opposite of what we expect.  We'll want to keep a close eye on it in 
future years, and scratch our heads a lot in the meantime... but for 
observing, we can take it off the 2016 list.  This is another star which 
has succumbed to Berto's Boer ferocity.

3. The Hercules transient (1621+44). Wow. A photometric and 
spectroscopic gift to patrons of CVs.  And apparently within our ken to 
study at quiescence, too.  The coverage has been wonderful, and the star 
has been generous with its secrets and gracious with its timing - 
erupting in late May, when it transits near local midnight.  It's 
obviously gunning for publicity, and we'll oblige!  All hands on deck.

4. DQ Her.  Lots of very good data coming in, and even the 30-second 
data is proving quite adequate to time the 71-second oscillation - so 
much so that we don't particularly need that high time resolution any 
more (the spin ephemeris is nailed down).  But the light curve on 
orbital (4.6 hour) timescales is a different story.  That one looks 
promising but could really use more help from Europe.  Long runs in the 
European summer ate tough with the short nights... but try!  And for the 
norteamericanos, keep it up.

All for now*.  For both Enrique and me, summer has brought a respite 
from the job and the leisure to dive into these light curves.  We'll be 
able to supply more info on the analysis side.  (And feel free to write, 
too.)

joe p

*BTW, targets unmentioned doesn't mean "uninteresting" - just not yet 
fully digested.

____________________________________________________________
Center for Backyard Astrophysics (CBA) mailing lists
http://cbastro.org/communications/mailing-lists/ 



More information about the cba-public mailing list