(cba:news) DQ Her, V1223 Sgr, RX1654-19, and the Hercules transient
jop at astro.columbia.edu
Tue Jun 14 05:37:02 EDT 2016
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,
*BTW, targets unmentioned doesn't mean "uninteresting" - just not yet
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