WHOLE EARTH TELESCOPE

Thursday, March 15, 2012

DARC News, future plans, WET workshop in 2013

Hello everyone,

It has been a while since I've sent around an update.  Here's a
summary of what has been going on....

XCOV28 - this run holds the record for the number of targets covered!
We got good coverage for all of our targets.  For the DAs: the HS0507
FT is excellent (see attached).
The data set spans over 37 days.  HL Tau 76 also received good
coverage, especially at the end of the run. Its total light curve is
also over a month long.  We switched to G191-16 towards the end of the
run.  This star is a multiperiodic pulsator.  All three stars are
excellent candidates for light curve fitting. G132-16 is one of the
hotter pulsators we've looked at (12600 K).  We are hoping to use this
star, with G117-B15A, to pin down  convection on the hot end of the
instability strip.  Finally, my personal favorite for this run was
BPM31594.  This star is dominated by a main mode with a series of
harmonics, plus power near, but not precisely at,  the subharmonics.
It is also an excellent candidate for light curve fitting.
For the DBs: we obtained excellent coverage of EC04207.  This star is
dominated by a single mode with harmonics.  EC05221 turned out to be
an unstable pulsator, alot like R808.  The more data we added to its
light curve, the lower the FT amplitudes became.  We should definitely
re-observe this star at some point to see if it characteristics
change.

This run promises to add multiple new points to our map of convection
across both the DA and DB instability strips.

I have nearly finished with the referee report on the EC14012-1446
paper.  The report was very positive, with helpful suggestions.  I'm
planning on uploading he revised version
in a few days.  If anyone has any acknowledgements to add, please send
them to me.

Future plans:  we are planning a mini-campaign (DAMP05) for this
spring.  So far we have confirmed dates at Tubitak (April 19-28, May
10-12) and CTIO (May 7-16).  Our suggested
targets include GD165 and HS1531+7436.  If anyone is interested in
participating, let me know!!

There are preliminary plans to hold the 8th WET Workshop in February
2013 in Beijing, hosted by the Beijing Normal University.  It is very
early in the planning process, so please let
us know if you have any suggestions!!

Cheers,
Judi

Tuesday, December 6, 2011

Snow at McDonald Observatory

Sunday, December 4, 2011

Todd Watson and the 82 inch telescope at McDonald Observatory

Saturday, December 3, 2011

Target Stars Summary

Here's a quick summary of our target stars:

1)  HS0507+0434B has proven to be very much like EC14012-1446 and GD358.  We 
have identified multiplets associated with several of the modes, plus we have 
seen power grow as we have been observing:)  Take a look at the figure in the
blog. You can see how HS0507 has evolved during the run.
2) HL Tau 76 is always interesting.  Here we are seeing a wide range of 
pulsation frequencies - from 900 to 2500 microHz, some of which are 
multiplets. Some of these "modes" appear to comprise a series that is 
equally spaced in frequency, which is very interesting.  Many of these
frequencies also appear in Dolez 2005.  Of course, we also find 
numerous combination frequencies. Take a look at the web page under 
"Interesting Plots" to see the latest.  
3)G132-12 - this beginning of night target was chosen because of its 
temperature (reported as 12,800 K) and the fact that it only has one mode of 
pulsation (very low amplitude).  The idea is to gather enough cycles 
(period is about 212 s) to create a pulse shape which we can then use for 
convective light curve fitting.  Many of you might remember the figure 
from the EC14012 paper that shows our latest empirical relation.  We 
definitely need more hot stars, as G117-B15A is currently our only example.  
With the addition of WHT, Hawaii, and KPNO data, G132-12 has proven to be 
interesting.  Its pulsation mode is a multiplet with a splitting of 
around 4.1 microHz.  It may be an l=2 mode, but that is unclear. Of 
course, more data is needed:)
4)EC04207 - We have a beautiful FT of this star, thanks to contributions from 
Mt. John, SAAO, Prompt, and SOAR.  This is a large amplitude DB pulsator 
dominated by a single mode that is surprisingly stable. We are working 
towards an eventual pdot measurement.
5) EC05221 - very little is known about this fairly new DBV.  We now know
that it is the DB example of a type of white dwarf pulsator we like to call
the "soft and squishy" stars.  As we add more data to this star's light 
curve, the amplitudes in the FT continue to decrease.  This is a sign
of instability/amplitude modulation.  This star is very similar to R808
and G38-29.