Project #1

[Doug Welch]

Folks,

As I get an opportunity, I will describe several projects here. If
someone is seriously interested, I am willing to provide guidance and
assistance with these.

Cheers,
Doug

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Data-mining Project #1
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Goal: Searching for Galactic Type II Cepheids in
Eclipsing Binary Systems

Number currently known in the Milky Way: 1

Why: Soszynski et al (2008) found that a surprising
7 out of 197 Type II Cepheids in the Large Magellanic
Cloud were in eclipsing binary systems. This suggests
a very high rate of binarity and possibly a causal
relationship between binarity and Type II Cepheids.

Why Look in the Milky Way: Any systems found nearby
will be MUCH brighter and can have their characteristics
studied with much higher precision than in the LMC
where the systems are 14.5 to 18 mag at I.

Why hasn't it been done yet: Longer-period Type II Cepheids
have mildly unstable lightcurves and don't receive the
love and attention that their classical Cepheid counterparts
do. Also, sufficienly long sets of photometry in the
field have only recently become available with ASAS-3.

How would one go about it: Download stars classified as
CW from ASAS-3 website, remove the effects of the
pulsation lightcurve and look for eclipses in the
residuals.

Chance of success: High if all known galactic Type II Cepheid
lightcurves are examined. Even a lack of further detections
would be significant, indicating a difference between
Milky Way and LMC populations.

Additional long-term datasets will become available (like
ASAS-3N) and can be examined in the future.

Possibly related fact: Despite tens of thousands of RR Lyr
stars having been discovered, not a single binary RR Lyr
has been identified! (Yes, that's right, binary - not
just eclipsing binary!) Hunting RR Lyr binaries will be
another post!

References:

"The Optical Gravitational Lensing Experiment. The
OGLE-III Catalog of Variable Stars. II. Type II Cepheids
and Anomalous Cepheids in the Large Magellanic Cloud"
Soszynski et al, Acta Astronomica, 58, 293 (2008)
http://arxiv.org/abs/0811.3636

"TYC 1031 01262 1: The First Known Galactic Eclipsing
Binary with a Type II Cepheid Component"
Antipin, Sokolovsky, and Ignatieva
MNRAS, 379, L60-L62 (2007)
http://arxiv.org/abs/0705.0605

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[Shawn Dvorak]

Doug,

Do you know if anyone has taken up this challenge?  I had forgotten about this; I don't check gmail very often so it slipped my mind for quite awhile.  This seems like the ideal rainy summer season project.

Shawn

--

Shawn

[Stupendous_Man]

Interesting coincidence, this. I just finished the final draft of a
paper inspired by Doug's message today. I'll be submitting it to
JAAVSO Monday.

It will hit astro-ph at roughly the same time, so keep an eye out.

Oh, and the answer is: nope, no eclipsing binaries that I could find.
Darn.

[Doug Welch]

Hi Mike,

Yours was Project #2! As far as I know, Project #1 remains undone.

Glad to hear about the draft of Project #2!

Cheers,
Doug

[Thom Gandet]

Doug,

    Just reading the group posts for the first time, and this project got my attention right off.  I look for projects involving objects that are little-understood or of unknown types.  Very interesting results.  If you have room for another person to work on this project, please count me in!  Let me know what you need, and I'll start working on it as I can.  Are any of these stars candidates for visual observing?  With my set-up I can regularly get down to at least 13.5, 14.5 on really good nights.  I'm working on some RCB stars now, plus a couple of "unknown" types, with gaps in the RA coverage.

Regards,
Thom

[Doug Welch]

Hi Thom,

I am glad that you are interested! (Project #1 is listed below for those
who can't access the original Apr 23, 2010 post.)

Could you let me know a little bit more about what you've worked on
before and the analysis programs you have used etc (off-list, if you
prefer).

The most likely eclipses are probably not deep enough to be discernible
with visual observations and I expect that most of the CW stars in the
sky do not have sufficiently dense observations to work on without
involving surveys like ASAS-3 or OGLE.

Cheers,
Doug

========================================================================

Data-mining Project #1
----------------------

References:

[rich]

Hi Doug,

I'm an interested layman with extensive experience in data mining large data sets using Python but absolutely zero experience with variable star photometry.  I don't even own a telescope but am interested in using my own skill set is data mining.

Rich