[vsnet-campaign-orion 101] The Disappearing Act of KH 15D

[Taichi Kato]

The Disappearing Act of KH 15D

   The famous pre-main sequence star with disappearing eclipses.  The object
is well within reach of amateur telescopes (+CCDs).  Reporting backlog
observations (to vsnet-obs) is welcome.

Paper: astro-ph/0507578
Date: Mon, 25 Jul 2005 16:36:36 GMT   (389kb)

Title: The Disappearing Act of KH 15D: Photometric Results from 1995 to 2004
Authors: C.M. Hamilton, W. Herbst, F. J. Vrba, M. A. Ibrahimov, R. Mundt, C. A.
  L. Bailer-Jones, A. V. Filippenko, W. Li, V. J. S. Bejar, P. Abraham, M. Kun,
  A. Moor, J. Benko, S. Csizmadia, D. L. DePoy, R. W. Pogge, and J. L. Marshall
Comments: 55 pages, 18 figures, 1 color figure, to appear the September issue
  of the Astronomical Journal
\\
  We present results from the most recent (2002-2004) observing campaigns of
the eclipsing system KH 15D, in addition to re-reduced data obtained at Van
Vleck Observatory (VVO) between 1995 and 2000. Phasing nine years of
photometric data shows substantial evolution in the width and depth of the
eclipses. The most recent data indicate that the eclipses are now approximately
24 days in length, or half the orbital period. These results are interpreted
and discussed in the context of the recent models for this system put forward
by Winn et al. and Chiang & Murray-Clay. A periodogram of the entire data set
yields a highly significant peak at 48.37 +/- 0.01 days, which is in accord
with the spectroscopic period of 48.38 +/- 0.01 days determined by Johnson et
al. Another significant peak, at 9.6 days, was found in the periodogram of the
out-of-eclipse data at two different epochs. We interpret this as the rotation
period of the visible star and argue that it may be tidally locked in
pseudosynchronism with its orbital motion. If so, application of Hut's theory
implies that the eccentricity of the orbit is e = 0.65 +/- 0.01. Analysis of
the UVES/VLT spectra obtained by Hamilton et al. shows that the v sin(i) of the
visible star in this system is 6.9 +/- 0.3 km/sec. Using this value of v sin(i)
and the measured rotation period of the star, we calculate the lower limit on
the radius to be R = (1.3 +/- 0.1), R_Sun, which concurs with the value
obtained by Hamilton et al. from its luminosity and effective temperature. Here
we assume that i = 90 degrees since it is likely that the spin and orbital
angular momenta vectors are nearly aligned.
\\ ( http://arXiv.org/abs/astro-ph/0507578 ,  389kb)