[vsnet-chat 7123] AM CVn stars from the SDSS

[Taichi Kato]

AM CVn stars from the SDSS

   First confirmed eclipsing AM CVn star found!  Other new members are worth
monitoring, too.

Paper: astro-ph/0506730
Date: Wed, 29 Jun 2005 18:27:15 GMT   (89kb)

Title: Ultracompact AM CVn Binaries from the Sloan Digital Sky Survey: Three
  Candidates Plus the First Confirmed Eclipsing System
Authors: Scott F. Anderson (1), Daryl Haggard (1), Lee Homer (1), Nikhil R.
  Joshi (1), Bruce Margon (2), Nicole M. Silvestri (1), Paula Szkody (1),
  Michael A. Wolfe (1), Eric Agol (1), Andrew C. Becker (1), Arne Henden (3),
  Patrick B. Hall (4), Gillian R. Knapp (5), Michael W. Richmond (6), Donald P.
  Schneider (7), Gregory Stinson (1), J.C. Barentine (8), Howard J. Brewington,
  J. Brinkmann, Michael Harvanek, S.J. Kleinman, Jurek Krzesinski, Dan Long,
  Eric H. Neilsen, Atsuko Nitta, Stephanie A. Snedden ((1) Univ. of Wash., (2)
  STScI, (3) USNO, (4) York Univ., (5) Princeton, (6) RIT, (7) Penn. State, (8)
  APO.)
Comments: 7 pages, 3 figures, submitted to the Astronomical Journal
\\
  AM CVn systems are a rare (about a dozen previously known) class of
cataclysmic variables, arguably encompassing the shortest orbital periods (down
to about 10 minutes) of any known binaries. Both binary components are thought
to be degenerate (or partially so), likely with mass-transfer from a
helium-rich donor onto a white dwarf, driven by gravitational radiation.
Although rare, AM CVn systems are of high interest as possible SN Ia
progenitors, and because they are predicted to be common sources of gravity
waves in upcoming experiments such as LISA. We have identified four new AM CVn
candidates from the Sloan Digital Sky Survey (SDSS) spectral database. All four
show hallmark spectroscopic characteristics of the AM CVn class: each is devoid
of hydrogen features, and instead shows a spectrum dominated by helium. All
four show double-peaked emission, indicative of helium-dominated accretion
disks. Limited time-series CCD photometric follow-on data have been obtained
for three of the new candidates from the ARC 3.5m; most notably, a 28.3 minute
binary period with sharp, deep eclipses is discovered in one case, SDSS
J0926+3624. This is the first confirmed eclipsing AM CVn, and our data allow
initial estimates of binary parameters for this ultracompact system. The four
new SDSS objects also provide a substantial expansion of the currently
critically-small sample of AM CVn systems.
\\ ( http://arXiv.org/abs/astro-ph/0506730 ,  89kb)