New "Otero+" EBs

New EBs identified by Sebastian Otero and his colleagues:

Between 2003 and 2007, Sebastian Otero and his co-authors published a series of papers in which they "datamined" the ROTSE (NSVS), ASAS, and Hipparcos databases, discovering many new eclipsing binaries, and updating the description of others.  These stars (>1100) are particularly interesting because their brightness is in the "sweet spot" for amateur observers, roughly magnitudes 8 to 13.  Also, 88 of them are eccentric systems, with elliptical orbits and secondary eclipses not half-way between primary eclipses.

Sebastian generously provided several text files containing these lists of stars and their parameters.  Of the 1126 EBs listed, at least 172 already had been named in the GCVS, but the Otero et al. papers supplied updated information (usually the period).  Of the rest, all but 11  have now been named as of GCVS Name List 80.  The spreadsheet below is a compilation of the information provided by Sebastian, with the addition of the subsequently assigned GCVS name.  Matching of the assigned GCVS name was accomplished using an automated script, based on coordinates.  Various checks have been performed on the resulting matches, but errors are still possible.  Please report any errors you find in the spreadsheet to Gary Billings.

Some of these "new" stars have had few ToMs published since they were first identified by Otero and colleagues.  For those whose period is based only on ROTSE observations, predictions of eclipse times can now be in error by several hours.  Thus there is lots of opportunity for observing under-observed stars and contributing ToMs that will be valuable to future observers.

As an aid to observers, Shawn Dvorak at Rolling Hills Observatory has added these stars to his ephemeris generator, accessible from his home page.   Select the "Otero+" checkbox to get ephemerides for the stars discussed here.  This will check on the observability from your site, of Otero+ stars that are now in the GCVS, with periods less than 8 days.  Star with periods longer than that require more case-by-case observing planning (multiple nights).  They are included in the spreadsheet below, which includes their elements.

Suggested observing strategy: use the Rolling Hills ephemeris generator to create a list of candidates.  Then use one of the O-C sites to check how much the star has been observed (the BAV LkDB site, or BRNO O-C Gateway).  The Cracow site won't provide an O-C diagram for little-observed stars, but will give a count of observations, and an ephemeris based on the most recent observations they have (this will probably be more accurate than the predictions from the Rolling Hills site).   If there are lots of recent ToMs (> 2/yr), it is probably adequately observed.  If there are no ToMs other than those from the Otero et al. papers, then it needs observing.  Make as long a run as you can, because the eclipse could come several hours early or late.   Report your results via the usual channels (see Reporting page).

Stars that have no ToMs other than what Otero et al. published need observing the most.  Of those, stars based only on NSVS data are most in need of observations, because the NSVS used only data taken April 1999 through March 2000.  Stars that have both NSVS and ASAS ids are based on more data and will have less ephemeris error.

To "drill down" and get more information about individual stars:

  • of course, use VSX
  • the online IBVS papers where most of these stars were published, have links that will take you to the lightcurves for all the stars in that paper.  The only wrinkle is the stars will be identified as they were at the time the paper was published, e.g. often by NSVS ids, not GCVS.  But seeing the lightcurve is very useful for planning your observations.  The IBVS or EOJV number of the reference paper for each star can be obtained from VSX, or from the spreadsheet attached below, and is presented with the ephemeris presented on the Rolling Hills page.