AAVSO: American Association of Variable Star Observers

Proposal #90

Proposer (2108) Arne Henden (ahenden@gmail.com) obscode: HQA
Assigned To(3663) Dirk Terrell
Date SubmittedNov. 12, 2018

b Per is scheduled to enter a secondary eclipse around November 21 (AAVSO Alert Notice 655). This star, at magnitude V=4.6, is an ideal candidate for the BSM network. In the upcoming eclipse, the third star of the system (C) is predicted to pass behind the main A-B pair. The eclipse will take about 3 days and be about 0.1mag in depth at V.

As the A-B pair exhibit ellipsoidal variation of approximately 0.06mag, getting data before, during and after the eclipse is essential to make sure that accurate phasing of the ellipsoidal variation can be made, so that the ellipsoidal variation can be separated from the eclipse information. Likewise, an accurate measure of the depth at various wavelengths both helps in the understanding of the orbit, as well as the stellar classification and perhaps atmospheric structure of each star.

While the AN will result in a number of observers carefully monitoring the star, the fact that the eclipse occurs over several days means that more observations at widely separated sites are important to fill out the light curve and also guard against weather dropouts.

Towards this end, I would like to propose using the northern part of the BSM network to monitor b Per, starting as soon as possible and extending for two weeks after the eclipse. The cadence should be once/hour before/after the eclipse, with continuous time series observation during the 3-day eclipse, cycling through filters (recommended). The observing window is nearly optimal for this eclipse, with the target transiting a half hour after local midnight at the eclipse center.

For b Per, observations at BVRI are needed, with SU observations if possible with the mount limitations. Exposure times should be 5sec B, 3sec V, 2sec R, 2sec I, and 100sec SU, with a minimum of 3 exposures per filter. The data should be sent to my VPHOT account.

The primary result of this monitoring will be photometry submitted to the AID.

Target RA (H.HH) Dec (D.DD) Magnitude Telescope Observation Frequency Expiration Date Proprietary Term
b Per 4.304061 50.29550 4.75–4.57 No


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