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Alert Notice 507: Observations of the eclipsing binary b Persei

January 7, 2015: Dr. Robert Zavala (USNO-Flagstaff) and collaborators request observations of the bright variable star b Persei for the next two weeks, in hopes of catching a predicted eclipse on 2015 January 15 UT.  This is a follow-up to the February 2013 campaign announced in Alert Notice 476, and will be used as a photometric comparison for upcoming interferometric observations with the Navy Precision Optical Interferometer (NPOI) in Arizona.  Observers are asked to obtain time-series observations beginning immediately, with the most critical window of coverage being between 2015 January 9 and 2015 January 17 UT.

b Persei is located at the following (J2000) coordinates:

RA: 04 18 14.62 , Dec: +50 17 43.7

b Per is a bright star (V=4.598, B-V=0.054) and so is ideal for observers with photoelectric photometers or those using DSLR cameras.  Telescopic CCD observers may also be able to observe by stopping down larger apertures. Time-series observations with a V-filter are ideal; other filters may be used, but multicolor photometry is not required.

For photoelectric photometry, we have assigned the following stars as comparison and check:

Comparison star:
    SAO 24412, RA: 04 06 35.044 , Dec: +50 21 04.55 , V=4.285, B-V = -0.013

Check star:
    SAO 24512, RA: 04 16 43.087 , Dec: +53 36 42.47 , V=5.19, B-V = -0.05

DSLR observers may also find the nearby star SAO 39457 / HR 1330 a useful comparison star; it is available via VSP as the "55" comparison (V=5.456, B-V=0.219).

Dr. Zavala sends the following along with his request:

"[W]e wanted to try and involve AAVSO observers in a follow up to our successful detection of the b Persei eclipse of Feb 2013, AAVSO Alert Notice 476 and Special Notice 333.

Our goal now is to get good time resolution photometry as the third star passes in front of the close ellipsoidal binary. The potential for multiple eclipses exists. The close binary has a 1.5 day orbital period, and the eclipsing C component requires about 4 days to pass across the close binary pair.

For AAVSO observations a single filter would be fine, as our goal is to improve the timing resolution for the eclipse of the primary, and if possible detect an eclipse of the B component by C. The primary eclipse depth is 0.15 magnitudes. Photometry to 0.02 or 0.03 mags would be fine to detect this eclipse.

The eclipse prediction date is based on one orbital period from the 2013 eclipse and is:

JD 2457033.79 = 2015 01 11 UT

We'd like to see a baseline light level before and after eclipse(s) so observing roughly Jan 5-17 would be good. The period for high time resolution, if possible by AAVSO observers, is Jan 9-13 UT. This predicted eclipse time of minimum light is nominally daylight for the U.S. and we have about a +/- 1 day or less uncertainty.

For more information please see our b Persei eclipse web page at:

Please promptly submit all observations to the AAVSO via WebObs using the name "B PER".

This AAVSO Alert Notice was prepared by M. Templeton.


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