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Special Notice #162: Photometry of Beta Cephei

AAVSO Special Notice #162

Photometry of Beta Cephei
July 21, 2009

Noel Richardson (Georgia State University) has requested high-precision photometry of the bright variable beta Cephei, beginning on or about 2009 August 1 and continuing through 2009 August 7.  Beta Cep is the prototype of a class of short-period (4-5 hour) non-radial pulsators; Richardson and collaborators will be using a combination of optical interferometry (using CHARA), spectroscopic radial velocities (using the Ritter Observatory, Ohio), and optical photometry to directly measure the diameter variations as a function of pulsation phase.

Beta Cep is a bright (V ~ 3.2), blue (B-V ~ -0.2) and low-amplitude pulsating variable variable with a period of 0.19 days.  This observing program is ideally suited for PEP observers, or CCD observers with fully calibrated systems capable of performing transformed precision photometry of bright stars.

PEP observers submitting V-band data via PEPObs should use SAO 19432 (7 Cep, V=5.43; RA 21 27 46.14 , Dec +66 48 32.7) for the comparison, and SAO 19646 (V=6.45 ; RA 21 47 00.85 , Dec +70 09 03.2) for the check star.  Both of these stars were used in prior time series photometric observations (e.g. Pigulski & Boratyn 1992, A&A 253, 178), and both are also AAVSO comparison stars.

Those who have the capability of reducing their own data may use other nearby comparison and check stars, but are strongly advised to ensure they are not variable.  A table of existing nearby comparison stars may be obtained by entering the RA and Declination of Beta Cep into AAVSO Variable Star Plotter (, and selecting the "Field Photometry" check box.

PEP observers capable of obtaining and reducing time-series photometry are especially encouraged to participate, given the very short period of this star.  V-filtered observations are preferred.

Beta Cep is located at the following (J2000) coordinates:

RA: 21 28 39.60 , Dec: +70 33 39.0

Please submit data to the AAVSO using the name "BET CEP".

This AAVSO Special Notice was prepared by Matthew Templeton.

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