Narrow-Band Photometry of Babcock's Magnetic Star HD 215441.
Abstract
The eighth-magnitude A0p star HD 215441 was discovered by Horace W. Babcock in 1959 to have by far the largest effective magnetic field known. In October, 1959 the intensity was 34 400-~266 gauss. The star is unique in that its Zeeman pattern has been clearly resolved. We observed Babcock's star photoelectrically on 14 of 17 consecutive nights in September, 1960 with the 20-inch reflector of the Palomar Observatory in narrow bands at 5500, 4700, 4100 (half-width 200 A), and 3500 A (half-width about 300 A), during the course of a program of photoelectric narrow-Thand photometry of B. Str6mgren. The respective ranges of variation in the four wavelengths were approximately 0.18, 0.23, 0.23, and 0.27 mag. Pending final reduction, we tentatively note an increase in the range of variation from a value of 0.14 magnitudes, derived through broad-band photoelectric photometry (effective wavelength 4200 A) during the period August, 1959-February, 1960 by T. tarzebowski, Wroclaw Observatory. The six light-curves in yellow, blue, violet, ultraviolet, v-b, and u-v are approximately 1800 out of phase with b-y. The ranges of b-y, v-b, and u-v are approximately 0.07, 0.07, and 0.10 mag., respectively. tarzebowski derived a period of 9.49 days. Combination of his epoch with ours yields a possible period of 9.475 days. A slight suggestion of short- period variation seems to be worth following up. The star is unusually bright in the ultraviolet for its spectral class. The remainder of this paper is based upon unpublished observational data of Str6mgren. The anomalous location of several magnetic stars in his (l,c) classification, based on the strengths of H-beta and the Balmer discontinuity, respectively, is described in connection with the possibility of using narrowband criteria for the discovery of magnetic stars.
- Publication:
-
The Astronomical Journal
- Pub Date:
- March 1961
- DOI:
- 10.1086/108524
- Bibcode:
- 1961AJ.....66R..40C