2A 0311-227
Abstract
R. E. Griffiths and the HEAO-A3 Group of Harvard-Smithsonian Center for Astrophysics and Massachusetts Institute of Technology; M. J. Ward, Institute of Astronomy, University of Cambridge; J. C. Blades, Anglo-Australian Observatory; and A. S. Wilson, University of Maryland, report the optical identification of the x-ray source 2A 0311-227 (cf. IAUC 3324) with an AM-Her-type star. The source was precisely located by the HEAO-1 scanning modulation collimator, with resulting positional errors of 20" x 2', and there is only one star brighter than magnitude 19 within these errors. Spectrograms of this ~ fifteenth-magnitude star (R.A. = 3h12m00s.0, Decl. = -22o46'49", equinox 1950.0) were taken at the Mt. Stromlo 190-cm telescope using the Cassegrain spectrograph and photon counting array on 1978 Nov. 27 and at the 390-cm Anglo-Australian telescope using the RGO spectrograph and Image Photon Counting System on Dec. 2. The medium-dispersion spectra revealed an intense Balmer series in emission from H-alpha through H-10, together with a strong Balmer continuum. Emission lines were also observed at He I 4026, 4471 4921, 5015 and 5876 A; He II 4686 A; and C III-N III 4640 A. In view of the remarkable similarity of this spectrum to that of AM Her, including the unusual Balmer decrement, the x-ray source is identified with this new member of the AM-Her class. D. R. Hearn, Massachusetts Institute of Technology, reports that 2A 0311-227 was scanned with the x-ray detectors on SAS 3 between 1975 Dec. 22.1 and 1976 Jan. 2.4 UT. An average x-ray flux of 2 x 10**-11 erg cm**-2 s**-1 was detected in the 0.15-0.28-keV channel. Two individual scans with the best exposure to the source yielded 3-sigma detections. (The 0.4-0.8-keV flux was less than 10**-10 erg cm**-2 s**-1.) A fold of the x-ray data with the optical orbital period of 81 +/- 5 min reported by Boley et al. (IAUC 3324) provides weak evidence that the soft x-ray flux is modulated by 50-100 percent. The approximate epoch of x-ray minimum is 1975 Dec. 27.787 UT.
- Publication:
-
International Astronomical Union Circular
- Pub Date:
- February 1979
- Bibcode:
- 1979IAUC.3326....1G