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BD +60 73 = IGR J00370+6122

ATel #285; Ignacio Negueruela (Univ. Alicante), Pablo Reig (IESL, Foundation for Research and Technology-HELLAS)
on 22 May 2004; 21:09 UT
Credential Certification: Ignacio Negueruela (ignacio@dfists.ua.es)

Subjects: Optical, X-ray, Binary, Neutron Star, Star, Variables

Referred to by ATel #: 312

A classification spectrum of BD +60 73, reported to be the optical counterpart to IGR J00370+6122 (ATel #281), was taken on the night of 2003 July 7th with the 2.5-m Issac Newton telescope at La Palma. The derived spectral type is BN0.5II-III, where the composite luminosity class indicates an intermediate luminosity. The Nitrogen enhancement is moderately high, with numerous NII lines being rather stronger than corresponds to the spectral type. There is, however, no obvious Carbon depletion.

UBV photometry is reported by Hiltner (1956, ApJS 2, 389) and Haug (1970, A&AS 1, 35). Their values are identical within the errors and give V=9.64, (B-V)=0.57. Assuming Mv=-5.2, intermediate between the values for luminosity class II and III, we obtain E(B-V)=0.78 and DM=12.4, corresponding to d=3.0 kpc, a typical value for the "far" component of Cas OB5 (Ampel 1964, AcA 14, 52).

A low resolution spectrum covering the yellow/red region of the spectrum was taken on 2004 May 21st, using the 1.3-m telescope at Skinakas (Crete). HeI 5875, HeI 6678 and H-alpha seem to be strongly in absorption, as is morphologically normal for the spectral type. BD +60 73 does not apper to be a Be stars.

Accretion from a relatively low-density wind in an eccentric orbit would explain the low X-ray luminosity and strong orbital modulation reported in ATel #281.