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The identification of the optical/IR counterpart of the 15.8-s transient X-ray pulsar XTE J1946+274

F. Verrecchia·G. L. Israel·I. Negueruela·S. Covino·V. F. Polcaro·J. S. Clark·I. A. Steele·R. Gualandi·R. Speziali·L. Stella
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Abstract

We report on the discovery of the optical/IR counterpart of the 15.8s transient X-ray pulsar XTE J1946+274. We re-analysed archival BeppoSAX observations of XTE J1946+274, obtaining a new refined position (a circle with 22" radius at 90% confidence level). Based on this new position we carried out optical and infra-red (IR) follow-up observations. Within the new error circle we found a relatively optical faint (B=18.6) IR bright (H=12.1) early type reddened star (V--R=1.6). The optical spectra show strong H-alpha and H-beta emission lines. The IR photometric observations of the field confirm the presence of an IR excess for the H-alpha--emitting star (K=11.6, J--H=0.6) which is likely surrounded by a circumstellar envelope. Spectroscopic and photometric data indicate a B0--1V--IVe spectral-type star located at a distance of 8--10kpc and confirm the Be-star/X-ray binary nature of XTE J1946+274.

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F. Verrecchia, G. L. Israel, I. Negueruela, S. Covino, V. F. Polcaro, J. S. Clark, I. A. Steele, R. Gualandi, R. Speziali, L. Stella. 2002-07-26. The identification of the optical/IR counterpart of the 15.8-s transient X-ray pulsar XTE J1946+274. https://doi.org/10.1051/0004-6361%3A20021087

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