Search for Optical/IR Counterparts of X-ray Pulsators

The identification of the optical and/or IR counterpart of X-ray pulsators plays an important role in the determination of the nature of the compact object (which is responsible for the pulsations). The spectral information and the presence of peculiar features (especially emission lines such as Halpha, Hbeta, HeI, HeII and/or non-thermal continua) are powerful tools to discern between an accreting neutron star in a binary system (often associated with O-B stars) from a cataclysmic variable (mainly K-M main sequence companion stars). Moreover the lack of a plausible optical counterpart or the presence of featureless optical spectra (black body-like) can be used to select isolated neutron stars accreting from the interstellar medium, anomalous X-ray pulsars and magnetars/soft gamma-ray repeaters.
Optical and IR observations (spectrospcopic and photometric) of the relevant fields including the X-ray position uncertainty circles of X-ray pulsators have been obtained since May 1998 with the following ground-based telescopes:
• 1.5m Danish, 21 nights (ESO, La Silla, Chile)
• 1.5m ESO, 2 nights (ESO, La Silla, Chile)
• 3.6m ESO, 2 nights (ESO, La Silla, Chile)
• 3.5m NTT, 6 nights (ESO, La Silla, Chile)
• 1.5m Cassini, 28 nights (Astronomical Observatory of Bologna, Loiano, Italy)
• 1.1m AZT-24 (Astronomical Observatory of Rome, CampoImperatore, Italy)
• 8.2m VLT-ESO (ESO, Cerro Paranal, Chile)
• 2.5m NOT-IAC  3 nights (ENO, La Palma Canary Islands, Spain)
So far (Dec 1999), we found the likely optical counterpart of the following X-ray pulsators:

• 1WGA J1958+3232 (paper available, X-rays, Optical Sp., Optical/IR, CV of the IP class)
• GS0834-43 (paper available, X-rays, Optical/IR)
• XTE J0111-7317 (IAU Circ. available,paper available,Optical (DSS) image )
• RX J0052-7319 (IAU Circ. available,paper available, paper on A&A)
• AX J1820-1434 (Proceedings of IAU Colloq. 175)
• XTE J1946+274 (paper in prep.)
• XTE J1855-02
• XTE J1739-30
• 2E0050-7247
• XTE J0055-724
• GS1843+009 (paper available, X-rays, Optical/IR images,Optical/IR spectra )
• Sct X-1
• KS 1947+300 = GRO J1948+32 (IAU Circ. available, paper in prep.)
• RX J0806.3+1527 (see the dedicated page, AM CVn)

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Edited by: GianLuca, OAR, Roma, Italy

gianluca@mporzio.astro.it

Last change 2002 March