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AX J1740.2-2903: X-ray Period and Optical Identification

ATEL # 2664; J.P. Halpern, E.V. Gotthelf (Columbia U.)
on 8 Jun 2010; 21:13 UT
Password Certification: Jules Halpern (jules@astro.columbia.edu)

Subjects: Optical, X-ray, Gamma Ray, Binaries, Cataclysmic Variables
Referred to by ATEL #: 2681

Further to the discussion of XMM-Newton and INTEGRAL/IBIS observations of this source by Malizia et al., arXiv:1006.1272, we report the discovery of periodicity in X-rays, as well as an optical spectroscopic identification.

We observed AX J1740.2-2903 with XMM-Newton for 8.2 ks on 2005 September 29. A strong periodic signal is detected in these data at P = 623+/-2 s, with a single-peaked pulse profile. The X-ray spectrum is well fitted by a power law of photon index Gamma = 0.6+/-0.2, column density NH = (5+/-2)e21, and flux F(1-10 keV)= 3.4e-12 erg cm-2 s-1. These spectral results are consistent with the analysis of the same data by Malizia et al., arXiv:1006.1272, who in addition show that the spectrum steepens into the INTEGRAL/IBIS 20-50 keV band.

The XMM-Newton position of the source, RA=17h40m16.03s, Decl.=-29d03'37.8" (J2000.0), is coincident with a USNO B1.0 star at RA=17h40m16.11s, Decl.=-29d03'37.9" (J2000.0) having magnitudes R1=18.04, B2=19.07, R2=18.78, I2=17.44. We obtained spectra of this star in the wavelength range 371-738 nm at a resolution of 0.8 nm using the 2.4m Hiltner telescope of the MDM Observatory on 2009 May 24 UT. Emission lines of H alpha, H beta, He I, and He II 468.6 nm, are evident at zero redshift. The relative strengths of the emission lines, as well as the moderate reddening, X-ray period, and X-ray spectral characteristics, suggest that this object is an intermediate polar.


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