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
Credential Certification: Jules Halpern (jules@astro.columbia.edu)
Subjects: Optical, X-ray, Gamma Ray, Binary, Cataclysmic Variable
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.
