Columbia University Astronomy and Astrophysics

Discovery of 113 s Pulsations in AX J1835.4-0737
D. J. Helfand, E. V. Gotthelf, & J. P. Halpern

An XMM-Newton observation of the source AX J1835.4-0737 obtained on 2004 September 19 reveals that it is a pulsar with period 112.84±0.03 s, at coordinates (J2000) R.A = 18h35m25.9s, Decl.=-07°36'50". Its spectrum can be fitted with a power law of photon index Γ = 1.70±0.15, column density NH=(8.6±0.8)×1022 cm-2, and flux F(2-10 keV)=5.34×10-12 ergs cm-2 s-1. A bright star in the 2MASS survey at coordinates (J2000) R.A.=18h35m25.82s, Decl.=-07°36'50.1" is coincident with the X-ray position, and has magnitudes J=12.06, H=8.52, K=6.55. It is not detected on the Digitized UK Schmidt sky-survey plates. IR spectroscopy should be obtained to classify this probable supergiant companion star.

AX J1835.4-0737 in the ASCA GIS
1994 April 8 1999 October 14
1994 1997

AX J1835.4-0737 in the XMM-Newton EPIC pn
(J2000) 18 35 25.9, -07 36 50 2004 September 18
XMM Light Curve
These XMM-Newton data become public on Oct. 7, 2005.

2MASS Identification (1.5'x1.5')
(J2000) 18 35 25.82, -07 36 50.1
2MASS J-band 2MASS H-band 2MASS K-band

An infrared spectrum was obtained by Ian McGreer at MDM on June 15, 2005, TBA.

MDM 1.3m I-band (1.1'x1.1')
(J2000) 18 35 25.82, -07 36 50.1
MDM 1.3m I-band MDM 1.3m I-band


Faint X-ray Sources Resolved in the ASCA Galactic Plane Survey and their Contribution to the Galactic Ridge X-ray Emission, M. Sugizaki, K. Mitsuda, H. Kaneda, K. Matsuzaki, S. Yamauchi, & K. Koyama, ApJS, 134, 77-102 (2001)

Buried Binaries: Supergiants Feeding X-ray Pulsars, D. J. Helfand, E.V. Gotthelf, & J. P. Halpern, A.A.S., 205, 102.12 (2004)


Last modified: February 4, 2006 Transient X-ray Source Page