XTE J1946+274

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Other Names: 2MASS J19453935+2721555 (Simbad)


RA 19h 45' 39.36", DEC +27° 21' 55.5"
RA 296.414000deg, DEC +27.365417deg
l 63.2072, b +1.3956

Binary system

X-ray Be transient
Distance: 8-10 kpc (Verrecchia et al. 2002)


Parameter Value Unit Reference
Porb 169.2+-0.6 days Wilson et al. (2003)
tau 2,451,558.7+-4 JD "
a sin i 640+-120 lt-sec "
e 0.33+-0.05 "
omega -91+-23 deg "
i ? deg -

Optical Companion

Spectral Class : B0-B1 IV-Ve (Verrecchia et al. 2002)

Parameter Value Unit Reference
Mopt 10-16 M Verrecchia et al. 2002
B 18.6 mag "
H 12.1 mag "

Available data

  • RXTE: PCA, HEXTE, 12 observations (86ks) in Sep/Oct 1998
  • RXTE: PCA, HEXTE, 24 observations (129ks) in Mar-Sep 2001
  • RXTE: PCA, HEXTE, Jun/Jul and Nov/Dec 2010
  • INTEGRAL: Jun/Oct/Nov 2010
  • SWIFT: 8 pointings, Nov/Dec 2010
  • SUZAKU: Nov 2010


The transient HMXB XTE J1946+274 was discovered 1998 (e.g. Smith & Takeshima 1998). The initial outburst lasted about 3 month, followed by several fainter outbursts seperated by ~80 days (Campana+ 1998). The source was in quiescence from 2001 until 2010, with the in principal same outburst behavior as 1998.

The outburst luminosity in 2010 reached ~120 mCrab (15-50keV) in the first outburst, and ~60 mCrab in the subsequent outbursts.


The spectrum of XTE J1946+274 can be successfully modelled by NPEX (Heindl+ 2001), but also by FDCO + 10keV feature (Mueller+ in prep.). Heindl+ (2001) found a cyclotron line at about 35keV in the initial outburst. The recent outburst in 2010 exhibit a possible cyclotron feature at about 25keV (Mueller+ in prep.)

Pulse Profile

The spin period is about 15.76 s (Mueller+ in prep.) with a spin up (-3.0+-0.3 s/s, Mueller+ in prep), possibly caused by orbital effects. The pulse profile shows a double peaked structure, also seen in, e.g., GRO J1008-57 and 4U 0115+634.