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Swift/XRT follow-up observation of the new X-ray source XTE J1701-407

ATEL # 1572; N. Degenaar and R. Wijnands (University of Amsterdam)
on 12 Jun 2008; 9:46 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Rudy Wijnands (

Subjects: X-ray, Request for Observations, Binaries, Black Holes, Neutron Stars, Transients

Following the discovery of the X-ray source XTE J1701-407 with RXTE/PCA (Atel #1569), we obtained a Swift/XRT observation of the source field on 2008-06-11, starting from UT 15:55:57. The XRT data shows one clear object within the 10 arcminute RXTE error circle for XTE J1701-407 (Atel #1569). The position of this source is found to be R.A. = 17:01:44.11 and Dec. = -40:51:27.93 (J2000), with an uncertainty of 3.6 arcseconds.

The Swift/XRT observation consists of two sets of data. The first set was ~400 seconds long and was obtained in WT (Windowed Timing) mode. The WT spectrum could be fit to an absorbed powerlaw model with a hydrogen column density of Nh~3.6 (-0.7,+0.8)E22 cm-2 and a photon index of ~2.1 (+/-0.4). The resulting absorbed and unabsorbed fluxes in the 2-10 keV band are ~2.0E-10 erg/cm2/s and ~2.8E-10 erg/cm2/s respectively. Both the spectral shape and the source flux of this Swift/XRT detection are consistent with the results for XTE J1701-407 from a pointed RXTE/PCA observation performed on 2008-06-09 (Atel #1569). For a distance of 8 kpc, the unabsorbed Swift/XRT flux translates into a source luminosity of ~2E36 erg/s.

The second set of data was carried out in the PC (Photon Counting) mode and amounts to ~600 seconds, starting at UT 16:08:20. To avoid pile-up, we extracted source photons from an annular region. The PC spectrum could be fit to an absorbed powerlaw model with a hydrogen column density of Nh~3.3 (-1.4,+1.6)E22 cm-2 and a photon index of ~2.0 (+/-0.6). The resulting 2-10 keV flux is ~2.1E-10 erg/cm2/s or ~2.8E-10 erg/cm2/s corrected for absorption. This is similar to the results of the WT data fits.

Observations of this new X-ray source in other wavelength regimes are encouraged.

We thank the Swift team for scheduling the observation.

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