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NuSTAR J163433-4738.7: A Fast X-Ray Transient in the Galactic Plane

Tomsick, John A. and Gotthelf, Eric V. and Rahoui, Farid and Assef, Roberto J. and Bauer, Franz E. and Bodaghee, Arash and Boggs, Steven E. and Christensen, Finn E. and Craig, William W. and Fornasini, Francesca M. and Grindlay, Jonathan and Hailey, Charles J. and Harrison, Fiona A. and Krivonos, Roman and Natalucci, Lorenzo and Stern, Daniel and Zhang, William W. (2014) NuSTAR J163433-4738.7: A Fast X-Ray Transient in the Galactic Plane. Astrophysical Journal, 785 (1). Art. No. 4. ISSN 0004-637X.

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During hard X-ray observations of the Norma spiral arm region by the Nuclear Spectroscopic Telescope Array (NuSTAR) in 2013 February, a new transient source, NuSTAR J163433-4738.7, was detected at a significance level of 8σ in the 3-10 keV bandpass. The source is consistent with having a constant NuSTAR count rate over a period of 40 ks and is also detected simultaneously by Swift at lower significance. The source is not significantly detected by NuSTAR, Swift, or Chandra in the days before or weeks after the discovery of the transient, indicating that the strong X-ray activity lasted between ~0.5 and 1.5 days. Near-infrared imaging observations were carried out before and after the X-ray activity, but we are not able to identify the counterpart. The combined NuSTAR and Swift energy spectrum is consistent with a power law with a photon index of Γ = 4.1^(+1.5)_(-1.0) (90% confidence errors), a blackbody with kT = 1.2 ± 0.3 keV, or a Bremsstrahlung model with kT = 3.0^(+2.1)_(-1.2) keV. The reduced-χ^2 values for the three models are not significantly different, ranging from 1.23 to 1.44 for 8 degrees of freedom. The spectrum is strongly absorbed with N_H = (2.8^(+2.3)_(-1.4)) x 10^(23) cm^(–2), (9^(+15)_(-7)) x 10^(22) cm^(–2), and (1.7^(+1.7)_(-0.9)) x 10^(23) cm^(–2), for the power-law, blackbody, and Bremsstrahlung models, respectively. Although the high column density could be due to material local to the source, it is consistent with absorption from interstellar material along the line of sight at a distance of 11 kpc, which would indicate an X-ray luminosity >10^(34) erg s^(–1). Although we do not reach a definitive determination of the nature of NuSTAR J163433-4738.7, we suggest that it may be an unusually bright active binary or a magnetar.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rahoui, Farid0000-0001-7655-4120
Assef, Roberto J.0000-0002-9508-3667
Bauer, Franz E.0000-0002-8686-8737
Boggs, Steven E.0000-0001-9567-4224
Harrison, Fiona A.0000-0003-2992-8024
Krivonos, Roman0000-0003-2737-5673
Stern, Daniel0000-0003-2686-9241
Additional Information:© 2014 American Astronomical Society. Received 2013 November 6; accepted 2014 February 7; published 2014 March 19. This work was supported under NASA Contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. The authors thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (Italy) and the California Institute of Technology (USA). R.J.A. was supported by Gemini-CONICYT grant 32120009. F.E.B. was supported by Basal-CATA PFB-06/2007 and CONICYT-Chile (through FONDECYT 1101024, Gemini-CONICYT 32120003, and Anillo ACT1101). L.N. wishes to acknowledge the Italian Space Agency (ASI) for financial support by ASI/INAF grant I/037/12/0-011/13. The authors thank Harvey Tananbaum for providing Chandra Director’s Discretionary Time for this project. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)32120009
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)FONDECYT 1101024
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)32120003
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ACT1101
Agenzia Spaziale Italiana (ASI)I/037/12/0-011/13
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:Galaxy: stellar content; stars: variables: general; surveys; X-rays: individual (NuSTAR J1634334738.7); X-rays: stars
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2014-63
Record Number:CaltechAUTHORS:20140606-135843500
Persistent URL:
Official Citation:NuSTAR J163433-4738.7: A Fast X-Ray Transient in the Galactic Plane John A. Tomsick et al. 2014 ApJ 785 4
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46133
Deposited By: Ruth Sustaita
Deposited On:06 Jun 2014 22:01
Last Modified:29 Nov 2017 00:45

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