NuSTAR OBSERVATION OF A TYPE I X-RAY BURST FROM GRS 1741.9-2853
- Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)
- Institut de Recherche en Astrophysique et Plantologie, UMR 5277, Toulouse (France)
- MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
- National Space Institute, Technical University of Denmark, Copenhagen (Denmark)
- Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)
- Cahill Center for Astronomy and Astrophysics, Caltech, Pasadena, CA 91125 (United States)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)
We report on two NuSTAR observations of GRS 1741.9-2853, a faint neutron star (NS) low-mass X-ray binary burster located 10' away from the Galactic center. NuSTAR detected the source serendipitously as it was emerging from quiescence: its luminosity was 6 × 10{sup 34} erg s{sup –1} on 2013 July 31 and 5 × 10{sup 35} erg s{sup –1} in a second observation on 2013 August 3. A bright, 800 s long, H-triggered mixed H/He thermonuclear Type I burst with mild photospheric radius expansion (PRE) was present during the second observation. Assuming that the luminosity during the PRE was at the Eddington level, an H mass fraction X = 0.7 in the atmosphere, and an NS mass M = 1.4 M {sub ☉}, we determine a new lower limit on the distance for this source of 6.3 ± 0.5 kpc. Combining with previous upper limits, this places GRS 1741.9-2853 at a distance of 7 kpc. Energy independent (achromatic) variability is observed during the cooling of the NS, which could result from the disturbance of the inner accretion disk by the burst. The large dynamic range of this burst reveals a long power-law decay tail. We also detect, at a 95.6% confidence level (1.7σ), a narrow absorption line at 5.46 ± 0.10 keV during the PRE phase of the burst, reminiscent of the detection by Waki et al. We propose that the line, if real, is formed in the wind above the photosphere of the NS by a resonant Kα transition from H-like Cr gravitationally redshifted by a factor 1 + z = 1.09, corresponding to a radius range of 29.0-41.4 km for a mass range of 1.4-2.0 M {sub ☉}.
- OSTI ID:
- 22364411
- Journal Information:
- Astrophysical Journal, Vol. 799, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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