%0 Generic %1 citeulike:13633438 %A Degenaar, N. %A Miller, J. M. %A Chakrabarty, D. %A Harrison, F. %A Kara, E. %A Fabian, A. C. %D 2015 %K imported %T A NuSTAR observation of disk reflection from close to the neutron star in 4U 1608-52 %U http://arxiv.org/abs/1505.07112 %X Studying the reflection of X-rays off the inner edge of the accretion disk in a neutron star low-mass X-ray binary, allows us to investigate the accretion geometry and to constrain the radius of the neutron star. We report on a NuSTAR observation of 4U 1608-52 obtained during a faint outburst in 2014 when the neutron star, which has a known spin frequency of 620 Hz, was accreting at \~1-2\% of the Eddington limit. The 3-79 keV continuum emission was dominated by a Gamma\~2 power law, with a \~1-2\% contribution from a kTbb\~0.3-0.6 keV black body component. The high-quality NuSTAR spectrum reveals the hallmarks of disk reflection; a broad iron line peaking near 7\~keV and a Compton back-scattering hump around \~20-30 keV. Modeling the disk reflection spectrum points to a binary inclination of i\~30-40 degrees and a small `coronal' height of h<8.5 GM/c2. Furthermore, our spectral analysis suggests that the inner disk radius extended to Rin\~7-10 GM/c2, close to the innermost stable circular obit. This constrains the neutron star radius to R<21 km and the redshift from the stellar surface to z>0.12, for a mass of M=1.5 Msun and a spin parameter of a=0.29.

@misc{citeulike:13633438, abstract = {{Studying the reflection of X-rays off the inner edge of the accretion disk in a neutron star low-mass X-ray binary, allows us to investigate the accretion geometry and to constrain the radius of the neutron star. We report on a NuSTAR observation of 4U 1608-52 obtained during a faint outburst in 2014 when the neutron star, which has a known spin frequency of 620 Hz, was accreting at \~{}1-2\% of the Eddington limit. The 3-79 keV continuum emission was dominated by a Gamma\~{}2 power law, with a \~{}1-2\% contribution from a kTbb\~{}0.3-0.6 keV black body component. The high-quality NuSTAR spectrum reveals the hallmarks of disk reflection; a broad iron line peaking near 7\~{}keV and a Compton back-scattering hump around \~{}20-30 keV. Modeling the disk reflection spectrum points to a binary inclination of i\~{}30-40 degrees and a small `coronal' height of h\<8.5 GM/c2. Furthermore, our spectral analysis suggests that the inner disk radius extended to Rin\~{}7-10 GM/c2, close to the innermost stable circular obit. This constrains the neutron star radius to R\<21 km and the redshift from the stellar surface to z\>0.12, for a mass of M=1.5 Msun and a spin parameter of a=0.29.}}, added-at = {2019-03-25T08:20:55.000+0100}, archiveprefix = {arXiv}, author = {Degenaar, N. and Miller, J. M. and Chakrabarty, D. and Harrison, F. and Kara, E. and Fabian, A. C.}, biburl = {https://www.bibsonomy.org/bibtex/2d901461f9628dff3e9ff31b6ed64e542/ericblackman}, citeulike-article-id = {13633438}, citeulike-linkout-0 = {http://arxiv.org/abs/1505.07112}, citeulike-linkout-1 = {http://arxiv.org/pdf/1505.07112}, day = 26, eprint = {1505.07112}, interhash = {ddb451711387c79369ea130116b9281a}, intrahash = {d901461f9628dff3e9ff31b6ed64e542}, keywords = {imported}, month = may, posted-at = {2015-05-30 23:16:43}, priority = {2}, timestamp = {2019-03-25T08:20:55.000+0100}, title = {{A NuSTAR observation of disk reflection from close to the neutron star in 4U 1608-52}}, url = {http://arxiv.org/abs/1505.07112}, year = 2015 }