CaltechAUTHORS
Published May 1, 2018 | Version Published + Accepted Version
Journal Article Open

Detection of Reflection Features in the Neutron Star Low-mass X-Ray Binary Serpens X-1 with NICER

Creators

  • 1. ROR icon University of Michigan–Ann Arbor
  • 2. ROR icon Wayne State University
  • 3. ROR icon Massachusetts Institute of Technology
  • 4. ROR icon University of Erlangen-Nuremberg
  • 5. ROR icon University of Cambridge
  • 6. ROR icon California Institute of Technology
  • 7. ROR icon Research Institute in Astrophysics and Planetology
  • 8. ROR icon Eureka Scientific
  • 9. ROR icon Netherlands Institute for Space Research
  • 10. ROR icon Technical University of Denmark
  • 11. ROR icon University of Maryland, College Park
  • 12. ROR icon National Space Science and Technology Center

Abstract

We present Neutron Star Interior Composition Explorer (NICER) observations of the neutron star (NS) low-mass X-ray binary Serpens X-1 during the early mission phase in 2017. With the high spectral sensitivity and low-energy X-ray passband of NICER, we are able to detect the Fe L line complex in addition to the signature broad, asymmetric Fe K line. We confirm the presence of these lines by comparing the NICER data to archival observations with XMM-Newton/Reflection Grating Spectrometer (RGS) and NuSTAR. Both features originate close to the innermost stable circular orbit (ISCO). When modeling the lines with the relativistic line model RELLINE, we find that the Fe L blend requires an inner disk radius of 1.4^(+0.2)_(-0.1) R_(ISCO) and Fe K is at 1.03^(+0.13)_(-0.03) R_(ISCO) (errors quoted at 90%). This corresponds to a position of 17.3^(+2.5)_(-1.2) km and 12.7^(+1.6)_(-0.4) km for a canonical NS mass (M_(NS) = 1.4 M⊙) and dimensionless spin value of a = 0. Additionally, we employ a new version of the RELXILL model tailored for NSs and determine that these features arise from a dense disk and supersolar Fe abundance.

Additional Information

© 2018 The American Astronomical Society. Received 2018 March 26; revised 2018 April 12; accepted 2018 April 16; published 2018 May 2. R.M.L. acknowledges funding through a NASA Earth and Space Science Fellowship. A.C.F. acknowledges ERC Advanced grant 340442. E.M.C. gratefully acknowledges NSF CAREER award AST-1351222.

Attached Files

Published - Ludlam_2018_ApJL_858_L5.pdf

Accepted Version - 1804.10214.pdf

Files

1804.10214.pdf

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Additional details

Identifiers

Eprint ID
86211
Resolver ID
CaltechAUTHORS:20180503-130325076

Related works

Describes
https://arxiv.org/abs/1804.10214 (URL)

Funding

NASA Earth and Space Science Fellowship
European Research Council (ERC)
340442
NSF
AST-1351222

Dates

Created
2018-05-03
Created from EPrint's datestamp field
Updated
2021-11-15
Created from EPrint's last_modified field