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A NICER View of Spectral and Profile Evolution for Three X-Ray-emitting Millisecond Pulsars

Rowan, Dominick M. and Ghazi, Zaynab and Lugo, Lauren and Spano, Elizabeth and Lommen, Andrea and Harding, Alice and Venter, Christo and Ludlam, Renee and Ray, Paul S. and Kerr, Matthew and Arzoumanian, Zaven and Bogdanov, Slavko and Deneva, Julia and Guillot, Sebastien and Lewandowska, Natalia and Markwardt, Craig B. and Ransom, Scott and Enoto, Teruaki and Wood, Kent S. and Gendreau, Keith C. (2020) A NICER View of Spectral and Profile Evolution for Three X-Ray-emitting Millisecond Pulsars. Astrophysical Journal, 892 (2). Art. No. 150. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20200409-115739757

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Abstract

We present two years of Neutron star Interior Composition Explorer (NICER) X-ray observations of three energetic rotation-powered millisecond pulsars (MSPs): PSRs B1937+21, B1821−24, and J0218+4232. We fit Gaussians and Lorentzians to the pulse profiles for different energy sub-bands of the soft X-ray regime to measure the energy dependence of pulse separation and width. We find that the separation between pulse components of PSR J0218+4232 decreases with increasing energy at >3σ confidence. The 95% upper limit on pulse separation evolution for PSRs B1937+21 and B1821−24 is less than 2 milliperiods per keV. Our phase-resolved spectral results provide updated constraints on the non-thermal X-ray emission of these three pulsars. The photon indices of the modeled X-ray emission spectra for each pulse component of PSR B1937+21 are inconsistent with each other at the 90% confidence level, suggesting different emission origins for each pulse. We find that the PSR B1821−24 and PSR J0218+4232 emission spectra are invariant with phase at the 90% confidence level. We describe the implications of our profile and spectral results in the context of equatorial current sheet emission models for these three MSPs with non-thermal, magnetospheric X-ray emission.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab718fDOIArticle
https://arxiv.org/abs/2001.11513arXivDiscussion Paper
ORCID:
AuthorORCID
Rowan, Dominick M.0000-0003-2431-981X
Lommen, Andrea0000-0003-4137-7536
Harding, Alice0000-0001-6119-859X
Venter, Christo0000-0002-2666-4812
Ludlam, Renee0000-0002-8961-939X
Ray, Paul S.0000-0002-5297-5278
Kerr, Matthew0000-0002-0893-4073
Bogdanov, Slavko0000-0002-9870-2742
Deneva, Julia0000-0003-1226-0793
Guillot, Sebastien0000-0002-6449-106X
Lewandowska, Natalia0000-0003-0771-6581
Markwardt, Craig B.0000-0001-9803-3879
Ransom, Scott0000-0001-5799-9714
Enoto, Teruaki0000-0003-1244-3100
Wood, Kent S.0000-0002-7376-3151
Additional Information:© 2020. The American Astronomical Society. Received 2019 November 1; revised 2020 January 27; accepted 2020 January 28; published 2020 April 7. This work was supported by NASA through the NICER mission and the Astrophysics Explorers Program. D.R., L.L., and Z.G. acknowledge support from the NANOGrav Physics Frontiers Center (NSF award No. 1430284) and from Haverford College through the Louis Green Fund. E.S. acknowledges support from the Marian E. Koshland Integrated Natural Sciences Center Summer Scholar fund at Haverford College. R.M.L. acknowledges the support of NASA through Hubble Fellowship Program grant HST-HF2-51440.001. The authors thank K. Kalapotharakos for his insight on interpretation of our results, and M. Corcoran for his assistance in generating the space-weather model background. We also thank J. Cammisa for his input on data acquisition and handling. This research has made use of NASA's Astrophysics Data System Bibliographic Services (ADS) and the arXiv. Software: HEAsoft (v6.26.1 Nasa High Energy Astrophysics Science Archive Research Center (Heasarc), 2014), PINT (https://github.com/nanograv/pint), XSELECT (v2.4), XSPEC (v12.1.0 Arnaud 1996), NICERSoft (https://github.com/paulray/NICERsoft). Facility: NICER. -
Funders:
Funding AgencyGrant Number
NSFPHY-1430284
Haverford CollegeUNSPECIFIED
NASA Hubble FellowshipHST-HF2-51440.001
NASA Einstein FellowshipUNSPECIFIED
Subject Keywords:Millisecond pulsars ; Neutron stars ; X-ray astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Millisecond pulsars (1062); Neutron stars (1108); X-ray astronomy (1810)
Record Number:CaltechAUTHORS:20200409-115739757
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200409-115739757
Official Citation:Dominick M. Rowan et al 2020 ApJ 892 150
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102457
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:09 Apr 2020 20:20
Last Modified:09 Apr 2020 20:20

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