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NICER Observation of the Temporal and Spectral Evolution of Swift J1818.0−1607: A Missing Link between Magnetars and Rotation-powered Pulsars

Hu, Chin-Ping and Begiçarslan, Beste and Güver, Tolga and Enoto, Teruaki and Younes, George and Sakamoto, Takanori and Ray, Paul S. and Strohmayer, Tod E. and Guillot, Sebastien and Arzoumanian, Zaven and Palmer, David M. and Gendreau, Keith C. and Malacaria, C. and Wadiasingh, Zorawar and Jaisawal, Gaurava K. and Majid, Walid A. (2020) NICER Observation of the Temporal and Spectral Evolution of Swift J1818.0−1607: A Missing Link between Magnetars and Rotation-powered Pulsars. Astrophysical Journal, 902 (1). Art. No. 1. ISSN 1538-4357.

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We report on the hard X-ray burst and the first ~100 days of NICER monitoring of the soft X-ray temporal and spectral evolution of the newly discovered magnetar Swift J1818.0−1607. The burst properties are typical of magnetars with a duration of T₉₀ = 10 ± 4 ms and a temperature of kT = 8.4 ± 0.7 keV. The 2–8 keV pulse shows a broad, single-peak profile with a pulse fraction increasing with time from 30% to 43%. The NICER observations reveal strong timing noise with varying erratically by a factor of 10, with an average long-term spin-down rate of ν = (−2.48±0.03)×10⁻¹¹~s⁻², implying an equatorial surface magnetic field of 2.5 × 10¹⁴ G and a young characteristic age of ~470 yr. We detect a large spin-up glitch at MJD 58928.56 followed by a candidate spin-down glitch at MJD 58934.81, with no accompanying flux enhancements. The persistent soft X-ray spectrum of Swift J1818.0−1607 can be modeled as an absorbed blackbody with a temperature of ~1 keV. Its flux decayed by ~60% while the modeled emitting area decreased by ~30% over the NICER observing campaign. This decrease, coupled with the increase in the pulse fraction, points to a shrinking hot spot on the neutron star surface. Assuming a distance of 6.5 kpc, we measure a peak X-ray luminosity of 1.9 × 10³⁵ erg s⁻¹, lower than its spin-down luminosity of 7.2 × 10³⁵ erg s⁻¹. Its quiescent thermal luminosity is ≾1.7 × 10³⁴ erg s⁻¹, lower than those of canonical young magnetars. We conclude that Swift J1818.0−1607 is an important link between regular magnetars and high-magnetic-field, rotation-powered pulsars.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hu, Chin-Ping0000-0001-8551-2002
Begiçarslan, Beste0000-0001-5072-8444
Güver, Tolga0000-0002-3531-9842
Enoto, Teruaki0000-0003-1244-3100
Younes, George0000-0002-7991-028X
Sakamoto, Takanori0000-0001-6276-6616
Ray, Paul S.0000-0002-5297-5278
Strohmayer, Tod E.0000-0001-7681-5845
Guillot, Sebastien0000-0002-6449-106X
Palmer, David M.0000-0001-7128-0802
Malacaria, C.0000-0002-0380-0041
Wadiasingh, Zorawar0000-0002-9249-0515
Jaisawal, Gaurava K.0000-0002-6789-2723
Majid, Walid A.0000-0002-4694-4221
Additional Information:© 2020 The American Astronomical Society. Received 2020 June 6; revised 2020 August 18; accepted 2020 August 27; published 2020 October 7. We thank Professor Victoria Kaspi for useful discussions and the anonymous reviewer for valuable comments that improved this paper. This work was supported by the National Aeronautics and Space Administration (NASA) through the NICER mission and the Astrophysics Explorers Program. The NICER observation campaign was performed under the NICER GO2 program 3056 "Magnetic Energy Dissipation of Magnetar Outbursts Studied via Multiwavelength Follow-up Observation" (PI: Teruaki Enoto). This work partly made use of data supplied by the UK Swift Science Data Centre at the University of Leicester, and observations obtained with XMM-Newton and the ESA science mission with instruments and contributions directly funded by the ESA member states and NASA. C.-P.H. acknowledges support from the Japan Society for the Promotion of Science (JSPS; ID: P18318). T.G. has been supported in part by the Royal Society Newton Advanced Fellowship, NAF\R2\180592, and the Turkish Republic, Directorate of Presidential Strategy and Budget project, 2016K121370. T.E. has been supported by the JSPS/MEXT KAKENHI grant Nos. 16H02198 18H01246 and the Hakubi projects of Kyoto University and RIKEN. C.M. is supported by the NASA Postdoctoral Program at the Marshall Space Flight Center, administered by the Universities Space Research Association under contract with NASA. Z.W. acknowledges support from the NASA postdoctoral program. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This work has made use of the NASA Astrophysics Data System. Facility: NICER. - Software: HEASoft, XSPEC.
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)P18318
Royal SocietyNAF\R2\180592
Turkish Republic, Directorate of Presidential Strategy and Budget2016K121370
Japan Society for the Promotion of Science (JSPS)16H02198
Japan Society for the Promotion of Science (JSPS)18H01246
Kyoto UniversityUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
Subject Keywords:Pulsars ; Neutron stars ; Magnetars ; X-ray stars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Pulsars (1306); Neutron stars (1108); Magnetars (992); X-ray stars (1823)
Record Number:CaltechAUTHORS:20201008-073229255
Persistent URL:
Official Citation:Chin-Ping Hu et al 2020 ApJ 902 1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105908
Deposited By: Tony Diaz
Deposited On:08 Oct 2020 14:47
Last Modified:08 Oct 2020 14:47

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