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

Abstract

We report on the hard X-ray burst and the first ~100 days 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 $T_{90}=10\pm 4$ ms and a temperature of $kT=8.4\pm 0.7$ 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 $\dot{\nu }$ varying erratically by a factor of 10, with an average long-term spin-down rate of $\dot{\nu }=(-2.48\pm 0.03)\times 10^{-11}$~s${}^{-2}$, implying an equatorial surface magnetic field of $2.5\times 10^{14}$ G and a young characteristic age of $\sim$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 $1.9\times 10^{35}$ erg/s, lower than its spin-down luminosity of $7.2\times 10^{35}$ erg/s. Its quiescent thermal luminosity is $\lesssim 1.7\times 10^{34}$ erg/s, 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.

13 pages, 4 figures, 2tables, accepted for publication in ApJ

References in corpus (19)

• 1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
• Magnetar-like Emission from the Young Pulsar in Kes 75
• The Prelude to and Aftermath of the Giant Flare of 2004 December 27: Persistent and Pulsed X-ray Properties of SGR 1806-20 from 1993 to 2005
• A Magnetar-like Outburst from a High-B Radio Pulsar
• Magnetar-like activity from the central compact object in the SNR RCW103
• Timing and Flux Evolution of the Galactic Center Magnetar SGR J1745-2900
• The Five Year Fermi/GBM Magnetar Burst Catalog
• 30 Glitches in slow pulsars
• A very young radio-loud magnetar
• Magnetar-like X-ray Bursts from a Rotation Powered Pulsar, PSR J1119-6127
• Deep NuSTAR and Swift Monitoring Observations of the Magnetar 1E 1841-045
• The Sleeping Monster: NuSTAR observations of SGR 1806-20, 11 years after the Giant Flare
• Post-Outburst Radio Observations of the High Magnetic Field Pulsar PSR J1119-6127
• A radiatively-quiet glitch and anti-glitch in the magnetar 1E 2259+586
• Two new outbursts and transient hard X-rays from 1E 1048.1$-$5937
• Swift observations of two outbursts from the magnetar 4U 0142+61
• A systematic study of soft X-ray pulse profiles of magnetars in quiescence
• More than meets the eye: magnetars in disguise
• X-Ray Observations of Magnetar SGR 0501+4516 from Outburst to Quiescence

Cited by in corpus (16)

• Evidence for an abundant old population of Galactic ultra long period magnetars and implications for fast radio bursts
• The dynamic magnetosphere of Swift J1818.0$-$1607
• Pulse Peak Migration during the Outburst Decay of the Magnetar SGR 1830-0645: Crustal Motion and Magnetospheric Untwisting
• The X-ray evolution and geometry of the 2018 outburst of XTE J1810-197
• Multiwavelength Constraints on the Origin of a Nearby Repeating Fast Radio Burst Source in a Globular Cluster
• The 2022 high-energy outburst and radio disappearing act of the magnetar 1E 1547.0-5408
• Long term radio and X-ray evolution of the magnetar Swift J1818.0-1607
• Simultaneous 2.25/8.60 GHz observations of the newly discovered magnetar -- Swift J1818.0-1607
• High Frequency Radio Observations of Two Magnetars, PSR J1622$-$4950 and 1E 1547.0$-$5408
• Chandra observations of the newly discovered magnetar Swift J1818.0-1607
• X-ray burst and persistent emission properties of the magnetar SGR 1830-0645 in outburst
• VLA proper motion constraints on the origin, age, and potential magnetar future of PSR J1734$-$3333
• AstroSat observation of rapid Type-I thermonuclear burst from the low mass X-ray binary GX 3+1
• Multiwavelength Radiation from the Interaction between Magnetar Bursts and Companion Star in a Binary System
• A month of monitoring the new magnetar Swift J1555.2-5402 during an X-ray outburst
• A magnetar outburst with atypical evolution: the case of Swift J1555.2-5402