A Very Young Radio-loud Magnetar
Date Issued
2020
Author(s)
Esposito, P.
•
Rea, N.
•
Borghese, A.
•
Zelati, F. Coti
•
Viganò, D.
•
•
Tiengo, A.
•
•
•
•
Götz, D.
•
•
•
Dehman, C.
•
Ronchi, M.
•
•
Garcia-Garcia, A.
•
Graber, V.
•
•
Perna, R.
•
Castillo, G. A. Rodríguez
•
Turolla, R.
•
Zane, S.
Abstract
The magnetar Swift J1818.0-1607 was discovered in 2020 March when Swift detected a 9 ms hard X-ray burst and a long-lived outburst. Prompt X-ray observations revealed a spin period of 1.36 s, soon confirmed by the discovery of radio pulsations. We report here on the analysis of the Swift burst and follow-up X-ray and radio observations. The burst average luminosity was Lburst ∼ 2 × 1039 erg s-1 (at 4.8 kpc). Simultaneous observations with XMM-Newton and NuSTAR three days after the burst provided a source spectrum well fit by an absorbed blackbody ( NH = (1.13 ± 0.03) × 1023 cm-2 and kT = 1.16 ± 0.03 keV) plus a power law (Γ = 0.0 ± 1.3) in the 1-20 keV band, with a luminosity of ∼8 × 1034 erg s-1, dominated by the blackbody emission. From our timing analysis, we derive a dipolar magnetic field B ∼ 7 × 1014 G, spin-down luminosity E˙rot∼1.4×1036 erg s-1, and characteristic age of 240 yr, the shortest currently known. Archival observations led to an upper limit on the quiescent luminosity <5.5 × 1033 erg s-1, lower than the value expected from magnetar cooling models at the source characteristic age. A 1 hr radio observation with the Sardinia Radio Telescope taken about 1 week after the X-ray burst detected a number of strong and short radio pulses at 1.5 GHz, in addition to regular pulsed emission; they were emitted at an average rate 0.9 min-1 and accounted for ∼50% of the total pulsed radio fluence. We conclude that Swift J1818.0-1607 is a peculiar magnetar belonging to the small, diverse group of young neutron stars with properties straddling those of rotationally and magnetically powered pulsars. Future observations will make a better estimation of the age possible by measuring the spin-down rate in quiescence.
Volume
896
Issue
2
Start page
L30
Issn Identifier
2041-8205
Ads BibCode
2020ApJ...896L..30E
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
Esposito_2020_ApJL_896_L30.pdf
Description
Pdf editoriale
Size
919.99 KB
Format
Adobe PDF
Checksum (MD5)
cd5ec37f91e98b2cd33c8af9696b477f
Loading...
Name
2004.04083.pdf
Description
postprint
Size
2.2 MB
Format
Adobe PDF
Checksum (MD5)
45781bc07a6e04d4016ecb20d4dedef1