TY - JOUR
T1 - A Month of Monitoring the New Magnetar Swift J1555.2-5402 during an X-Ray Outburst
AU - Enoto, Teruaki
AU - Ng, Mason
AU - Hu, Chin Ping
AU - Güver, Tolga
AU - Jaisawal, Gaurava K.
AU - O'Connor, Brendan
AU - Gögüs, Ersin
AU - Lien, Amy
AU - Kisaka, Shota
AU - Wadiasingh, Zorawar
AU - Majid, Walid A.
AU - Pearlman, Aaron B.
AU - Arzoumanian, Zaven
AU - Bansal, Karishma
AU - Blumer, Harsha
AU - Chakrabarty, Deepto
AU - Gendreau, Keith
AU - Ho, Wynn C.G.
AU - Kouveliotou, Chryssa
AU - Ray, Paul S.
AU - Strohmayer, Tod E.
AU - Younes, George
AU - Palmer, David M.
AU - Sakamoto, Takanori
AU - Akahori, Takuya
AU - Eie, Sujin
PY - 2021
Y1 - 2021
N2 - The soft gamma-ray repeater Swift J1555.2−5402 was discovered by means
of a short burst detected with Swift BAT on 2021 June 3. Then, 1.6 hr
after the burst, the Neutron star Interior Composition Explorer (NICER)
started daily monitoring of this target for a month. The absorbed 2–10
keV flux stayed nearly constant at around 4 × 10−11 erg s−1 cm−2
during the monitoring, showing only a slight gradual decline. An
absorbed blackbody with a temperature of 1.1 keV approximates the soft
X-ray spectrum. A 3.86 s periodicity is detected, and the period
derivative is measured to be 3.05(7) × 10−11 s s−1.
The soft X-ray pulse shows a single sinusoidal shape with an rms pulsed
fraction that increases as a function of energy from 15% at 1.5 keV to
39% at 7 keV. The equatorial surface magnetic field, characteristic age,
and spin-down luminosity are derived under the dipole field
approximation to be 3.5 × 1014 G, 2.0 kyr, and 2.1 × 1034 erg s−1,
respectively. We detect 5 and 45 bursts with Swift/BAT and NICER,
respectively. Based on these properties, this new source is classified
as a magnetar. A hard X-ray power-law component that extends up to at
least 40 keV is detected with the Nuclear Spectroscopic Telescope Array
(NuSTAR). The 10–60 keV flux is ∼9 × 10−12 erg s−1 cm−2
with a photon index of ∼1.2. The pulsed fraction has a sharp cutoff at
around 10 keV with an upper limit (≲10%) in the hard-tail band. No radio
pulsations are detected during the DSN or VERA observations. The 7σ upper limits of the flux density are 0.043 and 0.026 mJy at the S and X bands, respectively
AB - The soft gamma-ray repeater Swift J1555.2−5402 was discovered by means
of a short burst detected with Swift BAT on 2021 June 3. Then, 1.6 hr
after the burst, the Neutron star Interior Composition Explorer (NICER)
started daily monitoring of this target for a month. The absorbed 2–10
keV flux stayed nearly constant at around 4 × 10−11 erg s−1 cm−2
during the monitoring, showing only a slight gradual decline. An
absorbed blackbody with a temperature of 1.1 keV approximates the soft
X-ray spectrum. A 3.86 s periodicity is detected, and the period
derivative is measured to be 3.05(7) × 10−11 s s−1.
The soft X-ray pulse shows a single sinusoidal shape with an rms pulsed
fraction that increases as a function of energy from 15% at 1.5 keV to
39% at 7 keV. The equatorial surface magnetic field, characteristic age,
and spin-down luminosity are derived under the dipole field
approximation to be 3.5 × 1014 G, 2.0 kyr, and 2.1 × 1034 erg s−1,
respectively. We detect 5 and 45 bursts with Swift/BAT and NICER,
respectively. Based on these properties, this new source is classified
as a magnetar. A hard X-ray power-law component that extends up to at
least 40 keV is detected with the Nuclear Spectroscopic Telescope Array
(NuSTAR). The 10–60 keV flux is ∼9 × 10−12 erg s−1 cm−2
with a photon index of ∼1.2. The pulsed fraction has a sharp cutoff at
around 10 keV with an upper limit (≲10%) in the hard-tail band. No radio
pulsations are detected during the DSN or VERA observations. The 7σ upper limits of the flux density are 0.043 and 0.026 mJy at the S and X bands, respectively
U2 - 10.3847/2041-8213/ac2665
DO - 10.3847/2041-8213/ac2665
M3 - Journal article
SN - 2041-8205
VL - 920
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L4
ER -