J/ApJ/901/L7 NIR obs. of the Gal. magnetar SGR 1935+215 with PGIR (De+, 2020)
Constraining the X-ray-infrared spectral index of second-timescale flares from
SGR 1935+2154 with Palomar Gattini-IR.
De K., Ashley M.C.B., Andreoni I., Kasliwal M.M., Soria R.,
Srinivasaragavan G.P., Cai Ce, Delacroix A., Greffe T., Hale D.,
Hankins M.J., Li C., McKenna D., Moore A.M., Ofek E.O., Smith R.M., Soon J.,
Travouillon T., Zhang S.
<Astrophys. J., 901, L7 (2020)>
=2020ApJ...901L...7D 2020ApJ...901L...7D
ADC_Keywords: Pulsars; Photometry, infrared
Keywords: Radio transient sources ; Magnetars ; Soft gamma-ray repeaters
Abstract:
The Galactic magnetar SGR 1935+2154 has been reported to produce the
first example of a bright millisecond-duration radio burst (FRB200428)
similar to the cosmological population of fast radio bursts (FRBs).
The detection of a coincident bright X-ray burst represents the first
observed multiwavelength counterpart of an FRB. However, the search
for similar emission at optical wavelengths has been hampered by the
high inferred extinction on the line of sight. Here, we present
results from the first search for second-timescale emission from the
source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR
observing system in the J band, enabled by a novel detector readout
mode that allows short exposure times of ∼0.84s with 99.9% observing
efficiency. With a total observing time of ∼12hr (∼47728 images)
during its 2020 outburst, we place median 3σ limits on the
second-timescale NIR fluence of ≲18Jy.ms (13.1 AB mag). The
corresponding extinction-corrected limit is ≲125Jy.ms for an
estimated extinction of AJ=2.0mag. Our observations were sensitive
enough to easily detect an NIR counterpart of FRB 200428 if the NIR
emission falls on the same power law as observed across its radio to
X-ray spectrum. We report nondetection limits from epochs of four
simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR
telescopes during our observations. These limits provide the most
stringent constraints to date on fluence of flares at ∼1014Hz, and
constrain the fluence ratio of the NIR emission to coincident X-ray
bursts to RNIR≲0.025 (fluence index ≳0.35).
Description:
Following the detection of the train of X-ray bursts from SGR1935+2154
(Palmer & BAT Team 2020GCN.27665....1S 2020GCN.27665....1S) and FRB 200428
(The CHIME/FRB Col. 2020Natur.587...54C 2020Natur.587...54C and Bochenek+ 2020Natur.587...59B 2020Natur.587...59B),
we triggered targeted observations of the source using the Palomar
Gattini-IR on UT 2020-05-01 and in two other modes spanning 2020-05-02
to 2020-05-31.
Palomar Gattini-IR (PGIR; De+ 2020PASP..132b5001D 2020PASP..132b5001D) is a wide-field,
near-infrared robotic time domain survey operating at Palomar
Observatory. Using a 30cm telescope mounted with a H2RG detector,
Gattini-IR achieves a field of view of 25 sq. deg. with a pixel scale
of 8.7" in J-band.
Objects:
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RA (ICRS) DE Designation(s)
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19 34 55.68 +21 53 48.2 SGR 1935+2154 = NAME Sgr J1935+2154
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig2.dat 47 47728 Measured standard deviation in fluxes
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See also:
J/ApJS/212/6 : The McGill magnetar catalog (Olausen+, 2014)
J/ApJS/218/11 : 5yr Fermi/GBM magnetar burst catalog (Collazzi+, 2015)
J/other/PASA/33.45 : FRBCAT: Fast Radio Burst (FRB) Catalog (Petroff+, 2016)
J/ApJS/232/17 : Spectral data of magnetar bursts (Kirmizibayrak+, 2017)
J/MNRAS/469/2313 : Radio pulsars post-glitchs (Gugercinoglu, 2017)
J/ApJ/896/L2 : ZTF obs. of FRB 180916.J0158+65 (Andreoni+, 2020)
Byte-by-byte Description of file: fig2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 yr Obs.Y Year of the observation start; UTC
6- 7 I2 "month" Obs.M Month of the observation start; UTC
9- 10 I2 d Obs.D Day of the observation start; UTC
12- 13 I2 h Obs.h Hour of the observation start; UTC
15- 16 I2 min Obs.m Minute of the observation start; UTC
18- 23 F6.3 s Obs.s Second of the observation start; UTC
25- 28 F4.2 s Exp [0.84/1.65] Exposure time
30- 38 E9.2 mJ/m2 Fluence [-6.1e-10/3.1e-10] Measured fluence
in erg/cm2 units
40- 47 E8.2 mJ/m2 e_Fluence [3.3e-11/2.3e-10] The 3σ limit on Fluence
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jan-2022