J/ApJ/922/154 Radio, opt. & X-ray afterglow obs. of GW170817 (Makhathini+, 2021)
The panchromatic afterglow of GW170817: the full uniform data set, modeling,
comparison with previous results, and implications.
Makhathini S., Mooley K.P., Brightman M., Hotokezaka K., Nayana A.J.,
Intema H.T., Dobie D., Lenc E., Perley D.A., Fremling C., Moldon J.,
Lazzati D., Kaplan D.L., Balasubramanian A., Brown I.S., Carbone D.,
Chandra P., Corsi A., Camilo F., Deller A., Frail D.A., Murphy T.,
Murphy E.J., Nakar E., Smirnov O., Beswick R.J., Fender R., Hallinan G.,
Heywood I., Kasliwal M., Lee B., Lu W., Rana J., Perkins S., White S.V.,
Jozsa G.I.G., Hugo B., Kamphuis P.
<Astrophys. J., 922, 154 (2021)>
=2021ApJ...922..154M 2021ApJ...922..154M
ADC_Keywords: Gravitational wave; Radio sources; X-ray sources; Optical
Keywords: Gravitational waves ; Gravitational wave astronomy ;
High energy astrophysics ; Neutron stars ; R-process
Abstract:
We present the full panchromatic afterglow light-curve data of
GW170817, including new radio data as well as archival optical and
X-ray data, between 0.5 and 940 days post-merger. By compiling all
archival data and reprocessing a subset of it, we have evaluated the
impact of differences in data processing or flux determination methods
used by different groups and attempted to mitigate these differences
to provide a more uniform data set. Simple power-law fits to the
uniform afterglow light curve indicate a t0.86±0.04 rise, a
t-1.92±0.12 decline, and a peak occurring at 155±4 days. The
afterglow is optically thin throughout its evolution, consistent with
a single spectral index (-0.584±0.002) across all epochs. This gives
a precise and updated estimate of the electron power-law index,
p=2.168±0.004. By studying the diffuse X-ray emission from the host
galaxy, we place a conservative upper limit on the hot ionized
interstellar medium density, <0.01cm-3, consistent with previous
afterglow studies. Using the late-time afterglow data we rule out any
long-lived neutron star remnant having a magnetic field strength
between 1010.4 and 1016G. Our fits to the afterglow data using an
analytical model that includes Very Long Baseline Interferometry
proper motion from Mooley+ (2018Natur.561..355M 2018Natur.561..355M), and a structured jet
model that ignores the proper motion, indicates that the proper-motion
measurement needs to be considered when seeking an accurate estimate
of the viewing angle.
Description:
We compiled all flux density upper limits from the literature (see
references given in Table 2). Flux densities in the case of radio
afterglow detections were compiled from Mooley+ (2018ApJ...868L..11M 2018ApJ...868L..11M)
and references therein, and optical (HST/F606W) afterglow detections
were reported in the Fong+ (2019ApJ...883L...1F 2019ApJ...883L...1F) reprocessing.
See Section 2.
We also report on new data obtained with the Karl G. Jansky Very Large
Array (VLA), MeerKAT, the Australia Telescope Compact Array (ATCA),
and enhanced Multi Element Remotely Linked Interferometer Network
(eMERLIN) radio telescopes between 180 and 780 days post-merger
spanning frequencies between 1.2 and 9GHz.
We observed GW170817 on 2018 December 18-20 and 2019 September 24-27
with the VLA (PI: Corsi; VLA/18B-204). The Wideband Interferometric
Digital Architecture (WIDAR) correlator was used at S band (2-4GHz).
See Section 2.1.
We observed GW170817 with the ATCA (PI: Dobie, Piro) over four epochs
between 2018 November to 2019 September (Table 2). All observations
used two bands of 2048MHz centered at 5.5 and 9.0GHz. See Section 2.2.
We reprocessed archival upgraded Giant Metrewave Radio Telescope
(uGMRT) Band 5 (1.0-1.4GHz) data. See Section 2.3.
GW170817 was observed with the MeerKAT telescope over seven epochs
between 2018 January 18 and September 2 (see Table 2). The first
observation was performed during the AR1 phase using 16 antennas,
while remaining observations used the full 64 antenna array. All
observations were centered at 1.3GHz using 4096 channels spanning
856MHz and an 8s integration time. see Section 2.4.
We observed GW170817 with the eMERLIN array between 2018 January and
March with 11 individual runs. Each run had a duration of 5-6hr.
Observations were conducted using the C band receiver tuned at
frequencies between 4.82 and 5.33GHz. See Section 2.5.
Reduced HST images were downloaded from the MAST archive. In Table 2
we report the upper limit from a previously unpublished data set. The
observations (PI: N. Tanvir) were carried out with the WFC3/UVIS
detector using F814W on 2018 August 08.4 and have a total exposure
time of 5.2ks. See Section 2.6.
We list the Chandra and XMM-Newton observational data on GW170817 used
here for spectral analysis in Table 3. See Section 2.7.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
13 09 48.08 -23 22 53.3 GW 170817 = GrW 170817
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 179 205 Radio afterglow measurements of GW170817
table3.dat 73 26 Chandra and XMM-Newton observational data
--------------------------------------------------------------------------------
See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
B/xmm : XMM-Newton Obs. Log (XMM-Newton Science Operation Center, 2012)
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
J/A+A/594/A116 : HI4PI spectra and column density maps (HI4PI team+, 2016)
J/A+A/598/A78 : The GMRT 150MHz all-sky radio survey (Intema+, 2017)
J/ApJS/230/7 : Spectral flux densities from 50MHz to 50GHz (Perley+, 2017)
J/ApJ/848/L16 : Counterpart of GW170817. I. DECam obs. (Soares-Santos+, 2017)
J/ApJ/851/L21 : UV-NIR compilation of GW170817 counterpart (Villar+, 2017)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Date UT observation date/range
20- 25 F6.2 d DeltaT [0.57/938] Time since GW detection
27- 36 A10 --- Inst Facility or Instrument used
38- 45 E8.2 GHz Freq [0.114/3000000000] Frequency
47- 47 A1 --- l_Flux Limit flag on Flux
49- 57 E9.3 uJy Flux [0.00013/44700] Flux density at Freq
59- 67 E9.3 uJy E_Flux [4.6e-05/0.00042]? Upper uncertainty in Flux
69- 77 E9.3 uJy e_Flux [5.9e-05/34]? Lower uncertainty in Flux
79- 79 A1 --- Rep? Reprocessed data? (Y)es or (N)o
81-179 A99 --- Ref Original reference bibcode(s)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Inst Instrument
9- 17 I9 --- ObsID [18955/811212701] Observation identifier
19- 23 F5.2 ks Exp [14.22/74.09] Exposure time
25- 35 A11 "Y/M/D" Date Date of observation (UT)
37- 44 A8 --- PI PI name
46 A1 --- l_CRate Limit flag on CRate
48- 51 F4.2 ks-1 CRate [0.02/2.17] X-ray count rate (1)
53- 56 F4.2 ks-1 e_CRate [0.03/0.4]? CRate uncertainty
58 A1 --- l_Flux Limit flag on Flux
60- 63 F4.2 10-17W/m2 Flux [0.06/3.46] 0.3-10keV flux, corrected for
Galactic absorption;
in 10-14erg/cm2/s units
65- 68 F4.2 10-17W/m2 e_Flux [0.08/0.92]? Lower uncertainty on Flux
70- 73 F4.2 10-17W/m2 E_Flux [0.08/1.14]? Upper uncertainty on Flux
--------------------------------------------------------------------------------
Note (1): Count rates are observed (not corrected for PSF losses) in the
0.5-8keV band for Chandra and 0.2-10keV band for XMM-Newton.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Mar-2023