J/ApJ/947/9 GW200224_222234 follow-up survey with Subaru & GTC (Ohgami+, 2023)
Follow-up survey for the binary black hole merger GW200224_222234 using
Subaru/HSC and GTC/OSIRIS.
Ohgami T., Gonzalez J.B., Tominaga N., Morokuma T., Utsumi Y., Niino Y.,
Tanaka M., Banerjee S., Poidevin F., Acosta-Pulido J.A., Perez-Fournon I.,
Munoz-Darias T., Akitaya H., Yanagisawa K., Sasada M., Yoshida M.,
Simunovic M., Ohsawa R., Tanaka I., Terai T., Takagi Y.,
The J-GEM collaboration
<Astrophys. J., 947, 9 (2023)>
=2023ApJ...947....9O 2023ApJ...947....9O
ADC_Keywords: Black holes; Gravitational wave; Spectra, optical; Redshifts
Keywords: Black holes ; Gravitational waves ; Surveys
Abstract:
The LIGO/Virgo detected a gravitational wave (GW) event, named
GW200224_222234 (also known as S200224ca) and classified as a
binary-black hole coalescence, on 2020 February 24. Given its
relatively small localization skymap (71deg2 for a 90% credible
region; revised to 50deg2 in GWTC-3), we performed target-
of-opportunity observations using the Subaru/Hyper Suprime-Cam (HSC)
in the r2 and z bands. Observations were conducted on 2020 February 25
and 28 and March 23, with the first epoch beginning 12.3hr after the
GW detection. The survey covered the highest-probability sky area of
56.6deg2, corresponding to a 91% probability. This was the first
deep follow-up (mr≳24, mz≳23) for a binary-black hole merger
covering >90% of the localization. By performing image subtraction and
candidate screening including light-curve fitting with transient
templates and examples, we found 22 off-nucleus transients that were
not ruled out as the counterparts of GW200224_222234 with our
Subaru/HSC data alone. We also performed GTC/OSIRIS spectroscopy of
the probable host galaxies for five candidates; two are likely to be
located within the 3D skymap, whereas the others are not. In
conclusion, 19 transients remain as possible optical counterparts of
GW200224_222234; but we could not identify a unique promising
counterpart. If there are no counterparts in the remaining candidates,
the upper limits of the optical luminosity are
νLν<5.2-1.9+2.4x1041erg/s and
νLν<1.8-0.6+0.8x1042erg/s in the r2 and z bands,
respectively, at ∼12hr after GW detection. We also discuss
improvements in the strategies of optical follow-ups for future GW
events.
Description:
The binary-black hole (BBH) coalescence GW200224_222234 was detected
by the LIGO/Virgo collaboration with their three detectors on
2020-February-24.
We conducted optical imaging observations using the Subaru/HSC on
2020 February 25 (day 1), 28 (day 4), and March 23 (day 28) in the r2
and z bands. To trigger our ToO follow-up as rapidly as possible, we
conducted the first observations in the r2 band, which had already
been set in the Subaru/HSC at the time of the gravitational wave (GW)
alert. The first exposure commenced on 2020 February 25 at 10:43 UTC,
corresponding to 12.3hr after GW detection. We selected 60 observation
pointings to cover the high-probability area in the BAYSTAR skymap for
the HEALPix grid with a resolution of NSIDE=64, which corresponds to
0.84deg2/pixel2, enabling overlap of the FoVs. Our survey area
covered 56.6deg2, corresponding to a cumulative probability of 91%
in the localization skymap refined in the GWTC-3 catalog using the
IMRPhenomXPHM model (Pratten+ 2021PhRvD.103j4056P 2021PhRvD.103j4056P).
See Section 2.
We searched for the optical counterpart using the image subtraction
technique. After screening for the sources detected in the difference
images via matching with the PS1 catalog and visual inspection, we
found 223 candidates. We adopted the templates of the Type Ia SN and
core-collapse supernova (CCSN) and examples of rapid transients (RTs)
and then found 201 candidates consistent with the SN templates and
likely not related to GW200224_222234.
22 objects, that is, 3 objects consistent only with RTs and 19 objects
inconsistent with all templates and examples, remained as the final
candidates of the optical counterpart of GW200224_222234.
See Section 3.
Optical spectroscopic observations were performed using the OSIRIS
instrument mounted on the 10.4m GTC telescope located at the Roque de
los Muchachos Observatory (Canary Islands, Spain). Five targets were
selected for spectroscopic follow-ups to determine the spectroscopic
redshift (spec-z) of the probable host galaxies of the candidates. The
selected targets were the PS1 extended objects associated with
JGEM20fud, JGEM20fyv, JGEM20gdm, JGEM20hdq, and JGEM20hen, which were
sufficiently bright in the z band for short exposures.
The observations were performed on 2021 February 10.
See Section 4.
Objects:
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RA (ICRS) DE Designation(s)
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- GW200224_222234 = GrW 200224 222234
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 46 60 Central coordinates and exposure times for the
observation pointings with the Subaru/HSC
for GW200224_222234
table5.dat 133 201 Information of the candidates consistent with
transient templates and its associated PS1
extended objects
table67.dat 112 22 Information on candidates that are inconsistent
with the templates of SNe and their associated
PS1 extended objects (Table 6) and information on
the 5 target galaxies selected for spectroscopy
(Table 7)
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See also:
J/ApJ/745/31 : HST Cluster Supernova Survey. VI. SNIa rate (Barbary+, 2012)
J/ApJ/794/23 : Pan-STARRS1 transients optical photometry (Drout+, 2014)
J/ApJ/848/L33 : Opt. follow-up of GW events with LCO (Arcavi+, 2017)
J/ApJ/848/L29 : Opt. follow-up of GW170817 counterpart (Diaz+, 2017)
J/ApJ/848/L16 : Counterpart of GW170817. I. DECam obs. (Soares-Santos+, 2017)
J/PASJ/70/28 : Subaru HSC counterpart candidates of GW170817 (Tominaga+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Seq [0/59] Pointing ID
4- 9 F6.2 deg RAdeg [171.5/177.9] Right Ascension of central
coordinate (J2000)
11- 16 F6.2 deg DEdeg [-15.1/-2.9] Declination of central coordinate
(J2000)
18- 19 I2 s EXPtRE1 [30] Exposure time per one visit in HSC-r2
band on 2020-02-25
21 I1 --- NUMRE1 [2] Number of visits in HSC-r2 band on
2020-02-25
23- 24 I2 s EXPtZE1 [30] Exposure time per one shot in HSC-z band
on 2020-02-25
26 I1 --- NUMZE1 [2] Number of visits in HSC-z band on
2020-02-25
28- 29 I2 s EXPtRE2 [30] Exposure time per one visit in HSC-r2
band on 2020-02-28
31 I1 --- NUMRE2 [2] Number of visits in HSC-r2 band on
2020-02-28
33- 34 I2 s EXPtZE2 [30] Exposure time per one shot in HSC-z band
on 2020-02-28
36 I1 --- NUMZE2 [2] Number of visit in HSC-z band on
2020-02-28
38- 39 I2 s EXPtRE3 [50/70] Exposure time per one visit in HSC-r2
band on 2020-03-23
41 I1 --- NUMRE3 [1] Number of visit in HSC-r2 band on
2020-03-23
43- 44 I2 s EXPtZE3 [35] Exposure time per one shot in HSC-z band
on 2020-03-23
46 I1 --- NUMZE3 [2] Number of visit in HSC-z band on
2020-03-23
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Source name
11- 16 F6.2 deg RAdeg [171.1/178.6] Right Ascension (J2000)
18- 23 F6.2 deg DEdeg [-15.8/-2.7] Declination (J2000)
25- 28 F4.1 arcsec Sep [1/15.2]? Angular separation from possible host
galaxy
30- 33 F4.2 --- zmean [0.03/0.52]? Estimated redshift of PS1 extended
object
35- 38 F4.2 --- e_zmean [0.01/0.2]? Standard deviation of Zmean
40- 43 F4.2 --- zSDSS [0.1/0.6]? SDSS photometric redshift
45- 48 F4.2 --- e_zSDSS [0.02/0.16]? Error of zSDSS
50- 52 I3 % P3D [0/100]? Probability of that possible host
galaxy is inside uncertainty of GW distance
54- 133 A80 --- Temp Probable transient templates
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Byte-by-byte Description of file: table67.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Source name
11- 12 I2 h RAh Hour of right ascension (J2000)
14- 15 I2 min RAm Minute of right ascension (J2000)
17- 21 F5.2 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 33 F4.1 arcsec DEs Arcsecond of declination (J2000)
35- 38 F4.1 arcsec Sep [1.6/14.9]? Separation, θsep
40- 41 I2 --- P3D [60/99]? Probability of that possible host is
inside uncertainty of GW distance
43- 55 A13 --- Temp Best-fit transient templates
57- 60 I4 --- xi [1/1562] ξ estimations; see Equation (1) in
Section 3.1
62- 63 I2 h RASh ? Spectroscopic target hour of right ascension
(J2000)
65- 66 I2 min RASm ? Spectroscopic target minute of right
ascension (J2000)
68- 72 F5.2 s RASs ? Spectroscopic target second of right
ascension (J2000)
74 A1 --- DES- Spectroscopic target sign of declination (J2000)
75- 76 I2 deg DESd ? Spectroscopic target degree of declination
(J2000)
78- 79 I2 arcmin DESm ? Spectroscopic target arcminute of declination
(J2000)
81- 84 F4.1 arcsec DESs ? Spectroscopic target arcsecond of declination
(J2000)
86- 89 F4.1 mag zmag [18.4/20.1]? z-band magnitude of the target
galaxy from the PS1 catalog
91- 94 F4.2 --- z [0.2/0.6]? Estimated redshift
96- 99 F4.2 --- e_z [0.03/0.1]? z uncertainty
101 A1 --- f_z Flag on z (1)
103- 107 F5.3 --- zspec [0.35/0.64]? Spectroscopic redshift
109- 112 E4.2 --- Prob [1e-08/0.76]? Probability of the association,
Passoc (2)
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Note (1): Flag as follows:
D = Photometric redshift z_SDSS from the SDSS catalog.
* = z_single and sigma_z calculated with Equations (2) and (3).
Note (2): See Equation 4 in Section 4. JGEM20fud and JGEM20fyv were close to
the highly probable region (Passoc=0.76 and 0.07, respectively) and
thus are possible counterparts of GW200224_222234.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 26-Mar-2025