LIGO/Virgo S190602aq

We have carried a search for X-ray candidates in Astrosat CZTI data in a 100 sec window around the trigger time of the BBH merger event S190602aq (UTC 2019-06-02 17:59:27.00, GraceDB event). CZTI is a coded aperture mask instrument that has considerable effective area for about 29% of the entire sky, but is also sensitive to brighter transients from the entire sky. At the time of merger, Astrosat's nominal pointing is (RA=295.71, DEC=-10.36), which is 134.4 deg away from the maximum probability location. In a time interval of 100 sec around the event, 51% of sky locations are visible in the satellite's frame and the rest of 49% with the inclusion of maximum probability location for the event are occulted by earth. 

CZTI data were de-trended to remove orbit-wise background variation. We then searched data from three of the four independent, identical quadrants to look for coincident spikes in the count rates. Searches were undertaken by binning the data in 0.1s, 1s, and 10s respectively. Statistical fluctuations in count rates were estimated by using data from 10 (+-5) neighbouring orbits. We selected confidence levels such that the probability of a false trigger in a 1000 sec window is 10^-4.We do not find any evidence for any hard X-ray transient in this window, in the CZTI energy range of 20-200 keV.

We convert our count rates into flux by assuming that the source spectrum is a power law with alpha = -1.0. We use a detailed mass model of the satellite to calculate the instrument response for every htm grid point that fall in 90% LIGO localization region and calculate flux limit in that direction. We get the following upper limits for source flux in the 20-200 keV band by taking a probability weighted mean of flux limit and are reported here :  

0.1 s: flux limit= 8.7 e-7 ergs/cm^2/s 
1.0 s: flux limit= 3.0 e-6 ergs/cm^2/s 
10.0 s: flux limit= 3.6 e-6 ergs/cm^2/s

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, 
S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa (Waseda U), Y. Shimizu, 
T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), 
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),

The CALET Gamma-ray Burst Monitor (CGBM) was operating at the
trigger time of S190602aq T0 = 2019-06-02 17:59:27.089 UT (The
LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ.
24717
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 ).

No CGBM on-board trigger occurred around the event time.  Based
on the LIGO-Virgo localization sky map, most of the high probability
area was within the field-of-view of the CGBM SGM.  The summed
LIGO probabilities inside the CGBM HXM (7-3000 keV) and SGM
(40 keV - 28 MeV) fields of view are 11% and 70%, respectively
(and 99% credible region of the initial localization map was above
the horizon).  The HXM and SGM fields of view were centered at
RA = 118.5 deg, Dec = 53.8 deg and  RA = 127.2 deg, Dec = 45.5 deg
at T0, respectively.

Based on the analysis of the light curve data with 0.125 sec
time resolution from T0-60 sec to T0+60 sec, we found no
significant excess (signal-to-noise ratio >= 7) around the trigger
time in either the HXM or the SGM data.

The CALET Calorimeter (CAL) was operating in the high energy
trigger mode at the trigger time of S190602aq. Using the CAL data,
we have searched for gamma-ray events in the 10-100 GeV
band from -60 sec to +60 sec from the GW trigger time and
found no candidates.
The 90% upper limit of CAL is 2.9x10^-4 erg/cm^2/s (10-100 GeV) when
the summed LIGO-Virgo probability reaches 5%.
The CAL FOV was centered at RA= 127.5 deg, DEC= 45.1 deg at T0.

Q. B. Yi, S. Xiao, C. Cai, Q. Luo, C. K. Li, 
X. B. Li, G. Li, J. Y. Liao, S. L. Xiong, 
C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, 
Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, 
Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

Insight-HXMT was taking data normally around the reported LIGO/Virgo 
S190602aq event (GCN #24717
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 ), trigger time 2019-06-02T17:59:27.089 UTC. 
At T0, more than 54% of the LIGO localization region was covered by 
Insight-HXMT without occultation by the Earth.

Within T0 +/- 100 s, no significant excess events (SNR > 3 sigma) are 
found in a search of the Insight-HXMT/HE raw light curves.

Assuming the GW counterpart GRB with three typical GRB Band spectral 
models, two typical duration timescales (1 s, 10 s) from the center 
of the LIGO-Virgo location probability map (RA=80 deg, DEC=-40 deg), 
the 5-sigma upper-limits fluence (0.2 - 5 MeV, incident energy) are 
reported below:

Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV):
1 s:   5.6e-08 erg cm^-2
10 s:  1.4e-07 erg cm^-2

Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV):
1 s:   1.1e-07 erg cm^-2
10 s:  2.6e-07 erg cm^-2

Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV):
1 s:   3.6e-07 erg cm^-2
10 s:  1.3e-06 erg cm^-2

All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (deposited energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the spacecraft.

Insight-HXMT is the first Chinese space X-ray telescope, which was 
funded jointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information could be found at: http://www.hxmt.org.

F. Onori (IAPS-Roma, Italy),
V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland)
J. Rodi (IAPS-Roma, Italy)
A. Coleiro (APC, France)
S. Mereghetti (INAF IASF-Milano, Italy)

on behalf of the INTEGRAL multi-messenger collaboration:
https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration

Using combination of INTEGRAL all-sky detectors (following Savchenko
et al. 2017, A&A 603, A46): SPI/ACS, IBIS/Veto, and IBIS  we have
performed a search for a prompt gamma-ray counterpart of S190602aq
(GCN 24717
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 ).

At the time of the event (2019-06-02 17:59:27 UTC, hereafter T0),
INTEGRAL was operating in nominal mode. The peak of the event
localization probability was at an angle of 128 deg with respect to
the spacecraft pointing axis. This orientation implies strongly
suppressed (3.9% of optimal) response of ISGRI, somewhat suppressed
(56% of optimal) response of IBIS/Veto, and strongly suppressed (29%
of optimal) response of SPI-ACS.

The background within +/-300 seconds around the event was very stable
(excess variance 1.1).

We have performed a search for any impulsive events in INTEGRAL SPI-
ACS (as described in Savchenko et al. 2012, A&A 541A, 122S), IBIS, and
IBIS/Veto data.

We do not detect any significant counterparts and estimate a 3-sigma
upper limit on the 75-2000 keV fluence of 3.8e-07 erg/cm^2 (within the
50% probability containment region of the source localization) for a
burst lasting less than 1 s with a characteristic short GRB spectrum
(an exponentially cut off power law with alpha=-0.5 and Ep=600 keV)
occurring at any time in the interval within 300 s around T0. For a
typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and
Ep=300 keV), the derived peak flux upper limit is ~3.7e-07 (1.2e-07)
erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range.

-- 
Dr. Francesca Onori
Postdoctoral Researcher
IAPS, via Fosso del Cavaliere, 100, 00133 - Rome, Italy
e-mail: francesca.onori@inaf.it
Tel: +39 06 45488128

P. Minaev, A. Pozanenko, S. Grebenev, I. Chelovekov on behalf of IKI GRB FuN 
collaboration report:

We used public data of SPI-ACS to perform a search for possible 
EM-counterpart of LIGO/Virgo S190602aq.   Before and after trigger time of 
S190602aq we did not find any significant candidate (at the level more than 
3 sigma) in time scales from 0.05 s up to 100 s.

The angle between the center of the error box of the S190602aq localization 
by LIGO/Virgo and the SPI  axis is 129  degrees, and the region of the LIGO 
probability is not occulted by the Earth.

The 3 sigma upper limits in the energy range of 75 - 1000 keV are 1.2 * 
10^-7 erg/cm2   (1 s time scale), and 1.2 * 10^-6 erg/cm2  (100 s time 
scale).

M. Axelsson (KTH and Stockholm Univ.), D. Kocevski (NASA/MSFC) and F. Longo (Univ. and INFN Trieste) report on behalf of the Fermi-LAT Collaboration:

We have searched data collected by the Fermi Large Area Telescope (LAT) on June 2, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190602aq (GCN 24717
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 ).

We define "instantaneous coverage" as the integral over the region of the LIGO probability map that is within the LAT field of view at a given a time, and "cumulative coverage" as the integral of the instantaneous coverage over time.

At the time of the trigger (T0 = 2019-06-02 17:59:27.089 UTC) the entire LIGO probability region was either obscured by the Earth or outside the Fermi-LAT field of view. Coverage of the region started around T0 + 500 s, and reached ~90% cumulative coverage at approximately T0 + 8 ks. The remaining area was not observed within 10 ks after the trigger time.

We performed a search for a transient counterpart within the observed region of the 90% contour of the LIGO map in a fixed time window from T0 + 500 s to T0+10 ks. No significant sources were found.

We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky, and no additional excesses were found. Energy flux upper bounds for the fixed time interval between 100 MeV and 1 GeV for this search vary between 1.9e-10 and 9.1e-08 [erg/cm^2/s].

The Fermi-LAT point of contact for this event is Francesco Longo (francesco.longo@ts.infn.it<mailto:francesco.longo@ts.infn.it>).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (NASA/GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
A. A. Breeveld (MSSL-UCL), A. P. Beardmore (U. Leicester),
D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC),
G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia(ASDC), S. Emery (UCL-MSSL),
P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU),
D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), J. A. Nousek (PSU),
S. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester),
J. P. Osborne (U. Leicester), C. Pagani (U. Leicester),
K. L. Page (U.Leicester), M. Perri (ASDC),
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU),
E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team:

We report the search results in the BAT data within T0 +/- 100 s of the
LVC event S190602aq (LIGO/VIRGO Collaboration GCN Circ. 24717
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 ),
where T0 is the LVC trigger time (2019-06-02T17:59:27.089 UTC).

The center of the BAT field of view (FOV) at T0 is
RA = 212.203 deg,
DEC = -45.287 deg,
and the ROLL angle is 240.648 deg.
The BAT FOV (>10% partial coding) covers 0.72% of the integrated
LVC localization probability, and 0.67% of the galaxy convolved
probability (Evans et al. 2016).

Within T0 +/- 100 s, no significant detections (signal-to-noise ratio
>~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms,
1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical
spectrum in the BAT energy range (i.e., a simple power-law model with a
power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper
limit in the 1-s binned light curve corresponds to a flux upper
limit (15-350 keV) of ~ 8.42 x 10^-8 erg/s/cm^2.

No event data are available within T0 +/- 100 s.

BAT retains decreased, but significant, sensitivity to rate increases for
gamma-ray events outside of its FOV. About 3.53% of the integrated LVC
localization probability was outside of the BAT FOV but above the
Earth's limb from Swift's location, and the corresponding flux upper limits
for this region are within roughly an order of magnitude higher than those
within the FOV.

The results of the BAT analysis are available at
https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190602aq/web/source.html

C.A. Wilson-Hodge and C. M. Hui (NASA/MSFC) report on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group

For S190602aq and using the initial bayestar.fits skymap, Fermi-GBM was observing 67.3% of the localization probability at event time. 

There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/ detection of GW trigger S190602aq (GCN 24717
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 ). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates.

Part of the LVC localization region is behind the Earth for Fermi, located at RA = 148.4 and Dec = -10.9 with a radius of 67.5 degrees.
We therefore set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395
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 , we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2):

Timescale ��Soft     Normal ����Hard
------------------------------------
0.1 s: ��������      4.3       7.5         17.0 
1.0 s: ��������      1.1       3.4          8.2
10 ��s:   ����      0.27      0.63         1.7 

Assuming the median luminosity distance of 797 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^49 erg/s):
Timescale ��Soft     Normal ����Hard
------------------------------------
0.1 s: ��������5.0 ������������������8.0         30.0 ������
1.0 s: ��������1.3 ������������������3.6         14.5 ������
10 ��s:   ����0.3          0.7          3.0��

F. Verrecchia (SSDC, and INAF-OAR), C. Casentini (INAF/IAPS), M. Tavani
(INAF/IAPS,
and Univ. Roma Tor Vergata), F. Lucarelli, C. Pittori (SSDC, and
INAF-OAR), M.
Cardillo, G. Piano A. Ursi (INAF/IAPS), A. Bulgarelli, V.
Fioretti, N. Parmiggiani
(INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), F. Longo (Univ. Trieste, and
INFN Trieste), report on behalf of the AGILE Team:

In response to the LIGO/Virgo GW event S190602aq at T0 = 2019-06-02 17:59:27.089
UTC (GCN #24717
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 ) a preliminary analysis of the AGILE exposure at T0 showed
 that
the S190602aq 90% c.l. localization region (LR) was not exposed by the Gamma-Ray
Imaging Detector (GRID). The closest exposure in time occurred at T0+100s
covering
about 100% of the LR at off-axis angles between 20 and 70 deg.

We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV
over a single time interval after T0, when good exposure of
the S190602aq 90% c.l. LR was available. The following preliminary GRID 3-sigma upper limit (UL) values
are obtained over a large area of the exposed LR:
(T0+100s; T0+200s): from 3.0e-08 to 4.7e-07 erg cm^-2 s^-1

An image of the AGILE-GRID 100s exposure near T0 is available at the site
https://tools.ssdc.asi.it/ImgView/Agile/S190602aq_T0+100s_d100s_FM_UL-E50la17

These measurements were obtained with AGILE observing a large portion of
the sky in
spinning mode. Additional analysis of AGILE data is in progress.

C.Casentini (INAF/IAPS), F.Verrecchia (SSDC, and INAF/OAR), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata), M.Cardillo, G.Piano, A.Ursi
(INAF/IAPS), F.Lucarelli, C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli,
V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia
(INAF/OA-Cagliari), F. Longo (Univ. Trieste, and INFN Trieste) report on
behalf of the AGILE Team:

In response to the LIGO/Virgo GW event S190602aq at T0 = 2019-06-02
17:59:27.089 (UT), a preliminary analysis of the AGILE minicalorimeter
(MCAL) triggered data found no event candidate within a time interval
covering +/- 15 sec from the LIGO/Virgo T0.

Three-sigma upper limits (ULs) are obtained for a 1 s integration time at
different celestial positions within the accessible 90% c.l. localization
region (LR) of S190602aq (about 100% of the LR), from a minimum of 1.6E-06
erg cm^-2 to a maximum of 9.4E-06 erg cm^-2 (assuming as spectral model a
single power law with photon index 1.5). The LR is exposed at off-axis
angles greater than 100 deg.

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress.

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov 
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

H.Levato 
(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias)

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) started inspect of the LIGO/Virgo S190602aq errorbox  7805 sec after trigger time at 2019-06-02 20:09:32 UT, with upper limit up to  19.7 mag. The observations began at zenit distance = 135 deg. The sun  altitude  is -56.0 deg. 

The galactic latitude b = -60 deg., longitude l = 98 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/ligo_1.php?id=10444

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    7896 | 2019-06-02 20:09:32 |         MASTER-SAAO | ( 11h 41m 04.89s , -53d 49m 46.57s) |   C |   180 | 19.5 |        
    8113 | 2019-06-02 20:13:10 |         MASTER-SAAO | ( 11h 35m 20.93s , -51d 49m 43.66s) |   C |   180 | 19.7 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

M. Sugizaki, N. Kawai (Tokyo Tech), H. Negoro (Nihon U.),
S. Sugita, M. Serino (AGU),
M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.),
S. Nakahira, T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, H. Nishida, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.),
M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai,
M. Tominaga (JAXA),
Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake
(Kyoto U.),
H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.),
M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU)
report on behalf of the MAXI team:

We examined MAXI/GSC all-sky X-ray images (2-20 keV)
after the LVC trigger S190602aq at 2019-06-02 17:59:27.089 UTC (GCN 24717
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 ).

At the trigger time of S190602aq, the high-voltage of MAXI/GSC was off,
and it was turned on at T0+871 sec (+14.5 min).
The first one-orbit (92 min) scan observation with GSC after the event
covered 100%
of the 90% credible region of the bayestar skymap from 19:02:18 to
19:22:28 UTC (T0+3771 to T0+4981 sec).

No significant new source was found in the region in the one-orbit
scan observation.
A typical 1-sigma averaged upper limit obtained in one scan observation
is 20 mCrab at 2-20 keV.

If you require information about X-ray flux by MAXI/GSC at specific coordinates,
please contact the submitter of this circular by email.

M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite Paris Diderot), M. Colomer (APC/Universite Paris Diderot)), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite Paris Diderot), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES  Collaboration:

Using on-line data from the ANTARES detector, we have performed a follow-up analysis of the recently reported LIGO/Virgo S190602aq event using the 90% contour of the bayestar probability map provided by the GW interferometers (GCN#24717
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 ). The ANTARES visibility at the time of the alert, together with the 50% and 90% contours of the probability map are shown at https://www.cppm.in2p3.fr/~dornic/events_runo3/S190602aq.png. Considering the location probability provided by the LIGO/Virgo collaborations, there is a 84% chance that the GW emitter was in the ANTARES **upgoing** field of view at the time of the alert. 

No up-going muon neutrino candidate events were recorded in the ANTARES sky during a +/- 500s time-window centered on the time (2019-06-02 17:59:27 UT) and in the 90% contour of the S190602aq event. The expected number of atmospheric background events in the region visible by ANTARES is 6.8e-5 in the +/- 500s time window. An extended search during +/- 1 hour gives no up-going muon neutrino coincidence. The expected number of atmospheric background events in the region visible by ANTARES is 4.9e-4 in this larger time window.

ANTARES is the largest undersea neutrino detector, installed in the Mediterranean Sea, and it is primarily sensitive to neutrinos in the TeV-PeV  energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky.

The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190602aq. At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (63.2 deg, 18.9 deg).
57% of the GW candidate sky location probability fell within our
observable field of view (0-45 deg zenith angle).

We performed a search for a short timescale emission using 6 sliding
time windows (dt = 0.3s, 1s, 3s, 10s, 30s and  100s), shifted forward
in time by 20% of their width. We searched the 95% probability
containment area in a timescale-dependent time period, from t0-5dt to
t0+10dt, where t0 is the time of the GW trigger.

No significant gamma-ray detection above the background was observed.

The sensitivity of this analysis is greatly dependent on zenith angle,
ranging from 14.4 deg to 45 deg for the area searched in this
analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the
80-800GeV energy range goes from 1.6e-6 erg/cm^2 to 1.1e-4 erg/cm^2
(8.6e-6 erg/cm^2 to 5.0e-4 erg/cm^2), depending on the zenith
angle.

HAWC is a TeV gamma ray water Cherenkov array located in the state of
Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and
monitors 2/3 of the sky every day with an instantaneous field-of-view
of ~2 sr.

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190602aq during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-06-02
17:59:27.089 UTC (GPS time: 1243533585.089). The candidate was found
by the PyCBC Live [1], CWB [2], SPIIR [3], GstLAL [4], and MBTAOnline
[5] analysis pipelines.

S190602aq is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.9e-09 Hz, or about one in 16
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190602aq

The classification of the GW signal, in order of descending
probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), NSBH (<1%),
or MassGap (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence against the lighter compact object having a mass < 3 solar
masses (HasNS: <1%). Using the masses and spins inferred from the
signal, there is strong evidence against matter outside the final
compact object (HasRemnant: <1%).

One skymap is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz, an updated localization generated by BAYESTAR
[6], distributed via GCN notice about 6 minutes after the candidate

For the bayestar.fits.gz skymap, the 90% credible region is 1172 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 797 +/- 238 Mpc (a posteriori mean +/- standard
deviation).

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
<https://emfollow.docs.ligo.org/userguide/>.

 [1] Nitz et al. PRD 98, 024050 (2018)
 [2] Klimenko et al. PRD 93, 042004 (2016)
 [3] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [4] Messick et al. PRD 95, 042001 (2017)
 [5] Adams et al. CQG 33, 175012 (2016)
 [6] Singer & Price PRD 93, 024013 (2016)

IceCube Collaboration (http://icecube.wisc.edu/) reports:

Searches [1,2] for track-like muon neutrino events detected by IceCube
consistent with the sky
localization of gravitational-wave candidate S190602aq in a time range of
1000 seconds [3] centered
on the alert event time (2019-06-02 17:51:07.089 UTC to 2019-06-02
18:07:47.089 UTC) have been performed.  During this time
period IceCube was collecting good quality data.  No significant track-like
events are found
in spatial coincidence of S190602aq calculated from the map circulated in
the 1-Preliminary notice.

IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE)to neutrino
point sources within
the locations spanned by the 90% spatial  containment of S190602aq ranges
from  0.029 to
0.732 GeV cm^-2 in a 1000 second time window.

The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector
operating at the
geographic South Pole, Antarctica. The IceCube realtime alert point of
contact can be
reached at roc@icecube.wisc.edu


[1] Bartos et al. arXiv:1810.11467
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  (2018) and Countryman et
al.arXiv:1901.05486
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  (2019)
[2] Braun et al., Astroparticle Physics 29, 299 (2008)
[3] Baret et al., Astroparticle Physics 35, 1 (2011)