LIGO/Virgo S240615dg
GCN Circular 36698
Subject
LIGO/Virgo S240615dg: Swift XRT observations, 39 X-ray sources
Date
2024-06-19T09:05:25Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
K.L. Page (U. Leicester), P.A. Evans (U. Leicester), J.A. Kennea (PSU),
A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris
(U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini
(INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J.
Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara
(PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia
(ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson
University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin
(UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P.
Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page
(UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB),
B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB),
E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team:
Swift has carried out 198 observations of the LVC error region for the
GW trigger S240615dg convolved with the 2MPZ catalogue (Bilicki et al.
2014, ApJS, 210, 9), using the 'bayestar' (version BAYESTAR.fits.gz) GW
localisation map. As this is a 3D skymap, galaxy distances were taken
into account in selecting which ones to observe. The observations
currently span from 3.1 ks to 86 ks after the LVC trigger, and the XRT
has covered 10.1 deg^2 on the sky (corrected for overlaps). This covers
75% of the probability in the 'BAYESTAR' (version BAYESTAR.fits.gz)
skymap, and 75% after convolving with the 2MPZ galaxy catalogue, as
described by Evans et al. (2016, MNRAS, 462, 1591). These pointings
and associated metadata have been reported to the Treasure Map (Wyatt
et al., 2020, ApJ, 894, 127;
http://treasuremap.space/alerts?graceids=S240615dg).
We have detected 39 X-ray sources. Each source is assigned a rank of
1-4 which describes how likely it is to be related to the GW trigger,
with 1 being the most likely and 4 being the least likely. The ranks
are described at https://www.swift.ac.uk/ranks.php.
We have found:
* 0 sources of rank 1
* 0 sources of rank 2
* 38 sources of rank 3
* 1 source of rank 4
RANK 3 sources
==============
These are uncatalogued X-ray sources, however they are not brighter
than previous upper limits, so do not stand out as likely counterparts
to the GW trigger.
| Source ID | RA | Dec | Err90 |
| S240615dg_X1 | 00h 29m 35.99s | +46d 06' 37.8" | 8.0" |
| S240615dg_X2 | 00h 33m 50.16s | +45d 33' 03.6" | 8.1" |
| S240615dg_X3 | 00h 24m 14.80s | +45d 53' 04.3" | 6.8" |
| S240615dg_X4 | 00h 24m 34.85s | +46d 01' 51.6" | 8.4" |
| S240615dg_X5 | 00h 23m 43.15s | +46d 00' 40.9" | 9.8" |
| S240615dg_X6 | 16h 35m 45.42s | -72d 36' 59.3" | 7.3" |
| S240615dg_X7 | 00h 35m 43.50s | +45d 29' 07.5" | 7.9" |
| S240615dg_X8 | 00h 34m 53.17s | +45d 43' 42.7" | 10.9" |
| S240615dg_X10 | 16h 20m 44.43s | -72d 48' 53.5" | 17.2" |
| S240615dg_X11 | 16h 35m 48.47s | -71d 28' 36.4" | 8.5" |
| S240615dg_X12 | 00h 25m 17.22s | +45d 34' 26.4" | 6.1" |
| S240615dg_X13 | 00h 25m 32.31s | +45d 21' 11.6" | 6.2" |
| S240615dg_X14 | 00h 24m 18.85s | +45d 25' 10.0" | 5.1" |
| S240615dg_X15 | 00h 25m 03.91s | +45d 24' 20.8" | 5.3" |
| S240615dg_X16 | 00h 25m 51.20s | +45d 26' 38.4" | 6.6" |
| S240615dg_X17 | 00h 25m 27.73s | +45d 16' 04.9" | 5.5" |
| S240615dg_X18 | 00h 24m 41.47s | +45d 32' 05.4" | 6.9" |
| S240615dg_X19 | 00h 24m 22.40s | +45d 23' 33.9" | 6.4" |
| S240615dg_X20 | 00h 25m 37.33s | +45d 28' 04.1" | 6.0" |
| S240615dg_X21 | 00h 25m 05.70s | +45d 27' 57.8" | 6.4" |
| S240615dg_X22 | 00h 25m 32.43s | +45d 15' 12.0" | 5.9" |
| S240615dg_X23 | 00h 24m 30.74s | +45d 28' 38.2" | 6.6" |
| S240615dg_X24 | 00h 25m 10.83s | +45d 24' 54.6" | 6.9" |
| S240615dg_X25 | 00h 24m 23.90s | +45d 26' 50.1" | 6.4" |
| S240615dg_X26 | 00h 24m 59.37s | +45d 19' 18.3" | 6.6" |
| S240615dg_X27 | 00h 24m 58.39s | +45d 14' 29.3" | 8.0" |
| S240615dg_X28 | 00h 24m 59.44s | +45d 18' 29.4" | 6.2" |
| S240615dg_X29 | 00h 24m 25.17s | +45d 14' 37.8" | 7.1" |
| S240615dg_X30 | 00h 24m 16.62s | +45d 22' 58.5" | 7.1" |
| S240615dg_X31 | 00h 25m 02.99s | +45d 31' 50.9" | 6.2" |
| S240615dg_X32 | 00h 24m 55.02s | +45d 20' 08.0" | 7.4" |
| S240615dg_X33 | 00h 24m 32.36s | +45d 27' 19.6" | 7.7" |
| S240615dg_X34 | 00h 25m 27.36s | +45d 27' 36.6" | 7.8" |
| S240615dg_X35 | 00h 25m 39.51s | +45d 24' 31.2" | 6.4" |
| S240615dg_X36 | 00h 24m 14.08s | +45d 26' 02.9" | 7.1" |
| S240615dg_X37 | 00h 25m 26.55s | +45d 18' 05.9" | 9.7" |
| S240615dg_X38 | 00h 24m 25.04s | +45d 20' 56.7" | 6.8" |
| S240615dg_X39 | 00h 23m 53.86s | +45d 21' 51.6" | 7.2" |
RANK 4 sources
==============
These are catalogued X-ray sources, showing no signs of outburst
compared to previous observations, so they are not likely to be related
to the GW trigger.
| Source ID | RA | Dec | Err90 |
| S240615dg_X9 | 00h 27m 42.35s | +45d 14' 56.5" | 7.5" |
For all flux conversions and comparisons with catalogues and upper
limits from other missions, we assumed a power-law spectrum with
NH=3x10^20 cm^-2, and photon index (Gamma)=1.7, unless otherwise
stated.
The results of the XRT automated analysis, including details of the
sources listed above, are online at
https://www.swift.ac.uk/LVC/S240615dg
This circular is an official product of the Swift XRT team.
GCN Circular 36705
Subject
LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
Date
2024-06-19T21:54:37Z (a year ago)
From
Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>
Via
Web form
D. Akl (AUS), M. Masek (FZU), C. Andrade (UMN), E. G. Elhosseiny (NRIAG), H. Peng (THU), L. Wang, A. Iskandar (XAO), S. Antier (OCA), S. Karpov (FZU), M. Coughlin (UMN), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), D. Turpin (CEA-Saclay/Irfu), N. Guessoum (AUS), T. Pradier (Unistra/IPHC), M. Prouza (FZU), on behalf of the GRANDMA collaboration:
We performed tiled observations of the LIGO/VIRGO event S240615dg (GCN 36669) with the 25 cm f/6.3 FRAM-CTA-N telescope located at Observatorio del Roque de los Muchachos, La Palma, Spain.
Observations were conducted from 2024-06-17T02:57:12.758 to 2024-06-17T04:09:15.193, 1.64 days after the GW trigger time. We obtained a total of 34 images in the Johnson R band, acquiring 2 consecutive 2-minute long exposures at the individual pointings in the table below, for a total of 4080 seconds. Using the Bibly Skymap as a reference, the observations covered 3.5 square degrees of the localization, corresponding to ~34.7% of the probability enclosed in the localization region.
Our low latency analysis (Karpov et al. 2021) did not reveal any significant candidate down to the limits listed in the table below (5 sigma, AB system).
+------------+-------------+---------+----------+-----------+--------------+
| T-T0 (hr) | MJD | Ra | Dec | Exposure | Lim.Mag. |
|------------+-------------+---------+----------+-----------+--------------|
| 39.35 | 60478.12306 | 6.79245 | 45.00000 | 120 | 17.13 |
| 39.38 | 60478.12452 | 6.79245 | 45.00000 | 120 | 17.33 |
| 39.42 | 60478.12609 | 8.02744 | 45.00000 | 120 | 17.23 |
| 39.46 | 60478.12755 | 8.02744 | 45.00000 | 120 | 17.24 |
| 39.49 | 60478.12913 | 8.28319 | 46.74757 | 120 | 17.22 |
| 39.53 | 60478.13059 | 8.28319 | 46.74757 | 120 | 17.25 |
| 39.57 | 60478.13216 | 7.00885 | 46.74757 | 120 | 17.10 |
| 39.60 | 60478.13362 | 7.00885 | 46.74757 | 120 | 17.21 |
| 39.64 | 60478.13520 | 8.71972 | 45.43689 | 120 | 17.27 |
| 39.67 | 60478.13666 | 8.71972 | 45.43689 | 120 | 17.17 |
| 39.71 | 60478.13823 | 6.22837 | 45.43689 | 120 | 17.07 |
| 39.75 | 60478.13969 | 6.22837 | 45.43689 | 120 | 17.13 |
| 39.78 | 60478.14128 | 8.85764 | 46.31068 | 120 | 17.16 |
| 39.82 | 60478.14273 | 8.85764 | 46.31068 | 120 | 17.00 |
| 39.86 | 60478.14431 | 6.32689 | 46.31068 | 120 | 17.06 |
| 39.89 | 60478.14577 | 6.32689 | 46.31068 | 120 | 17.14 |
| 39.93 | 60478.14734 | 6.17496 | 45.00000 | 120 | 17.16 |
| 39.97 | 60478.14880 | 6.17496 | 45.00000 | 120 | 17.31 |
| 40.00 | 60478.15038 | 8.92035 | 46.74757 | 120 | 17.33 |
| 40.04 | 60478.15184 | 8.92035 | 46.74757 | 120 | 17.37 |
| 40.08 | 60478.15341 | 8.64494 | 45.00000 | 120 | 17.43 |
| 40.11 | 60478.15487 | 8.64494 | 45.00000 | 120 | 17.40 |
| 40.15 | 60478.15642 | 7.35945 | 44.56311 | 120 | 17.42 |
| 40.18 | 60478.15788 | 7.35945 | 44.56311 | 120 | 17.43 |
| 40.22 | 60478.15946 | 6.37168 | 46.74757 | 120 | 17.52 |
| 40.26 | 60478.16092 | 6.37168 | 46.74757 | 120 | 17.54 |
| 40.29 | 60478.16251 | 7.71429 | 47.18447 | 120 | 17.35 |
| 40.33 | 60478.16397 | 7.71429 | 47.18447 | 120 | 17.46 |
| 40.37 | 60478.16555 | 6.74617 | 44.56311 | 120 | 17.53 |
| 40.40 | 60478.16701 | 6.74617 | 44.56311 | 120 | 17.49 |
| 40.44 | 60478.16859 | 9.40767 | 45.87379 | 120 | 17.24 |
| 40.48 | 60478.17005 | 9.40767 | 45.87379 | 120 | 17.24 |
| 40.51 | 60478.17163 | 8.35714 | 47.18447 | 120 | 17.42 |
| 40.55 | 60478.17309 | 8.35714 | 47.18447 | 120 | 17.42 |
+------------+-------------+---------+----------+-----------+--------------+
Our observations were coordinated through Skyportal (https://skyportal-icare.ijclab.in2p3.fr/).
GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger
Addicts) is a network of robotic telescopes connected all over the
world with both photometry and spectrometry capabilities for Time-
domain Astronomy (https://grandma.lal.in2p3.fr/).
Details on the FRAM telescopes are available on the GRANDMA web pages or at
https://grandma.ijclab.in2p3.fr/fram/
GCN Circular 36837
Subject
LIGO/Virgo S240615dg: Swift XRT observations, 28 futher X-ray sources
Date
2024-07-09T09:37:10Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans (U. Leicester), K.L. Page (U. Leicester), J.A. Kennea (PSU),
A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris
(U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini
(INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), J.J.
Delaunay (PSU), M. De Pasquale (University of Messina), S. Dichiara
(PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia
(ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson
University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin
(UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P.
Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page
(UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB),
B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB),
E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team:
Swift has carried out an extra 131 observations of the LVC error region
for the GW trigger S240615dg, re-observing the fields from our original
search (Page et al., GCN Circ. 36698). None of the 39 X-ray sources
reported previously show evidence for fading.
We have detected an additional 28 X-ray sources. Each source is
assigned a rank of 1-4 which describes how likely it is to be related
to the GW trigger, with 1 being the most likely and 4 being the least
likely. The ranks are described at https://www.swift.ac.uk/ranks.php.
We have found:
* 0 sources of rank 1
* 0 sources of rank 2
* 27 sources of rank 3
* 1 source of rank 4
RANK 3 sources
==============
These are uncatalogued X-ray sources, however they are not brighter
than previous upper limits, so do not stand out as likely counterparts
to the GW trigger.
| Source ID | RA | Dec | Err90 |
| S240615dg_X40 | 00h 29m 11.77s | +46d 23' 08.6" | 7.0" |
| S240615dg_X41 | 00h 35m 07.98s | +46d 06' 59.0" | 5.7" |
| S240615dg_X42 | 00h 29m 37.71s | +45d 16' 24.8" | 6.1" |
| S240615dg_X43 | 00h 27m 15.43s | +46d 12' 40.0" | 8.1" |
| S240615dg_X44 | 00h 35m 13.49s | +46d 06' 05.6" | 5.7" |
| S240615dg_X46 | 00h 25m 16.37s | +45d 52' 02.5" | 9.4" |
| S240615dg_X47 | 00h 28m 17.21s | +44d 57' 16.8" | 8.5" |
| S240615dg_X48 | 00h 31m 20.40s | +46d 49' 39.9" | 9.7" |
| S240615dg_X49 | 00h 35m 35.80s | +46d 23' 49.6" | 6.2" |
| S240615dg_X50 | 00h 35m 29.05s | +46d 08' 42.8" | 41.5" |
| S240615dg_X51 | 00h 25m 53.05s | +45d 34' 29.8" | 7.9" |
| S240615dg_X56 | 00h 25m 53.56s | +45d 29' 48.7" | 8.9" |
| S240615dg_X58 | 00h 31m 05.12s | +46d 33' 25.6" | 13.3" |
| S240615dg_X59 | 00h 31m 08.24s | +46d 32' 10.8" | 8.1" |
| S240615dg_X60 | 00h 35m 42.54s | +45d 48' 05.6" | 5.7" |
| S240615dg_X61 | 00h 29m 30.69s | +46d 40' 25.7" | 8.2" |
| S240615dg_X62 | 00h 27m 01.17s | +46d 30' 12.4" | 7.2" |
| S240615dg_X63 | 00h 29m 41.77s | +46d 37' 51.5" | 8.2" |
| S240615dg_X64 | 00h 28m 43.62s | +45d 01' 49.1" | 5.6" |
| S240615dg_X65 | 00h 29m 28.36s | +46d 42' 15.1" | 41.8" |
| S240615dg_X66 | 00h 33m 53.13s | +46d 45' 28.6" | 7.7" |
| S240615dg_X67 | 00h 33m 32.16s | +46d 08' 32.0" | 8.0" |
| S240615dg_X68 | 00h 25m 25.85s | +45d 33' 41.3" | 5.9" |
| S240615dg_X69 | 00h 32m 33.84s | +46d 47' 32.5" | 8.6" |
| S240615dg_X70 | 00h 28m 46.16s | +46d 05' 15.6" | 8.3" |
| S240615dg_X71 | 00h 28m 30.50s | +46d 19' 12.1" | 6.2" |
| S240615dg_X72 | 00h 28m 09.61s | +46d 18' 20.6" | 7.4" |
RANK 4 sources
==============
These are catalogued X-ray sources, showing no signs of outburst
compared to previous observations, so they are not likely to be related
to the GW trigger.
| Source ID | RA | Dec | Err90 |
| S240615dg_X45 | 00h 35m 39.42s | +45d 48' 41.3" | 8.8" |
For all flux conversions and comparisons with catalogues and upper
limits from other missions, we assumed a power-law spectrum with
NH=3x10^20 cm^-2, and photon index (Gamma)=1.7, unless otherwise
stated.
The results of the XRT automated analysis, including details of the
sources listed above, are online at
https://www.swift.ac.uk/LVC/S240615dg
This circular is an official product of the Swift XRT team.