TITLE: GCN CIRCULAR NUMBER: 25847 SUBJECT: LIGO/Virgo S190923y: No significant candidates in TAROT-GRANDMA observations DATE: 19/09/26 01:48:57 GMT FROM: Damien Turpin at NAOC (CAS) D. Turpin (NAOC), P. Hello (LAL), K. Noysena (Artemis, IRAP), C. Thoene (HETH/IAA-CSIC), M. Boer (Artemis), N. Christensen (Artemis), L. Eymar (Artemis), A. Klotz (IRAP), S. Antier (APC), S. Basa (LAM), D. Corre (LAL), M. Coughlin (Caltech), D. Coward (OzGrav-UWA), J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), D. A. Kann (HETH/IAA-CSIC), C. Lachaud (APC), N. Leroy (LAL) report on behalf of the TAROT network and GRANDMA collaborations: We performed tiled observations of the LIGO/Virgo S190923y event with the TAROT-Reunion (TRE), TAROT-Calern (TCA) and TAROT-Chili (TCH) telescopes operating in the visible located respectively at Les Makes astronomical observatory, the Cote d'Azur observatory and La Silla ESO observatory (LaS/ESO). The observation started on 09/23/19 16:30:12 UTC for TRE which corresponds approximately to 215 minutes after the GW trigger time. For TCA it started on 09/23/19 18:22:31 UTC which corresponds approximately to 327 minutes after the GW trigger time. For TCH it started on 09/23/19 23:42:17 UTC which corresponds approximately to 647 minutes after the GW trigger time. We performed the following tiled observations : +-------+------------+------------+---------+---------+---------+ | Tele  | TStart     | TEnd       | RA      | DEC     |   Proba | | scope | [UTC]      | [UTC]      | [deg]   | [deg]   |     [%] | |-------|------------+------------+---------+---------+---------| |  TRE  | 2019-09-23 | 2019-09-25 | 250.909 | -40.909 |     1.2 | |       | 16:30:12   | 18:18:14   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 243.243 | -32.727 |     1.1 | |       | 16:43:24   | 16:01:15   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 243.117 | -28.636 |     1.1 | |       | 16:55:50   | 16:13:27   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 245.455 | -40.909 |     1   | |       | 17:08:55   | 16:26:45   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 285     | -73.636 |     0.8 | |       | 17:21:15   | 19:09:01   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 243     | -24.545 |     0.8 | |       | 17:40:29   | 16:58:26   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 256.154 | -53.182 |     1.6 | |       | 17:56:56   | 17:33:16   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 249.677 | -45     |     1.5 | |       | 18:16:07   | 17:52:26   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 246.857 | -36.818 |     1.4 | |       | 18:29:19   | 18:05:44   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 276     | -69.545 |     1   | |       | 19:13:36   | 21:19:48   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 265.714 | -61.364 |     1.2 | |       | 21:05:15   | 20:41:36   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 270     | -65.455 |     1.2 | |       | 21:17:59   | 20:54:39   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 90      | 4.091   |     1.1 | |       | 21:35:17   | 23:37:06   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-26 | 85.909  | 0       |     1   | |       | 21:56:18   | 00:02:43   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 85.909  | 4.091   |     0.8 | |       | 22:15:29   | 21:51:45   |         |         |         | |  TRE  | 2019-09-23 | 2019-09-25 | 91.034  | 8.182   |     1.5 | |       | 23:09:44   | 22:46:17   |         |         |         | |  TRE  | 2019-09-24 | 2019-09-24 | 248.108 | -32.727 |     0.7 | |       | 18:28:15   | 18:34:32   |         |         |         | |  TRE  | 2019-09-24 | 2019-09-25 | 260.425 | -57.273 |     1.4 | |       | 19:22:29   | 20:24:29   |         |         |         | |-------|------------+------------+---------+---------+---------| |  TCA  | 2019-09-23 | 2019-09-25 | 150.95  | 48.27   |     0.1 | |       | 18:22:31   | 02:58:48   |         |         |         | |  TCA  | 2019-09-23 | 2019-09-25 | 89.075  | 11.156  |     0.1 | |       | 23:41:57   | 03:19:06   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-24 | 81.575  | -9.256  |     0.1 | |       | 00:27:20   | 03:03:58   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-24 | 80.112  | -11.112 |     0.1 | |       | 00:40:21   | 00:46:41   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-26 | 79.7    | -9.256  |     0.1 | |       | 00:47:07   | 00:23:08   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-26 | 92.783  | 3.733   |     0.1 | |       | 00:53:52   | 00:29:56   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 146.538 | 46.414  |     0.2 | |       | 01:26:35   | 02:32:55   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 149.185 | 46.414  |     0.2 | |       | 01:33:22   | 02:35:21   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 151.832 | 46.414  |     0.2 | |       | 01:40:06   | 02:46:24   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 148.223 | 48.27   |     0.1 | |       | 01:59:17   | 03:05:36   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 145.495 | 48.27   |     0.1 | |       | 02:06:01   | 03:12:21   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-24 | 142.768 | 48.27   |     0.1 | |       | 02:18:25   | 02:24:45   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 153.677 | 48.27   |     0.1 | |       | 02:25:12   | 18:31:12   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 156.405 | 48.27   |     0.1 | |       | 02:31:57   | 18:38:00   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 83.022  | -7.401  |     0.1 | |       | 02:38:42   | 01:14:45   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 159.132 | 48.27   |     0.1 | |       | 02:50:52   | 18:57:10   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 147.433 | 42.703  |     0.1 | |       | 03:04:26   | 04:08:35   |         |         |         | |  TCA  | 2019-09-24 | 2019-09-25 | 161.859 | 48.27   |     0.1 | |       | 03:30:18   | 02:06:41   |         |         |         | |-------+------------+------------+---------+---------+---------+ |  TCH  | 2019-09-23 | 2019-09-25 | 261.239 | -54.505 |     0.2 | |       | 23:42:17   | 03:18:23   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 251.119 | -52.686 |     0.2 | |       | 00:03:52   | 23:38:03   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 243.214 | -36.323 |     0.2 | |       | 00:08:26   | 23:44:47   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-26 | 265.656 | -69.05  |     0.1 | |       | 00:34:28   | 00:10:43   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 239.646 | -21.777 |     0.2 | |       | 02:05:45   | 00:41:50   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 239.014 | -19.959 |     0.2 | |       | 02:24:51   | 01:01:21   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 285.466 | -70.868 |     0.2 | |       | 02:50:54   | 23:57:11   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-26 | 296.15  | -74.505 |     0.1 | |       | 03:29:45   | 00:36:07   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 265.656 | -58.141 |     0.2 | |       | 05:14:24   | 06:20:43   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 93.211  | 5.495   |     0.2 | |       | 05:53:19   | 06:59:50   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 92.787  | 10.95   |     0.4 | |       | 06:26:33   | 07:32:51   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 94.624  | 10.95   |     0.4 | |       | 06:33:19   | 07:39:36   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 90.95   | 10.95   |     0.3 | |       | 06:40:04   | 07:46:20   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 94.148  | 9.132   |     0.3 | |       | 06:46:48   | 07:53:05   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 96.46   | 10.95   |     0.2 | |       | 07:01:09   | 08:05:28   |         |         |         | |  TCH  | 2019-09-24 | 2019-09-25 | 94.07   | 7.314   |     0.2 | |       | 07:18:38   | 08:24:58   |         |         |         | |  TCH  | 2019-09-25 | 2019-09-26 | 239.793 | -27.707 |     0.2 | |       | 01:27:40   | 00:03:57   |         |         |         | |  TCH  | 2019-09-25 | 2019-09-25 | 242.134 | -21.777 |     0.1 | |       | 01:46:49   | 01:53:08   |         |         |         | |-------+------------+------------+---------+---------+---------+ TStart and TEnd refers respectively to the time of the first and last exposure for a given tile. Observations are not necessarily continuous in this interval. The Probability refers to the 2D spatial probability of the GW skymap enclosed in a given tile. Each TRE tile is 4.2x4.2 degrees and 1.9x1.9 degrees for TCA and TCH. These observations cover about 25.5% the cumulative probability of the Bayestar skymap available on Sep 23, 2019 13:01:56 UTC. The typical limiting magnitude is 17.0 and 18.0 for a 60.0 s exposure for TRE and TCA/TCH, respectively. The coverage map is available at: https://grandma-owncloud.lal.in2p3.fr/index.php/s/Y2sXYjRmkubuRrw No significant transient candidates were found during our low latency analysis. 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 spectroscopy capabilities for Time- domain Astronomy (https://grandma.lal.in2p3.fr/). Details on the TRE, TCA and TCH telescopes are available on the GRANDMA web pages or on  http://tarot.obs-hp.fr/. This circular is citable.