TITLE: GCN CIRCULAR NUMBER: 24162 SUBJECT: LIGO/Virgo S190421ar: TAROT-GRANDMA observation report. DATE: 19/04/24 09:57:13 GMT FROM: Martin Blazek at HETH/IAA-CSIC M. Blazek (IAA/CSIC), M. Boer (Artemis), N. Christensen (Artemis), L. Eymar (Artemis), A. Klotz (IRAP), R. Laugier (Artemis), K. Noysena (Artemis, 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), P. Hello (LAL), C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC), X. Wang (THU) Report on behalf of the TAROT network and GRANDMA collaborations. We performed tiled observations of LIGO/VIRGO event S190421ar (GCN #24141) with the TAROT-Reunion (Les Makes Observatory, La RĂ©union Island, France) telescope operating in clear filter. The observation started on 04/22/19 17:19:22 UTC which corresponds approximately to 19.7 hours after the GW trigger time. We performed the following tiled observations : +---------------------+---------------------+---------+---------+-------+ | Tstart | Tend | RA | DEC | Proba | | [UTC] | [UTC] | [deg] | [deg] | [%] | |---------------------+---------------------+---------+---------+-------| | 2019-04-22 17:19:22 | 2019-04-23 01:37:03 | 205.714 | -60 | 2.6 | | 2019-04-22 17:32:30 | 2019-04-23 01:05:10 | 204.179 | -38.571 | 2.5 | | 2019-04-22 17:44:37 | 2019-04-23 01:18:28 | 203.774 | -51.429 | 2.4 | | 2019-04-22 18:00:09 | 2019-04-22 20:18:14 | 204.828 | -47.143 | 2.8 | | 2019-04-22 19:39:33 | 2019-04-23 00:11:50 | 210 | -55.714 | 2.6 | | 2019-04-22 19:52:45 | 2019-04-22 22:12:51 | 203.226 | -42.857 | 2.5 | | 2019-04-22 20:50:10 | 2019-04-22 22:26:08 | 210.566 | -51.429 | 2.3 | +---------------------+---------------------+---------+---------+-------+ The Probability refers to the 2D spatial probability of the GW skymap enclosed in a given tile. Each tile is 4.2x4.2 degrees. These observations cover about 17% of the cumulative probability of the skymap. The typical 3-sigma limiting magnitude for a two minutes exposure is 17 mag. The coverage map is available at: grandma-owncloud.lal.in2p3.fr/index.php/s/0O3ZreoLvm7VIOD Optical transient candidates will be sent through another GCN circular depending on our data 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 spectrometry capabilities for Time- domain Astronomy (https://grandma.lal.in2p3.fr/). Details on the TAROT telescopes are available on the GRANDMA web pages or on http://tarot.obs-hp.fr/