TITLE: GCN CIRCULAR NUMBER: 25474 SUBJECT: LIGO/Virgo S190814bv: MASTER prediscovery and postdiscovery observations DECam candidate DG19wxnjc/AT2019npv field DATE: 19/08/25 15:40:32 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, D. Vlasenko, E. Gorbovskoy, F.Balakin, N.Tyurina, V. Kornilov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V. Vladimirov, D.Zimnukhov, V. Senik, A.Chasovnikov, A.Pozdnyakov,D.Kuvshinov, V. Topolev (Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), 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), D. Buckley (South African Astronomical Observatory SAAO), N.M. Budnev, O. Gress, 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) All observations was done under the MASTER target of opportunity program that includes the results of population synthesis by Scenario Machine (Lipunov et al., "First LIGO events: binary black holes mergings", New Astronomy, Vol. 2, p. 43-52, 1997). There are number arhive images just before trigger. One (GCN 25354) of our previous circulars was sent erroneously. Here we give the correct schedule of our observations. MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the LIGO/Virgo S190814bv errorbox 1327 sec after trigger time at 2019-08-14 21:32:46 UT (Lipunov et al., GCN 25322). MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the LIGO/Virgo S190814bv errorbox 1351 sec after trigger time at 2019-08-14 21:33:10 UT, with upper limit up to 19.4 mag (Lipunov et al., GCN 25322). MASTER-Tavrida robotic telescope located at Crimea started inspect of the LIGO/Virgo S190814bv errorbox 1373 sec after trigger time at 22019-08-14 21:33:32 UT. MASTER-IAC robotic telescope located at Tenerife (Spain) started inspect of the LIGO/Virgo S190814bv errorbox 4200 sec after trigger time at 2019-08-14 22019-08-14 22:20:39 UT. Our coadded images limit is: 10367 | 2019-08-15 00:01:56 | C | 1440 | 20.6 | Coadd 11174 | 2019-08-15 00:12:22 | C | 540 | 19.9 | Coadd 22253 | 2019-08-15 03:20:01 | C | 360 | 19.3 | Coadd 87165 | 2019-08-15 21:23:44 | C | 360 | 18.5 | Coadd 97387 | 2019-08-16 00:13:46 | C | 540 | 19.0 | Coadd 108618 | 2019-08-16 03:20:57 | C | 1080 | 19.3 | Coadd ~5 days| 2019-08-20 21:00:43 | C | 540 | 20.1 | Coadd ~6 days| 2019-08-21 19:55:47 | C | 540 | 20.7 | Coadd We see host galaxy and OT on some images. For example Robot find MASTER OT J005332.32-234958.5 at 23 Aug: Date RA Dec Tube OT mag unfiltered 2019-08-23 02:45:31.4 00h 53m 32.32s, -23d 49m 58.48s W 20.1 However, the object is visible at the limit and therefore reduction is continuated. The Alert page is availabl at https://master.sai.msu.ru/site/master2/ligo_1.php?id=10685&nb=1 This message can be cited. [GCN OPS NOTE(26aug19): Per author's request, the "LIGO/Virgo" prefix was added to the Subject line.]