TITLE:   GCN CIRCULAR
NUMBER:  24340
SUBJECT: LIGO/Virgo S190426c: GRAWITA transients from Asiago Schmidt wide field observations
DATE:    19/04/29 10:31:43 GMT
FROM:    Andrea Melandri at INAF-OAB  <andrea.melandri@inaf.it>

L. Izzo (IAA), R. Carini (INAF-OAR), S. Yang (INAF-OAPd), L. Tomasella (INAF-OAPd), E. Cappellaro (INAF-OAPd), G. Greco (Univ. Urbino), R. Martone (U. Ferrara), S. Benetti (INAF-OAPd), M.T. Botticella (INAF-OAC), M. Branchesi (GSSI), S. Campana (INAF-OAB), S. Covino (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), M. Della Valle (INAF-OAC), A. Melandri  (INAF-OAB), S. Piranomonte (INAF-OAR), A. Rossi (INAF-OAS), E. Brocato (INAF-OAAb, INAF-OAR), on behalf of GRAWITA report:

We carried out observations of LIGO/Virgo S190426c (LVC, GCN Circ. 24237) with the Schmidt Telescope located at the INAF Asiago Observatory (Italy). The observations were taken in the r-sloan band on 2019-04-26 starting on 22:16:27 UT. Each pointing covers an area of 1x1 deg and each exposure was of 90 s. The covered area captured a contained probability of ~1.6% of the GW skymap (LALInference1, submitted by LIGO/Virgo EM Follow-Up on Apr 27, 2019 11:50:29 UTC).

The pointings are centered on the following UT times and coordinates RA(J2000), Dec(J2000):

2019-04-26T22:27:23  22:19:19.87  +82:59:58
2019-04-26T22:32:38  22:19:20.51  +84:59:59
2019-04-26T22:37:08  21:59:57.43  +83:00:00
2019-04-26T22:40:52  22:00:00.31  +84:00:00
2019-04-26T22:44:49  21:59:59.51  +84:59:59

A preliminary analysis of the dataset reveals the presence of the following transient sources (ID, RA(J2000, Dec(J2000), r(AB) mag, probability by LALInference1 skymap): 

GRAWITA_J215716.26+832239.4    21:57:16.26    +83:22:39.4  15.1   within 30% c.r.   
GRAWITA_J220104.54+834836.9    22:01:04.54    +83:48:36.9  16.9   within 30% c.r.  
GRAWITA_J220050.38+844436.5    22:00:50.38    +84:44:36.5  16.7   within 20% c.r.    

There are no known source at the position of these sources and no minor planets. Inspection of archival Pan-STARRS images reveals no objects at the position of GRAWITA_J215716.26+832239.4 and GRAWITA_J220104.54+834836.9, while a faint source can be recognised at the position of GRAWITA_J220050.38+844436.5.

Subsequently, we carried out follow-up observations, starting at 22:58:43 UT on 2019-04-28, with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy (https://goo.gl/Dqvqhf) of GRAWITA_J220104.54+834836.9 and GRAWITA_J220050.38+844436.5. Both sources are no longer detected down to a 3sigma limiting magnitude of R(AB)>19.4.

Further analysis is in progress.