GRANDMA observations of ZTF/Fink transients during summer 2021

Abstract

We present our follow-up observations with GRANDMA of transient sources revealed by the Zwicky Transient Facility (ZTF). Over a period of six months, all ZTF alerts were examined in real time by a dedicated science module implemented in the Fink broker, which will be used filtering of transients discovered by the Vera C. Rubin Observatory. In this article, we present three selection methods to identify kilonova candidates. Out of more than 35 million alerts, a hundred sources have passed our selection criteria. Six were then followed-up by GRANDMA (by both professional and amateur astronomers). The majority were finally classified either as asteroids or as supernovae events. We mobilized 37 telescopes, bringing together a large sample of images, taken under various conditions and quality. To complement the orphan kilonova candidates, we included three additional supernovae alerts to conduct further observations during summer 2021. We demonstrate the importance of the amateur astronomer community that contributed images for scientific analyses of new sources discovered in a magnitude range r′ = 17 − 19 mag. We based our rapid kilonova classification on the decay rate of the optical source that should exceed 0.3 mag/day. GRANDMA’s follow-up determined the fading rate within 1.5 ± 1.2 days post-discovery, without waiting for further observations from ZTF. No confirmed kilonovae were discovered during our observing campaign. This work will be continued in the coming months in the view of preparing for kilonova searches in the next gravitational-wave observing run O4.

A Data Science Platform to Enable Time-domain Astronomy

“…In the case of fritz, it uses Kowalski, 42 an open-source, multisurvey data archive and alert broker (Duev et al 2019) for performing filtering and crossmatches, including rejection of bogus objects (Duev et al 2019); some science groups also rely on AMPEL (Nordin et al 2019). In the case of icare, it relies on ZTF-Fink (Aivazyan et al 2022), including its filtering capabilities targeting fast transients, to select promising candidates.…”

“…We expect to migrate this optional microservice to the main SkyPortal codebase in the near future so that it can benefit the SkyPortal community at large. In the context of GRANDMA, three specific Fink filters targeting alerts associated with fast transients have been deployed (Aivazyan et al 2022). One of the filters is based on the output score of a dedicated science module implementing a fast transient classification algorithm, and all filters were used in two subsequent follow-up campaigns of optical transients to search for orphan kilonovae (Biswas et al 2022).…”

GRANDMA and HXMT Observations of GRB 221009A: The Standard Luminosity Afterglow of a Hyperluminous Gamma-Ray Burst—In Gedenken an David Alexander Kann

“…The Global Rapid Advanced Network for Multi-messenger Addicts (GRANDMA; Antier et al 2020aAntier et al , 2020bAivazyan et al 2022) is a collaboration of ground-based facilities dedicated to time-domain astronomy and focused on electromagnetic follow-up of gravitational-wave candidates and other transients, such as GRBs. Its network contains 36 telescopes from 30 observatories, 42 institutions, and groups from 18 countries.…”

Astronomical seeing at Maidanak Observatory with differential image motion monitor

“…2 These include blazars, gravitationally lensed systems, gamma ray bursts, variable stars, supernovae, exoplanets, minor planets, and electromagnetic follow-up of gravitational wave candidates. [3][4][5][6] The previous period of intensive studies of the atmospheric turbulence and meteorology of the Maidanak Observatory in Uzbekistan was the period of 1996 to 2003. 7 Various parameters of the atmosphere that influence astronomical image quality in optics were studied.…”

“…These include blazars, gravitationally lensed systems, gamma ray bursts, variable stars, supernovae, exoplanets, minor planets, and electromagnetic follow-up of gravitational wave candidates 3 – 6 …”