[vsnet-grb-info 24974] LIGO/Virgo S200114f: Gemini Spectra of AT 2020vu, AT 2020vw, AT 2020vy, and AT 2020vz

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27073
SUBJECT: LIGO/Virgo S200114f: Gemini Spectra of AT 2020vu, AT 2020vw, AT 2020vy, and AT 2020vz
DATE:    20/02/15 02:15:40 GMT
FROM:    Curtis McCully at Las Cumbres Observatory  <cmccully at lco.global>

Curtis McCully (LCO), Daichi Hiramatsu (LCO/UCSB), Jamison Burke
(LCO/UCSB), Jennifer Andrews (UA), Craig Peligrino (LCO/UCSB), D. Andrew
Howell (LCO/UCSB), Iair Arcavi (Tel Aviv University), Reinaldo de Carvalho:
(Unicid/Unicsul), Francisco Förster (Universidad de Chile), Ryan Foley
(UCSC), David Coulter (UCSC), Charles Kilpatrick (UCSC), David Sand (UA),
Stefano Valenti (UC Davis), Marcelle Soares-Santos (Brandeis), Sandro
Rembold (UFSM), Armin Rest (STSci), Daniel Kasen (UC Berkeley), Brian
Metzger (Columbia), Anthony Piro (Carnegie Obs.), Eliot Quataert (UC
Berkeley), Enrico Ramirez-Ruiz (UCSC), J. Craig Wheeler (UT Austin), Franz
Bauer (Pontificia Universidad Catolica de Chile), Joshua Bloom (UC
Berkeley), Thomas Brink (UC Berkeley), Jeff Cooke (Swinburne University of
Technology), Alejandro Clocchiatti (Pontificia Universidad Catolica de
Chile), Alexei V. Filippenko (UC Berkeley), Wendy Freedman (University of
Chicago), Peter Garnavich (Notre Dame), Jorge Ernesto Horvath (Universidade
de Sao Paulo), Saurabh Jha (Rutgers), Robert Kirshner (Gordon and Betty
Moore Foundation), Kevin Krisciunas (Texas A&M), Huan Lin (FNAL), Barry
Madore (Carnegie Obs.),  Martin Makler (Centro Brasileiro de Pesquisas
Físicas), Gautham Narayan (UIUC), Xavier Prochaska (UCSC), Adam Riess
(STSci), Riccardo Sturani (UFRN), Nicholas Suntzeff (Texas A&M), Masaomi
Tanaka (Tohoku University), Douglas Tucker (FNAL), Jozsef Vinko (Konkoly
Observatory), Lifan Wang (Texas A&M), Carlos Contreras (STSci), Chris
D'Andrea (UPenn), Georgios Dimitriadis (UCSC), David Jones (UCSC), Michael
Lundquist (UA), Felipe Olivares (INCT/UDA), Antonella Palmese (FNAL),
Yen-Chen Pan: (NAOJ), Daniel Scolnic (University of Chicago), WeiKang Zheng
(UC Berkeley), Antonio Bernardo (Universidade de Sao Paulo), K. Azalee
Bostroem (UC Davis), Ariadna Murguia Berthier (UCSC), Ósmar Rodríguez
(Universidad Nacional Andres Bello), César Rojas-Bravo (UCSC), Matthew
Siebert (UCSC), and Iruatã Souza (Centro Brasileiro de Pesquisas)

Following the detection of S200114f (LIGO/Virgo Collaboration, GCN 26734),
the Zwicky Transient Facility reported a list of possible optical
counterparts (Andreoni et al., GCN 26741). We triggered our follow-up
program on the Gemini Telescopes (GS-2019B-Q-115; PI McCully) to classify
the candidates. We obtained optical spectra of AT 2020vu, 2020vw, 2020vy,
and 2020vz using the GMOS instrument on Gemini South. These targets were
chosen because they were visible from Chile as Gemini North was closed due
to bad weather. They were observed consecutively starting at 2020-01-16
01:55 UTC, less than 48 hours after merger detection.

These targets were triggered using the TOM Toolkit (Street et al., 2018,
arXiv 1806.09557) through Gemini's programmatic interface.

The spectra were reduced using a combination of Gemini IRAF tasks and
custom Python routines (https://github.com/cmccully/lcogtgemini). We used
both SNID (Blondin & Tonry 2007, ApJ, 666, 1024) and Superfit (Howell et
al. 2005, ApJ, 634, 1190) to classify these transients. Throughout, we
adopt a Hubble constant of H_0 =  71 km/s/Mpc and a flat cosmological model
with a dark energy density of 0.7. The classifications and spectra have
been uploaded to the Transient Name Server (TNS).



For AT 2020vz, we find a best fit using Superfit of SN 2005cl, a Type IIn
SN, at +15 days with redshift z = 0.25. This corresponds to an absolute
magnitude of -19.4, consistent with this type of supernova.
https://wis-tns.weizmann.ac.il/object/2020vz

AT 2020vy was best fit by SN 1999aa before peak brightness at z = 0.24. At
this redshift, the source has an absolute magnitude of -19.2, consistent
with a SN Ia. https://wis-tns.weizmann.ac.il/object/2020vy



AT 2020vu is consistent with a quasar. The spectrum exhibits a strong,
broad feature near 5360 A. Assuming this is Mg II, the quasar is at  z =
0.91. At this redshift, there are also spectral features consistent with
the hydrogen Balmer series and [O III].
https://wis-tns.weizmann.ac.il/object/2020vu

For AT 2020vw, the best fit is with a normal SN Ia near peak brightness at
z = 0.23, consistent with the absolute magnitude estimate of -19.0 at that
distance. https://wis-tns.weizmann.ac.il/object/2020vw

Therefore, we conclude that all of these transients (AT 2020vy, 2020vz,
2020vu, and 2020vw) are not associated with the GW alert S200114f.



We thank the Gemini team for their rapid response and assistance in
obtaining these observations.