GCN Circular 25252
Subject
GRB 190719C: VLT/X-shooter spectroscopic redshift of the host galaxy
Date
2019-08-01T22:01:30Z (5 years ago)
From
Andrea Rossi at INAF <andrea.rossi@inaf.it>
A. Rossi (INAF-OAS), K. E. Heintz (Univ. Iceland), J. P. U. Fynbo
(DAWN/NBI), D. B. Malesani (DTU Space), A. de Ugarte Postigo
(HETH/IAA-CSIC, DARK/NBI), S. D. Vergani (Obs. Paris/GEPI and CNRS), D.
A. Kann, C. C. Thoene, L. Izzo (HETH/IAA-CSIC), S. Campana (INAF-OAB),
G. Pugliese, L. Kaper (Univ. Amsterdam), C. Kouveliotou (GWU), and N. R.
Tanvir (Univ. Leicester) report on behalf of the Stargate collaboration:
We observed the location of the candidate host galaxy (Malesani et al.,
GCN 25110; Heintz et al., GCN 25144) of GRB 190719C (Ambrosi et al., GCN
25106; Poolakkil & Meegan, GCN 25130) using the ESO VLT UT2 (Kueyen)
equipped with the X-shooter spectrograph. Our spectra cover the
wavelength range 3000-21000 AA, and consist of 4 exposures by 600 s
each. Our observations started on 2019 August 01 at 00:48:20 UT, ~13.4
days after the GRB detection. The slit was centred on the nucleus of the
nearby object visible in the Pan-STARRS archival images, and was
oriented in order to include the afterglow position.
While only weak continuum is visible, several clear emission lines are
detected in the near-infrared arm. We identify the [O ii] 3727/3729
doublet, Hbeta, [O iii] 4959, and [O iii] 5007, at a common redshift z =
2.469.
No clear emission (lines nor continuum) is detected at the location of
the afterglow, so we have no direct measurement of the GRB redshift. The
random association probability with the Pan-STARRS object is however
rather small (~3*10^-3), suggesting a physical connection. We also note
that the Pan-STARRS galaxy is exceptionally luminous, with an absolute
magnitude M = -22.9 AB (computed at 1800 AA rest frame). The measured
offset would correspond to 6.6 kpc in projection - a rather large value
but not surprising for such a bright host. In conclusion, we propose z =
2.469 as the redshift of GRB 190719C.
We acknowledge excellent support from the ESO observing staff in
Paranal, in particular Gaspare Lo Curto, Marcela Espinoza, Boris
Haeussler, Aleksandra Solarz, and Steffen Mieske.