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GCN Circular 9655

Subject
GRB 090709A: deep optical observation with the 10.4m GTC
Date
2009-07-11T12:18:38Z (15 years ago)
From
Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct@iaa.es>
A. J. Castro-Tirado (IAA-CSIC Granada), A. de Ugarte Postigo (OAB-INAF),
J. Gorosabel, S. Guziy, M. Jel�nek (IAA-CSIC), P. Kub�nek (IAA-CSIC and
GACE Valencia), D. P�rez-Ram�rez (Univ. de Ja�n), N. Mirabal (UCM Madrid),
A. Llorente, J. M. Castro Cer�n (ESAC Villafranca del Castillo), C.
Alvarez (IAC/GTC La Palma) and J. Cepa (IAC Tenerife),

report:

�Following the detection of GRB 090709A by Swift (Morris et al. GCNC
9625), we have conducted follow-up observations with the 10.4-m Gran
Telescopio Canarias (GTC) at the Observatorio del Roque de los Muchachos
of the Instituto de Astrof�sica de Canarias, in the island of La Palma.
Images in the i�-band filter (7 x 300-s) under 1�.0 seeing were gathered
with the OSIRIS instrument (Cepa et al. 2009, in prep.) on 11 July 2009,
00:45 UT (i.e. 41 hr after the event).

At the position of the reported nIR/optical afterglow (Aoki et al. GCNC
9634, Morgan et al. GCNC 9635, Cenko et al. GCNC 9646) we detect no single
object down to i� ~ 25.5 (preliminary 3-sigma limit), or i� ~ 25.2 when
taking into account the foreground Galactic extinction. We note two nearby
faint objects, which lie 3�.3 south-east and 4� north of the afterglow.

The stacked GTC .jpg image is available at the following link:
http://www.iaa.es/~gss/GRB090709A

Although we cannot exclude that GRB 090709A occurred in a low redshift
galaxy (Butler et al. GCNC 9639, Guidorzi et al. GCNC 9648), our
non-detection of a host galaxy, together with the reported 8-s
quasi-periodic oscillations (Markwardt et al. GCN 9645, Golenetskii et al.
9647, Gotz et al. GCNC 9649, Ohno et al. GCNC 9653) and the fact that the
event is at galactic coordinates of about (l = 91, b = 20) cannot rule out
that the initial observed gamma-ray emission arose from a nearby magnetar
candidate in the Milky Way, much closer than GRB 070610 / SWIFT
J195509+261406 (Castro-Tirado et al. 2008, Nature 455, 506).
Multiwavelength observations are encouraged.

We acknowledge the excellent support from the GRANTECAN staff.�


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