Swift J1822.3-1606: Optical spectroscopy of the counterpart candidates from the 10.4m GTC
ATel #3518; A. de Ugarte Postigo (DARK/NBI), T. Munoz-Darias (INAF-OAB, IAC)
on 28 Jul 2011; 18:28 UT
Credential Certification: Antonio de Ugarte Postigo (adeugartepostigo@gmail.com)
Subjects: Optical, Soft Gamma-ray Repeater
We have performed optical spectroscopy of the two objects (S1 and S2; ATEL #3496, #3502) present within the Swift/XRT error circle of the Soft Gamma-ray Repeater (SGR) candidate, Swift J1822.3-1606 (ATEL #3488, #3489, #3490, #3491, #3493, #3501, #3503). Observations were performed on July 20, 2011 using the OSIRIS spectrograph at the 10.4m Gran Telescopio de Canarias (GTC) telescope in La Palma, Spain. Two 900 s exposures were performed using the grism R500B, which covers the spectral range ~3500-8800 Angstrom with a spectral resolution R~500. We detect the continuum of both objects above ~ 6000 Angstrom. Preliminary analysis of the data reveals the presence of the CaII triplet of absorption lines (8498, 8542, 8662 Angstrom) in both objects, being more prominent in S2. No other emission or absorption features are evident in the spectrum of the objects at this stage of the analysis.
The presence of the CaII triplet, its intensity and the spectral index that we measure (once corrected for extinction) are consistent with G - early M spectral type stars, being S2 being earlier than S1. This result is in agreement with ATEL #
3515, strongly suggesting that none of these objects are the counterparts of the SGR candidate.
We thank the GTC staff for their excellent support and in particular Rene Rutten.
