Difference: GCNCIRCULAR21638 ( vs. 1)

R. Chornock (Ohio University) and E. Berger (Harvard) report on behalf of a larger collaboration:

We have been obtaining a sequence of near-infrared spectroscopy (range 1-1.8 microns) of the optical counterpart (SSS17a: Coulter et al., GCN 21529; Allam et al., GCN 21530) of LIGO/Virgo G298048 (GCNs 21509, 21513) using FLAMINGOS2 on Gemini-South (PI: Chornock).

Our initial spectra, taken on 20170819 at 00:45 UT (~1.5 days after the LIGO/Virgo event) have a smooth blue continuum. Data taken the following night show a few broad, low-amplitude features starting to develop. An initial reduction of data taken on 20170821 at 23:40 UT (~4.5 days after the LIGO/Virgo event) shows that these features (including a possible spectral peak near 1.05 microns) have strengthened. Analysis is ongoing and further observations are planned to constrain the potential presence of lanthanide opacities in the near-infrared.

We thank the Gemini staff, particularly Hwihyun Kim, Gonzalo Diaz, Pablo Candia, and Laura Ferrarese for their support of these operations.

-- ShaonGhosh - 22 Aug 2017