[AAVSO-HEN] GRB 090618: BOAO V-band Observation

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  9541
SUBJECT: GRB 090618: BOAO V-band Observation
DATE:    09/06/21 06:09:55 GMT
FROM:    Myungshin Im at Seoul Nat U  <mim at astro.snu.ac.kr>

  M. Im (CEOU/Seoul National Univ), Y.-B. Jeon (KASI), and
  Y. Urata (NCU)

   We observed GRB090618 (Schady et al. GCN 9512) in V using
  a 15.5cm refractor at Bohyunsan Optical Astronomical Observatory
  in Korea, operarted by the Korea Astronomy Space Science Institute.
   A series of exposures were taken starting at 2009 June 18, 11:54:19.
   The afterglow, identified earlier by many groups
  (GCN 9513, 9514, 9515, 9520, 9522), was clearly detected
  at V=17.9 +- 0.1 magnitude at mid-time of 2009 12:55:07
  (about 4hr 26.6min after the BAT trigger).
   The photometry was calibrated against nearby SDSS stars
  where the transformation of SDSS magnitude to V-band magnitude
  was carried out using the recipe of Chonis & Gaskell (2008).