TITLE: GCN CIRCULAR NUMBER: 25563 SUBJECT: GRB 190829A: NOT optical afterglow detection and spectroscopy DATE: 19/08/30 03:42:22 GMT FROM: Daniel Perley at Liverpool JMU K. E. Heintz (Univ. of Iceland), J. P. U. Fynbo (DAWN/NBI), P. Jakobsson (Univ. of Iceland), D. Xu (NAOC), D. A. Perley (LJMU), D. B. Malesani (DTU space), and J. Viuho (NOT), report on behalf of a larger collaboration: We observed the Swift-detected GRB 190829A (Dichiara et al., GCN 25552) with the Nordic Optical Telescope (NOT) equipped with AlFOSC. We obtained 3x300s r-band images at a mid-time of 02:03:52 UT on August 30 (i.e. 6.1 hr post-burst). We clearly detect the optical counterpart reported by Xu et al. (GCN 25555), superimposed on the SDSS galaxy J025810.28-085719.2 at z=0.08 as noted previously. We measure a preliminary magnitude of r(AB) = 18.9 +/- 0.1 for this source, calibrated against photometry of nearby field stars from the Pan-STARRS catalog. Following the imaging sequence, we obtained a series of spectra with an integration time of 4x600s using grism 4 (covering 320-960 nm), beginning at 02:27:42 UT. The spectrum shows a featureless red continuum, with no clear absorption lines to identify the redshift. Since the continuum is detected at all observed wavelengths we can place a limit on the redshift of z < 1.8. DisclaimerNone