Discovery of GRB 020405 and Its Late Red Bump

P.A.Price,1,2 S.R.Kulkarni,2 E.Berger,2 D.W.Fox,2 J.S.Bloom,2 S.G.Djorgovski,2 D.A.Frail,3 T.J.Galama,2 F.A.Harrison,2 P.McCarthy,4 D.E.Reichart,2 R.Sari,5 S.A.Yost,2 H.Jerjen,1 K.Flint,6 A.Phillips,7 B.E.Warren,1 T.S.Axelrod,1 R.A.Chevalier,8 J.Holtzman,9 R.A.Kimble,10 B.P.Schmidt,1 J.C.Wheeler,11 F.Frontera,12,13 E.Costa,12 L.Piro,12 K.Hurley,14 T.Cline,15 C.Guidorzi,13 E.Montanari,13 E.Mazets,16 S.Golenetskii,16 I.Mitrofanov,17 D.Anfimov,17 A.Kozyrev,17 M.Litvak,17 A.Sanin,17 W.Boynton,18 C.Fellows,18 K.Harshman,18 C.Shinohara,18 A.Gal-Yam,19 E.Ofek,19 and Y.Lipkin19

1 Research School of Astronomy and Astrophysics,Mount Stromlo Observatory, via Cotter Road, Weston, ACT 2611, Australia.
2 Palomar Observatory, 105-24, California Institute of Technology, Pasadena, CA 91125.
3 National Radio Astronomy Observatory, P.O. Box O, Socorro,NM87801.
4 Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101.
5 Theoretical Astrophysics, 130-33, California Institute of Technology, Pasadena, CA 91125.
6UCO/Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064.
7 School of Physics, University of New South Wales, Sydney,NSW 2052, Australia.
8Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818.
9 Department of Astronomy, MSC 4500, New Mexico State University, P.O. Box 30001, Las Cruces,NM88003.
10Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Code 681, Greenbelt,MD20771.
11Astronomy Department, University of Texas, Austin, TX 78712.
12Istituto Astrofisica Spaziale e Fisica Cosmica, CNR, Area di Tor Vergata, Via Fosso del Cavaliere 100, 00133 Rome, Italy.
13Dipartimento di Fisica, Universita di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy.
14University of California, Space Sciences Laboratory, Berkeley, CA 94720.
15NASA Goddard Space Flight Center, Code 661, Greenbelt,MD20771.
16 Ioffe Physico-Technical Institute, Saint Petersburg 194021, Russia.
17Space Research Institute, Profsojuznaya Str. 84/32, 117810 Moscow, Russia.
18 Department of Planetary Sciences, Lunar and Planetary Laboratory, Tucson, AZ 85721-0092.
19School of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel.

Abstract - We present the discovery of GRB 020405 made with the Interplanetary Network (IPN). With a duration of 60 s, the burst appears to be a typical long-duration event. We observed the 75 arcmin2 IPN error region with the Mount Stromlo Observatory's 50 inch robotic telescope and discovered a transient source that subsequently decayed and was also associated with a variable radio source. We identify this source as the afterglow of GRB 020405. Subsequent observations by other groups found varying polarized flux and established a redshift of 0.690 to the host galaxy. Motivated by the low redshift, we triggered observations with WFPC2 on board the Hubble Space Telescope (HST). Modeling the early ground-based data with a jet model, we find a clear red excess over the decaying optical light curves that is present between day 10 and day 141 (the last HST epoch). This bump has the spectral and temporal features expected of an underlying supernova (SN). In particular, the red color of the putative SN is similar to that of the SN associated with GRB 011121 at late time. Restricting the sample of GRBs to those with z < 0.7, a total of five bursts, red bumps at late times are found in GRB 970228, GRB 011121, and GRB 020405. It is possible that the simplest idea, namely, that all long-duration gamma-ray bursts have underlying SNe with a modest dispersion in their properties (especially peak luminosity), is sufficient to explain the nondetections.
DOI: 10.1086/374730 -