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Astron. Astrophys. 354, 473-479 (2000)

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Near-infrared detection and optical follow-up of the GRB990705 afterglow * **

N. Masetti 1, E. Palazzi 1, E. Pian 1, L.K. Hunt 2, M. Méndez 3,4, F. Frontera 1,5, L. Amati 1, P.M. Vreeswijk 3, E. Rol 3, T.J. Galama 3, J. van Paradijs  ***  3,6, L.A. Antonelli 7, L. Nicastro 8, M. Feroci 9, G. Marconi 7, L. Piro 9, E. Costa 9, C. Kouveliotou 10,11, A.J. Castro-Tirado 12,13, R. Falomo 14, T. Augusteijn 15, H. Böhnhardt 15, C. Lidman 15, L. Vanzi 15, K.M. Merrill 16, C.D. Kaminsky 17, M. van der Klis 3, M.H.M. Heemskerk 3, F. van der Hooft 3, E. Kuulkers 18,19, H. Pedersen 20 and S. Benetti 21

1 Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy
2 Centro per l'Astronomia Infrarossa e lo Studio del Mezzo Interstellare, CNR, Largo E. Fermi 5, 50125 Firenze, Italy
3 Astronomical Institute, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
4 Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata, Argentina
5 Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy
6 Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899, USA
7 Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monteporzio Catone, Italy
8 Istituto di Fisica Cosmica con Applicazioni all'Informatica, CNR, Via U. La Malfa 153, 90146 Palermo, Italy
9 Istituto di Astrofisica Spaziale CNR, Via del Fosso del Cavaliere, 00131 Rome, Italy
10 Universities Space Research Association, Huntsville, AL 35800, USA
11 NASA Marshall Space Flight Center, ES-84, Huntsville, AL 35812, USA
12 Instituto de Astrofísica de Andalucía (IAA-CSIC), P.O. Box 03004, 18080, Granada, Spain
13 Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, P.O. Box 50737, 28080, Madrid, Spain
14 Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padua, Italy
15 European Southern Observatory, Casilla 19000, Santiago, Chile
16 National Optical Astronomy Observatories, 950 North Cherry Avenue, P.O. Box 26732, Tucson, AZ 85726, USA
17 Center for Astrophysical Research in Astronomy, Yerkes Observatory, University of Chicago, 373 W. Geneva St, Williams Bay, WI 53191, USA
18 Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
19 Astronomical Institute, Utrecht University, P.O. Box 80000, 3507 TA Utrecht, The Netherlands
20 Copenhagen University Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
21 Telescopio Nazionale Galileo, Centro Galileo Galilei, Calle Alvarez de Abreu 70, 38700 Santa Cruz de La Palma, Canary Islands, Spain

Received 2 August 1999 / Accepted 8 December 1999


Optical and near-infrared observations of the GRB990705 error box were carried out with ESO telescopes at La Silla and Paranal in Chile and with the NOAO SPIREX 0.6-meter telescope in Antarctica. We detected the counterpart of this GRB in the near-infrared H band and optical V band. The power-law decline of the near-infrared lightcurve is rather steep with a decay index [FORMULA] [FORMULA] 1.7 in the first hours, and a possible steepening after one day. Broadband spectral analysis of the optical/near-infrared afterglow suggests that this GRB took place in a high density environment. A deep optical image obtained at Antu (VLT-UT1) about 5 days after the GRB trigger shows at the position of the transient an extended object which might be the host galaxy of GRB990705.

Key words: gamma rays: bursts – radiation mechanisms: non-thermal – galaxies: general

* Based on observations collected at the European Southern Observatory, La Silla and Paranal, Chile
** Based on observations collected with NOAO facilities
*** Deceased on November 2, 1999

Send offprint requests to: Nicola Masetti (masetti@tesre.bo.cnr.it)

© European Southern Observatory (ESO) 2000

Online publication: February 9, 2000