Hubble Space Telescope and Palomar imaging of GRB 990123

Implications for the nature of gamma-ray bursts and their hosts

Andrew S. Fruchter, S. E. Thorsett, Mark R. Metzger, Kailash C. Sahu, Larry Petro, Mario Livio, Henry Ferguson, Elena Pian, David W. Hogg, Titus Galama, Theodore R. Gull, Chryssa Kouveliotou, Duccio Macchetto, Jan Van Paradijs, Holger Pedersen, Alain Smette

    Research output: Contribution to journalArticle

    Abstract

    We report on Hubble Space Telescope and Palomar optical images of the field of GRB 990123, obtained in 1999 February 8 and 9. We find that the optical transient (OT) associated with GRB 990123 is located on an irregular galaxy, with a magnitude of V = 24.20 ± 0.15. The strong metal absorption lines seen in the spectrum of the OT, along with the low probability of a chance superposition, lead us to conclude that this galaxy is the host of the gamma-ray burst (GRB). The OT is projected within the ∼1″ visible stellar field of the host, nearer the edge than the center. We cannot, on this basis, rule out the galactic nucleus as the site of the GRB, since the unusual morphology of the host may be the result of an ongoing galactic merger, but our demonstration that this host galaxy has extremely blue optical-to-infrared colors more strongly supports an association between GRBs and star formation. We find that the OT magnitude in 1999 February 9.05, V = 25.45 ± 0.15, is about 1.5 mag fainter than expected from the extrapolation of the decay rate found in earlier observations. A detailed analysis of the OT light curve suggests that its fading has gone through three distinct phases: an early, rapid decline (fv ∝ t-1.6 for t < 0.1 days); a slower, intermediate decline power-law decay (fv ∝ t-1.1 for 0.1 < t < 2 days); and then a more rapid decay (at least as steep as fv oc t-1.8 for t > 2 days). The break to a steeper slope at late times may provide evidence that the optical emission from this GRB was highly beamed.

    Original languageEnglish (US)
    JournalAstrophysical Journal
    Volume519
    Issue number1 PART 2
    StatePublished - Jul 1 1999

    Fingerprint

    gamma ray bursts
    Hubble Space Telescope
    merger
    galaxies
    galactic nuclei
    irregular galaxies
    star distribution
    fading
    metal
    light curve
    decay rates
    light emission
    star formation
    extrapolation
    slopes
    color
    metals

    Keywords

    • Cosmology: observations
    • Gamma rays: bursts
    • Stars: formation

    ASJC Scopus subject areas

    • Space and Planetary Science

    Cite this

    Fruchter, A. S., Thorsett, S. E., Metzger, M. R., Sahu, K. C., Petro, L., Livio, M., ... Smette, A. (1999). Hubble Space Telescope and Palomar imaging of GRB 990123: Implications for the nature of gamma-ray bursts and their hosts. Astrophysical Journal, 519(1 PART 2).

    Hubble Space Telescope and Palomar imaging of GRB 990123 : Implications for the nature of gamma-ray bursts and their hosts. / Fruchter, Andrew S.; Thorsett, S. E.; Metzger, Mark R.; Sahu, Kailash C.; Petro, Larry; Livio, Mario; Ferguson, Henry; Pian, Elena; Hogg, David W.; Galama, Titus; Gull, Theodore R.; Kouveliotou, Chryssa; Macchetto, Duccio; Van Paradijs, Jan; Pedersen, Holger; Smette, Alain.

    In: Astrophysical Journal, Vol. 519, No. 1 PART 2, 01.07.1999.

    Research output: Contribution to journalArticle

    Fruchter, AS, Thorsett, SE, Metzger, MR, Sahu, KC, Petro, L, Livio, M, Ferguson, H, Pian, E, Hogg, DW, Galama, T, Gull, TR, Kouveliotou, C, Macchetto, D, Van Paradijs, J, Pedersen, H & Smette, A 1999, 'Hubble Space Telescope and Palomar imaging of GRB 990123: Implications for the nature of gamma-ray bursts and their hosts', Astrophysical Journal, vol. 519, no. 1 PART 2.
    Fruchter AS, Thorsett SE, Metzger MR, Sahu KC, Petro L, Livio M et al. Hubble Space Telescope and Palomar imaging of GRB 990123: Implications for the nature of gamma-ray bursts and their hosts. Astrophysical Journal. 1999 Jul 1;519(1 PART 2).
    Fruchter, Andrew S. ; Thorsett, S. E. ; Metzger, Mark R. ; Sahu, Kailash C. ; Petro, Larry ; Livio, Mario ; Ferguson, Henry ; Pian, Elena ; Hogg, David W. ; Galama, Titus ; Gull, Theodore R. ; Kouveliotou, Chryssa ; Macchetto, Duccio ; Van Paradijs, Jan ; Pedersen, Holger ; Smette, Alain. / Hubble Space Telescope and Palomar imaging of GRB 990123 : Implications for the nature of gamma-ray bursts and their hosts. In: Astrophysical Journal. 1999 ; Vol. 519, No. 1 PART 2.
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    abstract = "We report on Hubble Space Telescope and Palomar optical images of the field of GRB 990123, obtained in 1999 February 8 and 9. We find that the optical transient (OT) associated with GRB 990123 is located on an irregular galaxy, with a magnitude of V = 24.20 ± 0.15. The strong metal absorption lines seen in the spectrum of the OT, along with the low probability of a chance superposition, lead us to conclude that this galaxy is the host of the gamma-ray burst (GRB). The OT is projected within the ∼1″ visible stellar field of the host, nearer the edge than the center. We cannot, on this basis, rule out the galactic nucleus as the site of the GRB, since the unusual morphology of the host may be the result of an ongoing galactic merger, but our demonstration that this host galaxy has extremely blue optical-to-infrared colors more strongly supports an association between GRBs and star formation. We find that the OT magnitude in 1999 February 9.05, V = 25.45 ± 0.15, is about 1.5 mag fainter than expected from the extrapolation of the decay rate found in earlier observations. A detailed analysis of the OT light curve suggests that its fading has gone through three distinct phases: an early, rapid decline (fv ∝ t-1.6 for t < 0.1 days); a slower, intermediate decline power-law decay (fv ∝ t-1.1 for 0.1 < t < 2 days); and then a more rapid decay (at least as steep as fv oc t-1.8 for t > 2 days). The break to a steeper slope at late times may provide evidence that the optical emission from this GRB was highly beamed.",
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    KW - Stars: formation

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