Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment

N. Mirabal; J. P. Halpern; S. R. Kulkarni; S. Castro; J. S. Bloom; S. G. Djorgovski; T. J. Galama; F. A. Harrison; D. A. Frail; P. A. Price; D. E. Reichart; H. Ebeling; A. Bunker; S. Dawson; A. Dey; H. Spinrad; D. Stern

doi:10.1086/342619

Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment

N. Mirabal^*, J. P. Halpern, S. R. Kulkarni, S. Castro, J. S. Bloom, S. G. Djorgovski, T. J. Galama, F. A. Harrison, D. A. Frail, P. A. Price, D. E. Reichart, H. Ebeling, A. Bunker, S. Dawson, A. Dey, H. Spinrad, D. Stern

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

We present sequential optical spectra of the afterglow of GRB 010222 obtained 1 day apart using the Low-Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck Telescopes. Three low-ionization absorption systems are spectroscopically identified at z ₁ = 1.47688, z₂ = 1.15628, and z₃ = 0.92747. The higher resolution ESI spectrum reveals two distinct components in the highest redshift system at z_1a = 1.47590 and z_1b = 1.47688. We interpret the z_1b = 1.47688 system as an absorption feature of the disk of the host galaxy of GRB 010222. The best-fitted power-law optical continuum and [Zn/Cr] ratio imply low dust content or a local gray dust component near the burst site. In addition, we do not detect strong signatures of vibrationally excited states of H₂. If the gamma-ray burst took place in a superbubble or young stellar cluster, there are no outstanding signatures of an ionized absorber either. Analysis of the spectral time dependence at low resolution shows no significant evidence for absorption-line variability. This lack of variability is confronted with time-dependent photoionization simulations designed to apply the observed flux from GRB 010222 to a variety of assumed atomic gas densities and cloud radii. The absence of time dependence in the absorption lines implies that high-density environments are disfavored. In particular, if the GRB environment was dust free, its density was unlikely to exceed n_{H I} = 10² cm ^-3. If depletion of metals onto dust is similar to Galactic values or less than solar abundances are present, then n_{H I} ≥ 2 × 10⁴ cm^-3 is probably ruled out in the immediate vicinity of the burst.

Original language	English
Pages (from-to)	818-832
Number of pages	15
Journal	Astrophysical Journal
Volume	578
Issue number	2 I
DOIs	https://doi.org/10.1086/342619
Publication status	Published - 20 Oct 2002
Externally published	Yes

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Mirabal, N., Halpern, J. P., Kulkarni, S. R., Castro, S., Bloom, J. S., Djorgovski, S. G., Galama, T. J., Harrison, F. A., Frail, D. A., Price, P. A., Reichart, D. E., Ebeling, H., Bunker, A., Dawson, S., Dey, A., Spinrad, H., & Stern, D. (2002). Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment. Astrophysical Journal, 578(2 I), 818-832. https://doi.org/10.1086/342619

@article{a6f70ba89a9d4cc784e52de5ac27d124,

title = "Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment",

abstract = "We present sequential optical spectra of the afterglow of GRB 010222 obtained 1 day apart using the Low-Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck Telescopes. Three low-ionization absorption systems are spectroscopically identified at z 1 = 1.47688, z2 = 1.15628, and z3 = 0.92747. The higher resolution ESI spectrum reveals two distinct components in the highest redshift system at z1a = 1.47590 and z1b = 1.47688. We interpret the z1b = 1.47688 system as an absorption feature of the disk of the host galaxy of GRB 010222. The best-fitted power-law optical continuum and [Zn/Cr] ratio imply low dust content or a local gray dust component near the burst site. In addition, we do not detect strong signatures of vibrationally excited states of H2. If the gamma-ray burst took place in a superbubble or young stellar cluster, there are no outstanding signatures of an ionized absorber either. Analysis of the spectral time dependence at low resolution shows no significant evidence for absorption-line variability. This lack of variability is confronted with time-dependent photoionization simulations designed to apply the observed flux from GRB 010222 to a variety of assumed atomic gas densities and cloud radii. The absence of time dependence in the absorption lines implies that high-density environments are disfavored. In particular, if the GRB environment was dust free, its density was unlikely to exceed nH I = 102 cm -3. If depletion of metals onto dust is similar to Galactic values or less than solar abundances are present, then nH I ≥ 2 × 104 cm-3 is probably ruled out in the immediate vicinity of the burst.",

keywords = "Cosmology: observations, Galaxies: ISM, Galaxies: abundances, Galaxies: star clusters, Gamma rays: bursts",

author = "N. Mirabal and Halpern, {J. P.} and Kulkarni, {S. R.} and S. Castro and Bloom, {J. S.} and Djorgovski, {S. G.} and Galama, {T. J.} and Harrison, {F. A.} and Frail, {D. A.} and Price, {P. A.} and Reichart, {D. E.} and H. Ebeling and A. Bunker and S. Dawson and A. Dey and H. Spinrad and D. Stern",

year = "2002",

month = oct,

day = "20",

doi = "10.1086/342619",

language = "English",

volume = "578",

pages = "818--832",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2 I",

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Mirabal, N, Halpern, JP, Kulkarni, SR, Castro, S, Bloom, JS, Djorgovski, SG, Galama, TJ, Harrison, FA, Frail, DA, Price, PA, Reichart, DE, Ebeling, H, Bunker, A, Dawson, S, Dey, A, Spinrad, H & Stern, D 2002, 'Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment', Astrophysical Journal, vol. 578, no. 2 I, pp. 818-832. https://doi.org/10.1086/342619

TY - JOUR

T1 - Time-dependent optical spectroscopy of GRB 010222

T2 - Clues to the gamma-ray burst environment

AU - Mirabal, N.

AU - Halpern, J. P.

AU - Kulkarni, S. R.

AU - Castro, S.

AU - Bloom, J. S.

AU - Djorgovski, S. G.

AU - Galama, T. J.

AU - Harrison, F. A.

AU - Frail, D. A.

AU - Price, P. A.

AU - Reichart, D. E.

AU - Ebeling, H.

AU - Bunker, A.

AU - Dawson, S.

AU - Dey, A.

AU - Spinrad, H.

AU - Stern, D.

PY - 2002/10/20

Y1 - 2002/10/20

N2 - We present sequential optical spectra of the afterglow of GRB 010222 obtained 1 day apart using the Low-Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck Telescopes. Three low-ionization absorption systems are spectroscopically identified at z 1 = 1.47688, z2 = 1.15628, and z3 = 0.92747. The higher resolution ESI spectrum reveals two distinct components in the highest redshift system at z1a = 1.47590 and z1b = 1.47688. We interpret the z1b = 1.47688 system as an absorption feature of the disk of the host galaxy of GRB 010222. The best-fitted power-law optical continuum and [Zn/Cr] ratio imply low dust content or a local gray dust component near the burst site. In addition, we do not detect strong signatures of vibrationally excited states of H2. If the gamma-ray burst took place in a superbubble or young stellar cluster, there are no outstanding signatures of an ionized absorber either. Analysis of the spectral time dependence at low resolution shows no significant evidence for absorption-line variability. This lack of variability is confronted with time-dependent photoionization simulations designed to apply the observed flux from GRB 010222 to a variety of assumed atomic gas densities and cloud radii. The absence of time dependence in the absorption lines implies that high-density environments are disfavored. In particular, if the GRB environment was dust free, its density was unlikely to exceed nH I = 102 cm -3. If depletion of metals onto dust is similar to Galactic values or less than solar abundances are present, then nH I ≥ 2 × 104 cm-3 is probably ruled out in the immediate vicinity of the burst.

AB - We present sequential optical spectra of the afterglow of GRB 010222 obtained 1 day apart using the Low-Resolution Imaging Spectrometer (LRIS) and the Echellette Spectrograph and Imager (ESI) on the Keck Telescopes. Three low-ionization absorption systems are spectroscopically identified at z 1 = 1.47688, z2 = 1.15628, and z3 = 0.92747. The higher resolution ESI spectrum reveals two distinct components in the highest redshift system at z1a = 1.47590 and z1b = 1.47688. We interpret the z1b = 1.47688 system as an absorption feature of the disk of the host galaxy of GRB 010222. The best-fitted power-law optical continuum and [Zn/Cr] ratio imply low dust content or a local gray dust component near the burst site. In addition, we do not detect strong signatures of vibrationally excited states of H2. If the gamma-ray burst took place in a superbubble or young stellar cluster, there are no outstanding signatures of an ionized absorber either. Analysis of the spectral time dependence at low resolution shows no significant evidence for absorption-line variability. This lack of variability is confronted with time-dependent photoionization simulations designed to apply the observed flux from GRB 010222 to a variety of assumed atomic gas densities and cloud radii. The absence of time dependence in the absorption lines implies that high-density environments are disfavored. In particular, if the GRB environment was dust free, its density was unlikely to exceed nH I = 102 cm -3. If depletion of metals onto dust is similar to Galactic values or less than solar abundances are present, then nH I ≥ 2 × 104 cm-3 is probably ruled out in the immediate vicinity of the burst.

KW - Cosmology: observations

KW - Galaxies: ISM

KW - Galaxies: abundances

KW - Galaxies: star clusters

KW - Gamma rays: bursts

UR - http://www.scopus.com/inward/record.url?scp=0012087418&partnerID=8YFLogxK

U2 - 10.1086/342619

DO - 10.1086/342619

M3 - Article

SN - 0004-637X

VL - 578

SP - 818

EP - 832

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2 I

ER -

Time-dependent optical spectroscopy of GRB 010222: Clues to the gamma-ray burst environment

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