Stephen Holland

Publications (7)18.07 Total impact

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  Available from: Frederic Courbin

  Article: The Late Afterglow and Host Galaxy of GRB 990712

  Jens Hjorth, Stephen Holland, Frederic Courbin, Arnon Dar, Lisbeth F. Olsen, and Marco Scodeggio
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  ABSTRACT: We present deep Hubble Space Telescope (HST) imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48-123 days after the burst occurred. The magnitudes of the host (R = 21.9, V = 22.5) and optical afterglow (R = 25.4, V = 25.8, 47.7 days after the burst) favor a scenario in which the optical light follows a pure power-law decay with an index of α ~ -1.0. We find no evidence for a contribution from a supernova like SN 1998bw. This suggests that either there are multiple classes of long-duration gamma-ray bursts or that the peak luminosity of the supernova was more than 1.5 mag fainter than SN 1998bw. The HST images and EFOSC2 spectra indicate that the gamma-ray burst was located in a bright, extended feature (possibly a star-forming region) 1.4 kpc from the nucleus of a 0.2L galaxy at z = 0.434, possibly a Seyfert 2 galaxy. The late-time afterglow and host galaxy of GRB 990712 bear some resemblance to those of GRB 970508.
  The Astrophysical Journal 12/2008; 534(2):L147. · 6.02 Impact Factor
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  Available from: David Bersier

  Article: Infrared and Optical Observations of GRB 030115 and its Extremely Red Host Galaxy: Implications for Dark Bursts

  Andrew Levan, Andrew Fruchter, James Rhoads, Bahram Mobasher, Nial Tanvir, Javier Gorosabel, Evert Rol, Chryssa Kouveliotou, Ian Dell'Antonio, Michael Merrill, [......], Johan Fynbo, Peter Garnavich, Stephen Holland, Jens Hjorth, Peter Nugent, Elena Pian, Alain Smette, Bjarne Thomsen, Stephen E. Thorsett, and Ralph Wijers
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  ABSTRACT: We present near-infrared (NIR) and optical observations of the afterglow of GRB 030115. Discovered in an infrared search at Kitt Peak 5 hr after the burst trigger, this afterglow is the faintest ever observed in the R band at such an early epoch and exhibits very red colors, with R - K ≈ 6. The optical magnitude of the afterglow of GRB 030115 is fainter than many upper limits for other bursts, suggesting that without early NIR observations it would have been classified as a "dark" burst. Both the color and optical magnitude of the afterglow are likely due to dust extinction at moderate redshift z > 2 and indicate that at least some optical afterglows are very faint due to dust along the line of sight. Multicolor Hubble Space Telescope observations were also taken of the host galaxy and the surrounding field. Photometric redshifts imply that the host and a substantial number of faint galaxies in the field are at z ~ 2.5. The overdensity of galaxies is sufficiently great that GRB 030115 may have occurred in a rich high-redshift cluster. The host galaxy shows extremely red colors (R - K = 5) and is the first GRB host to be classified as an extremely red object (ERO). Some of the galaxies surrounding the host also show very red colors, while the majority of the cluster are much bluer, indicating ongoing unobscured star formation. As it is thought that much of high-redshift star formation occurs in highly obscured environments, it may well be that GRB 030115 represents a transition object, between the relatively unobscured afterglows seen to date and a population of objects that are very heavily extinguished, even in the NIR.
  The Astrophysical Journal 12/2008; 647(1):471. · 6.02 Impact Factor
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  Available from: J. P. U. Fynbo

  Article: GRB 020410: A Gamma-Ray Burst Afterglow Discovered by Its Supernova Light

  Andrew Levan, Peter Nugent, Andrew Fruchter, Ingunn Burud, David Branch, James Rhoads, Alberto Castro-Tirado, Javier Gorosabel, José María Castro Cerón, Stephen E. Thorsett, [......], Johan Fynbo, Peter Garnavich, Stephen Holland, Jens Hjorth, Palle Møller, Elena Pian, Nial Tanvir, Mihail Ulanov, Ralph Wijers, and Stan Woosley
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  ABSTRACT: We present the discovery and monitoring of the optical transient (OT) associated with GRB 020410. The fading OT was found by Hubble Space Telescope (HST) observations taken 28 and 65 days after burst at a position consistent with the X-ray afterglow, making this the first time that the optical afterglow of a gamma-ray burst (GRB) has been discovered by an orbiting observatory. Subsequent reexamination of early ground-based observations revealed that a faint OT was present 6 hr after burst, confirming the source association with GRB 020410. A deep nondetection after one week requires that the OT rebrightened between day 7 and day 28, and further late-time HST data taken approximately 100 days after burst imply that it is very red (Fν ν-2.7). We compare both the flux and color of the excess with supernova models and show that the data are best explained by the presence of a Type Ib/c supernova at a redshift z ≈ 0.5, which occurred roughly coincident with the day of the GRB.
  The Astrophysical Journal 12/2008; 624(2):880. · 6.02 Impact Factor
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  Available from: arxiv.org

  Article: 23 High Redshift Supernovae from the IfA Deep Survey: Doubling the SN Sample at z>0.7

  Brian J. Barris, John Tonry, Stephane Blondin, Peter Challis, Ryan Chornock, Alejandro Clocchiatti, Alexei Filippenko, Peter Garnavich, Stephen Holland, Saurabh Jha, [......], Nicholas Suntzeff, H. Aussel, K. C. Chambers, M. S. Connelley, D. Donovan, J. P. Henry, N. Kaiser, M. C. Liu, E. L. Martin, R. J. Wainscoat
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  ABSTRACT: We present photometric and spectroscopic observations of 23 high redshift supernovae spanning a range of z=0.34-1.03, 9 of which are unambiguously classified as Type Ia. These supernovae were discovered during the IfA Deep Survey, which began in September 2001 and observed a total of 2.5 square degrees to a depth of approximately m=25-26 in RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional observations continuing until April 2002. We give a brief description of the survey motivations, observational strategy, and reduction process. This sample of 23 high-redshift supernovae includes 15 at z>0.7, doubling the published number of objects at these redshifts, and indicates that the evidence for acceleration of the universe is not due to a systematic effect proportional to redshift. In combination with the recent compilation of Tonry et al. (2003), we calculate cosmological parameter density contours which are consistent with the flat universe indicated by the CMB (Spergel et al. 2003). Adopting the constraint that Omega_total = 1.0, we obtain best-fit values of (Omega_m, Omega_Lambda)=(0.33, 0.67) using 22 SNe from this survey augmented by the literature compilation. We show that using the empty-beam model for gravitational lensing does not eliminate the need for Omega_Lambda > 0. Experience from this survey indicates great potential for similar large-scale surveys while also revealing the limitations of performing surveys for z>1 SNe from the ground. Comment: 67 pages, 12 figures, 12 tables, accepted for publication in the Astrophysical Journal
  10/2003;
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  Available from: Andreas O. Jaunsen

  Article: Optical observations of the dark Gamma-Ray Burst GRB 000210

  Javier Gorosabel, Jens Hjorth, Holger Pedersen, Brian L. Jensen, Lisbeth F. Olsen, Lise Christensen, Evencio Mediavilla, Rafael Barrena, Johan U. Fynbo, Michael I. Andersen, Andreas O. Jaunsen, Stephen Holland, Niels Lund
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  ABSTRACT: We report on optical observations on GRB 000210 obtained with the 2.56-m Nordic Optical Telescope and the 1.54-m Danish Telescope starting 12.4 hours after the gamma-ray event. The content of the X-ray error box determined by the Chandra satellite is discussed. Comment: 3 pages, 1 postscript figure. To appear in the proceedings of the October 2000 Rome Workshop on ``Gamma-Ray Bursts in the Afterglow Era''
  09/2001;
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  Available from: arxiv.org

  Article: Star-Forming Regions near GRB 990123

  Stephen Holland, Jens Hjorth
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  ABSTRACT: We reduced the Hubble Space Telescope Space Telescope Imaging Spectrograph images of the gamma-ray burst GRB 990123 that were obtained on 8-9 February 1999 and find V_0 = 25.36 +/- 0.10, which corresponds to a flux of 0.258 +/- 0.023 micro-Jy for the optical transient 16.644 days after the burst's peak. The probable host galaxy has V_0 = 24.25 +/- 0.07 (= 0.716 +/- 0.046 micro-Jy) and the optical transient is located 0.65 arcseconds (= 5.5 kpc) south of the galaxy's nucleus. We fit and subtracted a scaled point-spread function to the optical transient and found evidence for three bright knots situated within 0.5 arcseconds (= 4.3 kpc) of the optical transient. Each knot has V_0 ~ 28.1 +/- 0.3, a rest-frame V-band luminosity of between approximately 5e8 L_Sun and 8e8 L_Sun, and a star-formation rate of at least 0.1-0.2 Solar masses per year. The knots are centrally concentrated with full-width at half-maximum of approximately 0.17 arcseconds (= 1.5 kpc). Their sizes and luminosities are consistent with their being star-forming regions. The optical transient is located 0.15 arcseconds (= 1.3 kpc) southeast of the centre of one of these knots.
  03/1999;
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  Available from: arxiv.org

  Article: Stellar Populations Beyond the Local Group with the NGST

  Stephen Holland, Bjarne Thomsen
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  ABSTRACT: We present simulated J- and K-band observations of stars in the Virgo and Coma clusters of galaxies using the proposed Next Generation Space Telescope with a Near-Infrared Camera, and discuss some of the science results that might be obtained. The proposed telescope will be able to resolve the brightest ~3 magnitudes of the red giant branch in the halos of galaxies in the Virgo Cluster and may be able to resolve stars at the tip of the red giant branch in the Coma Cluster. The simulations show that the background light is more important than the size of the aperture in determining the limiting magnitude of the observations. Therefore, we recomment that the Next Generation Space Telescope be placed in a 1 x 3 a.u. orbit to minimize background light.
  07/1998;