GRB 090426: The Environment of a Rest-Frame 0.35-second Gamma-Ray Burst at Redshift z=2.609 (2009)
Levesque, Emily M., Bloom, Joshua S., Butler, Nathaniel R., Perley, Daniel A., Cenko, S. Bradley, Prochaska, J. Xavier, ...
We present the discovery of an absorption-line redshift of z = 2.609 for GRB 090426, establishing the first firm lower limit to a redshift for a gamma-ray burst with an observed duration of 90%...
Tejos, Nicolas, Lopez, Sebastian, Prochaska, J. Xavier, Bloom, Joshua S., Chen, Hsiao-Wen, Dessauges-Zavadsky, Miroslava, ...
We revisit echelle spectra (spectral resolution R ~ 40000) of 8 Gamma-Ray Burst afterglows to obtain the incidence (dN/dz) of weak intervening Mg II systems at a mean redshift of = 1.5. We show that...
Ellison, Sara L., Lopez, Sebastian
The Complete Optical and Radio Absorption Line System (CORALS) survey has previously been used to demonstrate that the number density, gas and metals content of z>1.6 damped Lyman alpha systems is...
The Galactic Deuterium Abundance and Dust Depletion: Insights From an Expanded Ti/H Sample (2007)
Ellison, Sara L., Prochaska, Jason X., Lopez, Sebastian
The primordial abundance of deuterium (D/H) yields a measure of the density of baryons in the universe and is an important complement to determinations from cosmic microwave background (CMB)...
On the Incidence of C IV Absorbers Along the Sightlines to Gamma-Ray Bursts (2007)
Tejos, Nicolas, Lopez, Sebastian, Prochaska, Jason X., Chen, Hsiao-Wen, Dessauges-Zavadsky, Miroslava
We report on the statistics of strong (W_r > 0.15 A) C IV absorbers at z=1.5-3.5 toward high-redshift gamma-ray bursts (GRBs). In contrast with a recent survey for strong Mg II absorption systems at...
High-Precision Measurements of Delta alpha/alpha from QSO Absorption Spectra (2006)
Levshakov, Sergei A., Molaro, Paolo, Lopez, Sebastian, D'Odorico, Sandro, Centurion, Miriam, Bonifacio, Piercarlo, ...
Precise radial velocity measurements (delta v/c ~ 10^{-7}) of FeII lines in damped Ly-alpha systems from very high quality VLT/UVES spectra of quasars HE0515-4414 and Q1101-264 are used to probe...
The source of metals in the high-redshift lyman-_ forest (2006)
The source of metals in the high-redshift lyman-_ forest
The source of metals in the high-redshift lyman- a forest (2006)
El bosque" Ly frecuentemente exhibe líneas de absorción de elementos pesados, pero la fuente del enriquecimiento metálico aún no se entiende a cabalidad. Se presentan inigualables espectros de...
Discovery of a Galaxy Cluster in the Foreground of the Wide-Separation Quasar Pair UM425 (2005)
Green, Paul J., Infante, Leopoldo, Lopez, Sebastian, Aldcroft, Thomas L., Winn, Josh N.
We report the discovery of a cluster of galaxies in the field of UM425, a pair of quasars separated by 6.5arcsec. Based on this finding, we revisit the long-standing question of whether this quasar...
On the Nature of the Heat Source for Damped Lya Systems (2004)
Wolfe, Arthur M., Howk, J. Chris, Gawiser, Eric, Prochaska, Jason X., Lopez, Sebastian
We investigate the heat source of the neutral gas comprising DLAs. Unlike the Lya forest, where the extragalactic background radiation field ionizes and heats the gas, we find that grain...
Ellison, Sara L., Pettini, Max, Churchill, Chris W., Hook, Isobel M., Lopez, Sebastian, Rix, Samantha A., ...
We present a brief overview of the ongoing Complete Optical and Radio Absorption Line System (CORALS) survey. We review the results of our survey for z>2.2 damped Lyman alpha systems (DLAs) and...
Lopez, Sebastian, Ellison, Sara L.
(abridged) Following our previous work on metal abundances of a double damped Ly-alpha system with a line-of-sight separation ~2000 km/s (Ellison & Lopez 2001), we present VLT UVES abundances of 3...
Lopez, Sebastian, Reimers, Dieter, D'Odorico, Sandro, Prochaska, Jason X.
We have obtained a high resolution, high S/N UVES spectrum of the bright QSO HE2243-6031 to analyze the damped Ly-alpha system (DLA) observed at z=2.33. The metallicity of this system is 1/12 solar...
Unusual Metal Abundances in a Pair of Damped Lyman Alpha Systems at z~2 (2001)
Ellison, Sara L., Lopez, Sebastian
We present high resolution spectroscopic observations of two neighbouring damped Lya systems (DLAs) along the same line of sight towards B2314-409. Due to their separation (v ~ 2000 km/s) and the...
Reimers, Dieter, Baade, Robert, Hagen, Hans-Juergen, Lopez, Sebastian
STIS Echelle observations at a resolution of 10 km/s and UVES/VLT spectroscopy at a resolution of 7 km/s of the luminous QSO HE 0515-4414 (z_em = 1.73, B = 15.0) reveal four intervening O VI...
A nearly symmetric double-image gravitational lens (2000)
Winn, Joshua N., Hewitt, Jacqueline N., Patnaik, Alok R., Schechter, Paul L., Schommer, Robert A., Lopez, Sebastian, ...
We report the discovery of a new double-image gravitational lens resulting from our search for lenses in the southern sky. Radio source PMN J2004-1349 is composed of two compact components separated...
HST spectroscopy of the double QSO HS 1216+5032 AB (2000)
Lopez, Sebastian, Hagen, Hans-Juergen, Reimers, Dieter
(Abridged) We report on HST FOS observations of the double QSO HS 1216+5032 AB (z(A)=1.455; z(B)=1.451, and angular separation theta=9 arcsec). An unusual broad-absorption-line (BAL) system is...
First estimate of the time delay in HE 1104-1805 (1998)
Wisotzki, Lutz, Wucknitz, Olaf, Lopez, Sebastian, Soerensen, Anton Norup
We present first results from five years of spectrophotometric monitoring of the bright double QSO and gravitational lens HE 1104-1805. The quasar has varied considerably over this time, while the...
Detection of the lensing galaxy in HE 2149-2745 (1998)
Lopez, Sebastian, Wucknitz, Olaf, Wisotzki, Lutz
We have obtained new BVR-band images of the gravitationally lensed QSO pair HE 2149-2745 A,B (QSO redshift z=2.033; angular separation theta_AB=1.71 arcsec), under 1 arcsec seeing conditions....
Lopez, Sebastian, Reimers, Dieter, Rauch, Michael, Sargent, Wallace L. W., Smette, Alain
Using new HST/FOS, NTT/EMMI, and Keck/HIRES spectra of the gravitationally-lensed double QSO HE 1104-1805 AB (z=2.31, \theta=3.2), and assuming UV photoionization by a metagalactic radiation field,...