Search Publications
Notes on the convection in the ATLAS9 model atmospheres.
Castelli, F.; Gratton, R. G.; Kurucz, R. L.
The mixing-length theory for the convection, as it is used in the ATLAS9 code (Kurucz, 1993a), is summarized and discussed. We investigated the effect of the modification called ``approximate overshooting'' on the model structure of the Sun and of stars with T_eff_ included between 4000K and 8500K, logg included between 2.5 and 4.5, and metallicit…
Reddening and Star Formation in Starburst Galaxies
Calzetti, Daniela
The reddening properties and the star formation history of a sample of 19 starburst galaxies are investigated using multiwavelength spectroscopy and infrared broad band photometry. New photometric data in the J, H, and K bands of the central starburst regions are supplemented with previously published spectra, covering the wavelength range 0.12-2.…
Cross-correlation characteristics of OB stars from IUE spectroscopy
Howarth, Ian D.; Prinja, Raman K.; Siebert, Kaj W. +1 more
We present a catalogue of homogeneous measures of the linewidth parameter, v_esin i, for 373 O-type stars and early B supergiants (including the separate components of 25 binary and three triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a `template' spectrum of tauSco. We also tabulate terminal v…
LBDS 53W091: An Old, Red Galaxy at z = 1.552
Windhorst, Rogier; Dey, Arjun; Spinrad, Hyron +4 more
The weak radio source LBDS 53W091 is associated with a very faint (R ~ 24.5) red (R - K ~ 5.8) galaxy. Long spectroscopic integrations with the W. M. Keck telescope have provided an absorption-line redshift, z = 1.552 +/- 0.002. The galaxy has a rest frame ultraviolet spectrum very similar to that of an F6 V star, and a single-burst old stellar po…
Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars.
Eriksson, K.; Gustafsson, B.; Asplund, M. +1 more
We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum opacities have been used together with realistic line absorption data for atomic and molecular …
Synthetic Spectra of Hydrodynamic Models of Type Ia Supernovae
Baron, E.; Branch, David; Hauschildt, Peter H. +2 more
We present detailed non-LTE synthetic spectra of hydrodynamic supernovae (SNe) Ia models. We make no assumptions about the form of the spectrum at the inner boundary. We calculate both Chandrasekhar-mass deflagration models and sub-Chandrasekhar ``helium detonators.'' Gamma-ray deposition is handled in a simple, accurate manner. We have parameteri…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. IX. Ultraviolet Observations of Fairall 9
Shull, J. M.; Malkan, M. A.; Martin, P. G. +53 more
An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with the International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). While the results of this campaign are more ambiguous than those of…
Optical-IUE observations of the gamma-ray loud BL Lacertae object S5 0716+714: data and interpretation.
Maraschi, L.; Ghisellini, G.; Pian, E. +14 more
We monitored the BL Lac object S5 0716+714 in the optical band during the period November 1994 - April 1995, which includes the time of a γ-ray observation by the Energetic Gamma Ray Experiment Telescope (EGRET) on February 14-28, 1995. The light curves in the R and B bands show fast fluctuations superimposed on longer timescale variations. The co…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XI. Intensive Monitoring of the Ultraviolet Spectrum of NGC 7469
Shull, J. M.; Malkan, M. A.; Nandra, K. +54 more
From 1996 June 10 to July 29, the International Ultraviolet Explorer monitored the Seyfert 1 galaxy NGC 7469 continuously in an attempt to measure time delays between the continuum and emission-line fluxes. From the time delays, one can estimate the size of the region dominating the production of the UV emission lines in this source. We find the s…
Patchy intergalactic He II absorption in HE 2347-4342. II. The possible discovery of the epoch of He-reionization
Reimers, D.; Wamsteker, W.; Rodriguez-Pascual, P. +3 more
We report on observations of redshifted Heii303.8 Angstroms absorption in the high-redshift QSO HE2347-4342 (z=2.885, V=16.1) with the Goddard High Resolution Spectrograph on board HST in its low resolution mode (bigtriangleup lambda = 0.7 Angstroms). With f_λ=3.6\ 10(-15) ergcm(-2) s(-1) Angstroms(-1) at the expected position of Heii304 Angstroms…