Search Publications
The absolute magnitude of the early type MK standards from HIPPARCOS parallaxes
Gomez, A. E.; Jaschek, C.
We analyse the standards of the MK system with the help of Hipparcos parallaxes, using only stars for which the error of the absolute magnitude is <= 0.3 mag. We find that the main sequence is a wide band and that, although in general giants and dwarfs have different absolute magnitudes, the separation between luminosity classes V and III is no…
On the Association of Gamma-Ray Bursts with Supernovae
Galama, T. J.; Hurley, K.; Kouveliotou, C. +7 more
The recent discovery of a supernova (SN 1998bw) seemingly associated with GRB 980425 adds a new twist to the decades-old debate over the origin of gamma-ray bursts. To investigate the possibility that some (or all) bursts are associated with supernovae, we performed a systematic search for temporal/angular correlations using catalogs of BATSE and …
High-Resolution Near-Infrared Imaging of the Orion 114-426 Silhouette Disk
Schneider, Glenn; Rieke, Marcia; Bally, John +6 more
We present the first high-resolution near-infrared images of the edge-on silhouette circumstellar disk, Orion 114-426, made using NICMOS on the Hubble Space Telescope. Images taken against the bright nebular background of the ionized hydrogen Paα line at 1.87 µm show the major axis of the disk to be approximately 20% smaller than at 0.6 &mic…
The shock structure in the protoplanetary nebula M1-92: imaging of atomic and H_2 line emission
Sahai, R.; Alcolea, J.; Bujarrabal, V. +2 more
We present HST imaging of continuum (5500 Angstroms) and atomic line (Hα , [OI] 6300 Angstroms, [SII] 6717 and 6731 Angstroms, and [OIII] 5007 Angstroms) emissions in the protoplanetary nebula M 1-92. Ground based imaging of 2$() µm continuum and H_2 ro-vibrational (S(1) v=3D1-0 and v=3D2-1 lines) emission has been also performed. The 5500 A…
The Coronae of Moderate-Mass Giants in the Hertzsprung Gap and the Clump
Ayres, Thomas R.; Brown, Alexander; Wood, Brian E. +3 more
We have used the Röentgensatellit (ROSAT), the Extreme Ultraviolet Explorer (EUVE), and the Hubble Space Telescope (HST) to measure X-ray and ultraviolet emissions of moderate-mass (~2-3 M⊙) giants in the Hertzsprung gap (spectral types early F to mid-G) and the post-helium flash ``clump'' (~G8-K0). Our motivation was to document the ev…
Non-parametric reconstruction of cluster mass distribution from strong lensing: modelling Abell 370.
Saha, Prasenjit; Williams, Liliya L. R.; Abdelsalam, Hanadi M.
The authors describe a new non-parametric technique for reconstructing the mass distribution in galaxy clusters with strong lensing, i.e. from multiple images of background galaxies. The observed positions and redshifts of the images are considered as rigid constraints, and through the lens (ray-trace) equation they provide us with linear constrai…
Birth and early evolution of a planetary nebula
Bobrowsky, Matthew; Sahu, Kailash C.; Parthasarathy, M. +1 more
The final expulsion of gas by a star as it forms a planetary nebula - the ionized shell of gas often observed surrounding a young white dwarf - is one of the most poorly understood stages of stellar evolution,. Such nebulae form extremely rapidly (about 100 years for the ionization) and so the formation process is inherently difficult to observe. …
Ejected Nebulae as Probes of the Evolution of Massive Stars in the Large Magellanic Cloud
Smith, Linda J.; Leitherer, Claus; Clampin, Mark +3 more
We present new Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) and ground-based long-slit spectroscopic observations of the nebulae around the two LMC luminous blue variables (LBVs) R127 (=HDE 269858) and R143 (=HDE 269929) and the Ofpe/WN9 star S119 (=HDE 269687). We have used the ground-based long-slit spectra to investigate the kin…
New Constraints on the Luminosity Evolution of Spheroidal Galaxies in Distant Clusters
Smail, I.; Poggianti, B. M.; Aragón-Salamanca, A. +6 more
We investigate various probes of luminosity evolution in the rich cluster environment, concentrating in particular on the spheroidal (E/S0) galaxies, using a newly constructed catalog of morphologically classified Hubble Space Telescope (HST) images of galaxies observed in the cores of 13 clusters with redshifts 0.17 <= z <= 0.56. An importa…
Nonparametric Reconstruction of Abell 2218 from Combined Weak and Strong Lensing
Saha, Prasenjit; Williams, Liliya L. R.; Abdelsalam, Hanadi M.
We apply a new nonparametric technique to reconstruct, with uncertainties, the projected mass distribution of the inner region of Abell 2218 using combined strong and weak lensing constraints from multiple-image systems and arclets with known redshifts. The reconstructed mass map broadly resembles previous, less detailed parametric models, but whe…