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Deep Hubble Space Telescope Imaging of IC 1613. II. The Star Formation History
Dolphin, Andrew E.; Skillman, Evan D.; Cole, Andrew A. +5 more
We have taken deep images of an outlying field in the Local Group dwarf irregular galaxy IC 1613 with the WFPC2 aboard the Hubble Space Telescope in the standard broadband F555W (V, 8 orbits) and F814W (I, 16 orbits) filters. The photometry reaches to V=27.7 (MV=+3.4) and I=27.1 (MI=+2.8) at the 50% completeness level, the de…
Fe II/Mg II Emission-Line Ratio in High-Redshift Quasars
Vestergaard, M.; Dietrich, M.; Appenzeller, I. +1 more
We present results of the analysis of near-infrared spectroscopic observations of six high-redshift quasars (z>~4), emphasizing the measurement of the ultraviolet Fe II/Mg II emission-line strength to estimate the beginning of intense star formation in the early universe. To investigate the evolution of the Fe II/Mg II ratio over a wider range …
Remote infrared observations of parent volatiles in comets: A window on the early solar system
Dello Russo, N.; Mumma, M. J.; DiSanti, M. A. +3 more
Organic volatiles and water in Oort Cloud comets were investigated at infrared wavelengths. The detected species include H 2O, CO, CH 3OH, CH 4, C 2H 2, C 2H 6, OCS, HCN, NH 3, and H 2CO. Several daughter fragments (CN, OH, NH 2, etc.) are…
Blue Straggler Stars: A Direct Comparison of Star Counts and Population Ratios in Six Galactic Globular Clusters
Ferraro, Francesco R.; Sills, Alison; Paltrinieri, Barbara +2 more
The central regions of six Galactic globular clusters (GGCs) (M3, M80, M10, M13, M92, and NGC 288) have been imaged using HST-WFPC2 and the ultraviolet filters (F255W and F336W). The selected sample covers a large range in both central density (logρ0) and metallicity ([Fe/H]). In this paper, we present a direct cluster-to-cluster compar…
The INTEGRAL Burst Alert System
Götz, D.; Mereghetti, S.; Pedersen, H. +2 more
We describe the INTEGRAL Burst Alert System (IBAS): the automatic software for the rapid distribution of the coordinates of the Gamma-Ray Bursts detected by INTEGRAL. IBAS is implemented as a ground based system, working on the near-real time telemetry stream. During the first six months of operations, six GRB have been detected in the field of vi…
Continuous magnetic reconnection at Earth's magnetopause
Fuselier, S. A.; Mende, S. B.; Frey, H. U. +1 more
The most important process that allows solar-wind plasma to cross the magnetopause and enter Earth's magnetosphere is the merging between solar-wind and terrestrial magnetic fields of opposite sense-magnetic reconnection. It is at present not known whether reconnection can happen in a continuous fashion or whether it is always intermittent. Solar …
High-Resolution Spectroscopy of FU Orionis Stars
Herbig, G. H.; Duemmler, R.; Petrov, P. P.
High-resolution spectroscopy was obtained of the FU orionis stars FU Ori and V1057 Cyg between 1995 and 2002 with the SOFIN spectrograph at the Nordic Optical Telescope and with HIRES at Keck I. During these years FU Ori remained about 1 mag (in B) below its 1938-39 maximum brightness, but V1057 Cyg (B~10.5 at peak in 1970-1971) faded from about 1…
Gamma-ray emission from Wolf-Rayet binaries
Romero, G. E.; Benaglia, P.
In the colliding wind region of early-type binaries, electrons can be accelerated up to relativistic energies displaying power-law spectra, as demonstrated by the detection of non-thermal radio emission from several WR+OB systems. The particle acceleration region, located between the stars, is exposed to strong photon fields in such a way that inv…
Discovery of Early Optical Emission from GRB 021211
Peterson, B. A.; Price, P. A.; Harrison, F. A. +11 more
We report our discovery and early-time optical, near-infrared, and radio wavelength follow-up observations of the afterglow of the gamma-ray burst GRB 021211. Our optical observations, beginning 21 minutes after the burst trigger, demonstrate that the early afterglow of this burst is roughly 3 mag fainter than the afterglow of GRB 990123 at simila…
The Host Galaxies of Narrow-Line Seyfert 1 Galaxies: Evidence for Bar-Driven Fueling
Kraemer, S. B.; Crenshaw, D. M.; Gabel, J. R.
We present a study of the host galaxy morphologies of narrow- and broad-line Seyfert 1 galaxies (NLS1's and BLS1's) based on broadband optical images from the Hubble Space Telescope archives. We find that large-scale stellar bars, starting at ~1 kpc from the nucleus, are much more common in NLS1's than BLS1's. Furthermore, the fraction of NLS1 spi…