Search Publications
1997 December 12 Helical Coronal Mass Ejection. II. Density, Energy Estimates, and Hydrodynamics
Raymond, J. C.; Ciaravella, A.; Peres, G. +2 more
We use Ultraviolet Coronagraph and Spectrometer (UVCS) spectra to investigate the density range of the plasma ejected during the coronal mass ejection (CME) on 1997 December 12. Time-dependent ionization states for several phenomenological models, with the boundary conditions derived from the EUV Imaging Telescope (EIT) and UVCS observations, were…
Plasmoid Formation and Acceleration in the Solar Streamer Belt
Velli, Marco; Einaudi, Giorgio; Chibbaro, Sergio +1 more
The dynamical behavior of a configuration consisting of a plane fluid wake flowing in a current sheet embedded in a plasma sheet that is denser than its surroundings is discussed. This configuration is a useful model for a number of structures of astrophysical interest, such as solar coronal streamers, cometary tails, the Earth's magnetotail and G…
Identification of the Low-Mass X-Ray Binary and Faint X-Ray Sources in NGC 6652
Heinke, C. O.; Grindlay, J. E.; Edmonds, P. D.
We have detected three new X-ray point sources, in addition to the known low-mass X-ray binary (LMXB) X1832-330, in the globular cluster NGC 6652 with a Chandra 1.6 ks HRC-I exposure. Star 49 (MV~4.7), suggested by Deutsch and coworkers as the optical candidate for the LMXB, is identified (<0.3") not with the LMXB, but with another, …
An Upper Mass Limit for the Progenitor of the Type II-P Supernova SN 1999gi
Smartt, Stephen J.; Gilmore, Gerard F.; Trentham, Neil +2 more
Masses and progenitor evolutionary states of Type II supernovae remain almost unconstrained by direct observations. Only one robust observation of a progenitor (SN 1987A) and one plausible observation (SN 1993J) are available. Neither matched theoretical predictions, and in this Letter we report limits on a third progenitor (SN 1999gi). The Hubble…
Observational Constraints on the Abundance and Evolution of ``XCN'' in Interstellar Grain Mantles
Whittet, D. C. B.; Boogert, A. C. A.; Pendleton, Y. J. +3 more
The 4.62 µm ``XCN'' absorption feature, attributed to CN-bearing molecules in solids, is potentially an important diagnostic of the evolution of organic matter in the interstellar medium and the envelopes of newly formed stars. We report quantitative limits on the strength of this feature in the diffuse interstellar medium toward the reddene…
The Star Formation History of LGS 3
Dolphin, Andrew E.; Miller, Bryan W.; Lee, Myung Gyoon +2 more
We have determined the distance and star formation history of the Local Group dwarf galaxy LGS 3 from deep Hubble Space Telescope WFPC2 observations. LGS 3 is intriguing because ground-based observations showed that, while its stellar population is dominated by old, metal-poor stars, there is a handful of young, blue stars. Also, the presence of H…
Far-Infrared Detection of H3O+ in Sagittarius B2
Cernicharo, José; Goicoechea, Javier R.
We report the first far-infrared detection of the hydronium ion (H3O+) toward the Sagittarius B2 molecular cloud, near the Galactic center. Using the Infrared Space Observatory Long-Wavelength Spectrometer, we have detected three lines arising from the ν2 ground-state inversion mode (0+-->0-
Hα Proxies for EIT Crinkles: Further Evidence for Preflare ``Breakout''-Type Activity in an Ejective Solar Eruption
Qiu, Jiong; Wang, Haimin; Moore, Ronald L. +1 more
We present Hα observations from Big Bear Solar Observatory of an eruptive flare in NOAA Active Region 8210, occurring near 22:30 UT on 1998 May 1. Previously, using the EUV Imaging Telescope (EIT) on the SOHO spacecraft, we found that a pattern of transient, localized brightenings, which we call ``EIT crinkles,'' appears in the neighborhood of the…
STIS Echelle Observations of the Intrinsic UV Absorption in the Seyfert 1 Galaxy NGC 3783
Kraemer, S. B.; Crenshaw, D. M.; Gabel, J. R.
We present observations of the UV absorption lines in the Seyfert 1 galaxy NGC 3783, obtained with the medium resolution (λ/Δλ~40,000) echelle gratings of the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). The spectra reveal the presence of three kinematic components of absorption in Lyα, C IV, and N V, at radial …
The X-Ray Afterglow of GRB 000926 Observed by BeppoSAX and Chandra: A Mildly Collimated Fireball in a Dense Medium?
Piro, L.; Antonelli, L. A.; Frail, D. A. +8 more
We present X-ray observations of the afterglow of GRB 000926, performed around and after the break observed in the optical light curve 2 days after the burst. The steep X-ray light curve observed around the break confirms the presence of this feature in X-rays. However, the spectral and temporal properties are not consistent with a standard jet sc…