Search Publications
The very local Hubble flow
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +8 more
We present Hubble Space Telescope/WFPC2 images of eighteen galaxies situated in the vicinity of the Local Group (LG) as part of an ongoing snapshot survey of nearby galaxies. Their distances derived from the magnitude of the tip of the red giant branch are 1.92±0.10 Mpc (ESO 294-010), 3.06±0.37 (NGC 404), 3.15±0.32 (UGCA 105), 1.36±0.07 (Sex B), 1…
Physical parameters of the high-mass X-ray binary 4U1700-37
Kaper, L.; Crowther, P. A.; Goodwin, S. P. +4 more
We present the results of a detailed non-LTE analysis of the ultraviolet and optical spectrum of the O6.5 Iaf+ star
The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble constant
Treu, T.; Koopmans, L. V. E.
We combine lensing, stellar kinematic and mass-to-light ratio constraints to build a two-component (luminous plus dark) mass model of the early-type lens galaxy in PG1115+080. We find a total mass density profile steeper than r-2, effectively ρ~r-γ' with γ'= 2.35 +/- 0.1 +/- 0.05 (random + systematic). The stellar mass fracti…
The solar wind composition throughout the solar cycle: A continuum of dynamic states
Zurbuchen, T. H.; Gloeckler, G.; Fisk, L. A. +1 more
Variations in the speed and elemental and ionic charge composition of the solar wind are reported throughout the solar cycle, as observed by the SWICS instrument on Ulysses. The apparent bimodal nature of the solar wind during the solar minimum does not persist throughout the solar cycle. Rather, with increasing solar activity, a continuum of sola…
Active-Region Monitoring and Flare Forecasting I. Data Processing and First Results
Moon, Y. -J.; Wang, Haimin; Gallagher, Peter T.
This paper discusses a near real-time approach to solar active-region monitoring and flare prediction using the Big Bear Solar Observatory Active Region Monitor (ARM). Every hour, ARM reads, calibrates, and analyses a variety of data including: full-disk Hα images from the Global Hα Network; EUV, continuum, and magnetogram data from the Solar and …
Chandra Observations of ``The Antennae'' Galaxies (NGC 4038/4039). III. X-Ray Properties and Multiwavelength Associations of the X-Ray Source Population
Zezas, A.; Fabbiano, G.; Murray, S. S. +1 more
We investigate the nature of the luminous X-ray source population detected in a (72 ks) Chandra ACIS-S observation of NGC 4038/4039, the Antennae galaxies. We derive the average X-ray spectral properties of sources in different luminosity ranges, and we correlate the X-ray positions with radio, IR, and optical (Hubble Space Telescope) data. The X-…
A pulsating auroral X-ray hot spot on Jupiter
Dougherty, M. K.; Young, D. T.; Clarke, J. T. +12 more
Jupiter's X-ray aurora has been thought to be excited by energetic sulphur and oxygen ions precipitating from the inner magnetosphere into the planet's polar regions. Here we report high-spatial-resolution observations that demonstrate that most of Jupiter's northern auroral X-rays come from a `hot spot' located significantly poleward of the latit…
The Evolution of Field Early-Type Galaxies to z~0.7
Stiavelli, Massimo; Treu, Tommaso; Casertano, S. +2 more
We have measured the fundamental plane (FP) parameters for a sample of 30 field early-type galaxies (E/S0s) in the redshift range 0.1<z<0.66. We find that (i) the FP is defined and tight out to the highest redshift bin; (ii) the intercept γ evolves as dγ/dz=0.58+0.09-0.13 (for Ω=0.3, ΩΛ=0.7) or, in terms of a…
Formation and Fragmentation of Gaseous Spurs in Spiral Galaxies
Kim, Woong-Tae; Ostriker, Eve C.
Intermediate-scale spurs are common in spiral galaxies, but perhaps most distinctively evident in a recent image by Scoville & Rector showing a quasi-regular series of dust lanes projecting from the arms of M51. We investigate, using time-dependent numerical MHD simulations, how such spurs could form (and subsequently fragment) from the intera…
Solar flares, type III radio bursts, coronal mass ejections, and energetic particles
Cane, H. V.; Erickson, W. C.; Prestage, N. P.
In this correlative study between >20 MeV solar proton events, coronal mass ejections (CMEs), flares, and radio bursts it is found that essentially all of the proton events are preceded by groups of type III bursts and all are preceded by CMEs. These type III bursts (that are a flare phenomenon) usually are long-lasting, intense bursts seen in …