Search Publications
The Observation of Sunspot Light-Bridge Structure and Dynamics
Berger, T. E.; Berdyugina, S. V.
We present very high resolution multiwavelength images of a sunspot light bridge in NOAA Active Region 10132 taken at the Swedish 1 m Solar Telescope on La Palma on 2002 September 25. The adaptive optics-corrected images resolve 100 km scale bright grains on either side of an approximately 380 km dark lane in the center of the bridge. Movies of th…
Observational Constraints on Disk Heating as a Function of Hubble Type
Shapiro, Kristen L.; Gerssen, Joris; van der Marel, Roeland P.
Current understanding of the secular evolution of galactic disks suggests that this process is dominated by two or more ``heating'' mechanisms, which increase the random motions of stars in the disk. In particular, the gravitational influence of giant molecular clouds and irregularities in the spiral potential have been proposed to explain the obs…
Rotation, pulsations and magnetic field in V 2052 Ophiuchi : A new He-strong star
Frémat, Y.; Neiner, C.; Jankov, S. +7 more
Three years in the coronal life of AB Dor. I. Plasma emission measure distributions and abundances at different activity levels
Sanz-Forcada, J.; Micela, G.; Maggio, A.
The young active star AB Dor (K1 IV-V) has been observed 16 times in the last three years with the XMM-Newton and Chandra observatories, totalling 650 ks of high-resolution X-ray spectra. The XMM/RGS observations with the highest and lowest average emission levels have been selected to study the coronal properties of AB Dor in two different activi…
Imaging and Spectroscopic Investigations of a Solar Coronal Wave: Properties of the Wave Front and Associated Erupting Material
Harra, Louise K.; Sterling, Alphonse C.
Using spectral data from the Coronal Diagnostic Spectrometer (CDS) instrument on the Solar and Heliospheric Observatory spacecraft, we observe a coronal wave feature (often referred to as an EIT wave) that occurred in association with a solar eruption and flare on 1998 June 13. EUV images from the Transition Region and Coronal Explorer (TRACE) sat…
An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis
Heinke, Craig O.; Gilliland, Ronald L.; Edmonds, Peter D. +1 more
We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs…
Oxygen Gas-Phase Abundance Revisited
Moos, H. W.; André, M. K.; Ferlet, R. +7 more
We present new measurements of the interstellar gas-phase oxygen abundance along the sight lines toward 19 early-type Galactic stars at an average distance of 2.6 kpc. We derive O I column densities from Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) observations of the weak 1355 Å intersystem transition. We derive total hy…
Constraints on Active Region Coronal Heating
Golub, L.; Antiochos, S. K.; DeLuca, E. E. +2 more
We derive constraints on the time variability of coronal heating from observations of the so-called active region moss by the Transition Region and Coronal Explorer (TRACE). The moss is believed to be due to million-degree emission from the transition regions at the footpoints of coronal loops whose maximum temperatures are several million degrees…
Helicity Evolution in Emerging Active Regions
Pevtsov, Alexei A.; Maleev, Vasily M.; Longcope, Dana W.
We study the evolution of twist and magnetic helicity in the coronal fields of active regions as they emerge. We use multiday sequences of Solar and Heliospheric Observatory Michelson Doppler Interferometer magnetograms to characterize the region's emergence. We quantify the overall twist in the coronal field, α, by matching a linear force-free fi…
Empirically Determined Anisotropic Velocity Distributions and Outflows of O5+ Ions in a Coronal Streamer at Solar Minimum
Cranmer, S. R.; Kohl, J. L.; Frazin, R. A.
Empirical constraints on the O5+ velocity distributions and outflow speeds in a solar minimum equatorial streamer between 2.6 and 5.1 Rsolar are determined using a spectral synthesis code that includes O VI Doppler dimming. These constraints follow directly from UV spectra taken on 1996 October 12 with the Ultraviolet Coronag…