Search Publications
Homologous large-scale activity in solar eruptive events of 24-26 November 2000
Hudson, H. S.; Nitta, N. V.; Grechnev, V. V. +1 more
We study large-scale activity on the solar disk associated with a 24-26 November 2000 series of six recurrent major flares and "halo" coronal mass ejections (CMEs). The analysis is based mainly on the SOHO/EIT data, particularly by using properly rotated difference full-disk images with 12-min intervals at 195 Å as well as with 6-hour intervals at…
Correlation between speeds of coronal mass ejections and the intensity of geomagnetic storms
Wang, Haimin; Yurchyshyn, Vasyl; Abramenko, Valentyna
We studied the relationship between the projected speed of coronal mass ejections (CMEs), determined from a sequence of Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph Experiment (SOHO/LASCO) images, and the hourly averaged magnitude of the Bz component of the magnetic field in an interplanetary ejecta, as m…
Detection of Intergalactic He II Absorption at Redshift 3.5
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +5 more
The large number of quasars found in the Sloan Digital Sky Survey has allowed searches for elusive, clear lines of sight toward He II Lyα absorption, a sensitive probe of the intergalactic medium. The few known systems indicate that He II reionization occurs at z>3. We report the detection of a He II Lyα absorption edge in a quasar spectrum at …
Discovery of Massive Evolved Galaxies at z > 3 in the Hubble Ultra Deep Field
Chen, Hsiao-Wen; Marzke, Ronald O.
We have identified six early-type galaxies at z>2.8 in the central 5.76 arcmin2 Hubble Ultra Deep Field NICMOS region based on a pronounced broadband discontinuity between the NICMOS F110W and F160W bandpasses. These galaxies have red observed optical and near-infrared colors (ABF775W-ABF160W>=2) that cannot …
A Complete Atlas of Recalibrated Hubble Space Telescope Faint Object Spectrograph Spectra of Active Galactic Nuclei and Quasars. I. Pre-COSTAR Spectra
Koratkar, Anuradha P.; Evans, Ian N.
We have recalibrated all nonpolarimetric, pre-COSTAR, archival Hubble Space Telescope Faint Object Spectrograph UV and optical spectrophotometry of active galaxies and quasars in order to extract uniformly calibrated spectrophotometric data for further detailed scientific investigations. The raw archival spectra have been recalibrated using the la…
Lick Northern Proper Motion Program. III. Lick NPM2 Catalog
Monet, David G.; Hanson, Robert B.; Jones, Burton F. +1 more
The Lick Northern Proper Motion (NPM) program, a two-epoch (1947-1988) photographic survey of the northern two-thirds of the sky (δ>~-23deg), has measured absolute proper motions, on an inertial system defined by distant galaxies, for 378,360 stars in the magnitude range 8<~B<~18. The 1993 NPM1 Catalog contains 148,940 stars in…
The Low- and Intermediate-Mass Stellar Population in the Small Magellanic Cloud: The Central Stars of Planetary Nebulae
Villaver, Eva; Shaw, Richard A.; Stanghellini, Letizia
We present a study on the central stars (CSs) of planetary nebulae (PNs) observed in the Small Magellanic Cloud (SMC) with the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope (HST). The stellar magnitudes have been measured using broadband photometry, and Zanstra analysis of the nebulae provided the stell…
The Inner Ring of NGC 4736: Star Formation on a Resonant Pattern
Muñoz-Tuñón, Casiana; Aguerri, J. Alfonso L.; Caon, Nicola
We revise the explanation for the ``expanding H II regions ring'' of NGC 4736. From the analysis of long-slit spectra, we identify structures within the emission region previously reported in the literature as a single ring (former parameters: R~47", FWHM=21"). The H II ring is located at 35" (1.12 kpc) galactocentric distance, and its thickness i…
Pulsation Phase-Dependent Dust Shell Models for Oxygen-rich Asymptotic Giant Branch Stars
Suh, Kyung-Won
We investigate the spectral energy distributions (SEDs) of oxygen-rich asymptotic giant branch (AGB) stars at different pulsation phases using infrared observational data, including data from the Infrared Space Observatory. Comparing the results of detailed radiative transfer model calculations with observations, we explore the changes of the rele…
An X-ray review of MS 1054-0321: Hot or not?
Braito, V.; Tran, K. -V.; Della Ceca, R. +3 more
XMM-Newton observations are presented for the z=0.83 cluster of galaxies MS 1054-0321, the highest redshift cluster in the Einstein Extended Medium Sensitivity Survey (EMSS). The temperature inferred by the XMM-Newton data, T=7.2+0.7-0.6 keV, is much lower than the temperature previously reported from ASCA data, T=12.3+3…