Search Publications
Has Blending Compromised Cepheid-based Determinations of the Extragalactic Distance Scale?
Gibson, Brad K.; Sakai, Shoko; Maloney, Philip R.
We examine the suggestion that half of the galaxies observed by the Hubble Space Telescope Key Project and the Type Ia Supernova Calibration Team have had their distances systematically underestimated, by 0.1-0.3 mag in the distance modulus, because of the underappreciated influence of stellar profile blending on the Wide Field Camera chips. The s…
Velocity Shear-induced Mode Conversion in Solar Wind and Streamer Plasmas
Kaghashvili, Edisher Kh.; Esser, Ruth
The possible scenario of Alfvén wave transformation into other MHD waves due to inhomogeneous flow in different regions of solar wind/corona is examined. We have chosen four examples with different plasma parameters and velocity shear parameters as representative cases for the plasma conditions. Two of the cases are representative of coronal holes…
Very Large Telescope Observations of the Peculiar Globular Cluster NGC 6712: Discovery of a UV, Hα-Excess Star in the Core
Ferraro, Francesco R.; Paresce, Francesco; De Marchi, Guido +1 more
We present results from multiband observations in the central region of the cluster NGC 6712 with the ESO Very Large Telescope. Using high-resolution images we have identified three UV-excess stars. In particular, two of them are within the cluster core, a few arcseconds apart: the first object is star ``S,'' which previous studies identified as t…
Origin of Helical Coronal Disturbances from the Sun
Hori, K.
By combining data from the Nobeyama Radioheliograph and the LASCO coronagraph aboard the SoHO spacecraft, we report two helical coronal disturbances accompanying white-light coronal mass ejections (CMEs). These are activated prominences at the base, rotating around each vertical axis while moving on the solar surface with projected speeds of >=…
X-Ray Afterglow Detection of the Short Gamma-Ray Burst GRB 991014
Piro, L.; Antonelli, L. A.; Frontera, F. +14 more
GRB 991014 is one of the shortest gamma-ray bursts detected so far with the Wide Field Cameras aboard BeppoSAX, in both gamma rays and X-rays. The duration is 9.6 s in 2-28 keV and 3.2 s in 40 to 700 keV (as measured between the times when 5% and 95% of the burst photons have been accumulated). We have refined the InterPlanetary Network annulus of…
Optimal Masks for Low-Degree Solar Acoustic Modes
Kosovichev, A. G.; Toutain, T.
We suggest a solution to an important problem in observational helioseismology of the separation of lines of solar acoustic (p) modes of low angular degree in oscillation power spectra by constructing optimal masks for Doppler images of the Sun. Accurate measurements of oscillation frequencies of low-degree modes are essential for the determinatio…
Studying the Pulsation of Mira Variables in the Ultraviolet
Wood, B. E.; Karovska, M.
We present results from an empirical study of the Mg II h and k emission lines of selected Mira variable stars, using spectra from the International Ultraviolet Explorer (IUE). The stars all exhibit similar Mg II behavior during the course of their pulsation cycles. The Mg II flux always peaks after optical maximum near pulsation phase φ=0.2-0.5, …
Another Faint Ultraviolet Object Associated with a Globular Cluster X-Ray Source: The Case of M92
Ferraro, Francesco R.; Paltrinieri, Barbara; Fusi Pecci, Flavio +2 more
The core of the metal-poor galactic globular cluster M92 (NGC 6341) has been observed with Wide Field Planetary Camera 2 (WFPC2) on the Hubble Space Telescope through visual, blue, and mid-UV filters in a program devoted to studying the evolved stellar population in a selected sample of galactic globular clusters. In the UV (m255, m
Ultraviolet Imaging of the Galaxy Cluster CL 0939+4713 (Abell 851) at z=0.41
Dressler, Alan; Cappellari, Michele; Bertola, Francesco +3 more
The first UV F300W and F218W WFPC2 observations of the rich galaxy cluster CL 0939+4713 at z=0.41 are presented and discussed. UV/optical two-color and color-magnitude diagrams of the sources detected in the F300W waveband are constructed. Thanks to preexisting Hubble Space Telescope (HST) optical images of the same field, a morphological classifi…
Global Solar Corona Revealed by Time Series Observations
Raymond, J. C.; Li, Jing; Kuhn, J. +2 more
Time series observations at UV (Extreme Ultraviolet Imaging Telescope/Solar and Heliospheric Observatory) and X-ray (Soft X-Ray Telescope/Yohkoh) wavelengths reveal properties of the global solar corona that are not easily identified in a single image. A median-filtering technique that rejects features varying with time is used to isolate backgrou…