55,937 research outputs found
Abnormal oscillation modes in a waning light bridge
A sunspot acts as a waveguide in response to the dynamics of the solar
interior; the trapped waves and oscillations could reveal its thermal and
magnetic structures.
We study the oscillations in a sunspot intruded by a light bridge, the
details of the oscillations could reveal the fine structure of the magnetic
topology.
We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly data to
analyse the oscillations in the emission intensity of light bridge plasma at
different temperatures and investigate their spatial distributions.
The extreme ultraviolet emission intensity exhibits two persistent
oscillations at five-minute and sub-minute ranges. The spatial distribution of
the five-minute oscillation follows the spine of the bridge; whereas the
sub-minute oscillations overlap with two flanks of the bridge. Moreover, the
sub-minute oscillations are highly correlated in spatial domain, however, the
oscillations at the eastern and western flanks are asymmetric with regard to
the lag time. In the meanwhile, jet-like activities are only found at the
eastern flank.
Asymmetries in forms of oscillatory pattern and jet-like activities
\textbf{are} found between two flanks of a granular light bridge. Based on our
study and recent findings, we propose a new model of twisted magnetic field for
a light bridge and its dynamic interactions with the magnetic field of a
sunspot.Comment: 5 figures, Accepted version in A&
SDSS AGNs with X-ray Emission from ROSAT PSPC Pointed Observations
We present a sample of 1744 type 1 active galactic nuclei (AGNs) from the
Sloan Digital Sky Survey (SDSS DR4) spectroscopic catalog with X-ray
counterparts in the White-Giommi-Angelini Catalog (WGACAT) of ROSAT PSPC
pointed observations. Of 1744 X-ray sources, 1410 (80.9%) are new AGN
identifications. Of 4574 SDSS DR4 AGNs for which we found radio matches in the
catalog of radio sources from the FIRST catalog, 224 turned up in our sample of
SDSS X-ray AGNs. The sample objects are given in a catalog that contains
optical and X-ray parameters along with radio emission parameters where
available. We illustrate the content of our catalog and its potential for AGN
science by providing statistical relationships for the catalog data. The
potential of the morphological information is emphasized by confronting the
statistics of optically resolved and unresolved AGNs. The immediate properties
of the catalog objects include significant correlation of X-ray and optical
fluxes, which is consistent with expectations. Also expected is the decrease of
X-ray flux toward higher redshifts. The X-ray to optical flux ratio for the
unresolved AGNs exhibits a decline toward higher redshifts, in agreement with
previous results. The resolved AGNs, however, display the opposite trend. At a
given optical brightness, X-ray fluxes of radio-quiet AGNs by a factor of 2. We
caution, however, that because of the variety of selection effects present in
both the WGACAT and the SDSS, the interpretation of any relationships based on
our sample of X-ray AGNs requires a careful analysis of these effects.Comment: 34 pages, 18 figure
Origins of Inert Higgs Doublets
We consider beyond the standard model embedding of inert Higgs doublet
fields. We argue that inert Higgs doublets can arise naturally in grand unified
theories where the necessary associated symmetry can occur automatically.
Several examples are discussed.Comment: 14 pages, 1 table, no figure. References adde
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