485 research outputs found
Compact Radio Cores in Seyfert Galaxies
We have observed a sample of 157 Seyfert galaxies with a 275 km baseline
radio interferometer to search for compact, high brightness temperature radio
emission from the active nucleus. We obtain the surprising result that compact
radio cores are much more common in Seyfert 2 than in Seyfert 1 galaxies, which
at first seems to be inconsistent with orientation unification schemes. We
propose a model, involving optical depth effects in the narrow-line region,
which can reconcile our result with the standard unified scheme. (Accepted for
publication in ApJ 1994 Sep 10)Comment: 21 pages and 7 figures, uuencoded tar-compressed postscript files,
ATP18
Interaction of threat expressions and eye gaze: an event-related potential study
he current study examined the interaction of fearful, angry, happy, and neutral expressions with left, straight, and right eye gaze directions. Human participants viewed faces consisting of various expression and eye gaze combinations while event-related potential (ERP) data were collected. The results showed that angry expressions modulated the mean amplitude of the P1, whereas fearful and happy expressions modulated the mean amplitude of the N170. No influence of eye gaze on mean amplitudes for the P1 and N170 emerged. Fearful, angry, and happy expressions began to interact with eye gaze to influence mean amplitudes in the time window of 200â400 ms. The results suggest early processing of expression influence ERPs independent of eye gaze, whereas expression and gaze interact to influence later ERPs
Rapid Rotation of Low-Mass Red Giants Using APOKASC: A Measure of Interaction Rates on the Post-main-sequence
We investigate the occurrence rate of rapidly rotating (10 km
s), low-mass giant stars in the APOGEE-Kepler (APOKASC) fields with
asteroseismic mass and surface gravity measurements. Such stars are likely
merger products and their frequency places interesting constraints on stellar
population models. We also identify anomalous rotators, i.e. stars with 5 km
s10 km s that are rotating significantly faster
than both angular momentum evolution predictions and the measured rates of
similar stars. Our data set contains fewer rapid rotators than one would expect
given measurements of the Galactic field star population, which likely
indicates that asteroseismic detections are less common in rapidly rotating red
giants. The number of low-mass moderate (5-10 km s) rotators in our
sample gives a lower limit of 7% for the rate at which low-mass stars interact
on the upper red giant branch because single stars in this mass range are
expected to rotate slowly. Finally, we classify the likely origin of the rapid
or anomalous rotation where possible. KIC 10293335 is identified as a merger
product and KIC 6501237 is a possible binary system of two oscillating red
giants.Comment: 39 pages, 8 figures, 4 tables. Accepted for publication in the
Astrophysical Journal. For a brief video discussing key results from this
paper see http://youtu.be/ym_0nV7_YqI . The full table 1 is available at
http://www.astronomy.ohio-state.edu/~tayar/tab1_full.tx
Pair Creation and an X-ray Free Electron Laser
Using a quantum kinetic equation coupled to Maxwell's equation we study the
possibility that focused beams at proposed X-ray free electron laser facilities
can generate electric field strengths large enough to cause spontaneous
electron-positron pair production from the QED vacuum. Our approach yields the
time and momentum dependence of the single particle distribution function.
Under conditions reckoned achievable at planned facilities, repeated cycles of
particle creation and annihilation take place in tune with the laser frequency.
However, the peak particle number density is insensitive to this frequency and
one can anticipate the production of a few hundred particle pairs per laser
period. Field-current feedback and quantum statistical effects are small and
can be neglected in this application of non-equilibrium quantum mean field
theory.Comment: 4 pages, LaTeX2
Methanol Masers as Tracers of Circumstellar Disks
We show that in many methanol maser sources the masers are located in lines,
with a velocity gradient along them which suggests that the masers are situated
in edge-on circumstellar, or protoplanetary, disks. We present VLBI
observations of the methanol maser source G309.92+0.48, in the 12.2 GHz
transition, which confirm previous observations that the masers in this source
lie along a line. We show that such sources are not only linear in space but,
in many cases, also have a linear velocity gradient. We then model these and
other data in both the 6.7 GHz and the 12.2 GHz transition from a number of
star formation regions, and show that the observed spatial and velocity
distribution of methanol masers, and the derived Keplerian masses, are
consistent with a circumstellar disk rotating around an OB star. We consider
this and other hypotheses, and conclude that about half of these methanol
masers are probably located in edge-on circumstellar disks around young stars.
This is of particular significance for studies of circumstellar disks because
of the detailed velocity information available from the masers.Comment: 38 pages, 13 figures accepted by Ap
Target Selection for the SDSS-IV APOGEE-2 Survey
APOGEE-2 is a high-resolution, near-infrared spectroscopic survey observing
roughly 300,000 stars across the entire sky. It is the successor to APOGEE and
is part of the Sloan Digital Sky Survey IV (SDSS-IV). APOGEE-2 is expanding
upon APOGEE's goals of addressing critical questions of stellar astrophysics,
stellar populations, and Galactic chemodynamical evolution using (1) an
enhanced set of target types and (2) a second spectrograph at Las Campanas
Observatory in Chile. APOGEE-2 is targeting red giant branch (RGB) and red
clump (RC) stars, RR Lyrae, low-mass dwarf stars, young stellar objects, and
numerous other Milky Way and Local Group sources across the entire sky from
both hemispheres. In this paper, we describe the APOGEE-2 observational design,
target selection catalogs and algorithms, and the targeting-related
documentation included in the SDSS data releases.Comment: 19 pages, 6 figures. Accepted to A
Limits to sustained energy intake XXIV : impact of suckling behaviour on the body temperatures of lactating female mice
We would like to thank the animal house staff and all members of the Energetics group for their invaluable help at various stages throughout the project. This work was supported by Natural Environment Research Council grant (NERC, NE/C004159/1). YG was supported by a scholarship from the rotary foundation. LV was supported by a Rubicon grant from the Netherlands Scientific Organisation (NWO).Peer reviewedPublisher PD
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