21,723 research outputs found
WASP-1: A lithium- and metal-rich star with an oversized planet
In this paper we present our results of a comprehensive spectroscopicanalysis
of WASP-1, the host star to the exoplanet WASP-1b. We derive T_eff = 6110 +/-
45 K, log g = 4.28 +/- 0.15, and [M/H] = 0.23 +/- 0.08, and also a high
abundance of lithium, log n(Li) = 2.91 +/- 0.05. These parameters suggests an
age for the system of 1-3 Gyr and a stellar mass of 1.25-1.35 M_sun. This means
that WASP-1 has properties very similar to those of HD 149026, the host star
for the highest density planet yet detected. Moreover, their planets orbit at
comparable distances and receive comparable irradiating fluxes from their host
stars. However, despite the similarity of WASP-1 with HD 149026, their planets
have strongly different densities. This suggests that gas-giant planet density
is not a simple function of host-star metallicity or of radiation environment
at ages of ~2 Gyr.Comment: Accepted for publication in MNRAS. 6 pages, 4 figure
Average motion of emerging solar active region polarities I: Two phases of emergence
Our goal is to constrain models of active region formation by tracking the
average motion of active region polarity pairs as they emerge onto the surface.
We measured the motion of the two main opposite polarities in 153 emerging
active regions (EARs) using line-of-sight magnetic field observations from the
Solar Dynamics Observatory Helioseismic Emerging Active Region (SDO/HEAR)
survey (Schunker et al. 2016). We first measured the position of each of the
polarities eight hours after emergence and tracked their location forwards and
backwards in time. We find that, on average, the polarities emerge with an
east-west orientation and the separation speed between the polarities
increases. At about 0.1 days after emergence, the average separation speed
reaches a peak value of 229 +/- 11 m/s, and then starts to decrease, and about
2.5 days after emergence the polarities stop separating. We also find that the
separation and the separation speed in the east-west direction are
systematically larger for active regions with higher flux. Our results reveal
two phases of the emergence process defined by the rate of change of the
separation speed as the polarities move apart. Phase 1 begins when the opposite
polarity pairs first appear at the surface, with an east-west alignment and an
increasing separation speed. We define Phase 2 to begin when the separation
speed starts to decrease, and ends when the polarities have stopped separating.
This is consistent with the picture of Chen, Rempel, & Fan (2017): the peak of
a flux tube breaks through the surface during Phase 1. During Phase 2 the
magnetic field lines are straightened by magnetic tension, so that the
polarities continue to move apart, until they eventually lie directly above
their anchored subsurface footpoints.Comment: accepted A&
Thanks, but no thanks: women's avoidance of help-seeking in the context of a dependency-related stereotype
The stereotype that women are dependent on men is a commonly verbalized, potentially damaging aspect of benevolent sexism. We investigated how women may use behavioral disconfirmation of the personal applicability of the stereotype to negotiate such sexism. In an experiment (N = 86), we manipulated female college studentsâ awareness that women may be stereotyped by men as dependent. We then placed participants in a situation where they needed help. Women made aware of the dependency stereotype (compared to controls who were not) were less willing to seek help. They also displayed a stronger negative correlation between help-seeking and post help-seeking affect - such that the more help they sought, the worse they felt. We discuss the relevance of these findings for research concerning womenâs help-seeking and their management of sexist stereotyping in everyday interaction. We also consider the implications of our results for those working in domains such as healthcare, teaching and counseling, where interaction with individuals in need and requiring help is common
Getting it right: for Care Experienced students in Higher education
Commissioned by UCL Access and Widening Participation Office, this research
investigated the experiences of students in Higher Education when they have a
background of having lived in local authority care as children. Previously known as
âcare leaversâ, this group is now known as âcare experiencedâ young people. Care
experienced young people are much less likely to achieve the academic qualifications,
overcome the practical obstacles and reconcile the personal difficulties necessary to
attend university than other young people who have not been in care, and when they
do get to university, there is a relatively high chance they will withdraw early. The aim of
the current study is to explore what happens at university, from the perspective of both
institutional arrangements, and current and former studentsâ experience, to encourage,
or discourage, care experienced students to follow their chosen study programme
Reconstruction of thermally-symmetrized quantum autocorrelation functions from imaginary-time data
In this paper, I propose a technique for recovering quantum dynamical
information from imaginary-time data via the resolution of a one-dimensional
Hamburger moment problem. It is shown that the quantum autocorrelation
functions are uniquely determined by and can be reconstructed from their
sequence of derivatives at origin. A general class of reconstruction algorithms
is then identified, according to Theorem 3. The technique is advocated as
especially effective for a certain class of quantum problems in continuum
space, for which only a few moments are necessary. For such problems, it is
argued that the derivatives at origin can be evaluated by Monte Carlo
simulations via estimators of finite variances in the limit of an infinite
number of path variables. Finally, a maximum entropy inversion algorithm for
the Hamburger moment problem is utilized to compute the quantum rate of
reaction for a one-dimensional symmetric Eckart barrier.Comment: 15 pages, no figures, to appear in Phys. Rev.
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