1,968 research outputs found
Interaction of Close-in Planets with the Magnetosphere of their Host Stars I: Diffusion, Ohmic Dissipation of Time Dependent Field, Planetary Inflation, and Mass Loss
The unanticipated discovery of the first close-in planet around 51 Peg has
rekindled the notion that shortly after their formation outside the snow line,
some planets may have migrated to the proximity of their host stars because of
their tidal interaction with their nascent disks. If these planets indeed
migrated to their present-day location, their survival would require a halting
mechanism in the proximity of their host stars. Most T Tauri stars have strong
magnetic fields which can clear out a cavity in the innermost regions of their
circumstellar disks and impose magnetic induction on the nearby young planets.
Here we consider the possibility that a magnetic coupling between young stars
and planets could quench the planet's orbital evolution. After a brief
discussion of the complexity of the full problem, we focus our discussion on
evaluating the permeation and ohmic dissipation of the time dependent component
of the stellar magnetic field in the planet's interior. Adopting a model first
introduced by C. G. Campbell for interacting binary stars, we determine the
modulation of the planetary response to the tilted magnetic field of a
non-synchronously spinning star. We first compute the conductivity in the young
planets, which indicates that the stellar field can penetrate well into the
planet's envelope in a synodic period. For various orbital configurations, we
show that the energy dissipation rate inside the planet is sufficient to induce
short-period planets to inflate. This process results in mass loss via Roche
lobe overflow and in the halting of the planet's orbital migration.Comment: 47 pages, 12 figure
The Psychological Science Accelerator: Advancing Psychology through a Distributed Collaborative Network
Concerns have been growing about the veracity of psychological research. Many findings in psychological science are based on studies with insufficient statistical power and nonrepresentative samples, or may otherwise be limited to specific, ungeneralizable settings or populations. Crowdsourced research, a type of large-scale collaboration in which one or more research projects are conducted across multiple lab sites, offers a pragmatic solution to these and other current methodological challenges. The Psychological Science Accelerator (PSA) is a distributed network of laboratories designed to enable and support crowdsourced research projects. These projects can focus on novel research questions, or attempt to replicate prior research, in large, diverse samples. The PSA’s mission is to accelerate the accumulation of reliable and generalizable evidence in psychological science. Here, we describe the background, structure, principles, procedures, benefits, and challenges of the PSA. In contrast to other crowdsourced research networks, the PSA is ongoing (as opposed to time-limited), efficient (in terms of re-using structures and principles for different projects), decentralized, diverse (in terms of participants and researchers), and inclusive (of proposals, contributions, and other relevant input from anyone inside or outside of the network). The PSA and other approaches to crowdsourced psychological science will advance our understanding of mental processes and behaviors by enabling rigorous research and systematically examining its generalizability
Episodic mass loss in binary evolution to the Wolf-Rayet phase: Keck and HST proper motions of RY Scuti's nebula
Binary mass transfer via Roche-lobe overflow (RLOF) is a key channel for
producing stripped-envelope Wolf-Rayet (WR) stars and may be critical to
account for SN Ib/c progenitors. RY Scuti is an extremely rare example of a
massive binary star caught in this brief but important phase. Its toroidal
nebula indicates equatorial mass loss during RLOF, while the mass-gaining star
is apparently embedded in an opaque accretion disk. RY Scuti's toroidal nebula
has two components: an inner ionised double-ring system, and an outer dust
torus that is twice the size of the ionised rings. We present two epochs of
Lband Keck NGS-AO images of the dust torus, plus three epochs of HST images of
the ionised gas rings. Proper motions show that the inner ionised rings and the
outer dust torus came from two separate ejection events roughly 130 and 250 yr
ago. This suggests that RLOF in massive contact binaries can be accompanied by
eruptive and episodic burst of mass loss, reminiscent of LBVs. We speculate
that the repeating outbursts may arise in the mass gainer from instabilities
associated with a high accretion rate. If discrete mass-loss episodes in other
RLOF binaries are accompanied by luminous outbursts, they might contribute to
the population of extragalactic optical transients. When RLOF ends for RY
Scuti, the overluminous mass gainer, currently surrounded by an accretion disk,
will probably become a B[e] supergiant and may outshine the hotter mass-donor
star that should die as a Type Ib/c supernova.Comment: 15 pages, 7 figures, submitted to MNRA
Characterizing and Improving the Data Reduction Pipeline for the Keck OSIRIS Integral Field Spectrograph
OSIRIS is a near-infrared (1.0--2.4 m) integral field spectrograph
operating behind the adaptive optics system at Keck Observatory, and is one of
the first lenslet-based integral field spectrographs. Since its commissioning
in 2005, it has been a productive instrument, producing nearly half the laser
guide star adaptive optics (LGS AO) papers on Keck. The complexity of its raw
data format necessitated a custom data reduction pipeline (DRP) delivered with
the instrument in order to iteratively assign flux in overlapping spectra to
the proper spatial and spectral locations in a data cube. Other than bug fixes
and updates required for hardware upgrades, the bulk of the DRP has not been
updated since initial instrument commissioning. We report on the first major
comprehensive characterization of the DRP using on-sky and calibration data. We
also detail improvements to the DRP including characterization of the flux
assignment algorithm; exploration of spatial rippling in the reduced data
cubes; and improvements to several calibration files, including the
rectification matrix, the bad pixel mask, and the wavelength solution. We
present lessons learned from over a decade of OSIRIS data reduction that are
relevant to the next generation of integral field spectrograph hardware and
data reduction software design.Comment: 18 pages, 16 figures; accepted for publication in A
Keck-I MOSFIRE Spectroscopy of Compact Star-Forming Galaxies at \u3cem\u3ez\u3c/em\u3e ≳ 2: High Velocity Dispersions in Progenitors of Compact Quiescent Galaxies
We present Keck-I MOSFIRE near-infrared spectroscopy for a sample of 13 compact star-forming galaxies (SFGs) at redshift 2 ≤ z ≤ 2.5 with star formation rates of SFR ~ 100 M ☉ yr–1 and masses of log(M/M ☉) ~10.8. . . .
For the remainder of the abstract, please visit:
http://dx.doi.org/10.1088/0004-637X/795/2/14
New Raffaelea species (Ophiostomatales) from the USA and Taiwan associated with ambrosia beetles and plant hosts
Raffaelea (Ophiostomatales) is a genus of more than 20 ophiostomatoid fungi commonly occurring in
symbioses with wood-boring ambrosia beetles. We examined ambrosia beetles and plant hosts in the USA and
Taiwan for the presence of these mycosymbionts and found 22 isolates representing known and undescribed
lineages in Raffaelea. From 28S rDNA and β-tubulin sequences, we generated a molecular phylogeny of
Ophiostomatales and observed morphological features of seven cultures representing undescribed lineages
in Raffaelea s. lat. From these analyses, we describe five new species in Raffaelea s. lat.: R. aguacate, R.
campbellii, R. crossotarsa, R. cyclorhipidia, and R. xyleborina spp. nov. Our analyses also identified two plantpathogenic
species of Raffaelea associated with previously undocumented beetle hosts: (1) R. quercivora, the
causative agent of Japanese oak wilt, from Cyclorhipidion ohnoi and Crossotarsus emancipatus in Taiwan, and
(2) R. lauricola, the pathogen responsible for laurel wilt, from Ambrosiodmus lecontei in Florida. The results of
this study show that Raffaelea and associated ophiostomatoid fungi have been poorly sampled and that future
investigations on ambrosia beetle mycosymbionts should reveal a substantially increased diversity.The United States
Department of Agriculture (USDA) Forest Service (FS)-SRS Coop
agreement 14-CA-11330130-032, USDA-FS-FHP Coop agreement
12-CA-11420004-042, USDA Farm Bill agreement 12-8130-0377-
CA, National Science Foundation grant DEB 1256968 and the Department of Science and
Technology/ National Research Foundation Centre of Excellence in
Tree Health Biotechnology (CTHB), South Africa.http://www.imafungus.orgam2017Forestry and Agricultural Biotechnology Institute (FABI)Microbiology and Plant Patholog
The Psychological Science Accelerator: Advancing Psychology through a Distributed Collaborative Network
Concerns have been growing about the veracity of psychological research. Many findings in psychological science are based on studies with insufficient statistical power and nonrepresentative samples, or may otherwise be limited to specific, ungeneralizable settings or populations. Crowdsourced research, a type of large-scale collaboration in which one or more research projects are conducted across multiple lab sites, offers a pragmatic solution to these and other current methodological challenges. The Psychological Science Accelerator (PSA) is a distributed network of laboratories designed to enable and support crowdsourced research projects. These projects can focus on novel research questions, or attempt to replicate prior research, in large, diverse samples. The PSA\u27s mission is to accelerate the accumulation of reliable and generalizable evidence in psychological science. Here, we describe the background, structure, principles, procedures, benefits, and challenges of the PSA. In contrast to other crowdsourced research networks, the PSA is ongoing (as opposed to time-limited), efficient (in terms of re-using structures and principles for different projects), decentralized, diverse (in terms of participants and researchers), and inclusive (of proposals, contributions, and other relevant input from anyone inside or outside of the network). The PSA and other approaches to crowdsourced psychological science will advance our understanding of mental processes and behaviors by enabling rigorous research and systematically examining its generalizability
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