9 research outputs found
Variables in the Southern Polar Region Evryscope 2016 Dataset
The regions around the celestial poles offer the ability to find and
characterize long-term variables from ground-based observatories. We used
multi-year Evryscope data to search for high-amplitude (~5% or greater)
variable objects among 160,000 bright stars (Mv < 14.5) near the South
Celestial Pole. We developed a machine learning based spectral classifier to
identify eclipse and transit candidates with M-dwarf or K-dwarf host stars -
and potential low-mass secondary stars or gas giant planets. The large
amplitude transit signals from low-mass companions of smaller dwarf host stars
lessens the photometric precision and systematics removal requirements
necessary for detection, and increases the discoveries from long-term
observations with modest light curve precision. The Evryscope is a robotic
telescope array that observes the Southern sky continuously at 2-minute
cadence, searching for stellar variability, transients, transits around exotic
stars and other observationally challenging astrophysical variables. In this
study, covering all stars 9 < Mv < 14.5, in declinations -75 to -90 deg, we
recover 346 known variables and discover 303 new variables, including 168
eclipsing binaries. We characterize the discoveries and provide the amplitudes,
periods, and variability type. A 1.7 Jupiter radius planet candidate with a
late K-dwarf primary was found and the transit signal was verified with the
PROMPT telescope network. Further followup revealed this object to be a likely
grazing eclipsing binary system with nearly identical primary and secondary K5
stars. Radial velocity measurements from the Goodman Spectrograph on the 4.1
meter SOAR telescope of the likely-lowest-mass targets reveal that six of the
eclipsing binary discoveries are low-mass (.06 - .37 solar mass) secondaries
with K-dwarf primaries, strong candidates for precision mass-radius
measurements.Comment: 32 pages, 17 figures, accepted to PAS
Patient and caregiver assessment of the benefits from the clinical use of amyloid PET imaging
INTRODUCTION:
Few studies to date have explored patient and caregiver views on the clinical use of amyloid positron emission tomography (PET).
METHODS:
A 7-item questionnaire assessing patient and caregiver views (510 total respondents) toward amyloid PET imaging was advertised broadly through alz.org/trialmatch.
RESULTS:
We received 510 unique responses from 48 US states, 2 Canadian provinces, the Dominican Republic, and Greece. Both patients and caregivers indicated that they would want to receive amyloid imaging if offered the opportunity. Over 88% of respondents had a positive response (∼10% with neutral and 2% with negative responses) to whether amyloid PET should be offered routinely and be reimbursed. Such information was felt to be useful for long-term legal, financial, and health care planning. Respondents identifying with early age cognitive decline (younger than 65 y) were more likely to explore options for disability insurance (P=0.03). Responders from the Midwest were more likely to utilize information from amyloid imaging for legal planning (P=0.02), disability insurance (P=0.02), and life insurance (P=0.04) than other US regions.
DISCUSSION:
Patients and caregivers supported the use of amyloid PET imaging in clinical practice and felt that the information would provide significant benefits particularly in terms of future planning
EVR-CB-001: An evolving, progenitor, white dwarf compact binary discovered with the Evryscope
We present EVR-CB-001, the discovery of a compact binary with an extremely
low mass () helium core white dwarf progenitor (pre-He
WD) and an unseen low mass () helium white dwarf (He
WD) companion. He WDs are thought to evolve from the remnant helium-rich core
of a main-sequence star stripped during the giant phase by a close companion.
Low mass He WDs are exotic objects (only about .2 of WDs are thought to be
less than .3 ), and are expected to be found in compact binaries.
Pre-He WDs are even rarer, and occupy the intermediate phase after the core is
stripped, but before the star becomes a fully degenerate WD and with a larger
radius () than a typical WD. The primary component of
EVR-CB-001 (the pre-He WD) was originally thought to be a hot subdwarf (sdB)
star from its blue color and under-luminous magnitude, characteristic of sdBs.
The mass, temperature (), and surface gravity
() solutions from this work are lower than values for
typical hot subdwarfs. The primary is likely to be a post-RGB, pre-He WD
contracting into a He WD, and at a stage that places it nearest to sdBs on
color-magnitude and - diagrams. EVR-CB-001 is expected to
evolve into a fully double degenerate, compact system that should spin down and
potentially evolve into a single hot subdwarf star. Single hot subdwarfs are
observed, but progenitor systems have been elusive.Comment: 14 pages, 11 figures. Published in The Astrophysical Journa
Variables in the Southern Polar Region Evryscope 2016 Data Set
The regions around the celestial poles offer the ability to find and characterize long-term variables from ground-based observatories. We used multi-year Evryscope data to search for high-amplitude (≈5% or greater) variable objects among 160,000 bright stars (mv σ limiting magnitude of g = 16 in dark time. In this study, covering all stars 9 M⊙) secondaries with K-dwarf primaries, strong candidates for precision mass–radius measurements
Metabolic suppression in thecosomatous pteropods as an effect of low temperature and hypoxia in the eastern tropical North Pacific
Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Marine Biology 159 (2012): 1955-1967, doi:10.1007/s00227-012-1982-x.Many pteropod species in the eastern tropical north Pacific Ocean migrate vertically each day, transporting organic matter and respiratory carbon below the thermocline. These migrations take species into cold (15-10ºC) hypoxic water (< 20 µmol O2 kg-1) at depth. We measured the vertical distribution, oxygen consumption and ammonia excretion for seven species of pteropod, some of which migrate and some which remain in oxygenated surface waters throughout the day. Within the upper 200 meters of the water column, changes in water temperature result in a ~60-75% reduction in respiration for most species. All three species tested under hypoxic conditions responded to low O2 with an additional ~35-50% reduction in respiratory rate. Combined, low temperature and hypoxia suppress the metabolic rate of pteropods by ~80-90%. These results shed light on the ways in which expanding regions of hypoxia and surface ocean warming may impact pelagic ecology.This work was funded by National Science Foundation grants to K. Wishner and B. Seibel (OCE – 0526502 and OCE – 0851043) and to K. Daly (OCE – 0526545), the University of Rhode Island, and the Rhode Island Experimental Program to Stimulate Competitive Research Fellowship program.2013-06-3