DUSTY WDs IN THE WISE ALL SKY SURVEY ∩ SDSS Barber, Sara D; KILIC, MUKREMIN; Brown, Warren R ...
The Astrophysical journal,
05/2014, Letnik:
786, Številka:
2
Journal Article
Recenzirano
A recent cross-correlation between the Sloan Digital Sky Survey (SDSS) Data Release 7 White Dwarf Catalog with the Wide-Field Infrared Survey Explorer(WISE) all-sky photometry at 3.4, 4.6, 12, and 22 ...mu m performed by Debes et al. resulted in the discovery of 52 candidate dusty white dwarfs (WDs). However, the 6" WISE beam allows for the possibility that many of the excesses exhibited by these WDs may be due to contamination from a nearby source. We present MMT + SAG Wide-Field InfraRed Camera J- and H-band imaging observations (0".5-1".5 point spread function) of 16 of these candidate dusty WDs and confirm that four have spectral energy distributions (SEDs) consistent with a dusty disk and are not accompanied by a nearby source contaminant. The remaining 12 WDs have contaminated WISE photometry and SEDs inconsistent with a dusty disk when the contaminating sources are not included in the photometry measurements. We find the frequency of disks around single WDs in the WISE intersection SDSS sample to be 2.6%-4.1 %. One of the four new dusty WDs has a mass of 1.04 M sub(middot in circle) (progenitor mass 5.4 M sub(middot in circle)) and its discovery offers the first confirmation that massive WDs (and their massive progenitor stars) host planetary systems.
We have discovered a detached pair of white dwarfs (WDs) with a 12.75 minute orbital period and a 1315 km s--1 radial velocity amplitude. We measure the full orbital parameters of the system using ...its light curve, which shows ellipsoidal variations, Doppler boosting, and primary and secondary eclipses. The primary is a 0.25 M tidally distorted helium WD, only the second tidally distorted WD known. The unseen secondary is a 0.55 M carbon-oxygen WD. The two WDs will come into contact in 0.9 Myr due to loss of energy and angular momentum via gravitational wave radiation. Upon contact the systems may merge (yielding a rapidly spinning massive WD), form a stable interacting binary, or possibly explode as an underluminous Type Ia supernova. The system currently has a gravitational wave strain of 10--22, about 10,000 times larger than the Hulse-Taylor pulsar; this system would be detected by the proposed Laser Interferometer Space Antenna gravitational wave mission in the first week of operation. This system's rapid change in orbital period will provide a fundamental test of general relativity.
Alcohol-related liver disease (ALD) ranges from never-decompensated ALD (ndALD) to the life-threatening decompensated phenotype, known as alcohol-related hepatitis (AH). A multidimensional study of ...the clinical, histological and molecular features of these subtypes is lacking.
Two large cohorts of patients were recruited in an international, observational multicentre study: a retrospective cohort of patients with ndALD (n=110) and a prospective cohort of patients with AH (n=225). Clinical, analytical, immunohistochemistry and hepatic RNA microarray analysis of both disease phenotypes were performed.
Age and mean alcohol intake were similar in both groups. AH patients had greater aspartate amino transferase/alanine amino transferase ratio and lower gamma-glutamyl transferase levels than in ndALD patients. Patients with AH demonstrated profound liver failure and increased mortality. One-year mortality was 10% in ndALD and 50% in AH. Histologically, steatosis grade, ballooning and pericellular fibrosis were similar in both groups, while advanced fibrosis, Mallory-Denk bodies, bilirubinostasis, severe neutrophil infiltration and ductular reaction were more frequent among AH patients. Transcriptome analysis revealed a profound gene dysregulation within both phenotypes when compare to controls. While ndALD was characterised by deregulated expression of genes involved in matrisome and immune response, the development of AH resulted in a marked deregulation of genes involved in hepatocyte reprogramming and bile acid metabolism.
Despite comparable alcohol intake, AH patients presented with worse liver function compared with ndALD patients. Bilirubinostasis, severe fibrosis and ductular reaction were prominent features of AH. AH patients exhibited a more profound deregulation of gene expression compared with ndALD patients.
The Mass Profile of the Galaxy to 80 kpc Gnedin, Oleg Y; Brown, Warren R; Geller, Margaret J ...
Astrophysical journal. Letters,
09/2010, Letnik:
720, Številka:
1
Journal Article
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Odprti dostop
The Hypervelocity Star Survey presents the currently largest sample of radial velocity measurements of halo stars out to 80 kpc. We apply spherical Jeans modeling to these data in order to derive the ...mass profile of the Galaxy. We restrict the analysis to distances larger than 25 kpc from the Galactic center, where the density profile of halo stars is well approximated by a single power law with logarithmic slope between -3.5 and -4.5. With this restriction, we also avoid the complication of modeling a flattened Galactic disk. In the range 25 kpc < r < 80 kpc, the radial velocity dispersion declines remarkably little; a robust measure of its logarithmic slope is between -0.05 and -0.1. The circular velocity profile also declines remarkably little with radius. The allowed range of V{sub c} (80 kpc) lies between 175 and 231 km s{sup -1}, with the most likely value of 193 km s{sup -1}. Compared with the value at the solar location, the Galactic circular velocity declines by less than 20% over an order of magnitude in radius. Such a flat profile requires a massive and extended dark matter halo. The mass enclosed within 80 kpc is 6.9{sup +3.0} {sub -1.2} x 10{sup 11} M {sub sun}. Our sample of radial velocities is large enough that the biggest uncertainty in the mass is not statistical but systematic, dominated by the density slope and anisotropy of the tracer population. Further progress requires modeling observed data sets within realistic simulations of galaxy formation.
To explore the effects of singing training on respiratory function, voice, mood, and quality of life for people with quadriplegia.
Randomized controlled trial.
Large, university-affiliated public ...hospital, Victoria, Australia.
Participants (N=24) with chronic quadriplegia (C4-8, American Spinal Injury Association grades A and B).
The experimental group (n=13) received group singing training 3 times weekly for 12 weeks. The control group (n=11) received group music appreciation and relaxation for 12 weeks. Assessments were conducted pre, mid-, immediately post-, and 6-months postintervention.
Standard respiratory function testing, surface electromyographic activity from accessory respiratory muscles, sound pressure levels during vocal tasks, assessments of voice quality (Perceptual Voice Profile, Multidimensional Voice Profile), and Voice Handicap Index, Profile of Mood States, and Assessment of Quality of Life instruments.
The singing group increased projected speech intensity (P=.028) and maximum phonation length (P=.007) significantly more than the control group. Trends for improvements in respiratory function, muscle strength, and recruitment were also evident for the singing group. These effects were limited by small sample sizes with large intersubject variability. Both groups demonstrated an improvement in mood (P=.002), which was maintained in the music appreciation and relaxation group after 6 months (P=.017).
Group music therapy can have a positive effect on not only physical outcomes, but also can improve mood, energy, social participation, and quality of life for an at-risk population, such as those with quadriplegia. Specific singing therapy can augment these general improvements by improving vocal intensity.
ABSTRACT We measure the three components of velocity dispersion, R, θ, φ, for stars within 6 < R < 30 kpc of the Milky Way using a new radial velocity sample from the MMT telescope. We combine our ...measurements with previously published data so that we can more finely sample the stellar halo. We use a maximum likelihood statistical method for estimating mean velocities, dispersions, and covariances assuming only that velocities are normally distributed. The alignment of the velocity ellipsoid is consistent with a spherically symmetric gravitational potential. From the spherical Jeans equation, the mass of the Milky Way is with an uncertainty of 40%. We also find a region of discontinuity, 15 R 25 kpc, where the estimated velocity dispersions and anisotropies diverge from their anticipated values, confirming the break observed by others. We argue that this break in anisotropy is physically explained by coherent stellar velocity structure in the halo, such as the Sgr stream. To significantly improve our understanding of halo kinematics will require combining radial velocities with future Gaia proper motions.
We describe new radial velocity and X-ray observations of extremely low-mass white dwarfs (ELM WDs, ~0.2 M ) in the Sloan Digital Sky Survey Data Release 4 and the MMT Hypervelocity Star survey. We ...identify four new short period binaries, including two merger systems. These observations bring the total number of short period binary systems identified in our survey to 20. No main-sequence or neutron star companions are visible in the available optical photometry, radio, and X-ray data. Thus, the companions are most likely WDs. Twelve of these systems will merge within a Hubble time due to gravitational wave radiation. We have now tripled the number of known merging WD systems. We discuss the characteristics of this merger sample and potential links to underluminous supernovae, extreme helium stars, AM CVn systems, and other merger products. We provide new observational tests of the WD mass-period distribution and cooling models for ELM WDs. We also find evidence for a new formation channel for single low-mass WDs through binary mergers of two lower mass objects.
CfA4: LIGHT CURVES FOR 94 TYPE Ia SUPERNOVAE Hicken, Malcolm; Challis, Peter; Kirshner, Robert P ...
The Astrophysical journal. Supplement series,
06/2012, Letnik:
200, Številka:
2
Journal Article
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We present multi-band optical photometry of 94 spectroscopically confirmed Type Ia supernovae (SNe Ia) in the redshift range 0.0055-0.073, obtained between 2006 and 2011. There are a total of 5522 ...light-curve points. We show that our natural-system SN photometry has a precision of <, ~0.03 mag in B Vr'i', <, ~0.06 mag in u', and <, ~0.07 mag in U for points brighter than 17.5 mag and estimate that it has a systematic uncertainty of 0.014,0.010,0.012,0.014, 0.046, and 0.073 mag in B Vr'i'u'U, respectively. Comparisons of our standard-system photometry with published SN Ia light curves and comparison stars reveal mean agreement across samples in the range of ~0.00-0.03 mag. We discuss the recent measurements of our telescope-plus-detector throughput by direct monochromatic illumination by Cramer et al. This technique measures the whole optical path through the telescope, auxiliary optics, filters, and detector under the same conditions used to make SN measurements. Extremely well characterized natural-system passbands (both in wavelength and over time) are crucial for the next generation of SN Ia photometry to reach the 0.01 mag accuracy level. The current sample of low-z SNe Ia is now sufficiently large to remove most of the statistical sampling error from the dark-energy error budget. But pursuing the dark-energy systematic errors by determining highly accurate detector passbands, combining optical and near-infrared (NIR) photometry and spectra, using the nearby sample to illuminate the population properties of SNe Ia, and measuring the local departures from the Hubble flow will benefit from larger, carefully measured nearby samples.
Of more than a thousand known cataclysmic variables (CVs), where a white dwarf is accreting from a hydrogen-rich star, only a dozen have orbital periods below 75 minutes1-9. One way to achieve these ...short periods requires the donor star to have undergone substantial nuclear evolution before interacting with the white dwarf10-14, and it is expected that these objects will transition to helium accretion. These transitional CVs have been proposed as progenitors of helium CVs13-18. However, no known transitional CV is expected to reach an orbital period short enough to account for most of the helium CV population, leaving the role of this evolutionary pathway unclear. Here we report observations of ZTFJ1813+4251, a 51-minute-orbital-period, fully eclipsing binary system consisting of a star with a temperature comparable to that of the Sun but a density 100 times greater owing to its helium-rich composition, accreting onto a white dwarf. Phase-resolved spectra, multi-band light curves and the broadband spectral energy distribution allow us to obtain precise and robust constraints on the masses, radii and temperatures of both components. Evolutionary modelling shows that ZTFJ1813+4251 is destined to become a helium CV binary, reaching an orbital period under 20 minutes, rendering ZTFJ1813+4251 a previously missing link between helium CV binaries and hydrogen-rich CVs.
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