570 research outputs found
The Very Short Period M Dwarf Binary SDSS J001641-000925
We present follow-up observations and analysis of the recently discovered
short period low-mass eclipsing binary, SDSS J001641-000925. With an orbital
period of 0.19856 days, this system has one of the shortest known periods for
an M dwarf binary system. Medium-resolution spectroscopy and multi-band
photometry for the system are presented. Markov chain Monte Carlo modeling of
the light curves and radial velocities yields estimated masses for the stars of
M1 = 0.54 +/- 0.07 Msun and M2 = 0.34 +/- 0.04 Msun, and radii of R1 = 0.68 +/-
0.03 Rsun and R2 = 0.58 +/- 0.03 Rsun respectively. This solution places both
components above the critical Roche overfill limit, providing strong evidence
that SDSS J001641-000925 is the first verified M-dwarf contact binary system.
Within the follow-up spectroscopy we find signatures of non-solid body rotation
velocities, which we interpret as evidence for mass transfer or loss within the
system. In addition, our photometry samples the system over 9 years, and we
find strong evidence for period decay at the rate of dP/dt ~8 s/yr. Both of
these signatures raise the intriguing possibility that the system is in
over-contact, and actively losing angular momentum, likely through mass loss.
This places SDSS J001641-000925 as not just the first M-dwarf over-contact
binary, but one of the few systems of any spectral type known to be actively
undergoing coalescence. Further study SDSS J001641-000925 is on-going to verify
the nature of the system, which may prove to be a unique astrophysical
laboratory.Comment: 11 figures, ApJ Accepte
The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
We present the design and performance of the multi-object fiber spectrographs
for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon
Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999
on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the
spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II
surveys, enabling a wide variety of Galactic and extra-galactic science
including the first observation of baryon acoustic oscillations in 2005. The
spectrographs were upgraded in 2009 and are currently in use for BOSS, the
flagship survey of the third-generation SDSS-III project. BOSS will measure
redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha
absorption of 160,000 high redshift quasars over 10,000 square degrees of sky,
making percent level measurements of the absolute cosmic distance scale of the
Universe and placing tight constraints on the equation of state of dark energy.
The twin multi-object fiber spectrographs utilize a simple optical layout
with reflective collimators, gratings, all-refractive cameras, and
state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in
two channels over a bandpass covering the near ultraviolet to the near
infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven
heritage, the spectrographs were upgraded for BOSS with volume-phase
holographic gratings and modern CCD detectors, improving the peak throughput by
nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000
nm, and increasing the number of fibers from 640 to 1000 per exposure. In this
paper we describe the original SDSS spectrograph design and the upgrades
implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and
accepted by AJ. Provides background for the instrument responsible for SDSS
and BOSS spectra. 4th in a series of survey technical papers released in
Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral
Classification), and arXiv:1208.0022 (BOSS Overview
The Luminosity and Mass Functions of Low-Mass Stars in the Galactic Disk: I. The Calibration Region
We present measurements of the luminosity and mass functions of low-mass
stars constructed from a catalog of matched Sloan Digital Sky Survey (SDSS) and
2 Micron All Sky Survey (2MASS) detections. This photometric catalog contains
more than 25,000 matched SDSS and 2MASS point sources spanning ~30 square
degrees on the sky. We have obtained follow-up spectroscopy, complete to J=16,
of more than 500 low mass dwarf candidates within a 1 square degree sub-sample,
and thousands of additional dwarf candidates in the remaining 29 square
degrees. This spectroscopic sample verifies that the photometric sample is
complete, uncontaminated, and unbiased at the 99% level globally, and at the
95% level in each color range. We use this sample to derive the luminosity and
mass functions of low-mass stars over nearly a decade in mass (0.7 M_sun > M_*
> 0.1 M_sun). We find that the logarithmically binned mass function is best fit
with an M_c=0.29 log-normal distribution, with a 90% confidence interval of
M_c=0.20--0.50. These 90% confidence intervals correspond to linearly binned
mass functions peaking between 0.27 M_sun and 0.12 M_sun, where the best fit MF
turns over at 0.17 M_sun. A power law fit to the entire mass range sampled
here, however, returns a best fit of alpha=1.1 (where the Salpeter slope is
alpha = 2.35). These results agree well with most previous investigations,
though differences in the analytic formalisms adopted to describe those mass
functions can give the false impression of disagreement. Given the richness of
modern-day astronomical datasets, we are entering the regime whereby stronger
conclusions can be drawn by comparing the actual datapoints measured in
different mass functions, rather than the results of analytic analyses that
impose structure on the data a priori. (abridged)Comment: Accepted for publication in the Astronomical Journal. 21 pages,
emulateapj format, 12 figures. Figures 1, 4, 11 and 12 degraded for astroph;
full resolution version available for download at
http://www.cfa.harvard.edu/~kcovey
CaMKK2 as an emerging treatment target for bipolar disorder
Current pharmacological treatments for bipolar disorder are inadequate and based on serendipitously discovered drugs often with limited efficacy, burdensome side-effects, and unclear mechanisms of action. Advances in drug development for the treatment of bipolar disorder remain incremental and have come largely from repurposing drugs used for other psychiatric conditions, a strategy that has failed to find truly revolutionary therapies, as it does not target the mood instability that characterises the condition. The lack of therapeutic innovation in the bipolar disorder field is largely due to a poor understanding of the underlying disease mechanisms and the consequent absence of validated drug targets. A compelling new treatment target is the Ca2+-calmodulin dependent protein kinase kinase-2 (CaMKK2) enzyme. CaMKK2 is highly enriched in brain neurons and regulates energy metabolism and neuronal processes that underpin higher order functions such as long-term memory, mood, and other affective functions. Loss-of-function polymorphisms and a rare missense mutation in human CAMKK2 are associated with bipolar disorder, and genetic deletion of Camkk2 in mice causes bipolar-like behaviours similar to those in patients. Furthermore, these behaviours are ameliorated by lithium, which increases CaMKK2 activity. In this review, we discuss multiple convergent lines of evidence that support targeting of CaMKK2 as a new treatment strategy for bipolar disorder
Optical and Radio Properties of Extragalactic Sources Observed by the FIRST and SDSS Surveys
We discuss the optical and radio properties of 30,000 FIRST sources
positionally associated with an SDSS source in 1230 deg of sky. The
majority (83%) of the FIRST sources identified with an SDSS source brighter
than r=21 are optically resolved. We estimate an upper limit of 5% for the
fraction of quasars with broad-band optical colors indistinguishable from those
of stars. The distribution of quasars in the radio flux -- optical flux plane
supports the existence of the "quasar radio-dichotomy"; 8% of all quasars with
i<18.5 are radio-loud and this fraction seems independent of redshift and
optical luminosity. The radio-loud quasars have a redder median color by 0.08
mag, and a 3 times larger fraction of objects with red colors. FIRST galaxies
represent 5% of all SDSS galaxies with r<17.5, and 1% for r<20, and are
dominated by red galaxies. Magnitude and redshift limited samples show that
radio galaxies have a different optical luminosity distribution than non-radio
galaxies selected by the same criteria; when galaxies are further separated by
their colors, this result remains valid for both blue and red galaxies. The
distributions of radio-to-optical flux ratio are similar for blue and red
galaxies in redshift-limited samples; this similarity implies that the
difference in their luminosity functions, and resulting selection effects, are
the dominant cause for the preponderance of red radio galaxies in flux-limited
samples. We confirm that the AGN-to-starburst galaxy number ratio increases
with radio flux, and find that radio emission from AGNs is more concentrated
than radio emission from starburst galaxies (abridged).Comment: submitted to AJ, color gif figures, PS figures available from
[email protected]
Galaxy Clustering in Early SDSS Redshift Data
We present the first measurements of clustering in the Sloan Digital Sky
Survey (SDSS) galaxy redshift survey. Our sample consists of 29,300 galaxies
with redshifts 5,700 km/s < cz < 39,000 km/s, distributed in several long but
narrow (2.5-5 degree) segments, covering 690 square degrees. For the full,
flux-limited sample, the redshift-space correlation length is approximately 8
Mpc/h. The two-dimensional correlation function \xi(r_p,\pi) shows clear
signatures of both the small-scale, ``fingers-of-God'' distortion caused by
velocity dispersions in collapsed objects and the large-scale compression
caused by coherent flows, though the latter cannot be measured with high
precision in the present sample. The inferred real-space correlation function
is well described by a power law, \xi(r)=(r/6.1+/-0.2 Mpc/h)^{-1.75+/-0.03},
for 0.1 Mpc/h < r < 16 Mpc/h. The galaxy pairwise velocity dispersion is
\sigma_{12} ~ 600+/-100 km/s for projected separations 0.15 Mpc/h < r_p < 5
Mpc/h. When we divide the sample by color, the red galaxies exhibit a stronger
and steeper real-space correlation function and a higher pairwise velocity
dispersion than do the blue galaxies. The relative behavior of subsamples
defined by high/low profile concentration or high/low surface brightness is
qualitatively similar to that of the red/blue subsamples. Our most striking
result is a clear measurement of scale-independent luminosity bias at r < 10
Mpc/h: subsamples with absolute magnitude ranges centered on M_*-1.5, M_*, and
M_*+1.5 have real-space correlation functions that are parallel power laws of
slope ~ -1.8 with correlation lengths of approximately 7.4 Mpc/h, 6.3 Mpc/h,
and 4.7 Mpc/h, respectively.Comment: 51 pages, 18 figures. Replaced to match accepted ApJ versio
Hereditary transthyretin amyloidosis: baseline characteristics of patients in the NEURO-TTR trial
Background: Hereditary transthyretin (ATTRm) amyloidosis is a rare, progressive and fatal disease with a range of clinical manifestations.Objective: This study comprehensively evaluates disease characteristics in a large, diverse cohort of patients with ATTRm amyloidosis.Methods: Adult patients (N = 172) with Stage 1 or Stage 2 ATTRm amyloidosis who had polyneuropathy were screened and enrolled across 24 investigative sites and 10 countries in the NEURO-TTR trial (www.clinicaltrials.gov, NCT01737398). Medical and disease history, quality of life, laboratory data, and clinical assessments were analyzed.Results: The NEURO-TTR patient population was diverse in age, disease severity, TTR mutation, and organ involvement. Twenty-seven different TTR mutations were present, with Val30Met being the most common (52%). One third of patients reported early onset disease (before age 50) and the average duration of neuropathy symptoms was 5.3 years. Symptoms affected multiple organs and systems, with nearly 70% of patients exhibiting broad involvement of weakness, sensory loss, and autonomic disturbance. Over 60% of patients had cardiomyopathy, with highest prevalence in the United States (72%) and lowest in South America/Australasia (33%). Cardiac biomarker NT-proBNP correlated with left ventricular wall thickness (p<.001). Quality of life, measured by Norfolk QoL-DN and SF-36 patient-reported questionnaires, was significantly impaired and correlated with disease severity.Conclusions: Baseline data from the NEURO-TTR trial demonstrates ATTRm amyloidosis as a systemic disease with deficits in multiple organs and body systems, leading to decreased quality of life. We report concomitant presentation of polyneuropathy and cardiomyopathy in most patients, and early involvement of multiple body systems
A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Early Data Release
We present a catalog of 224 broad absorption line quasars (BALQSOs) from the
Sloan Digital Sky Survey's Early Data Release Quasar Catalog, including a
relatively complete and homogeneous subsample of 131 BALQSOs. Since the
identification of BALQSOs is subject to considerable systematic uncertainties,
we attempt to create a complete sample of SDSS BALQSOs by combining the results
of two automated selection algorithms and a by-eye classification scheme. One
of these automated algorithms finds broad absorption line troughs by comparison
with a composite quasar spectrum. We present the details of this algorithm and
compare this method to that which uses a power-law fit to the continuum. The
BALQSOs in our sample are further classified as high-ionization BALQSOs
(HiBALs), low-ionization BALQSOs (LoBALs), and BALQSOs with excited iron
absorption features (FeLoBALs); composite spectra of each type are presented.
We further present a study of the properties of the BALQSOs in terms of the
balnicity distribution, which rises with decreasing balnicity. This
distribution of balnicities suggests that the fraction of quasars with
intrinsic outflows may be significantly underestimated.Comment: 36 pages, 7 figures (1 color), 2 tables, accepted by A
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