We report on the discovery that the nearby (∼6 pc) photometrically variable T2.5 dwarf SIMP J013656.5+093347 is a likely member of the ∼200 Myr old Carina-Near moving group with a probability of ...>99.9% based on its full kinematics. Our measurement of 50.9 0.8 km s−1 combined with the known rotation period inferred from variability measurements provide a lower limit of 1.01 0.02 on the radius of SIMP 0136+0933, an independent verification that it must be younger than ∼950 Myr, according to evolution models. We estimate a field interloper probability of 0.2% based on the density of field T0-T5 dwarfs. At the age of Carina-Near, SIMP 0136+0933 has an estimated mass of 12.7 1.0 and is predicted to have burned roughly half of its original deuterium. SIMP 0136+0933 is the closest known young moving group member to the Sun and is one of only a few known young T dwarfs, making it an important benchmark for understanding the atmospheres of young planetary-mass objects.
Researchers have several options when designing proteomics experiments. Primary among these are choices of experimental method, instrumentation and spectral interpretation software. To evaluate these ...choices on a proteome scale, we compared triplicate measurements of the yeast proteome by liquid chromatography tandem mass spectrometry (LC-MS/MS) using linear ion trap (LTQ) and hybrid quadrupole time-of-flight (QqTOF; QSTAR) mass spectrometers. Acquired MS/MS spectra were interpreted with Mascot and SEQUEST algorithms with and without the requirement that all returned peptides be tryptic. Using a composite target decoy database strategy, we selected scoring criteria yielding 1% estimated false positive identifications at maximum sensitivity for all data sets, allowing reasonable comparisons between them. These comparisons indicate that Mascot and SEQUEST yield similar results for LTQ-acquired spectra but less so for QSTAR spectra. Furthermore, low reproducibility between replicate data acquisitions made on one or both instrument platforms can be exploited to increase sensitivity and confidence in large-scale protein identifications.
An L Band Spectrum of the Coldest Brown Dwarf Morley, Caroline V.; Skemer, Andrew J.; Allers, Katelyn N. ...
The Astrophysical journal,
05/2018, Letnik:
858, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The coldest brown dwarf, WISE 0855, is the closest known planetary-mass, free-floating object and has a temperature nearly as cold as the solar system gas giants. Like Jupiter, it is predicted to ...have an atmosphere rich in methane, water, and ammonia, with clouds of volatile ices. WISE 0855 is faint at near-infrared wavelengths and emits almost all its energy in the mid-infrared. Skemer et al. presented a spectrum of WISE 0855 from 4.5-5.1 m (M band), revealing water vapor features. Here, we present a spectrum of WISE 0855 in the L band, from 3.4-4.14 m. We present a set of atmosphere models that include a range of compositions (metallicities and C/O ratios) and water ice clouds. Methane absorption is clearly present in the spectrum. The mid-infrared color can be better matched with a methane abundance that is depleted relative to solar abundance. We find that there is evidence for water ice clouds in the M band spectrum, and we find a lack of phosphine spectral features in both the L and M band spectra. We suggest that a deep continuum opacity source may be obscuring the near-infrared flux, possibly a deep phosphorous-bearing cloud, ammonium dihyrogen phosphate. Observations of WISE 0855 provide critical constraints for cold planetary atmospheres, bridging the temperature range between the long-studied solar system planets and accessible exoplanets. The James Webb Space Telescope will soon revolutionize our understanding of cold brown dwarfs with high-precision spectroscopy across the infrared, allowing us to study their compositions and cloud properties, and to infer their atmospheric dynamics and formation processes.
Background
Extension for Community Healthcare Outcomes (ECHO) and related models of medical tele-education are rapidly expanding; however, their effectiveness remains unclear. This systematic review ...examines the effectiveness of ECHO and ECHO-like medical tele-education models of healthcare delivery in terms of improved provider- and patient-related outcomes.
Methods
We searched English-language studies in PubMed, Embase, and PsycINFO databases from 1 January 2007 to 1 December 2018 as well as bibliography review. Two reviewers independently screened citations for peer-reviewed publications reporting provider- and/or patient-related outcomes of technology-enabled collaborative learning models that satisfied six criteria of the ECHO framework. Reviewers then independently abstracted data, assessed study quality, and rated strength of evidence (SOE) based on Cochrane GRADE criteria.
Results
Data from 52 peer-reviewed articles were included. Forty-three reported provider-related outcomes; 15 reported patient-related outcomes. Studies on provider-related outcomes suggested favorable results across three domains: satisfaction, increased knowledge, and increased clinical confidence. However, SOE was low, relying primarily on self-reports and surveys with low response rates. One randomized trial has been conducted. For patient-related outcomes, 11 of 15 studies incorporated a comparison group; none involved randomization. Four studies reported care outcomes, while 11 reported changes in care processes. Evidence suggested effectiveness at improving outcomes for patients with hepatitis C, chronic pain, dementia, and type 2 diabetes. Evidence is generally low-quality, retrospective, non-experimental, and subject to social desirability bias and low survey response rates.
Discussion
The number of studies examining ECHO and ECHO-like models of medical tele-education has been modest compared with the scope and scale of implementation throughout the USA and internationally. Given the potential of ECHO to broaden access to healthcare in rural, remote, and underserved communities, more studies are needed to evaluate effectiveness. This need for evidence follows similar patterns to other service delivery models in the literature.
We present final Spitzer trigonometric parallaxes for 361 L, T, and Y dwarfs. We combine these with prior studies to build a list of 525 known L, T, and Y dwarfs within 20 pc of the Sun, 38 of which ...are presented here for the first time. Using published photometry and spectroscopy as well as our own follow-up, we present an array of color–magnitude and color–color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. Using these characterizations, we assign each object a T(eff) value and judge sample completeness over bins of T(eff) and spectral type. Except for types ≥T8 and T(eff) < 600 K, our census is statistically complete to the 20 pc limit. We compare our measured space densities to simulated density distributions and find that the best fit is a power law (dN/dM ∝ M^(-α) with α = 0.6 ± 0.1. We find that the evolutionary models of Saumon & Marley correctly predict the observed magnitude of the space density spike seen at 1200 K < T(eff) < 1350 K, believed to be caused by an increase in the cooling timescale across the L/T transition. Defining the low-mass terminus using this sample requires a more statistically robust and complete sample of dwarfs ≥Y0.5 and with T(eff) < 400 K. We conclude that such frigid objects must exist in substantial numbers, despite the fact that few have so far been identified, and we discuss possible reasons why they have largely eluded detection.
We present a reorganization of the Oh et al. wide, comoving catalog of 4555 groups of stars (10,606 individual objects) identified in the Tycho Gaia Astrometric Survey (TGAS) into new and known ...coevolving groups of stars in the Milky Way. We use the BANYAN kinematic analysis tool to identify 1015 individual stars in the Oh et al. catalog that yielded a >80% probability in 1 of 27 known associations (e.g., the AB Doradus moving group, Columba, Upper Scorpius) in the vicinity of the Sun. Among the 27 groups uncovered by Oh et al. that had >10 connected components, we find that 4 are newly discovered. We use a combination of Tycho, Gaia, Two micron All Sky catalog, Wide Field Infrared Survey Explorer Mission, Galaxy Evolution Explorer, and Rontgen Satellite photometry as well as Gaia parallaxes to determine that these new groups are likely older than the Pleiades but younger than ∼1 Gyr. Using isochrone fitting, we find that the majority of these new groups have solar-type stars and solar-type metallicity. Among the 35 Oh et al. groups with five to nine members, we find that 19 also appear new and comoving, with Oh et al. Group 30 is particularly exciting as it is well within 100 pc (range of 77-90 pc) and also appears to be older than the Pleiades. For known star-forming regions, open clusters, and moving groups identified by Oh et al., we find that the majority were broken up into pieces over several Oh et al. groups (e.g., Lower Centaurus Crux members are spread over 26 Oh et al. groups); however, we found no correlation with positions of the groups on color-magnitude diagrams, and therefore no substructure of the association correlated with the Oh et al. designated group. We find that across the 27 groups tested by BANYAN there were 400 new members to 20 different associations uncovered by Oh et al. that require further vetting.
We report the discovery of WISE 2150-7520AB (W2150AB): a widely separated (∼341 au) very low-mass L1 + T8 co-moving system. The system consists of the previously known L1 primary 2MASS ...J21501592-7520367 and a newly discovered T8 secondary found at position 21:50:18.99–75:20:54.6 (MJD = 57947) using Wide-field Infrared Survey Explorer data via the Backyard Worlds: Planet 9 citizen science project. We present Spitzer ch1 and ch2 photometry (ch1–ch2 = 1.41 ± 0.04 mag) of the secondary and Folded-port InfraRed Echellette prism spectra of both components. The sources show no peculiar spectral or photometric signatures, indicating that each component is likely field age. Using all observed data and the Gaia DR2 parallax of 41.3593 ± 0.2799 mas for W2150A we deduce fundamental parameters of log(L(bol)/L(☉)) = −3.69 ± 0.01, T(eff) = 2118 ± 62 K, and an estimated mass = 72 ± 12 M(Jup) for the L1 and log(L(bol)/L(☉)) = −5.64 ± 0.02, T(eff) = 719 ± 61 K, and an estimated mass = 34 ± 22 M(Jup) for the T8. At a physical separation of ∼341 au this system has E(bin) = 1041 erg, making it the lowest binding energy system of any pair with M(tot) < 0.1 M(Sun) not associated with a young cluster. It is equivalent in estimated mass ratio, E(bin), and physical separation to the ∼2 Myr M7.25 + M8.25 binary brown dwarf 2MASS J11011926-7732383AB (2M1101AB) found in the Chameleon star-forming region. W2150AB is the widest companion system yet observed in the field where the primary is an L dwarf or later.
We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), the U.S. Naval Observatory (18), the New Technology Telescope (14), and the United ...Kingdom Infrared Telescope (9). To complete the 20 pc census of ≥T6 dwarfs, we combine these measurements with previously published trigonometric parallaxes for an additional 44 objects and spectrophotometric distance estimates for another 7. For these 235 objects, we estimate temperatures, sift into five 150 K wide Teff bins covering the range 300-1050 K, determine the completeness limit for each, and compute space densities. To anchor the high-mass end of the brown dwarf mass spectrum, we compile a list of early- to mid-L dwarfs within 20 pc. We run simulations using various functional forms of the mass function passed through two different sets of evolutionary code to compute predicted distributions in Teff. The best fit of these predictions to our L, T, and Y observations is a simple power-law model with 0.6 (where ), meaning that the slope of the field substellar mass function is in rough agreement with that found for brown dwarfs in nearby star-forming regions and young clusters. Furthermore, we find that published versions of the log-normal form do not predict the steady rise seen in the space densities from 1050 to 350 K. We also find that the low-mass cutoff to formation, if one exists, is lower than ∼5 MJup, which corroborates findings in young, nearby moving groups and implies that extremely low-mass objects have been forming over the lifetime of the Milky Way.
THE FIRST SPECTRUM OF THE COLDEST BROWN DWARF Skemer, Andrew J.; Morley, Caroline V.; Allers, Katelyn N. ...
Astrophysical journal. Letters,
08/2016, Letnik:
826, Številka:
2
Journal Article
Recenzirano
Odprti dostop
ABSTRACT The recently discovered brown dwarf WISE 0855 presents the first opportunity to directly study an object outside the solar system that is nearly as cold as our own gas giant planets. ...However, the traditional methodology for characterizing brown dwarfs-near-infrared spectroscopy-is not currently feasible, as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5-5.2 m spectrum, the same bandpass long used to study Jupiter's deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter's. The spectrum quality is high enough to allow for the investigation of dynamical and chemical processes that have long been studied in Jupiter's atmosphere, but now on an extrasolar world.
We present Spitzer Space Telescope variability monitoring observations of three low-gravity L dwarfs with previous detections of variability in the near-IR: 2MASS J0045+16, 2MASS J0501−00, and 2MASS ...J1425−36. We detect significant periodic variability in two of our targets, 2MASS J0045+16 and 2MASS J0501−00. We do not detect variability in 2MASS J1425−36. Combining our new rotation periods with rotational velocities, we calculate inclination angles of 22° 1°, , and for 2MASS J0045+16, 2MASS J0501−00, and 2MASS J1425−36, respectively. Our three new objects are consistent with the tentative relations between inclination, amplitude, and color anomaly previously reported. Objects with the highest variability amplitudes are inclined equator on, while the maximum observed amplitude decreases as the inclination angle decreases. We also find a correlation between the inclination angle and color anomaly for the sample of objects with measured inclinations. Compiling the entire sample of brown dwarfs with Spitzer variability detections, we find no enhancement in amplitude for young, early-L dwarfs compared to the field dwarf population. We find a possible enhancement in amplitude of low-gravity late-L dwarfs at 4.5 m. We do not find a correlation between amplitude ratio and spectral type for field dwarfs or for the young population. Finally, we compile the rotation periods of a large sample of brown dwarfs with ages 1 Myr-1 Gyr and compare the rotation rates predicted by evolutionary models assuming angular momentum conservation. We find that the rotation rates of the current sample of brown dwarfs fall within the expected range set by evolutionary models and breakup limits.
PDF
