We present eight new T4.5–T7.5 dwarfs identified in the UKIRT (United Kingdom Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) Data Release 1 (DR1). In addition we have ...recovered the T4.5 dwarf SDSS J020742.91+000056.2 and the T8.5 dwarf ULAS J003402.77−005206.7. Photometric candidates were picked up in two-colour diagrams over 190 deg2 (DR1) and selected in at least two filters. All candidates exhibit near-infrared spectra with strong methane and water absorption bands characteristic of T dwarfs and the derived spectral types follow the unified scheme of Burgasser et al.. We have found six new T4.5–T5.5 dwarfs, one T7 dwarf, one T7.5 dwarf and recovered a T4.5 dwarf and a T8.5 dwarf. We provide distance estimates which lie in the 15–85 pc range; the T7.5 and T8.5 dwarfs are probably within 25 pc of the Sun. We conclude with a discussion of the number of T dwarfs expected after completion of the LAS, comparing these initial results to theoretical simulations.
We have recently described the N-terminal RAS association domain family of genes, RASSF7-10. Previously, we cloned the N-terminal RASSF10 gene and demonstrated frequent methylation of the associated ...5'-CpG island in acute lymphoblastic leukemia. To characterize RASSF10 gene expression, we demonstrate that in developing Xenopus embryos, RASSF10 shows a very striking pattern in the rhombencephalon (hind brain). It is also expressed in other parts of the brain and other organs. Due to the well-defined expression pattern in the brain of Xenopus embryos, we analyzed the methylation status of the RASSF10-associated 5'-CpG island in astrocytic gliomas. RASSF10 was frequently methylated in WHO grade II-III astrocytomas and WHO grade IV primary glioblastomas (67.5%), but was unmethylated in grade I astrocytomas and in DNA from age matched control brain samples. RASSF10 gene expression both at the mRNA and protein levels could be switched back on in methylated glioma cell lines after treatment with 5-aza-2'-deoxycytidine. In secondary glioblastomas (sGBM), RASSF10 methylation was an independent prognostic factor associated with worst progression-free survival and overall survival and occurred at an early stage in their development. In cell culture experiments, overexpression of RASSF10 mediated a reduction in the colony forming ability of two RASSF10-methylated glioma cell lines. Conversely, RNAi-mediated knockdown of RASSF10-stimulated anchorage-independent growth of U87 glioma cells, increased their viability and caused an increase in the cells' proliferative ability. We generated and characterized a RASSF10-specific antibody and demonstrated for the first time that RASSF10 subcellular localization is cell-cycle dependent with RASSF10 colocalizing to centrosomes and associated microtubules during mitosis. This is the first report demonstrating that RASSF10 can act as a tumor suppressor gene and is frequently methylated in gliomas and can potentially be developed into a prognostic marker for sGBM.
We report the discovery of a brown dwarf on an eccentric orbit and with a semimajor axis that places it in the brown dwarf desert region around the star HD 191760. The star has a spectral type of ...G3IV/V and a metallicity (Fe/H) of 0.29 dex. HD 191760 adds to the small number of metal-rich stars with brown dwarf companions. The brown dwarf (HD 191760b) is found to have an orbital period of 505.57 ± 0.40 d and semimajor axis of 1.35 ± 0.01 au, placing it firmly in the brown dwarf desert. The eccentricity of HD 191760b is found to be 0.63 ± 0.01, meaning it reaches as close as 0.5 au from the host star. Dynamical simulations indicate that no inner planets could reside at separations beyond ∼0.17 au due to the disastrous gravity imposed by HD 191760b. In addition to these first results, we also refine the orbits found for the exoplanets around the stars HD 48265, HD 143361 and HD 154672. All one-planet solutions are in agreement with those previously published by the Magellan Planet Search.
A method is defined for identifying late-T and Y dwarfs in WISE down to low values of signal-to-noise. This requires a WISE detection only in the W2-band and uses the statistical properties of the ...WISE multiframe measurements and profile fit photometry to reject contamination resulting from non-point-like objects, variables and moving sources. To trace our desired parameter space, we use a control sample of isolated non-moving non-variable point sources from the Sloan Digital Sky Survey (SDSS), and identify a sample of 158 WISE
W2-only candidates down to a signal-to-noise limit of eight. For signal-to-noise ranges >10 and 8-10, respectively, ∼45 and ∼90 per cent of our sample fall outside the selection criteria published by the WISE team, mainly due to the type of constraints placed on the number of individual W2 detections. We present follow-up of eight candidates and identify WISE 0013+0634 and WISE 0833+0052, T8 and T9 dwarfs with high proper motion (∼1.3 and ∼1.8 arcsec yr−1). Both objects show a mid-infrared/near-infrared excess of ∼1-1.5 mag and are K band suppressed. Distance estimates lead to space motion constraints that suggest halo (or at least thick disc) kinematics. We then assess the reduced proper motion diagram of WISE ultracool dwarfs, which suggests that late-T and Y dwarfs may have a higher thick-disc/halo population fraction than earlier objects.
We present a study of age-related spectral signatures observed in 25 young low-mass objects that we have previously determined as possible kinematic members of five young moving groups: the Local ...Association (Pleiades moving group, age = 20-150 Myr), the Ursa Major group (Sirius supercluster, age = 300 Myr), the Hyades supercluster (age = 600 Myr), IC 2391 supercluster (age = 35-55 Myr) and the Castor moving group (age = 200 Myr). In this paper we characterize the spectral properties of observed high- or low-resolution spectra of our kinematic members by fitting theoretical spectral distributions. We study signatures of youth, such as lithium i 6708Å, Hα emission and other age-sensitive spectroscopic signatures in order to confirm the kinematic memberships through age constraints. We find that 21 (84 per cent) targets show spectroscopic signatures of youth in agreement with the age ranges of the moving group to which membership is implied. For two further objects, age-related constraints remain difficult to determine from our analysis. In addition, we confirm two moving group kinematic candidates as brown dwarfs.
ABSTRACT
We present an ultra‐cool dwarf (UCD) catalogue compiled from low southern Galactic latitudes and mid‐plane, from a cross‐correlation of the Two Micron All‐Sky Survey (2MASS) and the ...SuperCOSMOS survey. The catalogue contains 246 members identified from 5042 deg2 within 220° ≤ ℓ ≤ 360° and 0° < ℓ ≤ 30°, for |b| ≤ 15°. Sixteen candidates are spectroscopically confirmed in the near‐infrared as UCDs with spectral types from M7.5V to L9, the latest being the unusual blue L dwarf 2MASS J11263991−5003550. Our catalogue selection method is presented enabling UCDs from ∼M8V to the L–T transition to be selected down to a 2MASS limiting magnitude of Ks≃14.5 mag (for S/N ≥ 10). This method does not require candidates to have optical detections for catalogue inclusion. An optimal set of optical/near‐IR and reduced proper‐motion selection criteria have been defined that includes: an RF and IN photometric surface gravity test; a dual RF‐band variability check and an additional photometric classification scheme to selectively limit numbers of potential contaminants in regions of severe overcrowding. We identify four candidates as possible companions to nearby Hipparcos stars – observations are needed to identify these as potential benchmark UCD companions. We also identify 12 UCDs within a possible distance 20 pc, three are previously unknown of which two are estimated within 10 pc, complementing the nearby volume‐limited census of UCDs. An analysis of the catalogue spatial completeness provides estimates for distance completeness over three UCD MJ ranges, while Monte Carlo simulations provide an estimate of catalogue areal completeness at the 75 per cent level. We estimate a UCD space density of ρ(total) = (6.41 ± 3.01) × 10−3 pc−3 over the range of 10.5≤MJ≲14.9, similar to values measured at higher Galactic latitudes (|b|≳10∘) in the field population and obtained from more robust spectroscopically confirmed UCD samples.
We have used blue near-infrared colours to select a group of 12 spectroscopically confirmed United Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) T dwarfs later than T4. From ...amongst these, we identify the first two kinematic halo T-dwarf candidates. Blue near-infrared colours have been attributed to collisionally induced hydrogen absorption, which is enhanced by either high surface gravity or low metallicity. Proper motions are measured and distances estimated, allowing the determination of tangential velocities. U and V components are estimated for our objects by assuming V
rad= 0. From this, ULAS J0926+0835 is found to have U= 62 km s−1 and V=−140 km s−1, and ULAS J1319+1209 is found to have U= 192 km s−1 and V=−92 km s−1. These values are consistent with potential halo membership. However, these are not the bluest objects in our selection. The bluest is ULAS J1233+1219, with J−K=−1.16 ± 0.07, and surprisingly this object is found to have young disc-like U and V. Our sample also contains Hip 73786B, companion to the metal-poor K5 dwarf Hip 73786. Hip 73786 is a metal-poor star, with Fe/H =−0.3 ± 0.1 and is located at a distance of 19 ± 0.7 pc. U, V, W space velocity components are calculated for Hip 73786A and B, finding that U=−48 ± 7 km s−1, V=−75 ± 4 km s−1 and W=−44 ± 8 km s−1. From the properties of the primary, Hip 73786B is found to be at least 1.6-Gyr old. As a metal-poor object, Hip 73786B represents an important addition to the sample of known T dwarf benchmarks.
Summary Contact precautions, used to reduce the transmission of infectious diseases, include the wearing of gowns and gloves for room entry. Previous small studies have shown an association between ...contact precautions and increased symptoms of depression and anxiety. A retrospective cohort of all patients admitted to a tertiary care centre over two years was studied to assess the relationship between contact precautions and depression or anxiety. During the two-year period, there were 70 275 admissions including 28 564 unique non-intensive-care-unit (ICU), non-psychiatric admissions. After adjusting for potential confounders, contact precautions were associated with depression odds ratio (OR) 1.4, 95% confidence interval (CI) 1.2–1.5 but not with anxiety (OR 0.8, 95% CI 0.7–1.1) in the non-ICU population. Depression was 40% more prevalent among general inpatients on contact precautions.
We study a target sample of 68 low-mass objects (with spectral types in the range M4.5–L1) previously selected via photometric and astrometric criteria, as possible members of five young moving ...groups: the Local Association (Pleiades moving group, age = 20–150 Myr), the Ursa Mayor group (Sirius supercluster, age = 300 Myr), the Hyades supercluster (age = 600 Myr), IC 2391 supercluster (age = 35–55 Myr) and the Castor moving group (age = 200 Myr). In this paper, we assess their membership by using different kinematic and spectroscopic criteria. We use high-resolution echelle spectroscopic observations of the sample to measure accurate radial velocities. Distances are calculated and compared to those of the moving group from the literature, we also calculate the kinematic Galactic components (U,V,W) of the candidate members and apply kinematic criterion of membership to each group. In addition, we measure rotational velocities (v sin i) to place further constraints on membership of kinematic members. We find that 49 targets have young disc kinematics and that 36 of them possibly belong to one of our five moving groups. From the young disc target objects, 31 have rotational velocities in agreement with them belonging to the young disc population. We also find that one of our moving group candidates, 2MASS0123−3610, is a low-mass double lined spectroscopic binary, with probable spectral types around M7.
In many temperate and annual grasslands, above-ground net primary productivity (NPP) can be estimated by measuring peak above-ground biomass. Estimates of below-ground net primary productivity and, ...consequently, total net primary productivity, are more difficult. We addressed one of the three main objectives of the Global Primary Productivity Data Initiative for grassland systems to develop simple models or algorithms to estimate missing components of total system NPP. Any estimate of below-ground NPP (BNPP) requires an accounting of total root biomass, the percentage of living biomass and annual turnover of live roots. We derived a relationship using above-ground peak biomass and mean annual temperature as predictors of below-ground biomass (r2= 0.54; P = 0.01). The percentage of live material was 0.6, based on published values. We used three different functions to describe root turnover: constant, a direct function of above-ground biomass, or as a positive exponential relationship with mean annual temperature. We tested the various models against a large database of global grassland NPP and the constant turnover and direct function models were approximately equally descriptive (r2= 0.31 and 0.37), while the exponential function had a stronger correlation with the measured values (r2= 0.40) and had a better fit than the other two models at the productive end of the BNPP gradient. When applied to extensive data we assembled from two grassland sites with reliable estimates of total NPP, the direct function was most effective, especially at lower productivity sites. We provide some caveats for its use in systems that lie at the extremes of the grassland gradient and stress that there are large uncertainties associated with measured and modelled estimates of BNPP.
PDF
