Abstract
We report the discovery of eight new giant planets, and updated orbits for four known planets, orbiting dwarf and subgiant stars using the CORALIE, HARPS, and MIKE instruments as part of the ...Calan–Hertfordshire Extrasolar Planet Search. The planets have masses in the range 1.1–5.4 M
J's, orbital periods from 40 to 2900 d, and eccentricities from 0.0 to 0.6. They include a double-planet system orbiting the most massive star in our sample (HD147873), two eccentric giant planets (HD128356b and HD154672b), and a rare 14 Herculis analogue (HD224538b). We highlight some population correlations from the sample of radial velocity detected planets orbiting nearby stars, including the mass function exponential distribution, confirmation of the growing body of evidence that low-mass planets tend to be found orbiting more metal-poor stars than giant planets, and a possible period–metallicity correlation for planets with masses >0.1 M
J, based on a metallicity difference of 0.16 dex between the population of planets with orbital periods less than 100 d and those with orbital periods greater than 100 d.
Aims. In this work we present chromospheric activity indices, kinematics, radial-velocities, and rotational velocities for more than 850 FGK-type dwarfs and subgiant stars in the southern hemisphere ...and test how best to calibrate and measure S-indices from echelle spectra. Methods. We measured our parameters using the high-resolution and high-S/N FEROS echelle spectra acquired for this purpose. Results. We confirm the bimodal distribution of chromospheric activities for such stars and highlight the role that the more active K-dwarfs play in biasing the number of active stars. We show that the age-activity relationship does appear to continue to ages older than the Sun if we simply compare main sequence stars and subgiant stars with an offset of around 2.5 Gyr between the peaks of both distributions. Also we show evidence of an increased spin-down timescale for cool K dwarfs compared with earlier F and G type stars. We highlight that activities drawn from low-resolution spectra (R < 2500) significantly increase the rms scatter when calibrating onto common systems of measurements like the Mt. Wilson system. Also we show that older and widely used catalogues of activities in the south appear to be offset compared to more recent works at the ~0.1 dex level in \hbox{$\log R'_{\rm{HK}}$}logRHK′ through calibrator drift. In addition, we show how kinematics can be used to preselect inactive stars for future planet search projects. We see the well known trend between projected rotational velocity and activity, however we also find a correlation between kinematic space velocity and chromospheric activity. It appears that after the Vaughan-Preston gap there is a quick step function in the kinematic space motion towards a significantly broader spread in velocities. We speculate on reasons for this correlation and provide some model scenarios to describe the bimodal activity distribution through magnetic saturation, residual low level gas accretion, or accretion by the star of planets or planetesimals. Finally, we provide a new empirical measurement for the disk-heating law, using the latest age-activity relationships to reconstruct the age-velocity distribution for local disk stars. We find a value of 0.337 ± 0.045 for the exponent of this power law (i.e. σtot ∝ t0.337), in excellent agreement with those found using isochrone fitting methods and with theoretical disk-heating models.
High-resolution MR imaging is an emerging tool for evaluating intracranial artery disease. It has an advantage of defining vessel wall characteristics of intracranial vascular diseases. We ...investigated high-resolution MR imaging arterial wall characteristics of CNS vasculitis and reversible cerebral vasoconstriction syndrome to determine wall pattern changes during a follow-up period.
We retrospectively reviewed 3T-high-resolution MR imaging vessel wall studies performed on 26 patients with a confirmed diagnosis of CNS vasculitis and reversible cerebral vasoconstriction syndrome during a follow-up period. Vessel wall imaging protocol included black-blood contrast-enhanced T1-weighted sequences with fat suppression and a saturation band, and time-of-flight MRA of the circle of Willis. Vessel wall characteristics including enhancement, wall thickening, and lumen narrowing were collected.
Thirteen patients with CNS vasculitis and 13 patients with reversible cerebral vasoconstriction syndrome were included. In the CNS vasculitis group, 9 patients showed smooth, concentric wall enhancement and thickening; 3 patients had smooth, eccentric wall enhancement and thickening; and 1 patient was without wall enhancement and thickening. Six of 13 patients had follow-up imaging; 4 patients showed stable smooth, concentric enhancement and thickening; and 2 patients had resoluton of initial imaging findings. In the reversible cerebral vasoconstriction syndrome group, 10 patients showed diffuse, uniform wall thickening with negligible-to-mild enhancement. Nine patients had follow-up imaging, with 8 patients showing complete resolution of the initial findings.
Postgadolinium 3T-high-resolution MR imaging appears to be a feasible tool in differentiating vessel wall patterns of CNS vasculitis and reversible cerebral vasoconstriction syndrome changes during a follow-up period.
Colorectal cancers are one of the most prevalent tumour types worldwide and, despite the emergence of targeted and biologic therapies, have among the highest mortality rates. The Personalized ...OncoGenomics (POG) program at BC Cancer performs whole genome and transcriptome analysis (WGTA) to identify specific alterations in an individual's cancer that may be most effectively targeted. Informed using WGTA, a patient with advanced mismatch repair-deficient colorectal cancer was treated with the antihypertensive drug irbesartan and experienced a profound and durable response. We describe the subsequent relapse of this patient and potential mechanisms of response using WGTA and multiplex immunohistochemistry (m-IHC) profiling of biopsies before and after treatment from the same metastatic site of the L3 spine. We did not observe marked differences in the genomic landscape before and after treatment. Analyses revealed an increase in immune signalling and infiltrating immune cells, particularly CD8+ T cells, in the relapsed tumour. These results indicate that the observed anti-tumour response to irbesartan may have been due to an activated immune response. Determining whether there may be other cancer contexts in which irbesartan may be similarly valuable will require additional studies.
The promise of “personalized medicine” guided by an understanding of each individual's genome has been fostered by increasingly powerful and economical methods to acquire clinically relevant ...information. We describe the operational implementation of prospective genotyping linked to an advanced clinical decision‐support system to guide individualized health care in a large academic health center. This approach to personalized medicine entails engagement between patient and health‐care provider, identification of relevant genetic variations for implementation, assay reliability, point‐of‐care decision support, and necessary institutional investments. In one year, approximately 3,000 patients, most of whom were scheduled for cardiac catheterization, were genotyped on a multiplexed platform that included genotyping for CYP2C19 variants that modulate response to the widely used antiplatelet drug clopidogrel. These data are deposited into the electronic medical record (EMR), and point‐of‐care decision support is deployed when clopidogrel is prescribed for those with variant genotypes. The establishment of programs such as this is a first step toward implementing and evaluating strategies for personalized medicine.
Clinical Pharmacology & Therapeutics (2012); 92 1, 87–95. doi:10.1038/clpt.2011.371
VIRAC: the VVV Infrared Astrometric Catalogue Smith, L. C; Lucas, P. W; Kurtev, R ...
Monthly notices of the Royal Astronomical Society,
02/2018, Letnik:
474, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Abstract
We present VIRAC version 1, a near-infrared proper motion and parallax catalogue of the VISTA Variables in the Via Lactea (VVV) survey for 312 587 642 unique sources averaged across all ...overlapping pawprint and tile images covering 560 deg2 of the bulge of the Milky Way and southern disc. The catalogue includes 119 million high-quality proper motion measurements, of which 47 million have statistical uncertainties below 1 mas yr−1. In the 11 < Ks < 14 magnitude range, the high-quality motions have a median uncertainty of 0.67 mas yr−1. The catalogue also includes 6935 sources with quality-controlled 5σ parallaxes with a median uncertainty of 1.1 mas. The parallaxes show reasonable agreement with the Tycho-Gaia Astrometric Solution, though caution is advised for data with modest significance. The SQL data base housing the data is made available via the web. We give example applications for studies of Galactic structure, nearby objects (low-mass stars and brown dwarfs, subdwarfs, white dwarfs) and kinematic distance measurements of young stellar objects. Nearby objects discovered include LTT 7251 B, an L7 benchmark companion to a G dwarf with over 20 published elemental abundances, a bright L subdwarf, VVV 1256−6202, with extremely blue colours and nine new members of the 25 pc sample. We also demonstrate why this catalogue remains useful in the era of Gaia. Future versions will be based on profile fitting photometry, use the Gaia absolute reference frame and incorporate the longer time baseline of the VVV extended survey.
We present the spectroscopic analysis of a large sample of late-M, L, and T dwarfs from the United Kingdom Deep Infrared Sky Survey. Using the YJHK photometry from the Large Area Survey and the ...red-optical photometry from the Sloan Digital Sky Survey we selected a sample of 262 brown dwarf candidates and we have followed-up 196 of them using the echelle spectrograph X-shooter on the Very Large Telescope. The large wavelength coverage (0.30–2.48 μm) and moderate resolution (R ∼ 5000–9000) of X-shooter allowed us to identify peculiar objects including 22 blue L dwarfs, 2 blue T dwarfs, and 2 low-gravity M dwarfs. Using a spectral indices-based technique, we identified 27 unresolved binary candidates, for which we have determined the spectral type of the potential components via spectral deconvolution. The spectra allowed us to measure the equivalent width of the prominent absorption features and to compare them to atmospheric models. Cross-correlating the spectra with a radial velocity standard, we measured the radial velocity of our targets, and we determined the distribution of the sample, which is centred at −1.7 ± 1.2 km s−1 with a dispersion of 31.5 km s−1. Using our results, we estimated the space density of field brown dwarfs and compared it with the results of numerical simulations. Depending on the binary fraction, we found that there are (0.85 ± 0.55) × 10−3 to (1.00 ± 0.64) × 10−3 objects per cubic parsec in the L4–L6.5 range, (0.73 ± 0.47) × 10−3 to (0.85 ± 0.55) × 10−3 objects per cubic parsec in the L7–T0.5 range, and (0.74 ± 0.48) × 10−3 to (0.88 ± 0.56) × 10−3 objects per cubic parsec in the T1–T4.5 range. We notice that there seems to be an excess of objects in the L–T transition with respect to the late-T dwarfs, a discrepancy that could be explained assuming a higher binary fraction than expected for the L–T transition, or that objects in the high-mass end and low-mass end of this regime form in different environments, i.e. following different initial mass functions.
We report the discovery of a peculiar L dwarf from the United Kingdom Infrared Deep Sky Survey Large Area Survey, ULAS J222711−004547. The very red infrared photometry (MKO J − K = 2.79 ± 0.06, WISE ...W1−W2 = 0.65 ± 0.05) of ULAS J222711−004547 makes it one of the reddest brown dwarfs discovered so far. We obtained a moderate resolution spectrum of this target using the XSHOOTER spectrograph on the Very Large Telescope, and we classify it as L7pec, confirming its very red nature. Comparison to theoretical models suggests that the object could be a low-gravity L dwarf with a solar or higher than solar metallicity. Nonetheless, the match of such fits to the spectral energy distribution is rather poor, and this and other less red peculiar L dwarfs pose new challenges for the modelling of ultracool atmospheres, especially to the understanding of the effects of condensates and their sensitivity to gravity and metallicity. We determined the proper motion of ULAS J222711−004547 using the data available in the literature, and we find that its kinematics do not suggest membership of any of the known young associations. We show that applying a simple de-reddening curve to its spectrum allows it to resemble the spectra of the L7 spectroscopic standards without any spectral features that distinguish it as a low-metallicity or low-gravity dwarf. Given the negligible interstellar reddening of the field containing our target, we conclude that the reddening of the spectrum is mostly due to an excess of dust in the photosphere of the target. De-reddening the spectrum using extinction curves for different dust species gives surprisingly good results and suggests a characteristic grain size of ∼0.5 μm. We show that by increasing the optical depth, the same extinction curves allow the spectrum of ULAS J222711−004547 to resemble the spectra of unusually blue L dwarfs and even slightly metal-poor L dwarfs. Grains of similar size also yield very good fits when de-reddening other unusually red L dwarfs in the L5-L7.5 range. These results suggest that the diversity in near-infrared colours and spectra seen in late L dwarfs could be due to differences in the optical thickness of the dust cloud deck.
Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs
, it is the closest single star to the Sun; only the ...three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known
and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging
, astrometry
and direct imaging
, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future.
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.
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