In the ongoing HATNet survey we have detected a giant planet, with radius 1.33 plus or minus 0.06 R sub(Jup) and mass 1.06 plus or minus 0.12 M sub(Jup), transiting the bright (V = 10.5) star GSC ...03239-00992. The planet is in a circular orbit with period 3.852985 plus or minus 0.000005 days and midtransit epoch 2,454,035.67575 plus or minus 0.00028 (HJD). The parent star is a late F star with mass 1.29 plus or minus 0.06 M unk, radius 1.46 plus or minus 0.06 R unk, T sub(off) similar to 6570 plus or minus 80 K, Fe/H = -0.13 plus or minus 0.08, and age similar to 2.3 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(5) sub(7) Gyr. With this radius and mass, HAT-P-6b has somewhat larger radius than theoretically expected. We describe the observations and their analysis to determine physical properties of the HAT-P-6 system, and briefly discuss some implications of this finding.
Red subdwarfs in binary systems are crucial for both model calibration and spectral classification. We search for red subdwarfs in binary systems from a sample of high proper motion objects with ...Sloan Digital Sky Survey spectroscopy. We present here discoveries from this search, as well as highlight several additional objects of interest. We find 30 red subdwarfs in wide binary systems including: two with spectral type of esdM5.5, 6 companions to white dwarfs and 3 carbon-enhanced red subdwarfs with normal red subdwarf companions. 15 red subdwarfs in our sample are partially resolved close binary systems. With this binary sample, we estimate the low limit of the red subdwarf binary fraction of ∼10 per cent. We find that the binary fraction goes down with decreasing masses and metallicities of red subdwarfs. A spectroscopic esdK7 subdwarf + white dwarf binary candidate is also reported. 30 new M subdwarfs have spectral type of ≥M6 in our sample. We also derive relationships between spectral types and absolute magnitudes in the optical and near-infrared for M and L subdwarfs, and we present an M subdwarf sample with measured U, V, W space velocities.
We report the discovery of a planet transiting a moderately bright (V = 12.00) G star, with an orbital period of 2.788491 plus or minus 0.000025 days. From the transit light curve we determine that ...the radius of the planet is R sub(P) = 1.257 plus or minus 0.053 R sub(J). HAT-P-5b has a mass of M sub(P) = 1.06 plus or minus 0.11 M sub(J), similar to the average mass of previously known transiting exoplanets, and a density of unk = 0.66 plus or minus 0.11 g cm super(-3). We find that the center of transit is unk = 2.454, 241.77663 plus or minus 0.00022 days (HJD), and the total transit duration is 0.1217 plus or minus 0.0012 days.
We report on the discovery of HAT-P-10b, one of the lowest mass (0.487 ± 0.018 M J) transiting extrasolar planets (TEPs) discovered to date by transit searches. HAT-P-10b orbits the moderately bright ...V = 11.89 K dwarf GSC 02340-01714, with a period P = 3.7224747 ± 0.0000065 days, transit epoch Tc = 2454759.68683 ± 0.00016 (BJD), and duration 0.1090 ± 0.0008 days. HAT-P-10b has a radius of 1.005+0.032 -0.027 R J yielding a mean density of 0.594 ± 0.052 g cm-3. Comparing these observations with recent theoretical models we find that HAT-P-10b is consistent with a ~4.5 Gyr, almost pure hydrogen and helium gas giant planet with a 10 M {circled plus} core. With an equilibrium temperature of T eq = 1020 ± 17 K, HAT-P-10b is one of the coldest TEPs. Curiously, its Safronov number c = 0.053 ± 0.002 falls close to the dividing line between the two suggested TEP populations.
ABSTRACT
We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey. Although periodic light‐curve variability in low mass stars is generally ...dominated by photospheric star spot activity, M dwarf variability in the J band has not been as thoroughly investigated as at visible wavelengths. Spectral type estimates for a sample of over 200 000 objects are made using spectral type–colour relations, and over 9600 dwarfs (J < 17) with spectral types later than K7 were found. The light curves of the late‐type sample are searched for periodicity using a Lomb–Scargle periodogram analysis. A total of 68 periodic variable M dwarfs are found in the sample with periods ranging from 0.16 to 90.33 d, with amplitudes in the range of ∼0.009 to ∼0.115 in the J band. We simulate active M dwarfs with a range of latitude‐independent spot coverages and estimate a periodically variable fraction of 1–3 per cent for stars where spots cover more than 10 per cent of the star's surface. Our simulated spot distributions indicate that operating in the J band, where spot contrast ratios are minimized, enables variability in only the most active of stars to be detected. These findings affirm the benefits of using the J band for planetary transit searches compared to visible bands. We also serendipitously find a ΔJ > 0.2 mag flaring event from an M4V star in our sample.
The discovery of the T8.5 dwarf UGPS J0521+3640 Burningham, Ben; Lucas, P. W.; Leggett, S. K. ...
Monthly notices of the Royal Astronomical Society. Letters,
06/2011, Letnik:
414, Številka:
1
Journal Article
Recenzirano
ABSTRACT
We have carried out a search for late‐type T dwarfs in the UKIRT Infrared Deep Sky Survey Galactic Plane Survey 6th Data Release. The search yielded two persuasive candidates, both of which ...have been confirmed as T dwarfs. The brightest, UGPS J0521+3640, has been assigned the spectral type T8.5 and appears to lie at a distance of 7–9 pc. The fainter of the two, UGPS J0652+0324, is classified as a T5.5 dwarf and lies at an estimated distance of 28–37 pc. Warm‐Spitzer observations in IRAC channels 1 and 2, taken as part of the GLIMPSE360 Legacy Survey, are available for UGPS J0521+3640 and we used these data with the near‐infrared spectroscopy to estimate its properties. We find best‐fitting solar metallicity BT‐Settl models for Teff= 600 and 650 K and log g= 4.5 and 5.0. These parameters suggest a mass between 14 and 32MJ for an age between 1 and 5 Gyr. The proximity of this very cool T dwarf, and its location in the Galactic plane, makes it an ideal candidate for high‐resolution adaptive optics imaging to search for cool companions.
The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, ...which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that difference-photometry light curves present an important improvement for stars with J > 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the box-fitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J ≤ 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes.
Abstract
The Astropy Project supports and fosters the development of open-source and openly developed
Python
packages that provide commonly needed functionality to the astronomical community. A key ...element of the Astropy Project is the core package
astropy
, which serves as the foundation for more specialized projects and packages. In this article, we provide an overview of the organization of the Astropy project and summarize key features in the core package, as of the recent major release, version 2.0. We then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of interoperable packages. We conclude with a future outlook of planned new features and directions for the broader Astropy Project.
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