Abstract
We identify new Y- and T-type brown dwarfs from the
WISE All Sky
data release using images obtained in filters that divide the traditional near-infrared H and J bands into two ...halves—specifically
and CH
4
l in the H and J2, and J3 in the J. This proves to be very effective at identifying cool brown dwarfs via the detection of their methane absorption, as well as providing preliminary classification using methane colors and
WISE
-to-near-infrared colors. New and updated calibrations between T/Y spectral types and
–CH
4
l J3–W2, and
–W2 colors are derived, producing classification estimates good to a few spectral sub-types. We present photometry for a large sample of T and Y dwarfs in these filters, together with spectroscopy for 23 new ultra-cool dwarfs—2 Y dwarfs and 21 T dwarfs. We identify a further 8 new cool brown dwarfs, which we have high confidence are T dwarfs based on their methane photometry. We find that, for objects observed on a 4 m class telescope at J-band magnitudes of ∼20 or brighter,
–CH
4
l is the more powerful color for detecting objects and then estimating spectral types. Due to the lower sky background in the J-band, the J3 and J2 bands are more useful for identifying fainter cool dwarfs at
J
≳ 22. The J3–J2 color is poor at estimating spectral types. But fortunately, once J3–J2 confirms that an object
is
a cool dwarf, the J3–W2 color is very effective at estimating approximate spectral types.
We have used methane imaging techniques to identify the near-infrared counterpart of the bright Wide-field Infrared Survey Explorer (WISE) source WISE J163940.83-684738.6. The large proper motion of ...this source ( approximately 3".0 yr super(-1)) has moved it, since its original WISE identification, very close to a much brighter background star-it currently lies within 1".5 of the J = 14.90 + or - 0.04 star 2MASS 16394085-6847446. Observations in good seeing conditions using methane-sensitive filters in the near-infrared J band with the FourStar instrument on the Magellan 6.5 m Baade telescope, however, have enabled us to detect a near-infrared counterpart. We have defined a photometric system for use with the FourStar J2 and J3 filters, and this photometry indicates strong methane absorption, which unequivocally identifies it as the source of the WISE flux. Using these imaging observations we were then able to steer this object down the slit of the Folded-port Infrared Echellette spectrograph on a night of 0".6 seeing, and so obtain near-infrared spectroscopy confirming a Y0-Y0.5 spectral type. This is in line with the object's near-infrared-to-WISE J3 - W2 color. Preliminary astrometry using both WISE and FourStar data indicates a distance of 5.0 + or - 0.5 pc and a substantial tangential velocity of 73 + or - 8 kms super(-1). WISE J163940.83-684738.6 is the brightest confirmed Y dwarf in the WISE W2 passband and its distance measurement places it among the lowest luminosity sources detected to date.
Gliese 86 is a nearby K dwarf hosting a giant planet on a $\approx$16-day
orbit and an outer white dwarf companion on a $\approx$century-long orbit. In
this study we combine radial velocity data ...(including new measurements spanning
more than a decade) with high angular resolution imaging and absolute
astrometry from Hipparcos and Gaia to measure the current orbits and masses of
both companions. We then simulate the evolution of the Gl 86 system to
constrain its primordial orbit when both stars were on the main sequence; the
closest approach between the two stars was then about $9\,$AU. Such a close
separation limited the size of the protoplanetary disk of Gl 86 A and
dynamically hindered the formation of the giant planet around it. Our
measurements of Gl 86 B and Gl 86 Ab's orbits reveal Gl 86 as a system in which
giant planet formation took place in a disk truncated at $\approx$2$\,$AU. Such
a disk would be just big enough to harbor the dust mass and total mass needed
to assemble Gl 86 Ab's core and envelope, assuming a high disk accretion rate
and a low viscosity. Inefficient accretion of the disk onto Gl 86 Ab, however,
would require a disk massive enough to approach the Toomre stability limit at
its outer truncation radius. The orbital architecture of the Gl 86 system shows
that giant planets can form even in severely truncated disks and provides an
important benchmark for planet formation theory.
DISCOVERY OF THE Y1 DWARF WISE J064723.23–623235.5 Kirkpatrick, J Davy; Cushing, Michael C; GELINO, CHRISTOPHER R ...
Astrophysical journal/The Astrophysical journal,
10/2013, Letnik:
776, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the discovery of a very cold, very low mass, nearby brown dwarf using data from the NASA Wide-field Infrared Survey Explorer (WISE). The object, WISE J064723.23-623235.5, has a very red ...WISE color of W1-W2 > 3.77 mag and a very red Spitzer Space Telescope color of ch1-ch2 = 2.82 + or - 0.09 mag. In J sub(MKO)-ch2 color (7.58 + or - 0.27 mag) it is one of the two or three reddest brown dwarfs known. Our grism spectrum from the Hubble Space Telescope (HST) confirms it to be the seventeenth Y dwarf discovered, and its spectral type of Y1 + or - 0.5 makes it one of the four latest-type Y dwarfs classified. Astrometric imaging from Spitzer and HST, combined with data from WISE, provides a preliminary parallax of pi = 115 + or - 12 mas (d = 8.7 + or - 0.9 pc) and proper motion of mu = 387 + or - 25 mas yr super(-1) based on 2.5 yr of monitoring. The spectrum implies a blue J-H color, for which model atmosphere calculations suggest a relatively low surface gravity. The best fit to these models indicates an effective temperature of 350-400 K and a mass of ~5-30 M sub(Jup). Kinematic analysis hints that this object may belong to the Columba moving group, which would support an age of ~30 Myr and thus an even lower mass of <2 M sub(Jup), but verification would require a radial velocity measurement not currently possible for a J = 22.7 mag brown dwarf.
The GALAH survey: the data reduction pipeline Kos, Janez; Lin, Jane; Zwitter, Tomaž ...
Monthly Notices of the Royal Astronomical Society,
01/2017, Letnik:
464, Številka:
2
Journal Article
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA’s Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be ...of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of M(P) = 0.138 ± 0.023 M(J) (43.9 ± 7.3 Mꚛ), a radius of R(P) = 0.639 ± 0.013 R(J) (7.16 ± 0.15 Rꚛ), bulk density of 0.65 (+0.12,−0.11) (cgs), and period 18.38818 (+0.00085,−0.00084) days. TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M⁎ = 1.390 ± 0.046 M(sun), R⁎ = 1.888 ± 0.033 R(sun), T(eff) = 6075 ± 90 K, and 𝜈sin 𝑖 = 11.3 ± 0.5 km/s. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.
Abstract
Hot Jupiters—short-period giant planets—were the first extrasolar planets to be discovered, but many questions about their origin remain. NASA’s Transiting Exoplanet Survey Satellite (TESS), ...an all-sky search for transiting planets, presents an opportunity to address these questions by constructing a uniform sample of hot Jupiters for demographic study through new detections and unifying the work of previous ground-based transit surveys. As the first results of an effort to build this large sample of planets, we report here the discovery of 10 new hot Jupiters (TOI-2193A b, TOI-2207b, TOI-2236b, TOI-2421b, TOI-2567b, TOI-2570b, TOI-3331b, TOI-3540A b, TOI-3693b, TOI-4137b). All of the planets were identified as planet candidates based on periodic flux dips observed by TESS, and were subsequently confirmed using ground-based time-series photometry, high-angular-resolution imaging, and high-resolution spectroscopy coordinated with the TESS Follow-up Observing Program. The 10 newly discovered planets orbit relatively bright F and G stars (
G
< 12.5,
T
eff
between 4800 and 6200 K). The planets’ orbital periods range from 2 to 10 days, and their masses range from 0.2 to 2.2 Jupiter masses. TOI-2421b is notable for being a Saturn-mass planet and TOI-2567b for being a “sub-Saturn,” with masses of 0.322 ± 0.073 and 0.195 ± 0.030 Jupiter masses, respectively. We also measured a detectably eccentric orbit (
e
= 0.17 ± 0.05) for TOI-2207b, a planet on an 8 day orbit, while placing an upper limit of
e
< 0.052 for TOI-3693b, which has a 9 day orbital period. The 10 planets described here represent an important step toward using TESS to create a large and statistically useful sample of hot Jupiters.
We present Keck II laser guide star adaptive optics observations of the brown dwarf WISEP J061135.13-041024.0 showing it is a binary with a component separation of 0".4. This system is one of the six ...known resolved binaries in which the magnitude differences between the components show a reversal in sign between the Y/J band and the H/K bands. Deconvolution of the composite spectrum results in a best-fit binary solution with L9 and T1.5 components. We also present a preliminary parallax placing the system at a distance of 21.2 + or - 1.3 pc. Using the distance and resolved magnitudes we are able to place WISEP J061135.13-041024.0 AB on a color-absolute magnitude diagram, showing that this system contributes to the well-known "J-band bump" and the components' properties appear similar to other late-type L and early-type T dwarfs. Fitting our data to a set of cloudy atmosphere models suggests the system has an age >1 Gyr with WISE 0611-0410 A having an effective temperature (T sub(eff)) of 1275-1325 K and mass of 64-65 M sub(Jup), and WISE 0611-0410 B having T sub(eff) = 1075-1115 K and mass 40-65 M sub(Jup).
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