217 research outputs found
LBT observations of the HR 8799 planetary system: First detection of HR8799e in H band
We have performed H and Ks band observations of the planetary system around
HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES
Camera. The excellent instrument performance (Strehl ratios up to 80% in H
band) enabled detection the inner planet HR8799e in the H band for the first
time. The H and Ks magnitudes of HR8799e are similar to those of planets c and
d, with planet e slightly brighter. Therefore, HR8799e is likely slightly more
massive than c and d. We also explored possible orbital configurations and
their orbital stability. We confirm that the orbits of planets b, c and e are
consistent with being circular and coplanar; planet d should have either an
orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c.
Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion
resonances with c and d, while coplanar and circular orbits are allowed for a
5:2 resonance. The analysis of dynamical stability shows that the system is
highly unstable or chaotic when planetary masses of about 5 MJup for b and 7
MJup for the other planets are adopted. Significant regions of dynamical
stability for timescales of tens of Myr are found when adopting planetary
masses of about 3.5, 5, 5, and 5 Mjup for HR 8799 b, c, d, and e respectively.
These masses are below the current estimates based on the stellar age (30 Myr)
and theoretical models of substellar objects.Comment: 13 pages, 10 figures, A&A, accepte
On passion and moral behavior in achievement settings: The mediating role of pride
The Dualistic Model of Passion (Vallerand et al., 2003) distinguishes two types of passion: harmonious passion (HP) and obsessive passion (OP) that predict adaptive and less adaptive outcomes, respectively. In the present research, we were interested in understanding the role of passion in the adoption of moral behavior in achievement settings. It was predicted that the two facets of pride (authentic and hubristic; Tracy & Robins, 2007) would mediate the passion-moral behavior relationship. Specifically, because people who are passionate about a given activity are highly involved in it, it was postulated that they should typically do well and thus experience high levels of pride when engaged in the activity. However, it was also hypothesized that while both types of passion should be conducive to authentic pride, only OP should lead to hubristic pride. Finally, in line with past research on pride (Carver, Sinclair, & Johnson, 2010; Tracy et al., 2009), only hubristic pride was expected to negatively predict moral behavior, while authentic pride was expected to positively predict moral behavior. Results of two studies conducted with paintball players (N=163, Study 1) and athletes (N=296, Study 2) supported the proposed model. Future research directions are discussed in light of the Dualistic Model of Passion
Accreting Protoplanets in the LkCa 15 Transition Disk
Exoplanet detections have revolutionized astronomy, offering new insights
into solar system architecture and planet demographics. While nearly 1900
exoplanets have now been discovered and confirmed, none are still in the
process of formation. Transition discs, protoplanetary disks with inner
clearings best explained by the influence of accreting planets, are natural
laboratories for the study of planet formation. Some transition discs show
evidence for the presence of young planets in the form of disc asymmetries or
infrared sources detected within their clearings, as in the case of LkCa 15.
Attempts to observe directly signatures of accretion onto protoplanets have
hitherto proven unsuccessful. Here we report adaptive optics observations of
LkCa 15 that probe within the disc clearing. With accurate source positions
over multiple epochs spanning 2009 - 2015, we infer the presence of multiple
companions on Keplerian orbits. We directly detect H{\alpha} emission from the
innermost companion, LkCa 15 b, evincing hot (~10,000 K) gas falling deep into
the potential well of an accreting protoplanet.Comment: 35 pages, 3 figures, 1 table, 9 extended data item
Near-Infrared Multi-Band Photometry of the Substellar Companion GJ 758 B
GJ 758 B is a cold (~600K) companion to a Sun-like star at 29 AU projected
separation, which was recently detected with high-contrast imaging. Here we
present photometry of the companion in seven photometric bands from
Subaru/HiCIAO, Gemini/NIRI and Keck/NIRC2, providing a rich sampling of the
spectral energy distribution in the 1-5 micron wavelength range. A clear
detection at 1.58 micron combined with an upper limit at 1.69 micron shows
methane absorption in the atmosphere of the companion. The mass of the
companion remains uncertain, but an updated age estimate indicates that the
most likely mass range is ~30-40 Mjup. In addition, we present an updated
astrometric analysis that imposes tighter constraints on GJ 758 B's orbit and
identifies the proposed second candidate companion, "GJ 758 C", as a background
star.Comment: 10 pages, 4 figures, accepted for publication in ApJ Letters. New
version: Corrected a few numbers in the astrometry section (which were
already correct in the print version, but were based on an outdated
simulation in the astro-ph version
Constrains on planets around beta Pic with Harps radial velocity data
Context. The {\beta} Pictoris system with its debris disk and a massive giant
planet orbiting at \simeq 9 AU represents an ideal laboratory to study giant
planet formation and evolution as well as planet-disk interactions. {\beta} Pic
b can also help testing brightness-mass relations at young ages. Other planets,
yet undetected, may of course be present in the system. Aims. We aim at putting
direct constrains on the mass of {\beta} Pic b and at searching for additional
jovian planets on orbits closer than typically 2 AU. Methods. We use high
precision Harps data collected over 8 years since 2003 to measure and analyse
{\beta} Pic radial velocities. Results. We show that the true mass of {\beta}
Pic b is less than 10, 12, 15.5, 20 and 25 MJup if orbiting respectively at 8,
9, 10, 11 and 12 AU. This is the first direct constraint on the mass of an
imaged planet. The upper mass found is well in the range predicted by
brightness-mass relations provided by current "hot start" models. We also
exclude the presence of giant planets more massive than 2.5 MJup with periods
less than 100 days (hot Jupiters), more massive than 9 MJup for periods in the
range 100-500 days. In the 500-1000 day range, the detection limit is in the
brown dwarf domain. Beyond the intrinsic interest for {\beta} Pic, these
results show the possibilities of precise RV measurements of early type,
rapidly rotating stars.Comment: 6 pages, 9 figures, to appear in Astronomy and Astrophysic
Dynamical Masses of Young Stars I:Discordant Model Ages of Upper Scorpius
We present the results of a long term orbit monitoring program, using sparse
aperture masking observations taken with NIRC2 on the Keck-II telescope, of
seven G to M-type members of the Upper Scorpius subgroup of the Sco-Cen OB
association. We present astrometry and derived orbital elements of the binary
systems we have monitored, and also determine the age, component masses,
distance and reddening for each system using the orbital solutions and
multi-band photometry, including Hubble Space Telescope photometry, and a
Bayesian fitting procedure. We find that the models can be forced into
agreement with any individual system by assuming an age, but that age is not
consistent across the mass range of our sample. The G-type binary systems in
our sample have model ages of ~11.5 Myr, which is consistent with the latest
age estimates for Upper Scorpius, while the M-type binary systems have
significantly younger model ages of ~7 Myr. Based on our fits, this age
discrepancy in the models corresponds to a luminosity under-prediction of
0.8-0.15 dex, or equivalently an effective temperature over-prediction of
100-300 K for M-type stars at a given premain-sequence age. We also find that
the M-type binary system RXJ 1550.0-2312 has an age (~16 Myr) and distance (~90
pc) indicating that it is either a nearby young binary system or a member of
the Upper-Centaurus-Lupus subgroup with a 57% probability of membership.Comment: 16 pages, 8 figures, 9 tables, accepted for publication in Ap
A new L-dwarf member of the moderately metal-poor triple system HD 221356
We report on the discovery of a fourth component in the HD 221356 star
system, previously known to be formed by an F8V, slightly metal-poor primary
([Fe/H]=-0.26), and a distant M8V+L3V pair. In our ongoing common proper motion
search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have
detected a faint (J=13.76+/-0.04 mag) co-moving companion of the F8 star
located at angular separation of 12.13+/-0.18 arcsec (position angle of
221.8+/-1.7), corresponding to a projected distance of ~312 AU at 26 pc.
Near-infrared spectroscopy of the new companion, covering the 1.5-2.4 micron
wavelength range with a resolving power of R~600, indicates an L1+/-1 spectral
type. Using evolutionary models the mass of the new companion is estimated at
~0.08 solar masses, which places the object close to the stellar-substellar
borderline. This multiple system provides an interesting example of objects
with masses slightly above and below the hydrogen burning mass limit. The low
mass companions of HD 221356 have slightly bluer colours than field dwarfs with
similar spectral type, which is likely a consequence of the sub-solar
metallicity of the system.Comment: 7 pages, 4 figures, accepted for publication in MNRA
The young active star SAO 51891 (V383 Lac)
Our aim is investigating surface inhomogeneities of the young late-type star
SAO51891, from photosphere to upper chromosphere, analyzing contemporaneous
high-resolution spectra and broad-band photometry. The FOCES@CAHA spectral
range is used to determine spectral classification and derive vsini and Vrad.
The Li abundance is measured to estimate the age. The BVRIJHKs bands are used
to construct the SED. The variations of our BV fluxes and Teff are used to
infer the presence of photospheric spots and observe their behavior over time.
The chromospheric activity is studied applying the spectral subtraction
technique to Halpha, CaII H&K, Heps, and CaII IRT lines. We find SAO51891 to be
a young K0-1V star with Li abundance close to the Pleiades upper envelope,
confirming its youth (~100 Myr), also inferred from its kinematical membership
to the Local Association. We detect no IR excess from SED analysis, and
rotational modulation of luminosity, Teff, CaII, and Heps total fluxes. A spot
model with two active regions, ~240 K cooler than the surrounding photosphere,
fits our light/Teff curves, and reproduces the small-amplitude Vrad variations.
The anti-correlation of light curves and chromospheric diagnostics indicates
plages spatially associated with spots. The large amplitude observed in the
Heps-flux curve suggests that this line is very sensitive to the plage
presence. Finally, SAO51891 is a young active star, lacking significant amounts
of circumstellar dust or any evidence for low mass companions. The spots turn
out to be larger and warmer than those in less active MS stars. The Vrad
variation produced by spots has an amplitude comparable with those induced by
Jupiter-mass planets orbiting close to the star. SAO51891 is a good example of
star where the detection of planets may be hampered by the high activity level.Comment: 16 pages, 12 figures, 7 tables, accepted by Astronomy and
Astrophysics; abstract here was shortene
On the binary frequency of the lowest mass members of the pleiades with hubble space telescope wide field camera 3
E. V. Garcia, et al., “On the Binary Frequency of the Lowest mass Members of the Pleiades with Hubble Space Telescope Wide Field Camera 3”, The Astrophysical Journal, Vol. 804(1), May 2015. © 2015. The American Astronomical Society.We present the results of a Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging survey of 11 of the lowest mass brown dwarfs in the Pleiades known (25-40 MJup). These objects represent the predecessors to T dwarfs in the field. Using a semi-empirical binary point-spread function (PSF)-fitting technique, we are able to probe to 0.″ 03 (0.75 pixel), better than 2x the WFC3/UVIS diffraction limit. We did not find any companions to our targets. From extensive testing of our PSF-fitting method on simulated binaries, we compute detection limits which rule out companions to our targets with mass ratios of 0.7 and separations 4 AU. Thus, our survey is the first to attain the high angular resolution needed to resolve brown dwarf binaries in the Pleiades at separations that are most common in the field population. We constrain the binary frequency over this range of separation and mass ratio of 25-40 MJup Pleiades brown dwarfs to bePeer reviewe
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