81 research outputs found
New Extinction and Mass Estimates of the Low-mass Companion 1RXS 1609 B with the Magellan AO System: Evidence of an Inclined Dust Disk
We used the Magellan adaptive optics system to image the 11 Myr substellar
companion 1RXS 1609 B at the bluest wavelengths to date (z' and Ys). Comparison
with synthetic spectra yields a higher temperature than previous studies of
and significant dust extinction of
mag. Mass estimates based on the DUSTY tracks gives
0.012-0.015 Msun, making the companion likely a low-mass brown dwarf surrounded
by a dusty disk. Our study suggests that 1RXS 1609 B is one of the 25% of Upper
Scorpius low-mass members harboring disks, and it may have formed like a star
and not a planet out at 320 AU.Comment: 5 pages, 4 figures; accepted to ApJ
New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System
We used the Magellan adaptive optics (MagAO) system and its VisAO CCD camera
to image the young low mass brown dwarf companion CT Chamaeleontis B for the
first time at visible wavelengths. We detect it at r', i', z', and Ys. With our
new photometry and Teff~2500 K derived from the shape its K-band spectrum, we
find that CT Cha B has Av = 3.4+/-1.1 mag, and a mass of 14-24 Mj according to
the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r'
detection indicates that the companion has significant Halpha emission and a
mass accretion rate ~6*10^-10 Msun/yr, similar to some substellar companions.
Proper motion analysis shows that another point source within 2" of CT Cha A is
not physical. This paper demonstrates how visible wavelength AO photometry (r',
i', z', Ys) allows for a better estimate of extinction, luminosity, and mass
accretion rate of young substellar companions.Comment: Accepted for publication in ApJ; 6 figure
New Spatially Resolved Observations of the T Cha Transition Disk and Constraints on the Previously Claimed Substellar Companion
We present multi-epoch non-redundant masking observations of the T Cha
transition disk, taken at the VLT and Magellan in H, Ks, and L' bands. T Cha is
one of a small number of transition disks that host companion candidates
discovered by high-resolution imaging techniques, with a putative companion at
a position angle of 78 degrees, separation of 62 mas, and contrast at L' of 5.1
mag. We find comparable binary parameters in our re-reduction of the initial
detection images, and similar parameters in the 2011 L', 2013 NaCo L', and 2013
NaCo Ks data sets. We find a close-in companion signal in the 2012 NaCo L'
dataset that cannot be explained by orbital motion, and a non-detection in the
2013 MagAO/Clio2 L' data. However, Monte-carlo simulations show that the best
fits to the 2012 NaCo and 2013 MagAO/Clio2 followup data may be consistent with
noise. There is also a significant probability of false non-detections in both
of these data sets. We discuss physical scenarios that could cause the best
fits, and argue that previous companion and scattering explanations are
inconsistent with the results of the much larger dataset presented here.Comment: 25 pages, 22 figures, accepted for publication in Ap
Directly Imaged L-T Transition Exoplanets in the Mid-Infrared
Gas-giant planets emit a large fraction of their light in the mid-infrared
(3m), where photometry and spectroscopy are critical to our
understanding of the bulk properties of extrasolar planets. Of particular
importance are the L and M-band atmospheric windows (3-5m), which are the
longest wavelengths currently accessible to ground-based, high-contrast
imagers. We present binocular LBT AO images of the HR 8799 planetary system in
six narrow-band filters from 3-4m, and a Magellan AO image of the 2M1207
planetary system in a broader 3.3m band. These systems encompass the five
known exoplanets with luminosities consistent with LT transition
brown dwarfs. Our results show that the exoplanets are brighter and have
shallower spectral slopes than equivalent temperature brown dwarfs in a
wavelength range that contains the methane fundamental absorption feature
(spanned by the narrowband filters and encompassed by the broader 3.3m
filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry
caused by vertical mixing can explain the object's appearance. For the HR 8799
planets, we present new models that suggest the atmospheres must have patchy
clouds, along with non-equilibrium chemistry. Together, the presence of a
heterogeneous surface and vertical mixing presents a picture of dynamic
planetary atmospheres in which both horizontal and vertical motions influence
the chemical and condensate profiles.Comment: Accepted to Ap
Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet
Young giant exoplanets are a unique laboratory for understanding cool,
low-gravity atmospheres. A quintessential example is the massive extrasolar
planet Pic b, which is 9 AU from and embedded in the debris disk of the
young nearby A6V star Pictoris. We observed the system with first light
of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the
first CCD detection of this planet with MagAO+VisAO. Here we present four
MagAO+Clio images of Pic b at 3.1 m, 3.3 m, , and
, including the first observation in the fundamental CH band. To
remove systematic errors from the spectral energy distribution (SED), we
re-calibrate the literature photometry and combine it with our own data, for a
total of 22 independent measurements at 16 passbands from 0.99--4.8 m.
Atmosphere models demonstrate the planet is cloudy but are degenerate in
effective temperature and radius. The measured SED now covers 80\% of the
planet's energy, so we approach the bolometric luminosity empirically. We
calculate the luminosity by extending the measured SED with a blackbody and
integrating to find log(/) . From our
bolometric luminosity and an age of 233 Myr, hot-start evolutionary tracks
give a mass of 12.70.3 , radius of 1.450.02 , and
of 170823 K (model-dependent errors not included). Our
empirically-determined luminosity is in agreement with values from atmospheric
models (typically dex), but brighter than values from the field-dwarf
bolometric correction (typically dex), illustrating the limitations in
comparing young exoplanets to old brown dwarfs.Comment: Accepted to ApJ. 27 pages, 22 figures, 19 table
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