34 research outputs found
Benchmarking Gaia DR3 Apsis with the Hyades and Pleiades open clusters
The Gaia astrophysical parameters inference system (Apsis) provides
astrophysical parameter estimates for several to 100s of millions of stars. We
aim to benchmark Gaia DR3 Apsis. We have compiled about 1500 bona fide single
stars in the Hyades and Pleiades open clusters for validation of PARSEC
isochrones, and for comparison with Apsis estimates. PARSEC stellar isochrones
in the Gaia photometric system enable us to assign average ages and
metallicities to the clusters, and mass, effective temperature, luminosity, and
surface gravity to the individual stars. Apsis does not recover the single-age,
single-metallicity characteristic of the cluster populations. Ages assigned to
cluster members seemingly follow the input template for Galactic populations,
with earlier-type stars systematically being assigned younger ages than
later-type stars. Cluster metallicities are underestimated by 0.1 to 0.2 dex.
Effective temperature estimates are in general reliable. Surface gravity
estimates reveal strong systematics for specific ranges of Gaia BP-RP colours.
We caution that Gaia DR3 Apsis estimates can be subject to significant
systematics. Some of the Apsis estimates, like metallicity, might only be
meaningful for statistical studies of the time-averaged Galactic stellar
population, but are not recommended to be used for individual stars.Comment: Accepted for publication in A&A. Table 2 in its entirety can be
requested from the authors in machine-readable format (mrt), and will become
available via CDS. 8 pages, 6 figures. v2: Figure 6, right, updated based on
Gaia DR3 Apsis GSP-Spec quality flag
Characterising Young Visual M-dwarf Binaries with Near-Infrared Integral Field Spectra
We present the results from an integral field spectroscopy study of seven
close visual binary pairs of young M-dwarf multiple systems. The target systems
are part of the astrometric monitoring AstraLux program, surveying hundreds of
M-dwarf systems for multiplicity and obtaining astrometric epochs for orbital
constraints. Our new VLT/SINFONI data provides resolved spectral type
classification in the J, H and K bands for seven of these low-mass M-dwarf
binaries, which we determine by comparing them to empirical templates and
examining the strength of water absorption in the K-band. The medium resolution
K-band spectra also allows us to derive effective temperatures for the
individual components. All targets in the survey display several signs of
youth, and some have kinematics similar to young moving groups, or low surface
gravities which we determine from measuring equivalent widths of gravity
sensitive alkali lines in the J-band. Resolved photometry from our targets is
also compared with isochrones from theoretical evolutionary models, further
implying young ages. Dynamical masses will be provided from ongoing monitoring
of these systems, which can be seen as emblematic binary benchmarks that may be
used to calibrate evolutionary models for low-mass stars in the future.Comment: 12 pages, 5 figures, 8 tables, preprint, accepted for publication in
A&
Spectral characterization of newly detected young substellar binaries with SINFONI
We observe 14 young low-mass substellar objects in young moving groups using
the SINFONI IFS with LGS-AO to detect and characterize 3 candidate binary
systems. Together with the adopted young moving group ages we employ isochrones
from substellar evolutionary models to estimate individual masses for the
binaries. We find 2MASS J15104786-2818174 to be part of the
Myr Argus moving group and composed of a primary brown
dwarf with spectral type M and a fainter
companion, separated by mas. 2MASS J22025794-5605087 is
identified as an almost equal-mass binary in the AB Dor moving group, with a
projected separation of mas. Both components share spectral type
M, which with the adopted age of Myr yields
individual masses between . The observations of 2MASS
J15474719-2423493 are of lesser quality and we obtain no spectral
characterization for the target, but resolve two components separated by
mas which with the predicted young field age of Myr
yields individual masses below . Out of the 3 candidate binary
systems, 2MASS J22025794-5605087 has unambiguous spectroscopic signs of being a
bona-fide binary, while the other two will require second-epoch confirmation.
The small projected separations between the binary components corresponds to
physical separations of AU, allowing for astrometric monitoring
of just a few years in order to generate constrained orbital fits and dynamical
masses for the systems. In combination with their young ages, these binaries
will prove to be excellent benchmarks for calibrating substellar evolutionary
models down to a very low-mass regime.Comment: 17 pages, 14 figure
The discrepancy between dynamical and theoretical mass in the triplet-system 2MASS J10364483+1521394
We combine new Lucky Imaging astrometry from NTT/AstraLux Sur with already
published astrometry from the AstraLux Large M-dwarf Multiplicity Survey to
compute orbital elements and individual masses of the 2MASS J10364483+1521394
triple system belonging to the Ursa-Major moving group. The system consists of
one primary low-mass M-dwarf orbited by two less massive companions, for which
we determine a combined dynamical mass of $M_{\rm{B}+\rm{C}}= 0.48 \pm 0.14\
M_\odot1.00 \pm 0.030.24 \pm 0.07\ M_\odot3.2 \pm 0.3\ 30\%20.1 \pm 2.08.41^{+0.04}_{-0.02}\ $years.Comment: 9 pages, 7 figures, accepted for publication in Astronomy &
Astrophysic
SPOTS: The Search for Planets Orbiting Two Stars. III. Complete Sample and Statistical Analysis
Binary stars constitute a large percentage of the stellar population, yet
relatively little is known about the planetary systems orbiting them. Most
constraints on circumbinary planets (CBPs) so far come from transit
observations with the Kepler telescope, which is sensitive to close-in
exoplanets but does not constrain planets on wider orbits. However, with
continuous developments in high-contrast imaging techniques, this population
can now be addressed through direct imaging. We present the full survey results
of the Search for Planets Orbiting Two Stars (SPOTS) survey, which is the first
direct imaging survey targeting CBPs. The SPOTS observational program comprises
62 tight binaries that are young and nearby, and thus suitable for direct
imaging studies, with VLT/NaCo and VLT/SPHERE. Results from SPOTS include the
resolved circumbinary disk around AK Sco, the discovery of a low-mass stellar
companion in a triple packed system, the relative astrometry of up to 9
resolved binaries, and possible indications of non-background planetary-mass
candidates around HIP 77911. We did not find any CBP within 300 AU, which
implies a frequency upper limit on CBPs (1--15 ) of 6--10 %
between 30-300 AU. Coupling these observations with an archival dataset for a
total of 163 stellar pairs, we find a best-fit CBP frequency of 1.9 % (2--15
) between 1--300 AU with a 10.5 % upper limit at a 95 % confidence
level. This result is consistent with the distribution of companions around
single stars.Comment: 27 pages, 13 Figures, 7 Tables. Accepted for publication in A&
JWST/NIRCam Coronagraphy of the Young Planet-hosting Debris Disk AU Microscopii
High-contrast imaging of debris disk systems permits us to assess the
composition and size distribution of circumstellar dust, to probe recent
dynamical histories, and to directly detect and characterize embedded
exoplanets. Observations of these systems in the infrared beyond 2--3 m
promise access to both extremely favorable planet contrasts and numerous
scattered-light spectral features -- but have typically been inhibited by the
brightness of the sky at these wavelengths. We present coronagraphy of the AU
Microscopii (AU Mic) system using JWST's Near Infrared Camera (NIRCam) in two
filters spanning 3--5 m. These data provide the first images of the
system's famous debris disk at these wavelengths and permit additional
constraints on its properties and morphology. Conducting a deep search for
companions in these data, we do not identify any compelling candidates.
However, with sensitivity sufficient to recover planets as small as
Jupiter masses beyond ( au) with
confidence, these data place significant constraints on any massive companions
that might still remain at large separations and provide additional context for
the compact, multi-planet system orbiting very close-in. The observations
presented here highlight NIRCam's unique capabilities for probing similar disks
in this largely unexplored wavelength range, and provide the deepest direct
imaging constraints on wide-orbit giant planets in this very well studied
benchmark system.Comment: 27 pages, 14 figure
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b
We present the highest fidelity spectrum to date of a planetary-mass object.
VHS 1256 b is a 20 M widely separated (8\arcsec, a =
150 au), young, planetary-mass companion that shares photometric colors and
spectroscopic features with the directly imaged exoplanets HR 8799 c, d, and e.
As an L-to-T transition object, VHS 1256 b exists along the region of the
color-magnitude diagram where substellar atmospheres transition from cloudy to
clear. We observed VHS 1256~b with \textit{JWST}'s NIRSpec IFU and MIRI MRS
modes for coverage from 1 m to 20 m at resolutions of 1,000 -
3,700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium
are observed in several portions of the \textit{JWST} spectrum based on
comparisons from template brown dwarf spectra, molecular opacities, and
atmospheric models. The spectral shape of VHS 1256 b is influenced by
disequilibrium chemistry and clouds. We directly detect silicate clouds, the
first such detection reported for a planetary-mass companion.Comment: Accepted ApJL Iterations of spectra reduced by the ERS team are
hosted at this link:
https://github.com/bemiles/JWST_VHS1256b_Reduction/tree/main/reduced_spectr
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems IV: NIRISS Aperture Masking Interferometry Performance and Lessons Learned
We present a performance analysis for the aperture masking interferometry
(AMI) mode on board the James Webb Space Telescope Near Infrared Imager and
Slitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables,
AMI accesses inner working angles down to and even within the classical
diffraction limit. The scientific potential of this mode has recently been
demonstrated by the Early Release Science (ERS) 1386 program with a deep search
for close-in companions in the HIP 65426 exoplanetary system. As part of ERS
1386, we use the same dataset to explore the random, static, and calibration
errors of NIRISS AMI observables. We compare the observed noise properties and
achievable contrast to theoretical predictions. We explore possible sources of
calibration errors, and show that differences in charge migration between the
observations of HIP 65426 and point-spread function calibration stars can
account for the achieved contrast curves. Lastly, we use self-calibration tests
to demonstrate that with adequate calibration, NIRISS AMI can reach contrast
levels of mag. These tests lead us to observation planning
recommendations and strongly motivate future studies aimed at producing
sophisticated calibration strategies taking these systematic effects into
account. This will unlock the unprecedented capabilities of JWST/NIRISS AMI,
with sensitivity to significantly colder, lower mass exoplanets than
ground-based setups at orbital separations inaccessible to JWST coronagraphy.Comment: 20 pages, 12 figures, submitted to AAS Journal
The \textit{JWST} Early Release Science Program for Direct Observations of Exoplanetary Systems III: Aperture Masking Interferometric Observations of the star HIP\,65426 at
We present aperture masking interferometry (AMI) observations of the star HIP
65426 at as a part of the \textit{JWST} Direct Imaging Early
Release Science (ERS) program obtained using the Near Infrared Imager and
Slitless Spectrograph (NIRISS) instrument. This mode provides access to very
small inner working angles (even separations slightly below the Michelson limit
of for an interferometer), which are inaccessible with the
classical inner working angles of the \textit{JWST} coronagraphs. When combined
with \textit{JWST}'s unprecedented infrared sensitivity, this mode has the
potential to probe a new portion of parameter space across a wide array of
astronomical observations. Using this mode, we are able to achieve a contrast
of \,mag relative to the host star at a separation
of {\sim}0.07\arcsec but detect no additional companions interior to the
known companion HIP\,65426\,b. Our observations thus rule out companions more
massive than 10{-}12\,\rm{M\textsubscript{Jup}} at separations
from HIP\,65426, a region out of reach of ground or
space-based coronagraphic imaging. These observations confirm that the AMI mode
on \textit{JWST} is sensitive to planetary mass companions orbiting at the
water frost line, even for more distant stars at 100\,pc. This result
will allow the planning and successful execution of future observations to
probe the inner regions of nearby stellar systems, opening essentially
unexplored parameter space.Comment: 15 pages, 9 figures, submitted to ApJ Letter
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The JWST Early-release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 μ m Spectrum of the Planetary-mass Companion VHS 1256–1257 b
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is a MJup widely separated (∼8″, a = 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color–magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST's NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20 μm at resolutions of ∼1000–3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion