20 research outputs found
Near-Infrared Accretion Signatures from the Circumbinary Planetary-Mass Companion Delorme 1 (ab)b
Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ?1/430-45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong Hα emission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5-10 Myr. Here, we present the first NIR detection of accretion from the companion in Paβ, Pa?3, and Br?3 emission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, with L line ≈ 1-6 × 10-8 L ? across lines and epochs, while the binary host system shows no NIR hydrogen line emission (L line \u3c 0.32-11 × 10-7 L ?). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of Ṁpla?1/43 -4 × 10-8 M J yr-1, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b\u27s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (signal-to-noise ratio ?1/45) NIR hydrogen line emission
Peering into the Young Planetary System AB Pic. Atmosphere, Orbit, Obliquity & Second Planetary Candidate
We aim to revisit the system AB Pic which has a known companion at the
exoplanet/ brown-dwarf boundary. We based this study on a rich set of
observations to investigate the companion's orbit and atmosphere. We composed a
spectrum of AB Pic b merging archival VLT/SINFONI K-band data, with published
spectra at J and H-band (SINFONI) and Lp-band (Magellan-AO), and photometric
measurements (HST and Spitzer). We modeled the spectrum with ForMoSA, based on
two atmospheric models: ExoREM and BT-SETTL13. We determined the orbital
properties of b fitting the astrometric measurements from NaCo (2003 and 2004)
and SPHERE (2015). The orbital solutions favor a semi-major axis of 190au
viewed edge-on. With Exo-REM, we derive a T of 170050K and surface
gravity of 4.50.3dex, consistent with previous works, and we report for
the first time a C/O ratio of 0.580.08 (solar). The posteriors are
sensitive to the wavelength interval and the family of models used. Given the
2.1hr rotation period and our vsin(i) of 73km/s, we estimate for the
first time the true obliquity to be 45 or 135deg, indicating a
significant misalignment between the planet's spin and orbit orientations.
Finally, the existence of a proper motion anomaly between the Hipparcos and
Gaia eDR3 compared to our SPHERE detection limits and adapted radial velocity
limits indicate the existence of a 6M inner planet orbiting from
2 to 10au (40-200mas). The possible existence of an inner companion, together
with the likely miss-alignment of the spin axis orientation, strongly favor a
formation path by gravitational instability or core accretion within a disk
closer inside followed by dynamical interactions. Confirmation and
characterization of planet c and access to a broader wavelength coverage for
planet b will be essential to probe the uncertainties associated with the
parameters.Comment: 17 pages, 13 Figures, 6 Tables. Accepted for publication in A&A (31
of October
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
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. V. Do Self-consistent Atmospheric Models Represent JWST Spectra? A Showcase with VHS 1256–1257 b
This is the final version. Available on open access from IOP Publishing via the DOI in this recordThe unprecedented medium-resolution (Rλ ∼ 1500–3500) near- and mid-infrared (1–18 μm) spectrum provided by JWST for the young (140 ± 20 Myr) low-mass (12–20 MJup) L–T transition (L7) companion VHS 1256 b gives access to a catalog of molecular absorptions. In this study, we present a comprehensive analysis of this data set utilizing a forward-modeling approach applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, γ, fsed, and R. Our findings reveal that each parameter's estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS 1256 b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST's data for VHS 1256 b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models
The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. IV. NIRISS Aperture Masking Interferometry Performance and Lessons Learned
This is the final version. Available on open access from IOP Publishing via the DOI in this recordWe 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 data set 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 F380M AMI can reach contrast levels of ~9-10 mag at ≥λ/D. 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 lower-contrast ground-based AMI setups, at orbital separations inaccessible to JWST coronagraphy.National Science Foundation (NSF)NASAEuropean Union Horizon 2020Royal Societ
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 data set 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 F380M AMI can reach contrast levels of ∼9–10 mag at ≳λ/D. 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 lower-contrast ground-based AMI setups, at orbital separations inaccessible to JWST coronagraphy
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The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. V. Do Self-consistent Atmospheric Models Represent JWST Spectra? A Showcase with VHS 1256–1257 b
The unprecedented medium-resolution (R λ ∼ 1500–3500) near- and mid-infrared (1–18 μm) spectrum provided by JWST for the young (140 ± 20 Myr) low-mass (12–20 MJup) L–T transition (L7) companion VHS 1256 b gives access to a catalog of molecular absorptions. In this study, we present a comprehensive analysis of this data set utilizing a forward-modeling approach applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, γ, f sed, and R. Our findings reveal that each parameter’s estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS 1256 b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST’s data for VHS 1256 b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models
Emission line variability of young 10-30 Mjup companions : I. The case of GQ Lup b and GSC 06214-00210 b
Emission lines indicative of active accretion have been seen on a handful of
low-mass companions (M < 30 MJup) to stars. Line variability is ubiquitous on
stellar accretors but has never been characterized in detail on low-mass
companions and can give insights on the accretion mechanism at play. We
investigate the emission line variability of two low-mass companions (M<30
MJup) to stars to understand their accretion mechanisms. Using J-band
observations, we analyze the short to long-term variability of the HI Paschen
{\beta} emission line (1.282 {\mu}m) for GQ Lup b and GSC 06214-00210 b.
Archival spectroscopic observations are also examined to extend the time span.
We compare their line profiles and intensities to more massive accretors and
magnetospheric accretion and shock models. Both objects have HI Paschen {\beta}
flux variability that is moderate at short timescales (< 50 %) and increases at
longer timescales (~1000 % on decade timescales), resembling classical T Tauri
stars. GQ Lup b's line profiles are compatible with magnetospheric accretion.
GSC 06214-00210 b's profiles are reproduced by both magnetospheric accretion
and shock models, except for the brightest epoch for which the shock model is
highly favored. Both companions have C/O values broadly consistent with solar
values. While magnetospheric accretion is favored for GQ Lup b, higher
resolution (R > 10000) observations are required to disentangle the two
(non-exclusive) line formation mechanisms. The similarity in variability
behavior may support similar accretion mechanisms between these low-mass
companions and classical T Tauri stars. The significant variability observed at
months and longer timescales could explain the low yield of H{\alpha} imaging
campaigns.Comment: 21 pages, 10 figure
X-SHYNE: X-shooter spectra of young exoplanet analogs: I. A medium-resolution 0.65-2.5 μ m one-shot spectrum of VHS 1256-1257 b
International audienceWe present simultaneous 0.65-2.5 m medium resolution (3300 R 8100) VLT/X-shooter spectra of the relatively young (150-300 Myr) low-mass (19 5MJup) L-T transition object VHS 1256-1257 b, a known spectroscopic analog of HR8799d. The companion is a prime target for the JWST Early Release Science (ERS) and one of the highest-Amplitude variable brown dwarfs known to date. We compare the spectrum to the custom grids of cloudless ATMO models, exploring the atmospheric composition with the Bayesian inference tool ForMoSA. We also reanalyze low-resolution HST/WFC3 1.10-1.67 m spectra at minimum and maximum variability to contextualize the X-shooter data interpretation. The models reproduce the slope and most molecular absorption from 1.10 to 2.48 m self-consistently, but they fail to provide a radius and a surface gravity consistent with evolutionary model predictions. They do not reproduce the optical spectrum and the depth of the K I doublets in the J band consistently. We derived Te = 138054 K, log(g) = 3.970.48 dex, [M/H] = 0.210.29, and C/O 0.63. Our inversion of the HST/WFC3 spectra suggests a relative change of 27+6-5 K of the disk-integrated Te correlated with the near-infrared brightness. Our data anchor the characterization of that object in the near-infrared and could be used jointly to the ERS mid-infrared data to provide the most detailed characterization of an ultracool dwarf to date