We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the dust continuum emission at 1.3 mm and 12CO line emission of the transitional disk around DM Tau. DM Tau's disk is ...thought to possess a dust-free inner cavity inside a few au, from the absence of near-infrared excess on its spectral energy distribution (SED). Previous submillimeter observations were, however, unable to detect the cavity; instead, a dust ring ∼20 au in radius was seen. The excellent angular resolution achieved in the new ALMA observations, 43 × 31 mas, allows discovery of a 4 au radius inner dust ring, confirming previous SED modeling results. This inner ring is symmetric in continuum emission, but asymmetric in 12CO emission. The known (outer) dust ring at ∼20 au is recovered and shows azimuthal asymmetry with a strong-weak side contrast of ∼1.3. The gap between these two rings is depleted by a factor of ∼40 in dust emission relative to the outer ring. An extended outer dust disk is revealed, separated from the outer ring by another gap. The location of the inner ring is comparable to that of the main asteroid belt in the solar system. As a disk with a "proto-asteroid belt," the DM Tau system offers valuable clues to disk evolution and planet formation in the terrestrial-planet-forming region.
Abstract
We obtained spectra of the pre-main-sequence star AU Microscopii during a transit of its Neptune-sized planet to investigate its orbit and atmosphere. We used the high-dispersion ...near-infrared spectrograph InfraRed Doppler (IRD) on the Subaru telescope to detect the Doppler “shadow” from the planet and constrain the projected stellar obliquity. Modeling of the observed planetary Doppler shadow suggests a spin–orbit alignment of the system (
deg), but additional observations are needed to confirm this finding. We use both the IRD data and spectra obtained with NIRSPEC on Keck II to search for absorption in the 1083 nm line of metastable triplet He
i
by the planet’s atmosphere and place an upper limit for the equivalent width of 3.7 mÅ at 99% confidence. With this limit and a Parker wind model we constrain the escape rate from the atmosphere to
M
⊕
Gyr
−1
, comparable to the rates predicted by an X-ray and ultraviolet energy-limited escape calculation and hydrodynamic models, but refinement of the planet mass is needed for rigorous tests.
Direct imaging of gas giant exoplanets provides information on their atmospheres and the architectures of planetary systems. However, few planets have been detected in blind surveys with direct ...imaging. Using astrometry from the Gaia and Hipparcos spacecraft, we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770. We confirmed the detection of this planet with direct imaging using the Subaru Coronagraphic Extreme Adaptive Optics instrument. The planet, HIP 99770 b, orbits 17 astronomical units from its host star, receiving an amount of light similar to that reaching Jupiter. Its dynamical mass is 13.9 to 16.1 Jupiter masses. The planet-to-star mass ratio (7 to 8) × 10
is similar to that of other directly imaged planets. The planet's atmospheric spectrum indicates an older, less cloudy analog of the previously imaged exoplanets around HR 8799.
Abstract
We report the first detection of a hydroxyl radical (OH) emission signature in the planetary atmosphere outside the solar system, in this case, in the dayside of WASP-33b. We analyze ...high-resolution near-infrared emission spectra of WASP-33b taken using the InfraRed Doppler spectrograph on the 8.2 m Subaru telescope. The telluric and stellar lines are removed using a detrending algorithm,
SysRem
. The residuals are then cross-correlated with OH and H
2
O planetary spectrum templates produced using several different line lists. We check and confirm the accuracy of OH line lists by cross-correlating with the spectrum of GJ 436. As a result, we detect the emission signature of OH at
K
p
of
km s
−1
and
v
sys
of −0.3
km s
−1
with a signal-to-noise ratio (S/N) of 5.4 and a significance of 5.5
σ
. Additionally, we marginally detect H
2
O emission in the
H
-band with an S/N of 4.0 and a significance of 5.2
σ
using the POKAZATEL line list. However, no significant signal is detected using the HITEMP 2010, which might be due to differences in line positions and strengths, as well as the incompleteness of the line lists. Nonetheless, this marginal detection is consistent with the prediction that H
2
O is mostly thermally dissociated in the upper atmosphere of the ultra-hot Jupiters. Therefore, along with CO, OH is expected to be one of the most abundant O-bearing molecules in the dayside atmosphere of ultra-hot Jupiters and should be considered when studying their atmospheres.
We report ALMA Cycle 2 observations of 230 GHz (1.3 mm) dust continuum emission, and 12CO, 13CO, and C18O J = 2-1 line emission, from the Upper Scorpius transitional disk PZ99 J160421.7-213028, with ...an angular resolution of ∼ (35 au). Armed with these data and existing H-band scattered light observations, we measure the size and depth of the disk's central cavity, and the sharpness of its outer edge, in three components: sub- m-sized "small" dust traced by scattered light, millimeter-sized "big" dust traced by the millimeter continuum, and gas traced by line emission. Both dust populations feature a cavity of radius ∼70 au that is depleted by factors of at least 1000 relative to the dust density just outside. The millimeter continuum data are well explained by a cavity with a sharp edge. Scattered light observations can be fitted with a cavity in small dust that has either a sharp edge at 60 au, or an edge that transitions smoothly over an annular width of 10 au near 60 au. In gas, the data are consistent with a cavity that is smaller, about 15 au in radius, and whose surface density at 15 au is times smaller than the surface density at 70 au; the gas density grades smoothly between these two radii. The CO isotopologue observations rule out a sharp drop in gas surface density at 30 au or a double-drop model, as found by previous modeling. Future observations are needed to assess the nature of these gas and dust cavities (e.g., whether they are opened by multiple as-yet-unseen planets or photoevaporation).
Abstract
We present near-IR imaging polarimetry of five classical FU Ori-type objects (FU Ori, V1057 Cyg, V1515 Cyg, V1735 Cyg, Z CMa) with an ∼0.″1 resolution observed using HiCIAO+AO188 at the ...Subaru Telescope. We observed scattered light associated with circumstellar dust around four of them (i.e., all but V1515 Cyg). Their polarized intensity distribution shows a variety of morphologies with arms, tails or streams, spikes, and fragmented distributions, many of which were reported in our previous paper. The morphologies of these reflection nebulae significantly differ from many other normal young stellar objects (Class I–II objects). These structures are attributed to gravitationally unstable disks, trails of clump ejections, dust blown by a wind or a jet, and a stellar companion. We can consistently explain our results with the scenario that their accretion outbursts (FUor outbursts) are triggered by gravitationally fragmenting disks, and with the hypothesis that many low-mass young stellar objects experience such outbursts.
In an effort to measure the Rossiter-McLaughlin effect for the TRAPPIST-1 system, we performed high-resolution spectroscopy during transits of planets e, f, and b. The spectra were obtained with the ...InfraRed Doppler spectrograph on the Subaru 8.2 m telescope, and were supplemented with simultaneous photometry obtained with a 1 m telescope of the Las Cumbres Observatory Global Telescope. By analyzing the anomalous radial velocities, we found the projected stellar obliquity to be λ = 1 28° under the assumption that the three planets have coplanar orbits, although we caution that the radial-velocity data show correlated noise of unknown origin. We also sought evidence for the expected deformations of the stellar absorption lines, and thereby detected the "Doppler shadow" of planet b with a false-alarm probability of 1.7%. The joint analysis of the observed residual cross-correlation map including the three transits gave °. These results indicate that the the TRAPPIST-1 star is not strongly misaligned with the common orbital plane of the planets, although further observations are encouraged to verify this conclusion.
Abstract
We obtained high-resolution spectra of the ultracool M-dwarf TRAPPIST-1 during the transit of its planet “b” using two high-dispersion near-infrared spectrographs, the Infrared Doppler (IRD) ...instrument on the Subaru 8.2m telescope, and the Habitable Zone Planet Finder (HPF) instrument on the 10 m Hobby–Eberly Telescope. These spectroscopic observations are complemented by a photometric transit observation for planet “b” using the APO/ARCTIC, which assisted us in capturing the correct transit times for our transit spectroscopy. Using the data obtained by the new IRD and HPF observations, as well as the prior transit observations of planets “b,” “e” and “f” from IRD, we attempt to constrain the atmospheric escape of the planet using the He
i
triplet 10830 Å absorption line. We do not detect evidence for any primordial extended H-He atmospheres in all three planets. To limit any planet-related absorption, we place an upper limit on the equivalent widths of <7.754 mÅ for planet “b,” <10.458 mÅ for planet “e,” <4.143 mÅ for planet “f” at 95% confidence from the IRD data, and <3.467 mÅ for planet “b” at 95% confidence from HPF data. Using these limits along with a solar-like composition isothermal Parker wind model, we attempt to constrain the mass-loss rates for the three planets. For TRAPPIST-1b, our models exclude the highest possible energy-limited rate for a wind temperature <5000 K. This nondetection of extended atmospheres with low mean-molecular weights in all three planets aids in further constraining their atmospheric composition by steering the focus toward the search of high-molecular-weight species in their atmospheres.
Abstract
Precision radial velocity (RV) measurements in the near-infrared are a powerful tool to detect and characterize exoplanets around low-mass stars or young stars with higher magnetic activity. ...However, the presence of strong telluric absorption lines and emission lines in the near-infrared that significantly vary in time can prevent extraction of RV information from these spectra by classical techniques, which ignore or mask the telluric lines. We present a methodology and pipeline to derive precision RVs from near-infrared spectra using a forward-modeling technique. We applied this to spectra with a wide wavelength coverage (Y, J, and H bands, simultaneously), taken by the InfraRed Doppler (IRD) spectrograph on the Subaru 8.2 m telescope. Our pipeline extracts the instantaneous instrumental profile of the spectrograph for each spectral segment, based on a reference spectrum of the laser-frequency comb that is injected into the spectrograph simultaneously with the stellar light. These profiles are used to derive the intrinsic stellar template spectrum, which is free from instrumental broadening and telluric features, as well as model and fit individual observed spectra in the RV analysis. Implementing a series of numerical simulations using theoretical spectra that mimic IRD data, we test the pipeline and show that IRD can achieve <2 m s−1 precision for slowly rotating mid-to-late M dwarfs with a signal-to-noise ratio ≳100 per pixel at 1000 nm. Dependences of RV precision on various stellar parameters (e.g., Teff, vsin i, Fe/H) and the impact of telluric-line blendings on the RV accuracy are discussed through the mock spectra analyses. We also apply the RV-analysis pipeline to the observed spectra of GJ 699 and TRAPPIST-1, demonstrating that the spectrograph and the pipeline are capable of an RV accuracy of <3 m s−1 at least on a time-scale of a few months.
Abstract
Detailed chemical analyses of M dwarfs are scarce but necessary to constrain the formation environment and internal structure of planets being found around them. We present elemental ...abundances of 13 M dwarfs (2900 <
T
eff
< 3500 K) observed in the Subaru/IRD planet search project. They are mid- to late-M dwarfs whose abundance of individual elements has not been well studied. We use the high-resolution (∼70,000) near-infrared (970–1750 nm) spectra to measure the abundances of Na, Mg, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Sr by the line-by-line analysis based on model atmospheres, with typical errors ranging from 0.2 dex for Fe/H to 0.3–0.4 dex for other X/H. We measure radial velocities from the spectra and combine them with Gaia astrometry to calculate the Galactocentric space velocities
UVW
. The resulting Fe/H values agree with previous estimates based on medium-resolution
K
-band spectroscopy, showing a wide distribution of metallicity (−0.6 < Fe/H < +0.4). The abundance ratios of individual elements X/Fe are generally aligned with the solar values in all targets. While the X/Fe distributions are comparable to those of nearby FGK stars, most of which belong to the thin-disk population, the most metal-poor object, GJ 699, could be a thick-disk star. The
UVW
velocities also support this. The results raise the prospect that near-infrared spectra of M dwarfs obtained in the planet search projects can be used to grasp the trend of elemental abundances and the Galactic stellar population of nearby M dwarfs.
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