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Register a new userCharacterization of the inner disk around HD 141569 A from Keck/NIRC2 L-band vortex coronagraphy
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HD 141569 A is a pre-main sequence B9.5 Ve star surrounded by a prominent and complex circumstellar disk, likely still in a transition stage from protoplanetary to debris disk phase. Here, we present a new image of the third inner disk component of HD 141569 A made in the L band (3.8 micron) during the commissioning of the vector vortex coronagraph recently installed in the near-infrared imager and spectrograph NIRC2 behind the W.M. Keck Observatory Keck II adaptive optics system. We used reference point spread function subtraction, which reveals the innermost disk component from the inner working distance of $simeq 23$ AU and up to $simeq 70$ AU. The spatial scale of our detection roughly corresponds to the optical and near-infrared scattered light, thermal Q, N and 8.6 micron PAH emission reported earlier. We also see an outward progression in dust location from the L-band to the H-band (VLT/SPHERE image) to the visible (HST/STIS image), likely indicative of dust blowout. The warm disk component is nested deep inside the two outer belts imaged by HST NICMOS in 1999 (respectively at 406 and 245 AU). We fit our new L-band image and spectral energy distribution of HD 141569 A with the radiative transfer code MCFOST. Our best-fit models favor pure olivine grains, and are consistent with the composition of the outer belts. While our image shows a putative very-faint point-like clump or source embedded in the inner disk, we did not detect any true companion within the gap between the inner disk and the first outer ring, at a sensitivity of a few Jupiter masses.
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We report the discovery of a scattering component around the HD 141569 A circumstellar debris system, interior to the previously known inner ring. The discovered inner disk component, obtained in broadband optical light with HST/STIS coronagraphy, was imaged with an inner working angle of 0.25, and can be traced from 0.4 (~46 AU) to 1.0 (~116 AU) after deprojection using i=55deg. The inner disk component is seen to forward scatter in a manner similar to the previously known rings, has a pericenter offset of ~6 AU, and break points where the slope of the surface brightness changes. It also has a spiral arm trailing in the same sense as other spiral arms and arcs seen at larger stellocentric distances. The inner disk spatially overlaps with the previously reported warm gas disk seen in thermal emission. We detect no point sources within 2 (~232 AU), in particular in the gap between the inner disk component and the inner ring. Our upper limit of 9+/-3 M_J is augmented by a new dynamical limit on single planetary mass bodies in the gap between the inner disk component and the inner ring of 1 M_J, which is broadly consistent with previous estimates.
We present observations of the nearby (D$sim$100,pc) Herbig star HD~163296 taken with the vortex coronograph at Keck/NIRC2 in the L band (3.7~$mu$m), to search for planetary mass companions in the ringed disc surrounding this pre-main sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely associated with the first bright ring detected with ALMA in the $lambda$=1.3mm dust continuum at $sim$65~au. We also detect a point-like source at $sim$0farcs5 projected separation in the North-East direction, close to the inner edge of the second gap in the millimetre images. Comparing the point source photometry with the atmospheric emission models of non-accreting giant planets, we obtain a mass of 6--7~M$_J$ for a putative protoplanet, assuming a system age of 5~Myr. Based on the contrast at a 95% level of completeness calculated on the emission-free regions of our images, we set upper limits for the masses of giant planets of 8--15~M$_J$, 4.5--6.5~M$_J$ and 2.5-4.0~M$_J$ at the locations of the first, second and third gap in the millimetre dust continuum, respectively. Further deep, high resolution thermal IR imaging of the HD~163296 system are warranted, to confirm the presence and nature of the point source and to better understand the structure of the dust disc.
We present $L$-band imaging of the PDS 70 planetary system with Keck/NIRC2 using the new infrared pyramid wavefront sensor. We detected both PDS 70 b and c in our images, as well as the front rim of the circumstellar disk. After subtracting off a model of the disk, we measured the astrometry and photometry of both planets. Placing priors based on the dynamics of the system, we estimated PDS 70 b to have a semi-major axis of $20^{+3}_{-4}$~au and PDS 70 c to have a semi-major axis of $34^{+12}_{-6}$~au (95% credible interval). We fit the spectral energy distribution (SED) of both planets. For PDS 70 b, we were able to place better constraints on the red half of its SED than previous studies and inferred the radius of the photosphere to be 2-3~$R_{Jup}$. The SED of PDS 70 c is less well constrained, with a range of total luminosities spanning an order of magnitude. With our inferred radii and luminosities, we used evolutionary models of accreting protoplanets to derive a mass of PDS 70 b between 2 and 4 $M_{textrm{Jup}}$ and a mean mass accretion rate between $3 times 10^{-7}$ and $8 times 10^{-7}~M_{textrm{Jup}}/textrm{yr}$. For PDS 70 c, we computed a mass between 1 and 3 $M_{textrm{Jup}}$ and mean mass accretion rate between $1 times 10^{-7}$ and $5 times~10^{-7} M_{textrm{Jup}}/textrm{yr}$. The mass accretion rates imply dust accretion timescales short enough to hide strong molecular absorption features in both planets SEDs.
Context: Quantifying the gas content inside the dust gaps of transition disks is important to establish their origin. Aims: We seek to constrain the surface density of warm gas in the disk of HD 139614, a Herbig Ae star with a transition disk exhibiting a dust gap from 2.3 to 6 AU. Methods: We have obtained ESO/VLT CRIRES high-resolution spectra of CO ro-vibrational emission. We derived constraints on the disks structure by modeling the line-profiles, the spectroastrometric signal, and the rotational diagrams using flat Keplerian disk models. Results: We detected v=1-0 12CO, 2-1 12CO, 1-0 13CO, 1-0 C18O, and 1-0 C17O ro-vibrational lines. 12CO v=1-0 lines have an average width of 14 km/s, Tgas of 450 K and an emitting region from 1 to 15 AU. 13CO and C18O lines are on average 70 and 100 K colder, 1 and 4 km/s narrower, and are dominated by emission at R>6 AU. The 12CO v=1-0 line-profile indicates that if there is a gap in the gas it must be narrower than 2 AU. We find that a drop in the gas surface density (delta_gas) at R<5-6 AU is required to simultaneously reproduce the line-profiles and rotational diagrams of the three CO isotopologs. Delta_gas can range from 10^-2 to 10^-4 depending on the gas-to-dust ratio of the outer disk. We find that at 1<R<6 AU the gas surface density profile is flat or increases with radius. We derive a gas column density at 1<R<6 AU of NH=3x10^19 - 10^21 cm^-2. We find a 5sigma upper limit on NCO at R<1 AU of 5x10^15 cm^-2 (NH<5x10^19 cm^-2). Conclusions: The dust gap in the disk of HD 139614 has gas. The gas surface density in the disk at R<6 AU is significantly lower than the surface density expected from HD 139614s accretion rate assuming a viscous alpha-disk model. The gas density drop, the non-negative density gradient of the gas inside 6 AU, and the absence of a wide (>2 AU) gas gap suggest the presence of an embedded <2 MJ planet at around 4 AU.
We present a detailed multi-wavelength characterization of the multi-ring disk of HD 169142. We report new ALMA observations at 3 mm and analyze them together with archival 0.89 and 1.3 mm data. Our observations resolve three out of the four rings in the disk previously seen in high-resolution ALMA data. A simple parametric model is used to estimate the radial profile of the dust optical depth, temperature, density, and particle size distribution. We find that the multiple ring features of the disk are produced by annular accumulations of large particles, probably associated with gas pressure bumps. Our model indicates that the maximum dust grain size in the rings is $sim1$ cm, with slightly flatter power-law size distributions than the ISM-like size distribution ($psim3.5$) found in the gaps. In particular, the inner ring ($sim26$ au) is associated with a strong and narrow buildup of dust particles that could harbor the necessary conditions to trigger the streaming instability. According to our analysis, the snowlines of the most important volatiles do not coincide with the observed substructures. We explore different ring formation mechanisms and find that planet-disk interactions are the most likely scenario to explain the main features of HD 169142. Overall, our multi-wavelength analysis provides some of the first unambiguous evidence of the presence of radial dust traps in the rings of HD 169142. A similar analysis in a larger sample of disks could provide key insights on the impact that disk substructures have on the dust evolution and planet formation processes.
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