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Register a new userKeck/OSIRIS Pa$beta$ high-contrast imaging and updated constraints on PDS~70b
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We present a high-contrast imaging search for Pa$beta$ line emission from protoplanets in the PDS~70 system with Keck/OSIRIS integral field spectroscopy. We applied the high-resolution spectral differential imaging technique to the OSIRIS $J$-band data but did not detect the Pa$beta$ line at the level predicted using the parameters of cite{Hashimoto2020}. This lack of Pa$beta$ emission suggests the MUSE-based study may have overestimated the line width of H$alpha$. We compared our Pa$beta$ detection limits with the previous H$alpha$ flux and H$beta$ limits and estimated $A_{rm V}$ to be $sim0.9$ and 2.0 for PDS~70~b and c respectively. In particular, PDS~70~bs $A_{rm V}$ is much smaller than implied by high-contrast near-infrared studies, which suggests the infrared-continuum photosphere and the hydrogen-emitting regions exist at different heights above the forming planet.
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We report a new evaluation of the accretion properties of PDS~70b obtained with VLT/MUSE. The main difference from previous studies in Haffert et al. (2019) and Aoyama & Ikoma (2019) is in the mass accretion rate. Simultaneous multiple line observations, such as H$alpha$ and H$beta$, can better constrain the physical properties of an accreting planet. While we clearly detected H$alpha$ emissions from PDS~70b, no H$beta$ emissions were detected. We estimate the line flux of H$beta$ with a 3-$sigma$ upper limit to be 2.3~$times$~10$^{-16}$~erg~s$^{-1}$~cm$^{-2}$. The flux ratio $F_{rm Hbeta}$/$F_{rm Halpha}$ for PDS~70b is $<$~0.28. Numerical investigations by Aoyama et al. (2018) suggest that $F_{rm Hbeta}$/$F_{rm Halpha}$ should be close to unity if the extinction is negligible. We attribute the reduction of the flux ratio to the extinction, and estimate the extinction of H$alpha$ ($A_{rm Halpha}$) for PDS~70b to be $>$~2.0~mag using the interstellar extinction value. %The expected $A_{rm Halpha}$ value in the gap of the protoplanetary disk at the PDS~70b location is 2.4~mag, which is consistent with the estimated extinction. By combining with the H$alpha$ linewidth and the dereddening line luminosity of H$alpha$, %we derive the PDS~70b dynamical mass and mass accretion rate to be hashimotor{12~$pm$~3~$M_{rm Jup}$} and $gtrsim$~5~$times$~10$^{-7}$~$M_{rm Jup}$~yr$^{-1}$, respectively. we derive the PDS~70b mass accretion rate to be $gtrsim$~5~$times$~10$^{-7}$~$M_{rm Jup}$~yr$^{-1}$. The PDS~70b mass accretion rate is an order of magnitude larger than that of PDS~70. We found that the filling factor $f_{rm f}$ (the fractional area of the planetary surface emitting H$alpha$) is $gtrsim$0.01, which is similar to the typical stellar value. The small value of $f_{rm f}$ indicates that the H$alpha$ emitting areas are localized at the surface of PDS~70b.
High-contrast imaging of exoplanets and protoplanetary disks depends on wavefront sensing and correction made by adaptive optics instruments. Classically, wavefront sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wavefront sensor (PWFS). With this new module we observed SR~21, a young star that is brighter at NIR wavelengths than at optical wavelengths. Compared with the archival data of SR~21 taken with the optical wavefront sensing we achieved $sim$20% better Strehl ratio in similar natural seeing conditions. Further post-processing utilizing angular differential imaging and reference-star differential imaging confirmed the spiral feature reported by the VLT/SPHERE polarimetric observation, which is the first detection of the SR~21 spiral in total intensity at $L^prime$ band. We also compared the contrast limit of our result ($10^{-4}$ at $0farcs4$ and $2times10^{-5}$ at $1farcs0$) with the archival data that were taken with optical wavefront sensing and confirmed the improvement, particularly at $leq0farcs5$. Our observation demonstrates that the NIR PWFS improves AO performance and will provide more opportunities for red targets in the future.
HD113337 is a Main-Sequence F6V field star more massive than the Sun, hosting one (possibly two) radial velocity (RV) giant planet(s) and a cold debris disk (marked by an infrared excess). We used the VEGA interferometer on the CHARA array to measure HD113337 angular diameter, and derived its linear radius using the Gaia parallax. We computed the bolometric flux to derive its effective temperature and luminosity, and we estimated its mass and age using evolutionary tracks. We used Herschel images to partially resolve the outer disk, and high-contrast images of HD113337 with the LBTI to probe the 10-80 au separation range. Finally, we combined the deduced contrast maps with previous RV of the star using the MESS2 software to bring upper mass limits on possible companions at all separations up to 80 au, taking advantage of the constraints on the age and inclination (brought by the fundamental parameter analysis and the disk imaging, respectively). We derive a limb-darkened angular diameter of 0.386 $pm$ 0.009 mas that converts into a linear radius of 1.50 $pm$ 0.04 solar radius. The fundamental parameter analysis leads to an effective temperature of 6774 $pm$ 125 K, and to two possible age solutions: one young within 14-21 Myr and one old within 0.8-1.7 Gyr. We partially resolve the known outer debris disk and model its emission. Our best solution corresponds to a radius of 85 $pm$ 20 au, an extension of 30 $pm$ 20 au and an inclination within 10-30 degrees for the outer disk. The combination of imaging contrast limits, published RV, and our new age and inclination solutions leads to a first possible estimation of the true masses of the planetary companions: $sim 7_{-2}^{+4}$ Jupiter masses for HD113337 b (confirmed companion), and $sim 16_{-3}^{+10}$ Jupiter masses for HD113337 c (candidate). We also constrain possible additional companions at larger separations.
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.
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