Examinando por Autor "Cieza, Lucas"
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Ítem NaCo polarimetric observations of Sz 91 transitional disc: a remarkable case of dust filtering(Oxford University Press, 2020-02) Mauco, Karina; Olofsson, Johan; Canovas, Hector; . Schreiber, Matthias R; Christiaens, Valentin; Bayo, Amelia; Zurlo, Alice; Caceres, Claudio; Pinte, Christophe; Villaver, Eva; Girard, Julien H.; Cieza, Lucas; Montesinos, MatıasWe present polarized light observations of the transitional disc around Sz 91 acquired with VLT/NaCo at H (1.7μm) and Ks (2.2μm) bands. We resolve the disc and detect polarized emission up to ∼0.5 arcsec (∼80 au) along with a central cavity at both bands. We computed a radiative transfer model that accounts for the main characteristics of the polarized observations. We found that the emission is best explained by small, porous grains distributed in a disc with a ∼45 au cavity. Previous ALMA observations have revealed a large sub-mm cavity (∼83 au) and extended gas emission from the innermost (<16 au) regions up to almost 400 au from the star. Dynamical clearing by multiple low-mass planets arises as the most probable mechanism for the origin of Sz 91’s peculiar structure. Using new L - band ADI observations, we can rule out companions more massive than Mp ≥ 8 MJup beyond 45 au assuming hot-start models. The disc is clearly asymmetric in polarized light along the minor axis, with the north side brighter than the south side. Differences in position angle between the disc observed at sub-mm wavelengths with ALMA and our NaCo observations were found. This suggests that the disc around Sz 91 could be highly structured. Higher signal-to-noise near-IR and sub-mm observations are needed to confirm the existence of such structures and to improve the current understanding of the origin of transitional discs.Ítem No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals(Institute of Physics Publishing, 2019-05-20) Currie, Thayne; Marois, Christian; Cieza, Lucas; Mulders, Gijs D.; Lawson, Kellen; Caceres, Claudio; Rodriguez-Ruiz, Dary; Wisniewski, John; Guyon, Olivier; Brandt, Timothy D.; Kasdin, N. Jeremy; Groff, Tyler D.; Lozi, Julien; Chilcote, Jeffrey; Hodapp, Klaus; Jovanovic, Nemanja; Martinache, Frantz; Skaf, Nour; Lyra, Wladimir; Tamura, Motohide; Asensio-Torres, Ruben; Dong, Ruobing; Grady, Carol; Gerard, Benjamin; Fukagawa, Misato; Hand, Derek; Hayashi, Masahiko; Henning, Thomas; Kudo, Tomoyuki; Kuzuhara, Masayuki; Kwon, Jungmi; McElwain, Michael W.; Uyama, TaichiTwo studies utilizing sparse aperture-masking (SAM) interferometry and Hα differential imaging have reported multiple Jovian companions around the young solar-mass star, LkCa 15 (LkCa 15 bcd): the first claimed direct detection of infant, newly formed planets ("protoplanets"). We present new near-infrared direct imaging/spectroscopy from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) integral field spectrograph and multi-epoch thermal infrared imaging from Keck/NIRC2 of LkCa 15 at high Strehl ratios. These data provide the first direct imaging look at the same wavelengths and in the same locations where previous studies identified the LkCa 15 protoplanets, and thus offer the first decisive test of their existence. The data do not reveal these planets. Instead, we resolve extended emission tracing a dust disk with a brightness and location comparable to that claimed for LkCa 15 bcd. Forward-models attributing this signal to orbiting planets are inconsistent with the combined SCExAO/CHARIS and Keck/NIRC2 data. An inner disk provides a more compelling explanation for the SAM detections and perhaps also the claimed Hα detection of LkCa 15 b. We conclude that there is currently no clear, direct evidence for multiple protoplanets orbiting LkCa 15, although the system likely contains at least one unseen Jovian companion. To identify Jovian companions around LkCa 15 from future observations, the inner disk should be detected and its effect modeled, removed, and shown to be distinguishable from planets. Protoplanet candidates identified from similar systems should likewise be clearly distinguished from disk emission through modeling.