Magellan Adaptive Optics first-light observations of the exoplanet beta Pic b. II. 3-5 micron direct imaging with MagAO+Clio, and the empirical bolometric luminosity of a self-luminous giant planet

Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet $\beta$ Pic b, which is 9 AU from and embedded in the debris disk of the young nearby A6V star $\beta$ Pictoris. We observed the system with first light of the Magellan Adaptive Optics (MagAO) system. In Paper I we presented the first CCD detection of this planet with MagAO+VisAO. Here we present four MagAO+Clio images of $\beta$ Pic b at 3.1 $\mu$m, 3.3 $\mu$m, $L^\prime$, and $M^\prime$, including the first observation in the fundamental CH$_4$ band. To remove systematic errors from the spectral energy distribution (SED), we re-calibrate the literature photometry and combine it with our own data, for a total of 22 independent measurements at 16 passbands from 0.99--4.8 $\mu$m. Atmosphere models demonstrate the planet is cloudy but are degenerate in effective temperature and radius. The measured SED now covers $>$80\% of the planet's energy, so we approach the bolometric luminosity empirically. We calculate the luminosity by extending the measured SED with a blackbody and integrating to find log($L_{bol}$/$L_{Sun}$) $= -3.78\pm0.03$. From our bolometric luminosity and an age of 23$\pm$3 Myr, hot-start evolutionary tracks give a mass of 12.7$\pm$0.3 $M_{Jup}$, radius of 1.45$\pm$0.02 $R_{Jup}$, and $T_{eff}$ of 1708$\pm$23 K (model-dependent errors not included). Our empirically-determined luminosity is in agreement with values from atmospheric models (typically $-3.8$ dex), but brighter than values from the field-dwarf bolometric correction (typically $-3.9$ dex), illustrating the limitations in comparing young exoplanets to old brown dwarfs.Comment: Accepted to ApJ. 27 pages, 22 figures, 19 table

Imaging protoplanets: observing transition disks with non-redundant masking

Transition disks, protoplanetary disks with inner clearings, are promising objects in which to directly image forming planets. The high contrast imaging technique of non-redundant masking is well posed to detect planetary mass companions at several to tens of AU in nearby transition disks. We present non-redundant masking observations of the T Cha and LkCa 15 transition disks, both of which host posited sub-stellar mass companions. However, due to a loss of information intrinsic to the technique, observations of extended sources (e.g. scattered light from disks) can be misinterpreted as moving companions. We discuss tests to distinguish between these two scenarios, with applications to the T Cha and LkCa 15 observations. We argue that a static, forward-scattering disk can explain the T Cha data, while LkCa 15 is best explained by multiple orbiting companions.Comment: SPIE conference proceedin

Accreting Protoplanets in the LkCa 15 Transition Disk

Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1900 exoplanets have now been discovered and confirmed, none are still in the process of formation. Transition discs, protoplanetary disks with inner clearings best explained by the influence of accreting planets, are natural laboratories for the study of planet formation. Some transition discs show evidence for the presence of young planets in the form of disc asymmetries or infrared sources detected within their clearings, as in the case of LkCa 15. Attempts to observe directly signatures of accretion onto protoplanets have hitherto proven unsuccessful. Here we report adaptive optics observations of LkCa 15 that probe within the disc clearing. With accurate source positions over multiple epochs spanning 2009 - 2015, we infer the presence of multiple companions on Keplerian orbits. We directly detect H{\alpha} emission from the innermost companion, LkCa 15 b, evincing hot (~10,000 K) gas falling deep into the potential well of an accreting protoplanet.Comment: 35 pages, 3 figures, 1 table, 9 extended data item

MagAO Imaging of Long-period Objects (MILO). II. A Puzzling White Dwarf around the Sun-like Star HD 11112

The version of record, Rodigas, T. J. et al, 'MagAO Imaging of long-period objects (MILO). II. A puzzling white dwarf around the sun-like star HD 11112', The Astrophysical Journal, 831:177, November 2016, is available online via doi: 10.3847/0004-637X/831/2/177 © 2016. The American Astronomical Society. All rights reserved.HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2\fasec 2 (100 AU) at multiple wavelengths spanning 0.6-4 \microns ~and show that it is most likely a gravitationally-bound cool white dwarf. Modeling its spectral energy distribution (SED) suggests that its mass is 0.9-1.1 \msun, which corresponds to very high-eccentricity, near edge-on orbits from Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is $>2\sigma$ discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.Peer reviewedFinal Published versio

High-contrast imaging constraints on gas giant planet formation - The Herbig Ae/Be star opportunity

Planet formation studies are often focused on solar-type stars, implicitly considering our Sun as reference point. This approach overlooks, however, that Herbig Ae/Be stars are in some sense much better targets to study planet formation processes empirically, with their disks generally being larger, brighter and simply easier to observe across a large wavelength range. In addition, massive gas giant planets have been found on wide orbits around early type stars, triggering the question if these objects did indeed form there and, if so, by what process. In the following I briefly review what we currently know about the occurrence rate of planets around intermediate mass stars, before discussing recent results from Herbig Ae/Be stars in the context of planet formation. The main emphasis is put on spatially resolved polarized light images of potentially planet forming disks and how these images - in combination with other data - can be used to empirically constrain (parts of) the planet formation process. Of particular interest are two objects, HD100546 and HD169142, where, in addition to intriguing morphological structures in the disks, direct observational evidence for (very) young planets has been reported. I conclude with an outlook, what further progress we can expect in the very near future with the next generation of high-contrast imagers at 8-m class telescopes and their synergies with ALMA.Comment: Accepted by Astrophysics and Space Science as invited short review in special issue about Herbig Ae/Be stars; 12 pages incl. 5 figures, 2 tables and reference

A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation

We present new 1--1.25 micron (z and J band) Subaru/IRCS and 2 micron (K band) VLT/NaCo data for HR 8799 and a rereduction of the 3--5 micron MMT/Clio data first presented by Hinz et al. (2010). Our VLT/NaCo data yields a detection of a fourth planet at a projected separation of ~ 15 AU -- "HR 8799e". We also report new, albeit weak detections of HR 8799b at 1.03 microns and 3.3 microns. Empirical comparisons to field brown dwarfs show that at least HR 8799b and HR8799c, and possibly HR 8799d, have near-to-mid IR colors/magnitudes significantly discrepant from the L/T dwarf sequence. Standard cloud deck atmosphere models appropriate for brown dwarfs provide only (marginally) statistically meaningful fits to HR 8799b and c for unphysically small radii. Models with thicker cloud layers not present in brown dwarfs reproduce the planets' SEDs far more accurately and without the need for rescaling the planets' radii. Our preliminary modeling suggests that HR 8799b has log(g) = 4--4.5, Teff = 900K, while HR 8799c, d, and (by inference) e have log(g) = 4--4.5, Teff = 1000--1200K. Combining results from planet evolution models and new dynamical stability limits implies that the masses of HR 8799b, c, d, and e are 6--7 Mj, 7--10 Mj, 7--10 Mj and 7--10 Mj. 'Patchy" cloud prescriptions may provide even better fits to the data and may lower the estimated surface gravities and masses. Finally, contrary to some recent claims, forming the HR 8799 planets by core accretion is still plausible, although such systems are likely rare.Comment: 27 pages, 15 figures, Accepted for publication in The Astrophysical Journa

High Resolution Images of Orbital Motion in the Orion Trapezium Cluster with the LBT Adaptive Optics System

The new 8.4m LBT adaptive secondary AO system, with its novel pyramid wavefront sensor, was used to produce very high Strehl (75% at 2.16 microns) near infrared narrowband (Br gamma: 2.16 microns and [FeII]: 1.64 microns) images of 47 young (~1 Myr) Orion Trapezium theta1 Ori cluster members. The inner ~41x53" of the cluster was imaged at spatial resolutions of ~0.050" (at 1.64 microns). A combination of high spatial resolution and high S/N yielded relative binary positions to ~0.5 mas accuracies. Including previous speckle data, we analyse a 15 year baseline of high-resolution observations of this cluster. We are now sensitive to relative proper motions of just ~0.3 mas/yr (0.6 km/s at 450 pc) this is a ~7x improvement in orbital velocity accuracy compared to previous efforts. We now detect clear orbital motions in the theta1 Ori B2/B3 system of 4.9+/-0.3 km/s and 7.2+/-0.8 km/s in the theta1 Ori A1/A2 system (with correlations of PA vs. time at >99% confidence). All five members of the theta1 Ori B system appear likely as a gravitationally bound "mini-cluster". The very lowest mass member of the theta1 Ori B system (B4; mass ~0.2 Msun) has, for the first time, a clearly detected motion (at 4.3+/-2.0 km/s; correlation=99.7%) w.r.t B1. However, B4 is most likely in an long-term unstable (non-hierarchical) orbit and may "soon" be ejected from this "mini-cluster". This "ejection" process could play a major role in the formation of low mass stars and brown dwarfs.Comment: 27 pages, 14 figures, accepted for publication by the Astrophysical Journa