We present the first laboratory tests of Spatial Linear Dark Field Control (LDFC) approaching raw contrasts (5e-7) and separations (1.5–5.2 lambda/D) needed to image jovian planets around Sun-like stars with space-borne coronagraphs like Roman-CGI and image exo-Earths around low-mass stars with future ground-based 30m class telescopes. In four separate experiments and for a range of different perturbations, LDFC largely restores (to within a factor of 1.2–1.7) and maintains a dark hole whose contrast is degraded by phase errors by an order of magnitude. Our implementation of classical speckle nulling requires a factor of 2–5 more iterations and 20–50 DM commands to reach contrasts obtained by spatial LDFC. Our results provide a promising path forward to maintaining dark holes without relying on DM probing and in the low-flux regime, which may improve the duty cycle of high-contrast imaging instruments, increase the temporal correlation of speckles, and thus enhance our ability to image true solar system analogues in the next two decades.

The UCLA Planetarium hosts star shows and lectures on various astronomy topics, educating UCLA and the broader Los Angeles community about science and the wonders of the night sky. It serves over 4000 people per year, as UCLA Astronomy’s largest outreach effort. We host private shows for visiting school groups (30% of our attendees), shows for UCLA astronomy courses (20%), and weekly public shows for the community at large (50%). Our planetarium and its events are run exclusively by graduate students, who also maintain its historic projectors and dome. In the near future, we plan to improve and expand our outreach efforts in two specific ways. Our outreach efforts are free for educational groups, but we currently do not provide travel support for visiting schools. We plan to actively reach out to school groups from underserved communities and hope to raise funds to cover these schools’ field trip and travel expenses. We also plan to improve our science communication effectiveness, with strategies for improving volunteer recruitment, training volunteers on effective public speaking skills, and improving the quality of our existing repository of presentations. Of course, these in person events are on hold due to the ongoing pandemic; in the meantime, we are developing ways to serve our audience virtually. We recently hosted our first “virtual” planetarium show on YouTube Live, with over 1,700 viewers on the livestream and over 7,300 total viewers. We welcome any suggestions or ideas to help us improve our planetarium outreach efforts!

Kepler-411 is a K2V-type star with an average rotation period of 10.52 days, radius of 0.79 Rsun and mass of 0.83 Msun. This active star has at least four planets, three of them eclipse the star, the three larger planets are mini Neptunes with radii of 2.2, 3.47 and 3.46 Earth radii, and periods of 3.0, 7.8 and 58.0 days, respectively. This star was observed by the Kepler satellite for about 600 days showing a total number of 195 transit for planet Kepler-411 b, 76 transits Kepler-411c and 10 transits for planet Kepler-411d. When a planet transits its host star, it may occult a spot causing a detectable signal in the light curve. In this work we apply the model described in Silva (2003), to characterize the starspots, which resulted in the detection of a total of 45 spots in Kepler-411b, 143 spots in Kepler-411c transits and 10 spots in Kepler-411d transits. Analysis of the spots detected on the different transit latitudes of these planets yields a differential shear of 0.050 rd/d or a relative differential rotation of 8.3%, assuming a solar like rotation profile. Also, a total of 66 flares and superflares were detected on the light curve. Here, we discuss the relationship between the size and temperature of the starspots with statistical data on flares and superflares.

After protoplanets have acquired sufficient mass to open partial gaps in their natal protostellar disks, residual gas continues to diffuse onto some horseshoe streamlines under effect of viscous dissipation, and meander in and out of the planets’ Hill sphere. Inside the Hill sphere, the horseshoe streamlines intercept gas flow in circumplanetary disks. The host stars’ tidal perturbation induce a barrier across the converging streamlines’ interface. Viscous transfer of angular momentum across this tidal barrier determines the rate of mass diffusion from the horseshoe streamlines onto the circumplanetary disks, and eventually the accretion rate onto the protoplanets. We carry out a series of numerical simulations to test the influence of this tidal barrier on super-thermal planets. In weakly viscous disks, protoplanets’ accretion rate steeply decreases with their masses above the thermal limit. As their growth time scale exceeds the gas depletion time scale, their masses reach asymptotic values comparable to that of Jupiter. In relatively thick and strongly viscous disks, protoplanets’ asymptotic masses exceed several times that of Jupiter. Such massive protoplanets strongly excite the eccentricity of nearby horseshoe streamlines, destabilize orderly flow, substantially enhance the diffusion rate across the tidal barrier, and elevate their growth rate until their natal disk is severely depleted. Based on the upper fall-off in the observe mass distribution of known exoplanets, we suggest their natal disks had relatively low viscosity (α ∼ 10−3), modest thickness (H/R ∼ 0.03 − 0.05), and limited masses (comparable to that of minimum mass solar nebula model).

Traditionally, astronomers have separated giant planets from brown dwarfs based on the object’s mass. Objects more massive than 13 Jupiter masses but less massive than 80 Jupiter masses are considered to be brown dwarfs. However, in detail, the lower mass threshold is 11 to 16 Jupiter masses depending on the metallicity of the object. This betrays how arbitrary a purely mass-based distinction between planets and brown dwarfs is. Instead, we take a critical look at the population of brown dwarfs for which we have the most fundamental information: transiting brown dwarfs. Transiting brown dwarfs provide us their mass, radius, and sometimes age, which makes them useful for directly testing substellar evolutionary models. Through a better understanding of how well these models describe the population of transiting brown dwarfs, we will develop a better definition of what makes a brown dwarf different than a giant planet: its formation mechanism. It is certainly true that in the mass range spanning between giant planets and low-mass stars that the dominant formation mechanism must change in a significant way. If we can determine which mass or distribution of masses that this change occurs at, then we will have a more physical way to distinguish planets from brown dwarfs. This poster provides an overview of the substellar mass-radius diagram and highlights several of the recent discoveries facilitated by the TESS mission.

The eccentricity of the planet’s orbit and the inclination of the orbital plane carry important information about its formation and history. However, exoplanets detected via direct-imaging are often only observed for a very small fraction of their period, making it challenging to reliably estimate their orbits. The aim of this project is to investigate biases in the estimation of orbital parameters of directly-imaged exoplanets, particularly their eccentricities, and to define general guidelines to perform better estimations. For this, we constructed various orbits, and generated mock data for each spanning around 0.5% of their orbital period. We the Orbits For The Impatient (OFTI) algorithms to get orbit posteriors, and compared those to the true orbital parameters. We found that the inclination of the orbital plane is the parameter that most affects our estimations of eccentricity, with orbits that appear near-edge-on producing highly biased eccentricity posteriors. We also found a degeneracy between eccentricity and inclination that makes it ifficult to distinguish circular, edge-on orbits from eccentric, face-on orbits. For the exoplanet-imaging community, we propose practical recommendations, guidelines and warnings relevant to orbit-fitting.

The recent high spatial/spectral resolution observations have enabled constraining formation mechanisms of giant planets, especially at the final stages. The current interpretation of such observations is that these planets undergo magnetospheric accretion, suggesting the importance of planetary magnetic fields. We explore the properties of accreting, magnetized giant planets surrounded by their circumplanetary disks, using the physical parameters inferred for PDS 70 b/c. We compute the magnetic field strength and the resulting spin rate of giant planets, and find that these planets may possess magnetic dipole fields of either a few 10 G or a few 100 G; the former is the natural outcome of planetary growth and radius evolution, while the resulting spin rate cannot reproduce the observations. For the latter, a consistent picture can be drawn, where strong magnetic fields induced by hot planetary interiors, lead both to magnetospheric accretion and to spin-down due to disk locking. We also compute the properties of circumplanetary disks in the vicinity of these planets, taking into account planetary magnetic fields. The resulting surface density lies between the predictions of two empirically derived models of circumplanetary disks:the minimum mass subnebula model and the gas-starved model. Our model predicts a positive gradient of the surface density, which invokes the traps for both satellite migration and radially drifting dust particles. This work thus concludes that the final formation stages of giant planets are similar to those of low-mass stars such as brown dwarfs, as suggested by recent studies.

The most widely-studied mechanism of mass loss from extrasolar planets is photoevaporation via XUV ionization, primarily in the context of highly irradiated planets. However, the EUV dissociation of hydrogen molecules can also theoretically drive atmospheric evaporation on low-mass planets. For temperate planets such as the early Earth, impact erosion is expected to dominate in the traditional planetesimal accretion model, but it would be greatly reduced in pebble accretion scenarios, allowing other mass loss processes to be major contributors. We apply the same prescription for photoionization to this photodissociation mechanism and compare it to an analysis of other possible sources of mass loss in pebble accretion scenarios. We find that there is not a clear path to evaporating the primordial atmosphere accreted by an early Earth analog in a pebble accretion scenario. Impact erosion could remove ~2,300 bars of hydrogen if 1% of the planet’s mass is accr eted as planetesimals, while the combined photoevaporation processes could evaporate ~750 bars of hydrogen. Photodissociation is likely a subdominant, but significant component of mass loss. Similar results apply to super-Earths and mini-Neptunes. This mechanism could also preferentially remove hydrogen from a planet’s primordial atmosphere, thereby leaving a larger abundance of primordial water compared to standard dry formation models. We discuss the implications of these results for models of rocky planet formation including Earth’s formation and the possible application of this analysis to mass loss from observed exoplanets.

We present seven new transit light curves of the hot-Jupiter TrES-5b observed with the 2-m Himalayan Chandra Telescope, Hanle, India during 2016-2020 to look for the transit timing variation (TTV). For this study, total 59 transit light curves have been considered which include seven light curves from our new observations, 37 from the literature, and 15 from the Exoplanet Transit Database (ETD). In order to have homogeneously derived mid-transit times for precise TTV study, all the light curves were analyzed with a uniform procedure using the Transit Analysis Package (TAP). By fitting a linear ephemeris model to the mid-transit time data, we derive new transit ephemeris with $\chi^{2}_{red}= 2.43$ for TrES-5b, which is consistent and even more precise than the previous results. The best-fit ephemeris with $\chi^{2}_{red} >1$ indicates that the linear ephemeris model does not represent the transit time data well. To look for the periodicity in the timing residuals of linear ephemeris model, a generalized Lomb-Scargle periodogram is computed. However, we have not found any significant periodicity in the timing residuals. The highest peak power obtained in the periodogram at the frequency of 0.005232 rad/period has the false alarm probability (FAP) of 12%, which is found below from the threshold values (i.e. FAP =5% and 1%). This result enable us to conclude that the additional planet might not be present in the TrES-5 system. To confirm this, the further high-precision follow-up observation of the TrES-5 system would be required.

Kepler-289 is a three-planet system exhibiting Transit Timing Variations (TTVs). Kepler-289 contains two sub-Neptunes and one gas giant planet orbiting a young, Sun-like star whose light curve exhibits significant variability due to rotational modulation from starspots. All three planets orbit within 0.52 AU of the host star with orbital periods just below a 1:2:4 Laplace orbital resonance. We observe a transit of Kepler-289c with the WIRC instrument on the 200” Hale Telescope at Palomar Observatory, using diffuser-assisted photometry to achieve space-like photometric precision from the ground. This new transit observation extends the original four-year Kepler TTV baseline by an additional 6.5 years. We re-reduce the archival Kepler data with an improved stellar activity correction and carry out a joint fit with the Palomar data to constrain the transit shape and derive updated transit times. We then model the TTVs to determine the masses of the three planets and constrain their densities. Our new analysis results in improved mass and density estimates for all three planets, with the innermost planet showing the largest improvement.

Combining direct imaging astrometry and long-baseline radial velocity (RV) measurements of stellar binaries can provide precise constraints on their 3D orbits and yield dynamical masses for both components. We applied the combination of these methods to study HD104304, a binary system with a decades-long orbit containing a G8IV subgiant and a recently-discovered M dwarf companion. Using radial velocities collected over a timespan of two decades by Keck/HIRES and astrometry calculated from adaptive optics images taken by Keck/NIRC2, we explored models to jointly fit the astrometric orbital motion and RV trend. Previous studies of this system (Howard & Fulton, 2016) were unable to distinguish between two and three body solutions using RVs alone. However, we are able to break this degeneracy by incorporating images into the fit. We make 13-sigma dynamical mass measurements of the primary and secondary, and find that a slightly eccentric solution (e=0.3) is required. However, the dynamical mass we measure for the primary (~1.8 solar masses) is significantly higher than its well constrained spectroscopic mass of 1.02 solar masses. This hints at the need for a three-body solution to accurately model the observed trend in the HD 104304 system.

We study the properties of dust in disks to constrain models of planet formation. We measure and analyze the spectral index for the dust continuum emission at millimeter wavelengths for a sample of 24 young disks in the Upper Sco star-forming region. We do this by combining data taken with the ALMA telescope at wavelengths of 2.87 mm and 0.88 mm. Since the age of this region is ∼ 5 - 10 Myr, these results can constrain the properties of small solids in disks at the end of their lifetime. We examine whether dust trapping, which is key to the formation of planetesimals, happens only in much younger disks or if it is efficient all the way towards the end of the disk life cycle. Our results indicate that dust traps are present also in the relatively old disks in our sample, indicating that protoplanetary disks have the potential to form planetesimals during their entire lifetime. Our analysis also quantifies the effects of scattering by dust of the disk emission, a mechanism that has been recently proposed as potentially important to determine the fluxes of protoplanetary disks even at sub-mm/mm wavelengths. From preliminary results, based on the state-of-the-art radiative transfer code RADMC-3d, we infer that scattering is not effective for optically thin disk models, but could potentially play a significant role for optically thick models.

We report the discovery and validation of four extrasolar planets hosted by the nearby, bright, Sun-like (G3V) star HD~108236 using data from the Transiting Exoplanet Survey Satellite (TESS). We present transit photometry, reconnaissance and precise Doppler spectroscopy as well as high-resolution imaging, to validate the planetary nature of the objects transiting HD~108236, also known as the TESS Object of Interest (TOI) 1233. The innermost planet is a possibly-rocky super-Earth with a period of 3.79523+0.00047−0.00044 days and has a radius of 1.586±0.098 R⊕. The outer planets are sub-Neptunes, with potential gaseous envelopes, having radii of 2.068+0.10−0.091 R⊕, 2.72±0.11 R⊕, and 3.12+0.13−0.12 R⊕ and periods of 6.20370+0.00064−0.00052 days, 14.17555+0.00099−0.0011 days, and 19.5917+0.0022−0.0020 days, respectively. With V and Ks magnitudes of 9.2 and 7.6, respectively, the bright host star makes the transiting planets favorable targets for mass measurements and, potentially, for atmospheric characterization via transmission spectroscopy. HD~108236 is the brightest Sun-like star in the visual (V) band known to host four or more transiting exoplanets. The discovered planets span a broad range of planetary radii and equilibrium temperatures, and share a common history of insolation from a Sun-like star (R⋆=0.888±0.017 R⊙, Teff=5730±50 K), making HD 108236 an exciting, opportune cosmic laboratory for testing models of planet formation and evolution.

PTFO 8-8695 (CVSO 30) is a star in the 7-10 million year old Orion-OB1a cluster that shows brightness dips that resemble planetary transits. Although strong evidence against the planet hypothesis for this system has been presented, the possibility remains debated in the literature. To obtain further clues, we inspected data from the NASA TESS and the ESA Gaia missions. The Gaia data suggest that PTFO 8-8695 is a binary: the photometric data show it to be over-luminous with respect to members of its kinematic group, and the astrometric data are inconsistent with a single star. The TESS light curve shows two different photometric periods. The variability is dominated by a sinusoidal signal with a period of 11.98 hr, probably caused by stellar rotation. Also present is a 10.76 hr signal consisting of a not-quite sinusoid interrupted by hour-long dips, the type of signal previously interpreted as planetary transits. The phase of the dips is nearly 180° away from the phase of the originally reported dips. This makes the dips difficult to explain as planetary transits. Instead, we believe that PTFO 8-8695 is a pair of young and rapidly rotating M dwarfs, one of which shows the same “transient-dip” behavior that has been seen in at least 5 other cases. The origin of these transient dips is still unknown but likely involves circumstellar material. Combined with recent counter-arguments against the planetary nature of CI Tau b and V830 Tau b, the rejection of the planetary hypothesis for PTFO 8-8695b suggests that the number of known hot Jupiters younger than 100 Myr is approximately zero.

The recent discovery of thousands of protoplanetary disks and exoplanets has revealed that planet formation is a very efficient process in nature. There have been several theories to describe the many steps along this process, but it remains difficult to discover planets surrounding young stars. Thanks to its unprecedented angular resolution and sensitivity at radio wavelengths where the emission from the circumstellar material is optically thin, the future ngVLA telescope has the potential to transform our understanding of planet formation. In this presentation I will highlight the unprecedented imaging capabilities of the ngVLA using theoretical models of protoplanetary disks with varying planet and stellar masses. These theoretical models showcase the temporal evolution of the separation of gas and dust that in turn forms gaps and rings within the protoplanetary disk. These images will help shed light on how planets interact with disks and young stars, as well as on the properties of forming exoplanetary systems. Our findings suggest that the ngVLA would be capable of detecting the signatures in the disk of terrestrial planets at few astronomical units from the host star.