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With infrared flux contrasts larger than typically seen in hot Jupiter, tidally-locked white dwarf-brown dwarf binaries offer a superior opportunity to investigate atmospheric processes in irradiated atmospheres. NLTT5306 is such a system, with a M$_{BD}$ = 52 $\pm$ 3 M$_{Jup}$ brown dwarf orbiting a T$_{eff}$ = 7756 $\pm$ 35 K white dwarf with an ultra-short period of $\sim$102 min. We present HST/WFC3 spectroscopic phase curves of NLTT5306, consisting of 47 spectra from 1.1 to 1.7 microns with an average S/N=65 per wavelength. We extracted the phase-resolved spectra of the brown dwarf NLTT5306B, finding a small (, 31 pages, 25 figures, Accepted to Astrophysical Journal with video abstract. Video abstract available at https://www.rachaelamaro.com/research-1

We designed and tested near-infrared spectral indices to pre-select the most likely variable midand late-T dwarfs, which overlap in effective temperatures with directly-imaged exoplanets. We estimated the variability fraction of our sample in 38% which agrees with the variability fractions provided by past surveys for mid- to late-T dwarfs.

Giant planets within the habitable zones of the closest several stars can currently be imaged with ground-based telescopes. Within the next decade, the Extremely Large Telescopes (ELTs) will begin to image the habitable zones of a greater number of nearby stars with much higher sensitivity$-$ potentially imaging exo-Earths around the closest stars. To determine the most promising candidates for observations over the next decade, we establish a theoretical framework for the direct detectability of Earth$-$ to super-Jovian-mass exoplanets in the mid-infrared based on available atmospheric and evolutionary models. Of the 83 closest BAFGK type stars, we select 37 FGK type stars within 10 pc and 34 BA type stars within 30 pc with reliable age constraints. We prioritize targets based on a parametric model of a planet's effective temperature based on a star's luminosity, distance, and age, and on the planet's orbital semi-major axis, radius, and albedo. We then predict the most likely planets to be detectable with current 8-meter telescopes and with a 39-m ELT with up to 100 hours of observation per star. Putting this together, we recommend observation times needed for the detection of habitable-zone exoplanets spanning the range of very nearby temperate Earth-sized planets to more distant young giant planets. We then recommend ideal initial targets for current telescopes and the upcoming ELTs., Responded to the first highly positive referee report

External UV environment of stellar nurseries plays a major role on evolution of protoplanetary disks around young stellar objects. Photoevaporating protoplanetary disks (proplyds) have been found mainly around O stars in strong radiation environments, most of which are found in the Orion Nebula Cluster. However our recent studies also found proplyds in immediate vicinity of B stars, which implies that intermediate UV radiation environment can also affect disk evolution of young stellar objects, and potentially planet formation in such disks. We present our recent studies of proplyds around low mass young stellar- and sub-stellar objects, some of which may be potentially forming free-floating planetary mass objects. We will present our findings of the proplyds in NGC 1977 and NGC 2024, and show some selected proplyds around low mass sub-stellar objects. We will discuss the implication and the role of external UV environment in star and planet formation.&nbsp

High resolution spectroscopy of the lowest-mass stars and brown dwarfs reveals their origins, multiplicity, compositions and physical properties, with implications for the star formation and chemical evolution history of the Milky Way. We motivate the need for high-resolution, infrared spectroscopic surveys to reach these faint sources., 9 pages, submitted to Astro2020 Science White Paper Call

Provided that sufficient resources are deployed, we can look forward to an extraordinary future in which we will characterize potentially habitable planets. Until now, we have had to base interpretations of observations on habitability hypotheses that have remained untested. To test these theories observationally, we propose a statistical comparative planetology approach to questions of planetary habitability. The key objective of this approach will be to make quick and cheap measurements of critical planetary characteristics on a large sample of exoplanets, exploiting statistical marginalization to answer broad habitability questions. This relaxes the requirement of obtaining multiple types of data for a given planet, as it allows us to test a given hypothesis from only one type of measurement using the power of an ensemble. This approach contrasts with a "systems science" approach, where a few planets would be extensively studied with many types of measurements. A systems science approach is associated with a number of difficulties which may limit overall scientific return, including: the limited spectral coverage and noise of instruments, the diversity of exoplanets, and the extensive list of potential false negatives and false positives. A statistical approach could also be complementary to a systems science framework by providing context to interpret extensive measurements on planets of particular interest. We strongly recommend future missions with a focus on exoplanet characterization, and with the capability to study large numbers of planets in a homogenous way, rather than exclusively small, intense studies directed at a small sample of planets., Comment: White paper submitted in response to the solicitation of feedback for the "2020 Decadal Survey" by the National Academy of Sciences

This White Paper describes the opportunities for discovery of Jupiter-mass objects with 300K atmospheres. The discovery and characterization of such cold objects is vital for understanding the low-mass terminus of the initial mass function and for optimizing the study of exoplanets by the next generation of large telescopes, space probes and space missions., Comment: White Paper submitted for Astro2020 Science

The search for life on planets outside our solar system has largely been the province of the astrophysics community until recently. A major development since the NASA Astrobiology Strategy 2015 document (AS15) has been the integration of other NASA science disciplines (planetary science, heliophysics, Earth science) with ongoing exoplanet research in astrophysics. The NASA Nexus for Exoplanet System Science (NExSS) provides a forum for scientists to collaborate across disciplines to accelerate progress in the search for life elsewhere. Here we describe recent developments in these other disciplines, with a focus on exoplanet properties and environments, and the prospects for future progress that will be achieved by integrating emerging knowledge from astrophysics with insights from these fields., Comment: 8 pages including title page and references, 0 figures. This is a white paper submitted to the National Academies call on the Astrobiology Science Strategy for the Search for Life in the Universe (http://sites.nationalacademies.org/SSB/CurrentProjects/SSB_180812)

Deducing the cloud cover and its temporal evolution from the observed planetary spectra and phase curves can give us major insight into the atmospheric dynamics. In this paper, we present Aeolus, a Markov-Chain Monte Carlo code that maps the structure of brown dwarf and other ultracool atmospheres. We validated Aeolus on a set of unique Jupiter Hubble Space Telescope (HST) light curves. Aeolus accurately retrieves the properties of the major features of the jovian atmosphere such as the Great Red Spot and a major 5um hot spot. Aeolus is the first mapping code validated on actual observations of a giant planet over a full rotational period. For this study, we applied Aeolus to J and H-bands HST light curves of 2MASSJ21392676+0220226 and 2MASSJ0136565+093347. Aeolus retrieves three spots at the top-of-the-atmosphere (per observational wavelength) of these two brown dwarfs, with a surface coverage of 21+-3% and 20.3+-1.5% respectively. The Jupiter HST light curves will be publicly available via ADS/VIZIR., Comment: Accepted by ApJ; A high-quality version of this paper can be found at http://mapotofu.as.arizona.edu/poster/Karalidi_et_al_2015.pdf

Recent discoveries of variable brown dwarfs have provided us with a new window into their three-dimensional cloud structure. The highest variables are found at the L/T transition, where the cloud cover is thought to break up, but variability has been found to occur also for both cloudy L dwarfs and (mostly) cloud-free mid T dwarfs. We summarize results from recent HST programs measuring the spectral variability of brown dwarfs in the near-infrared and compare to results from ground-based programs. We discuss the patchy cloud structure of L/T transition objects, for which it is becoming increasingly certain that the variability does not arise from cloud holes into the deep hot regions but from varying cloud thickness. We present a new patchy cloud model to explain the spectral variability of 2MASSJ21392676+0220226. We also discuss the curious multi-wavelength variability behavior of the recently discovered very nearby early T dwarf WISE J104915.57-531906.1B (Luhman 16B) and the mid T dwarf 2MASS J22282889-431026., Comment: 4 pages, 1 figure, submitted to the proceedings of "Gaia and the unseen - the brown dwarf question", Torino, 24-26 March 2014, to be published in Memorie della Societa' Astronomica Italiana (SAIt), eds Ricky Smart, David Barrado, Jackie Faherty

Recent discoveries of variable brown dwarfs have provided us with a new window into their three dimensional cloud structure. The highest variables are found at the L/T transition where the cloud cover is thought to break up but variability has been found to occur also for both cloudy L dwarfs and (mostly) cloud free mid T dwarfs. We summarize results from recent HST programs measuring the spectral variability of brown dwarfs in the near infrared and compare to results from ground based programs. We discuss the patchy cloud structure of L/T transition objects for which it is becoming increasingly certain that the variability does not arise from cloud holes into the deep hot regions but from varying cloud thickness. We present a new patchy cloud model to explain the spectral variability of 2MASSJ21392676+0220226. We also discuss the curious multi wavelength variability behavior of the recently discovered very nearby early T dwarf WISE J104915.57 531906.1B (Luhman 16B) and the mid T dwarf 2MASS J22282889 431026.

We explore the extent to which Spitzer Infrared Spectrograph (IRS) spectra taken at low spectral resolution can be used in quantitative studies of organic molecular emission from disks surrounding low-mass young stars. We use Spitzer IRS spectra taken in both the high- and low-resolution modules for the same sources to investigate whether it is possible to define line indices that can measure trends in the strength of the molecular features in low-resolution data. We find that trends in the HCN emission strength seen in the high-resolution data can be recovered in low-resolution data. In examining the factors that influence the HCN emission strength, we find that the low-resolution HCN flux is modestly correlated with stellar accretion rate and X-ray luminosity. Correlations of this kind are perhaps expected based on recent observational and theoretical studies of inner disk atmospheres. Our results demonstrate the potential of using the large number of low-resolution disk spectra that reside in the Spitzer archive to study the factors that influence the strength of molecular emission from disks. Such studies would complement results for the much smaller number of circumstellar disks that have been observed at high resolution with IRS.

The NASA Exoplanet Exploration Program's SAG15 group has solicited, collected, and organized community input on high-level science questions that could be addressed with future direct imaging exoplanet missions and the type and quality of data answering these questions will require. Input was solicited through a variety of forums and the report draft was shared with the exoplanet community continuously during the period of the report development (Nov 2015 -- May 2017). The report benefitted from the input of over 50 exoplanet scientists and from multiple open-forum discussions at exoplanet and astrobiology meetings. The SAG15 team has identified three group of high-level questions, those that focus on the properties of planetary systems (Questions A1--A2), those that focus on the properties of individual planets (Questions B1--B4), and questions that relate to planetary processes (Questions C1--C4). The questions in categories A, B, and C require different target samples and often different observational approaches. For each questions we summarize the current body of knowledge, the available and future observational approaches that can directly or indirectly contribute to answering the question, and provide examples and general considerations for the target sample required., For the report with higher-resolution images and for updates and supporting documentations please visit http://eos-nexus.org/sag15/

This White Paper, submitted to the National Academy of Sciences' Astro2010 Decadal Review Committee, focuses on 2 central themes in the study of young brown dwarfs -- their formation mechanism and disk characteristics -- which are of direct relevance to fundamental questions of stellar and planetary origins and properties., Comment: 8 pages, 3 figures, Astro2010 Science White Paper (v2 has 2 references corrected/updated, and 3 repeated references in the v1 reference list removed)