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NASA NTRS2017

A Massive Shell of Supernova-Formed Dust in SNR G54.1+0.3

While theoretical models of dust condensation predict that most refractory elements produced in core-collapsesupernovae (SNe) efficiently condense into dust, a large quantity of dust has so far only been observed inSN1987A. We present an analysis of observations from the Spitzer Space Telescope, Herschel SpaceObservatory, Stratospheric Observatory for Infrared Astronomy, and AKARI of the infrared shell surrounding thepulsar wind nebula in the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at 21 m to amagnesium silicate grain species that has been invoked in modeling the ejecta-condensed dust in Cas A, whichexhibits the same spectral signature. If this species is responsible for producing the observed spectral feature andaccounts for a significant fraction of the observed infrared continuum, we find that it would be the dominantconstituent of the dust in G54.1+0.3, with possible secondary contributions from other compositions, such ascarbon, silicate, or alumina grains. The total mass of SN-formed dust required by this model is at least 0.3Me. Wediscuss how these results may be affected by varying dust grain properties and self-consistent grain heating models.The spatial distribution of the dust mass and temperature in G54.1+0.3 confirms the scenario in which the SNformeddust has not yet been processed by the SN reverse shock and is being heated by stars belonging to a clusterin which the SN progenitor exploded. The dust mass and composition suggest a progenitor mass of 1627Me andimply a high dust condensation efficiency, similar to that found for Cas A and SN1987A. The study providesanother example of significant dust formation in a Type IIP SN explosion and sheds light on the properties ofpristine SN-condensed dust.

Temim, Tea↗
NASA NTRS2016

Future Large-Aperture Ultraviolet/Optical/Infrared Space Observatory

Since the beginning of modern astronomical science in the early 1900s, astronomers have yearned to escape the turbulence and absorption of Earth's atmosphere by placing observatories in space. One of the first papers to lay out the advantages of space astronomy was by Lyman Spitzer in 1946, "Astronomical Advantages of an Extra-Terrestrial Observatory," though later in life he minimized the influence of this work. Since that time, and especially gaining momentum in the 1960s after the launch of Sputnik, astronomers, technologists, and engineers continued to advance, organizing scientific conferences, advocating for necessary technologies, and assessing sophisticated designs for increasingly ambitious space observations at ultraviolet, visual, and infrared (UVOIR) wavelengths. These community-wide endeavors, combined with the explosion in technological capability enabled by the Apollo era, led to rapid advancement in space observatory performance that culminated in the spectacularly successful Hubble Space Telescope (HST), launched in 1990 and still returning surpassing scientific results.

Thronson, Harley↗
NASA NTRS2016

Comet Dust: The Diversity of Primitive Particles and Implications

Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive particles has expanded significantly through microscale investigations of cosmic dust samples (IDPs and AMMs) and of comet dust samples (Stardust and Rosetta's COSIMA), as well as through remote sensing (spectroscopy and imaging) via Spitzer and via spacecraft encounters with 103P/Hartley 2 and 67P/Churyumov-Gerasimenko. Microscale investigations show that comet dust and cosmic dust are particles of unequilibrated materials, including aggregates of materials unequilibrated at submicron scales. We call unequilibrated materials "primitive" and we deduce they were incorporated into ice-­‐rich (H2O-, CO2-, and CO-ice) parent bodies that remained cold, i.e., into comets, because of the lack of aqueous or thermal alteration since particle aggregation; yet some Stardust olivines suggest mild thermal metamorphism. Primitive particles exhibit a diverse range of: structure and typology; size and size distribution of constituents; concentration and form of carbonaceous and organic matter; D-, N-, and O- isotopic enhancements over solar; Mg-, Fe-contentsof thesilicate minerals; the compositions and concentrations of sulfides, and of less abundant mineral species such as chondrules, CAIs and carbonates. The unifomity within a group of samples points to: aerodynamic sorting of particles and/or particle constituents; the inclusion of a limited range of oxygen fugacities; the inclusion or exclusion of chondrules; a selection of organics. The properites of primitive particles imply there were disk processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disk present at the time and in the region where the comets formed.

Comet dust is primitive and shows significant dive↗
NASA NTRS2017

Constraints on the Progenitor of SN 2010jl and Pre-existing Hot Dust in its Surrounding Medium

A search for the progenitor of SN 2010jl, an unusually luminous core-collapse supernova of Type IIn, using pre-explosion Hubble/WFPC2 and Spitzer/IRAC images of the region, yielded upper limits on the UV and near infrared (IR) fluxes from any candidate star. These upper limits constrain the luminosity and effective temperature of the progenitor, the mass of any pre-existing dust in its surrounding circumstellar medium (CSM), and dust proximity to the star. A lower limit on the CSM dust mass is required to hide a luminous progenitor from detection by Hubble. Upper limits on the CSM dust mass and constraints on its proximity to the star are set by requiring that the absorbed and reradiated IR emission not exceed the IRAC upper limits. Using the combined extinction-IR emission constraints, we present viable M(sub d)-R(sub 1) combinations, where M(sub d) and R(sub 1) are the CSM dust mass and its inner radius. These depend on the CSM outer radius, dust composition and grain size, and the properties of the progenitor. The results constrain the pre-supernova evolution of the progenitor, and the nature and origin of the observed post-explosion IR emission from SN 2010jl. In particular, an eta Car-type progenitor will require at least 4 mag of visual extinction to avoid detection by Hubble. This can be achieved with dust masses greater than approximately equal to 10(exp -3) solar mass (less than the estimated 0.2-0.5 solar mass around eta Car), which must be located at distances of greater than approximately equal to 10(exp 16) cm from the star to avoid detection by Spitzer.

Dwek, Eli↗
NASA NTRS2017

Understanding Breaks in Flare X-Ray Spectra: Evaluation of a Cospatial Collisional Return-Current Model

Hard X-ray (HXR) spectral breaks are explained in terms of a one-dimensional model with a cospatial return current. We study 19 flares observed by the Ramaty High Energy Solar Spectroscopic Imager with strong spectral breaks at energies around a few deka-keV, which cannot be explained by isotropic albedo or non-uniform ionization alone. We identify these breaks at the HXR peak time, but we obtain 8 s cadence spectra of the entire impulsive phase. Electrons with an initially power-law distribution and a sharp low-energy cutoff lose energy through return-current losses until they reach the thick target, where they lose their remaining energy through collisions. Our main results are as follows. (1) The return-current collisional thick-target model provides acceptable fits for spectra with strong breaks. (2) Limits on the plasma resistivity are derived from the fitted potential drop and deduced electron-beam flux density, assuming the return current is a drift current in the ambient plasma. These resistivities are typically 2-3 orders of magnitude higher than the Spitzer resistivity at the fitted temperature, and provide a test for the adequacy of classical resistivity and the stability of the return current. (3) Using the upper limit of the low-energy cutoff, the return current is always stable to the generation of ion-acoustic and electrostatic ion-cyclotron instabilities when the electron temperature is nine times lower than the ion temperature. (4) In most cases, the return current is most likely primarily carried by runaway electrons from the tail of the thermal distribution rather than by the bulk drifting thermal electrons. For these cases, anomalous resistivity is not required.

Alaoui, Meriem↗
NASA NTRS2018

Star & Planet Formation Studies and Opportunities with SOFIA

Star formation, the most fundamental process in the universe, is linked to planet formation and thus to the origin and evolution of life. We have a general outline of how planets and stars form, yet unraveling the details of the physics and chemistry continues to challenge us. The infrared and submillimeter part of the spectrum hold the most promise for studying the beginnings of star formation. The observational landscape recently shaped by Spitzer, Herschel and ALMA, continues to challenge our current theories. SOFIA, the Stratospheric Observatory for Infrared Astronomy, equipped with state-of-the-art infrared instrumentation to a vantage point at 45,000 feet (13.7 kilometers) flight altitude that is above 99.9 percent of the Earth's water vapor, enables observations in the infrared through terahertz frequencies not possible from the ground. SOFIA is a community observatory, about to start its sixth annual observing cycle. My talk will focus on recent results in advancing star and planet formation processes using SOFIAʼs imaging and polarimetric capabilities, and the upcoming science enabled by the 3rd generation instrument High-Resolution Mid-Infrared Spectrometer (HIRMES) to be commissioned in 2019. I will show how mid-infrared imaging is used to test massive star formation theories, how far-infrared polarimetry on sub-parsec scales is directly testing the role of magnetic fields in molecular clouds, and how velocity-resolved high-resolution spectroscopy will push forward our understanding of proto-planetary disk science. I will also summarize upcoming opportunities with the SOFIA observatory. For the latest news about your flying observatory, see https://sofia.usra.edu/.

Star formation↗
NASA NTRS2017

Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars. II. Planetary Systems Observed During Campaigns 1-7

We recently used near-infrared spectroscopy to improve the characterization of 76 low-mass stars around which K2 had detected 79 candidate transiting planets. 29 of these worlds were new discoveries that had not previously been published. We calculate the false positive probabilities that the transit-like signals are actually caused by non-planetary astrophysical phenomena and reject five new transit-like events and three previously reported events as false positives. We also statistically validate 17 planets (7 of which were previously unpublished), confirm the earlier validation of 22 planets, and announce 17 newly discovered planet candidates. Revising the properties of the associated planet candidates based on the updated host star characteristics and refitting the transit photometry, we find that our sample contains 21 planets or planet candidates with radii smaller than 1.25 solar radii, 18 super-Earths (1.25-2 solar radii), 21 small Neptunes (2-4 solar radii), three large Neptunes (4-6 solar radii), and eight giant planets (greater than 6 solar radii). Most of these planets are highly irradiated, but EPIC 206209135.04 (K2-72e, 1.29 from plus 0.19 to minus 0.18 solar radii), EPIC 211988320.01 (perihelion radius equals 2.86 from plus 0.16 to minus 0.15 solar radii), and EPIC 212690867.01 (2.20 from plus 0.19 to minus 0.18 solar radii) orbit within optimistic habitable zone boundaries set by the "recent Venus" inner limit and the "early Mars" outer limit. In total, our planet sample includes eight moderately irradiated 1.5-3 solar radii planet candidates (planetary flux greater than or approximately 20 times Earth's flux) orbiting brighter stars (Ks less than 11) that are well-suited for atmospheric investigations with the Hubble, Spitzer, and/or James Webb Space Telescopes. Five validated planets orbit relatively bright stars (Kp less than 12.5) and are expected to yield radial velocity semi-amplitudes of at least 2 meters per second. Accordingly, they are possible targets for radial velocity mass measurement with current facilities or the upcoming generation of red optical and near-infrared high-precision RV (Radial Velocity) spectrographs.

Dressing, Courtney D.↗
NASA NTRS2017

Evidence for a Dayside Thermal Inversion and High Metallicity for the Hot Jupiter WASP-18b

We find evidence for a strong thermal inversion in the dayside atmosphere of the highly irradiated hot Jupiter WASP-18b (equatorial temperature equals 2411 degrees Kelvin, mass equals 10.3 times the mass of Jupiter) based on emission spectroscopy from Hubble Space Telescope secondary eclipse observations and Spitzer eclipse photometry. We demonstrate a lack of water vapor in either absorption or emission at 1.4 microns. However, we infer emission at 4.5 microns and absorption at 1.6 microns that we attribute to CO, as well as a non-detection of all other relevant species (e.g., TiO, VO). The most probable atmospheric retrieval solution indicates a C/O ratio of 1 and a high metallicity (C/H equals 283 from plus 395 to minus 138 times solar). The derived composition and temperature/pressure profile suggest that WASP-18b is the first example of both a planet with a non-oxide driven thermal inversion and a planet with an atmospheric metallicity inconsistent with that predicted for Jupiter-mass planets at greater than 2 sigma. Future observations are necessary to confirm the unusual planetary properties implied by these results.

Sheppard, Kyle B.↗
NASA NTRS2017

Kelt-16b: A Highly Irradiated, Ultra-Short Period Hot Jupiter Nearing Tidal Disruption

We announce the discovery of KELT-16b, a highly irradiated, ultra-short period hot Jupiter transiting the relatively bright (visual magnitude equals 11.7) star TYC 2688-1839-1/KELT-16. A global analysis of the system shows KELT-16 to be an F7V star with effective temperature equal to 6236 plus or minus 54 degrees Kelvin, log g (sub asterisk) equal to 4.253 from plus 0.031 to minus 0.036, [Fe/H] equal to minus 0.002 from plus 0.086 to minus 0.085, mass (sub asterisk) equal to 1.211 from plus 0.043 to minus 0.046 times the solar mass, and radius (sub asterisk) equal to 1.360 from plus 0.064 o minus 0.053 times the solar radius. The planet is a relatively high-mass inflated gas giant with planetary mass equal to 2.75 from plus 0.016 to minus 0.15 times Jupiter's mass, planetary radius equal to 1.415 from plus 0.084 to minus 0.067 times Jupiter's radius, density planetary rho equal to 1.20 plus or minus 0.18 grams per cubic centimeter, surface gravity, log planetary gravity equal to 3.530 from plus 0.042 to minus 0.049, and equatorial temperature equal to 2453 from plus 55 to minus 47 degrees Kelvin. The best-fitting linear ephemeris is T(sub C) equal to 22457247.24791 plus or minus 0.00019 BJD (sub TDB) and P equal to 0.9689951 plus or minus 0.0000024 day. KELT-16b joins WASP-18b, -19b, -43b, -103b, and HATS-18b as the only giant transiting planets with periodicity P less than 1 day. Its ultra-short period and high irradiation make it a benchmark target for atmospheric studies by the Hubble Space Telescope, Spitzer, and eventually the James Webb Space Telescope. For example, as a hotter, higher-mass analog of WASP-43b, KELT-16b may feature an atmospheric temperature-pressure inversion and day-to-night temperature swing extreme enough for TiO to rain out at the terminator. KELT-16b could also join WASP-43b in extending tests of the observed mass-metallicity relation of the solar system gas giants to higher masses. KELT-16b currently orbits at a mere approximately 1.7 Roche radii from its host star, and could be tidally disrupted in as little as a few times 10 (sup 5) years (for a stellar tidal quality factor of Q (sup prime) (sub asterisk) equal to 10 (sup 5). Finally, the likely existence of a widely separated bound stellar companion in the KELT-16 system makes it possible that Kozai-Lidov (KL) oscillations played a role in driving KELT-16b inward to its current precarious orbit.

Oberst, Thomas E.↗
NASA NTRS2013

Vertical Settling and Radial Segregation of Large Dust Grains in the Circumstellar Disk of the Butterfly Star

Circumstellar disks are considered as the environment for the formation of planets. The growth of dust grains in these disks is the first step in the core accretion-gas capture planet formation scenario. Indicators as well as evidence of disk evolution can be traced in spatially resolved images and the spectral energy distribution (SED) of these objects. Aims. We aim at developing a model for the dust phase of the edge-on orientated circumstellar disk of the Butterfly Star which allows one to fit observed multi-wavelength images as well as the SED simultaneously. Our model is based on spatially resolved high angular resolution observations at 1.3 mm, 894 μm, 2.07 μm, 1.87 μm, 1.60 μm and 1.13 μm as well as an extensively covered SED ranging from 12 μm to 2.7 mm, including a detailed spectrum obtained with the Spitzer Space Telescope in the range from 12 μm to 38 μm. A parameter study based on a grid search method, involving the detailed analysis of every parameter, was performed to constrain the disk parameters and find the best-fit model for the independent observations. The individual observations were modeled simultaneously, using our continuum radiative transfer code MC3D. We derived a model that is capable of reproducing all of the observations of the disk at the same time. We find quantitative evidence for grain growth up to ~100 μm sized particles, vertical settling of larger dust grains toward the disk midplane, and radial segregation of the latter toward the central star. Our results are consistent with current theoretical models for the evolution of circumstellar disks and the early stages of planet formation.

Radiative transfer↗
NASA NTRS2013

Calibration of the Mid-Infrared Tully-Fisher Relation

Distance measures on a coherent scale around the sky are required to address the outstanding cosmological problemsof the Hubble constant and of departures from the mean cosmic flow. The correlation between galaxy luminositiesand rotation rates can be used to determine the distances to many thousands of galaxies in a wide range ofenvironments potentially out to 200 Mpc. Mid-infrared (3.6m) photometry with the Spitzer Space Telescope isparticularly valuable as a source of luminosities because it provides products of uniform quality across the sky.From a perch above the atmosphere, essentially the total magnitude of targets can be registered in exposures ofa few minutes. Extinction is minimal and the flux is dominated by the light from old stars, which is expected tocorrelate with the mass of the targets.In spite of the superior photometry, the correlation between mid-infrared luminosities and rotation rates extractedfrom neutral hydrogen profiles is slightly degraded from the correlation found with I-band luminosities. A colorcorrection recovers a correlation that provides comparable accuracy to that available at the I band (20 1in an individual distance) while retaining the advantages identified above. Without color correction, the relationbetween linewidth and [3.6] magnitudes is Mb,i,k,a [3.6] 20.34 9.74(logWimx 2.5). This description is foundwith a sample of 213 galaxies in 13 clusters that define the slope and 26 galaxies with Cepheid or tip of the red giant branch distances that define the zero point. A color-corrected parameter MC[3.6] is constructed that has reduced scatter: MC[3.6] 20.34 9.13(logWimx 2.5). Consideration of the seven calibration clusters beyond 50 Mpc, outside the domain of obvious peculiar velocities, provides a preliminary Hubble constant estimate of H0 74 4 km s1 Mpc1.

Mid-Infrared↗
NASA NTRS2014

10 meter Sub-Orbital Large Balloon Reflector (LBR)

The realization of a large, space-based 10 meter class telescope for far-infrared/THz studies has long been a goal of NASA. Such a telescope could study the origins of stars, planets, molecular clouds, and galaxies; providing a much needed means of following-up on tantalizing results from recent successful missions such as Spitzer, Herschel, and SOFIA. Indeed, Herschel began its life in the US space program as the Large Deployable Reflector (LDR) to be assembled in low Earth orbit by shuttle astronauts. Escalating costs and smaller federal budget allocations resulted in a downsizing of the mission. However, by combining successful suborbital balloon and ground-based telescope technologies, the dream of a 10 meter class telescope free of ~99% of the Earth's atmospheric absorption in the far-infrared can be realized. The same telescope can also be used to perform sensitive, high spectral and spatial resolution limb sounding studies of the Earth's atmosphere in greenhouse gases such as CO, ClO, O3, and water, as well as serve as a high flying hub for any number of telecommunications and surveillance activities. Flight times of 100+ days will be possible, with instruments having mass and power requirements in excess of ~500 kg and ~1 kW.Here we present the results of our NIAC Step 1, Phase B design study where each key aspect of the LBR concept is discussed and recommendations made for further study in Phase II.These aspects include realization of a large spherical reflecting surface, spherical corrector, pointing system, instrument module, and service module/gondola. Once each hardware component is introduced, a typical LBR Mission profile is described that enables the realization of a stratospheric 10 meter THz observatory and limb sounder. Verification of the design approach was achieved by using a combination of analytical modelling, lab testing of materials and techniques, and building a 3 meter rooftop LBR prototype.

Telescope↗
NASA NTRS2014

A Multi-Wavelength Investigation of the Radio-Loud Supernova PTF11qcj and its Circumstellar Environment

We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L (sub 5 gigahertz) approximates 10 (sup 29) ergs per second per hertz). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of approximately 10 (sup -4) the mass of the sun per year times (v (sub omega) divided by 1000 kilometers per second), and a velocity of approximately 0.3-0.5 c (the speed of light in a vacuum) for the fastest moving ejecta (at around 10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude M (sub r) approximately equal to -13 mag may have occurred approximately 2.5 years prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

Radio↗
NASA NTRS2018

A Deep X-Ray Look at Abell 2142-Viscosity Constraints from Kelvin-Helmholtz Eddies, a Displaced Cool Peak that Makes a Warm Core, and A Possible Plasma Depletion Layer

cold fronts in detail. We find that the southern cold front exhibits well-developed Kelvin–Helmholtz (KH) eddies seen in the sky plane. Comparing their wavelength and amplitude with those in hydrodynamic simulations of cold fronts in viscous gas, and estimating the gas tangential velocity from centripetal acceleration, we constrain the effective viscosity to be at most 1/5 of Spitzer isotropic viscosity, but consistent with full Braginskii anisotropic viscosity for magnetized plasma. While the northwestern front does not show obvious eddies, its shape and the structure of its brightness profile suggest KH eddies seen in projection. The southern cold front continues in a spiral to the center of the cluster, ending with another cold front only 12 kpc from the gas density peak. The cool peak itself is displaced ∼30 kpc from the brightest cluster galaxy (BCG) (the biggest such offset among centrally peaked clusters), while the X-ray emission on a larger scale is still centered on the BCG, indicating that the BCG is at the center of the gravitational potential and the cool gas is sloshing in it. The specific entropy index of the gas in the peak (K≈49 keV sq.cm) makes A2142 a rare “warm core”; apparently the large displacement of the cool peak by sloshing is the reason. Finally, we find a subtle narrow, straight channel with a 10% drop in X-ray brightness, aligned with the southern cold front—possibly a plasma depletion layer in projection.

Wang, Qian H. S.↗
NASA NTRS2019

The Origins Space Telescope

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryo cooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background limited sensitivity.

Leisawitz, D.↗
NASA NTRS2019

The Peculiar Volatile Composition of CO-Dominated Comet C/2016 R2 (PanSTARRS)

Comet C/2016 R2 (PanSTARRS) has a peculiar volatile composition, with CO being the dominant volatile, as opposed to H2O, and one of the largest N2/CO ratios ever observed in a comet. Using observations obtained with the Spitzer Space Telescope, NASA’s Infrared Telescope Facility, the 3.5 m Astrophysical Research Consortium telescope at Apache Point Observatory, the Discovery Channel Telescope at Lowell Observatory, and the Arizona Radio Observatory 10 m Submillimeter Telescope, we quantified the abundances of 12 different species in the coma of R2 PanSTARRS: CO, CO2, H2O, CH4, C2H6, HCN, CH3OH, H2CO, OCS, C2H2, NH3, and N2. We confirm the high abundances of CO and N2 and heavy depletions of H2O, HCN, CH3OH, and H2CO compared to CO reported by previous studies. We provide the first measurements (or most sensitive measurements/constraints) on H2O, CO2, CH4, C2H6, OCS, C2H2, and NH3, all of which are depleted relative to CO by at least 1–2 orders of magnitude compared to values commonly observed in comets. The observed species also show strong enhancements relative to H2O, and, even when compared to other species like CH4 or CH3OH, most species show deviations from typical comets by at least a factor of 2–3. The only mixing ratios found to be close to typical are CH3OH/CO2 and CH3OH/CH4. The CO2/CO ratio is within a factor of 2 of those observed for C/1995 O1 (Hale- Bopp) and C/2006 W3 (Christensen) at a similar heliocentric distance, though it is at least an order of magnitude lower than many other comets observed with AKARI. While R2 PanSTARRS was located at a heliocentric distance of 2.8 au at the time of our observations in 2018 January/February, we argue, using sublimation models and comparison to other comets observed at similar heliocentric distance, that this alone cannot account for the peculiar observed composition of this comet and therefore must reflect its intrinsic composition. We discuss possible implications for this clear outlier in compositional studies of comets obtained to date and encourage future dynamical and chemical modeling in order to better understand what the composition of R2 PanSTARRS tells us about the early solar system.

McKay, Adam J.↗
NASA NTRS2019

OGLE-2018-BLG-0022: First Prediction of an Astrometric Microlensing Signal from a Photometric Microlensing Event

In this work, we present the analysis of the binary microlensing event OGLE-2018-BLG-0022 that is detected toward the Galactic bulge field. The dense and continuous coverage with the high-quality photometry data from ground-based observations combined with the space-based Spitzer observations of this long timescale event enables us to uniquely determine the masses M1=0.40 ± 0.05Me and M2=0.13 ± 0.01Me of the individual lens components. Because the lens-source relative parallax and the vector lens-source relative proper motion are unambiguously determined, we can likewise unambiguously predict the astrometric offset between the light centroid of the magnified images (as observed by the Gaia satellite) and the true position of the source. This prediction can be tested when the individual-epoch Gaia astrometric measurements are released.

Han, Cheongho↗
NASA NTRS2019

High-Resolution Mid-Infrared Molecular Line Survey of the Orion Hot Core

The basic building blocks of life are synthesized in space as part of the natural stellar evolutionary cycle, whereby elements ejected into the interstellar medium by dying stars are incorporated back into the dense clouds, which form the next generation of stars and planets. The formation of stars and planets are fundamental to the evolution of matter in the Universe as complex molecules are created and destroyed during this step. Understanding these processes will allow us to answer “What is the relation between the molecules we see in the ISM and the molecular inventory of Earth and the terrestrial planets in the Solar System?” Measuring and cataloging the inventory of organic molecules and understanding their evolution requires observations over a broad wavelength range (IR, MIR, FIR, (sub)mm, and radio) to cover all stages of this evolutionary cycle needed to link interstellar material to that delivered to planets. High-resolution molecular line surveys provide chemical inventories for star forming regions and are essential for studying their chemistry, kinematics and physical conditions. Previous high spectral resolution surveys have been limited to radio, sub-mm and FIR wavelengths; however, Mid-infrared observations are the only way to study symmetric molecules that have no dipole moment and thus cannot be detected in the (sub)mm line surveys from ALMA. Past midinfrared missions such as ISO and Spitzer had low to moderate resolving power that were only able to link broad features with particular molecular bands and could not resolve the individual rovibrational transitions. JWST will provide exceptional sensitivity in the MIR, but will also not have sufficient spectral resolution, which can lead to confusion in identifying the contribution from strong to moderate strength molecular species. We present new results from an on-going high resolution (R ~ 60,000) line survey of the Orion hot core between 12.5 - 28.3 μm and 7 - 8 μm, using the EXES instrument on the SOFIA airborne observatory. SOFIA's higher-resolution and smaller beam compared to ISO allows us to spatially and spectrally isolate the emission towards the hot core. This survey will provide the best infrared measurements (to date) of molecular column densities and physical conditions, providing strong constraints on the current chemical network models for star forming regions. This survey will greatly enhance the inventory of resolved line features in the MIR, making it an invaluable reference to be used by the JWST and ALMA scientific communities.

Rangwala, Naseem↗