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NASA NTRS2003

A Proposed Robotic Astronomy Mission to the Lunar South Polar Regions

This paper outlines a possible mission to emplace a robotic infrared / submillimeter wave interferometer array near the lunar south pole. This region has now been investigated by the Clementine and Lunar Prospector missions, and by Earth-based radar, and its topography and thermal environment are fairly well-known. The area would be exceptionally suitable for infrared / submillimeter astronomy because of the continually low temperatures, approaching that of liquid nitrogen (77K) in some places. A submillimeter spaceborne interferometer mission, Submillimeter Probe of the Evolution of the Cosmic Structure (SPECS) has been proposed by John Mather and others, covering the 40 - 500 micron region with 3 formation flying telescopes. The present paper proposes a lunar adaptation of the SPECS concept, LSPECS. This adaptation would involve landing 4 telescopes on the area north of Shackleton crater at zero degrees longitude. This is in nearly year round darkness but is continually radar visible from Earth. The landed payload of LSPECS would include a telerobotic rover, 4 three meter submm telescopes, a solar power array to be emplaced on the continually sunlit north rim of Shackleton crater, and an S-band antenna for data relay to Earth. Passive cooling without the use of expendable cryogenics. might be possible, trading long exposure time for instrument temperatures above that of liquid helium. The LSPECS would permit long-term study of an extremely wide range of cosmic and solar system phenomena in the southern celestial hemisphere. For complete sky coverage, a similar installation near the north pole would be required. The LSPECS site would also be suitable other types of observation, such as optical interferometry or centimeter wavelength radio astronomy. The lunar south pole is also of great interest because of its extensive ice deposits, which may represent cometary infall with pre-biotic compounds.

Lowman, Paul D., Jr.↗

NASA NTRS1994

The search for brown dwarfs with infrared surveys

Infrared Astronomy Satellite (IRAS), ISO, Space Infrared Telescope Facility (SIRTF), WIRE, Deep Near-Infrared Survey (DENIS), and Two Micron All-Sky Survey (2MASS) observations were used to compute the maximum number of observable brown dwarfs for various infrared surveys by combining the maximum possible Oort limit (0.1 'missing' solar mass p/cu c) with all possible brown dwarf mass and age distributions. This approach shows what limits will be placed on the contribution of brown dwarfs to any possible 'missing mass' if no brown dwarfs are observed. I consider brown dwarfs with masses of 0.01-0.08 solar mass and ages of 10(exp 9)-10(exp 10) years. The full range of predicted numbers of brown dwarfs above approx. 6 times the noise of each of the below surveys is: IRAS Point Source Catalog, 0.02-6; IRAS Faint Source Catalog absolute value of b greater than 10 deg, 0.05-16; ISO (2 week 12 micrometer survey), 0.15-80; SIRTF (2 week 12 micrometer survey), 2.50-1600; WIRE (4 month 12 micrometer survey), 21.80-6000; DENIS(half sky) absolute value of b greater than 10 deg, 0.00-2000; and 2MASS(full sky) absolute value of b greater than 10 deg, 0.00-8800. A failure to find brown dwarfs in the IRAS FSC would just barely rule out about half of the mass-age range for Oort limit total masses. A failure to find brown dwarfs in 2MASS/DENIS would rule out roughly the same mass-age range, but would set a limit of 0.1-0.01 times the Oort mass in that mass-age region. No limits would be set for the other half of the mass-age range since both IRAS and 2MASS/DENIS have insufficient sensitivity for brown dwarfs with T less than 750 K. A failure to find brown dwarfs with ISO would rule out almost all of the mass-age range for Oort limit total masses, but would not set a significantly lower limit to the brown dwarf mass limit. A failure to find brown dwarfs with SIRTF or WIRE would rule out the entire mass-age range for Oort limit total masses and set an upper limit of 0.1-0.001 times the Oort mass. To date, about 18% of the IRAS FSC has been searched down to 6 sigma, and no brown dwarfs have been found. This sets a 95% upper limit of 3 in 18% of the sky, or 13 in the entire FSC for absolute value b greater than 10 deg. To begin to set useful limits from 2MASS or DENIS, approximately 400 square degrees needs to be analyzed. To date, only a few square degrees of results from the 2MASS prototype camera have been examined, with no brown dwarfs found so far.

Chester, T. J.↗

DOE OSTI2020

Early High-contrast Imaging Results with Keck/NIRC2-PWFS: The SR 21 Disk

High-contrast imaging of exoplanets and protoplanetary disks depends on wave front sensing and correction made by adaptive optics instruments. Classically, wave front sensing has been conducted at optical wavelengths, which made high-contrast imaging of red targets such as M-type stars or extincted T Tauri stars challenging. Keck/NIRC2 has combined near-infrared (NIR) detector technology with the pyramid wave front sensor (PWFS). With this new module we observed SR 21, a young star that is brighter at NIR wavelengths than at optical wavelengths. Compared with the archival data of SR 21 taken with the optical wave front sensing we achieved ~20% better Strehl ratio in similar natural seeing conditions. Further post-processing utilizing angular differential imaging and reference-star differential imaging confirmed the spiral feature reported by the Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch instrument polarimetric observation, which is the first detection of the SR 21 spiral in total intensity at L' band. We also compared the contrast limit of our result (10 -4 at 0.'4 and 2 × 10 -5 at 1.'0) with the archival data that were taken with optical wave front sensing and confirmed the improvement, particularly at ≤0.'5. Our observation demonstrates that the NIR PWFS improves AO performance and will provide more opportunities for red targets in the future.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

ACCESS: A Visual to Near-infrared Spectrum of the Hot Jupiter WASP-43b with Evidence of H{sub 2}O, but No Evidence of Na or K

We present a new ground-based visual transmission spectrum of the hot Jupiter WASP-43b, obtained as part of the ACCESS Survey. The spectrum was derived from four transits observed between 2015 and 2018, with combined wavelength coverage between 5300 and 9000 Å and an average photometric precision of 708 ppm in 230 Å bins. We perform an atmospheric retrieval of our transmission spectrum combined with literature Hubble Space Telescope/WFC3 observations to search for the presence of clouds/hazes as well as Na, K, Hα, and H{sub 2}O planetary absorption and stellar spot contamination over a combined spectral range of 5318–16420 Å. We do not detect a statistically significant presence of Na i or K i alkali lines, or Hα in the atmosphere of WASP-43b. We find that the observed transmission spectrum can be best explained by a combination of heterogeneities on the photosphere of the host star and a clear planetary atmosphere with H{sub 2}O. This model yields a log evidence of 8.26 ± 0.42 higher than a flat (featureless) spectrum. In particular, the observations marginally favor the presence of large, low-contrast spots over the four ACCESS transit epochs with an average covering fraction f{sub het}=0.27{sub −0.16}{sup +0.42} and temperature contrast ΔT = 132 K ± 132 K. Within the planet’s atmosphere, we recover a log H{sub 2}O volume mixing ratio of −2.78{sub −1.47}{sup +1.38}, which is consistent with previous H{sub 2}O abundance determinations for this planet.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1991

Measurement of the spectral signature of small carbon clusters at near and far infrared wavelengths

A significant percentage of the carbon inventory of the circumstellar and interstellar media may be in the form of large refractory molecules (or small grains) referred to as carbon clusters. At the small end, uneven numbers of carbon atoms seem to be preferred, whereas above 12 atoms, clusters containing an even number of carbon atoms appear to be preferred in laboratory chemistry. In the lab, the cluster C-60 appears to be a particularly stable form and has been nicknamed Bucky Balls because of its resemblance to a soccer ball and to geodesic domes designed by Buckminster Fuller. In order to investigate the prevalence of these clusters, and their relationship to the polycyclic aromatic hydrocarbons (PAHs) that have become the newest focus of IR astronomy, it is necessary to determine the spectroscopic characteristics of these clusters at near and far infrared wavelengths. Described here is the construction of a near to far IR laser magnetic resonance spectrometer that has been built at the University of California Berkeley in order to detect and characterize these spectra. The equipment produces carbon clusters by laser evaporation of a graphitic target. The clusters are then cooled in a supersonic expansion beam in order to simulate conditions in the interstellar medium (ISM). The expansion beam feeds into the spectrometer chamber and permits concentrations of clusters sufficiently high as to permit ultra-high resolution spectroscopy at near and far IR wavelengths. The first successful demonstration of this apparatus occurred last year when the laboratory studies permitted the observational detection of C-5 in the stellar outflow surrounding IRC+10216 in the near-IR. Current efforts focus on reducing the temperature of the supersonic expansion beam that transport the C clusters evaporated from a graphite target into the spectrometer down to temperatures as low as 1 K.

Tarter, J.↗

DOE OSTI2020

Using the Baryonic Tully–Fisher Relation to Measure H{sub o}

We explore the use of the baryonic Tully–Fisher relation (bTFR) as a new distance indicator. Advances in near-IR imaging and stellar population models, plus precise rotation curves, have reduced the scatter in the bTFR such that distance is the dominant source of uncertainty. Using 50 galaxies with accurate distances from Cepheids or the tip magnitude of the red giant branch, we calibrate the bTFR on a scale independent of H {sub o}. We then apply this calibrated bTFR to 95 independent galaxies from the SPARC sample, using CosmicFlows-3 velocities, to deduce the local value of H {sub o}. We find H {sub o} = 75.1 ± 2.3 (stat) ±1.5 (sys) km s{sup −1} Mpc{sup −1}.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2001

The Mid and Far IR Universe and Facilities To See It

Although half the luminosity of the universe appears in the band from 20-450 $\mu$m, almost nothing is known about the sources of this radiation. Moreover, many molecules, atoms, and ions of astrophysical interest have some of their strongest lines in this wavelength range. Now Infrared Astronomy Satellite (IRAS) and ISO have flown, Space Infrared Telescope Facility (SIRTF) is nearly ready, SOFIA is under construction, and NGST, ALMA, Herschel, Planck, and a dozen 8 m and a 25 m ground-based visible/near IR telescopes could all be operational by the end of decade. Nevertheless, the mid and far IR region will still not have telescopes that are comparable to neighboring bands in energy sensitivity or angular resolution, despite these many advances. What scientific questions will still be open, and what instrumentation will be required? We anticipate that cold filled-aperture telescopes operating out to 100 $\mu$m and cold imaging interferometers, operating out to about 450 $\mu$m in space could be very powerful, using direct detection rather than heterodyne systems. I will give a brief overview of the scientific questions that may still be open, the main factors governing the choice of equipment, and the technological developments that would be required to actually build and use these new facilities.

Mather, John C.↗

DOE OSTI2020

SCExAO/CHARIS Near-infrared Integral Field Spectroscopy of the HD 15115 Debris Disk

We present new, near-infrared (1.1–2.4 μm) high-contrast imaging of the debris disk around HD 15115 with the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS). The SCExAO/CHARIS resolves the disk down to ρ ∼ 0.″2 (r {sub proj} ∼ 10 au), a factor of ∼3–5 smaller than previous recent studies. We derive a disk position angle of PA ∼ 279.°4–280.°5 and an inclination of i ∼ 85.°3–86.2.°. While recent SPHERE/IRDIS imagery of the system could suggest a significantly misaligned two-ring disk geometry, CHARIS imagery does not reveal conclusive evidence for this hypothesis. Moreover, optimizing models of both one- and two-ring geometries using differential evolution, we find that a single ring having a Hong-like scattering phase function matches the data equally well within the CHARIS field of view (ρ ≲ 1″). The disk’s asymmetry, well evidenced at larger separations, is also recovered; the west side of the disk appears, on average, around 0.4 mag brighter across the CHARIS bandpass between 0.″25 and 1″. Comparing Space Telescope Imaging Spectrograph (STIS) 50CCD optical photometry (2000–10500 Å) with CHARIS near-infrared photometry, we find a red (STIS/50CCD−CHARIS broadband) color for both sides of the disk throughout the 0.″4–1″ region of overlap, in contrast to the blue color reported at similar wavelengths for regions exterior to ∼2″. Further, this color may suggest a smaller minimum grain size than previously estimated at larger separations. Finally, we provide constraints on planetary companions and discuss possible mechanisms for the observed inner disk flux asymmetry and color.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2001

Multiplexed Readout of Thermal Bolometers with Superconducting Transition Edge Thermometers

History shows that in astronomy, more is better. In the near future, direct detector arrays for the far-infrared and submillimeter will contain hundreds to thousands of elements. A multiplexed readout is necessary for practical implementation of such arrays, and has been developed using SQUIDs. The technology permits a 32 x 32 array of bolometers to be read out using approximately 100 wires rather than the >2000 needed with direct wiring. These bolometer arrays are made by micromachining techniques, using superconducting transition edge sensors as the thermistors. We describe the development of this multiplexed superconducting bolometer array architecture as a step toward bringing about the first astronomically useful arrays of this design. This technology will be used in the Submillimeter and Far Infrared Experiment (SAFIRE) instrument on Stratospheric Observatory for Infrared Astronomy (SOFIA), and is a candidate for a wide variety of other spectroscopic and photometric instruments.

Benford, Dominic J.↗

NASA NTRS1987

Infrared properties of dust grains derived from IRAS observations

The analysis of several diffuse interstellar clouds observed by the Infrared Astronomy Satellite (IRAS) is presented. The 60/100 micron flux ratios appear to be nearly constant in clouds with up to 1 sup m visual extinction at the center. Observations of a highly regular cloud in Chamaeleon show that the 12/100 micron ratio peaks at an intermediate radial distance and declines towards the center of the cloud. These observations indicate that nonequilibrium emission accounts only for the 12 and 25 micron bands; strong emission observed at the 60 micron band is probably due to equilibrium thermal radiation. The correlation of the 12 micron emission with a red excess observed for a high latitude cloud, L1780, is shown to be consistent with the assumption that both features are due to fluorescence by the same molecular species.

Chlewicki, G.↗

NASA NTRS2004

Where is Tropopause?

Much of the earth science that is being proposed for the Stratospheric Observatory for Infrared Astronomy (SOFIA) Upper-Deck Research Facility (SURF) deals with issues related to the tropopause, which will be near SOFIA'S flight level at mid-latitudes. Interpreting in situ or remote aerosol, hydrometeor, and trace gas measurements will require accurate knowledge of the tropopause location. Examples of such measurements are presented, and a brief discussion is given on the Microwave Temperature Profiler (MTP), which the earth science community has used in the past to determine the tropopause height.

in situ↗

DOE OSTI2020

Near-infrared Characterization of Four Massive Stars in Transition Phases

Massive stars typically undergo short-lived post-main-sequence evolutionary phases with strong mass loss and occasional mass eruptions. Many of such massive stars in transition phases have been identified based on their dusty envelopes. The ejected material often veils the stellar photospheres so that the central stars cannot be assigned proper spectral types and evolutionary stages. The infrared spectral range has proved to be ideal for the classification of evolved massive stars and for the characterization of their environments. To improve our knowledge on the central stars of four such dust-enshrouded objects, [GKF 2010] MN 83, [GKF 2010] MN 108, [GKF 2010] MN 109, and [GKF 2010] MN 112, we collect and present their first medium-resolution K-band spectra in the 2.3–2.47 μm region and discuss the location of the stars in the JHK color–color diagram. We find that the emission-line spectra of both MN 83 and MN 112 show characteristics typically seen in luminous blue variable (LBV) stars. In addition, we propose that the presence and strength of the newly reported Mg ii lines might be used as a new complementary criterion to identify LBV candidates. The spectra of the other two objects imply that MN 108 is an O-type supergiant, whereas MN 109 could be an LBV candidate in its active phase. We derive lower limits for the reddening toward the stars and find that three of all dereddened fall into the region of confirmed LBVs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

High-resolution Near-infrared Spectroscopic Study of Galactic Supernova Remnants. I. Kinematic Distances

We have carried out high-resolution near-infrared spectroscopic observations toward 16 Galactic supernova remnants (SNRs) showing strong H 2 emission features. A dozen bright H 2 emission lines are clearly detected for individual SNRs, and we have measured their central velocities, line widths, and fluxes. For all SNRs except one (G9.9–0.8), the H 2 line ratios are well consistent with that of thermal excitation at T ~ 2000 K, indicating that the H 2 emission lines are most likely from shock-excited gas and therefore that they are physically associated with the remnants. The kinematic distances to the 15 SNRs are derived from the central velocities of the H 2 lines using a Galactic rotation model. We derive for the first time the kinematic distances to four SNRs: G13.5+0.2, G16.0–0.5, G32.1–0.9, and G33.2–0.6. Among the remaining 11 SNRs, the central velocities of the H 2 emission lines for six SNRs are well consistent (±5 km s -1 ) with those obtained in previous radio observations, while for the other five SNRs (G18.1–0.1, G18.9–1.1, Kes 69, 3C 396, W49B) they are significantly different. We discuss the velocity discrepancies in these five SNRs. In G9.9–0.8, the H 2 emission shows nonthermal line ratios and narrow line width (~4 km s -1 ), and we discuss its origin.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2014

Origins of the Lunar and Planetary Laboratory, University of Arizona

The roots of the Lunar and Planetary Laboratory (LPL) extend deep into the rich fabric of G. P. Kuiper's view of the Earth as a planet and planetary systems as expected companions to most stars, as well as the post-war emergent technology of infrared detectors suitable for astronomy. These concepts and events began with Kuiper's theoretical work at Yerkes Observatory on the origin of the Solar System, his discovery of two planetary satellites and observational work with his near-infrared spectrometer on the then-new McDonald 82-inch telescope in the mid- to late-1940s. A grant for the production of a photographic atlas of the Moon in the mid-1950s enabled him to assemble the best existing images of the Moon and acquire new photographs. This brought E. A. Whitaker and D. W. G. Arthur to Yerkes. Others who joined in the lunar work were geologist Carl S. Huzzen and grad student E. P. Moore, as well as undergrad summer students A. B. Binder and D. P. Cruikshank (both in 1958). The Atlas was published in 1959, and work began on an orthographic lunar atlas. Kuiper's view of planetary science as an interdisciplinary enterprise encompassing astronomy, geology, and atmospheric physics inspired his vision of a research institution and an academic curriculum tuned to the combination of all the scientific disciplines embraced in a comprehensive study of the planets. Arrangements were made with the University of Arizona (UA) to establish LPL in affiliation with the widely recognized Inst. of Atmospheric Physics. Kuiper moved to the UA in late 1960, taking the lunar experts, graduate student T. C. Owen (planetary atmospheres), and associate B. M. Middlehurst along. G. van Biesbroeck also joined the migration to Tucson; Binder and Cruikshank followed along as new grad students. Astronomy grad student W. K. Hartmann came into the academic program at UA and the research group at LPL in 1961. Senior faculty affiliating with LPL in the earliest years were T. Gehrels, A. B. Meinel, H. L. Johnson, and F. J. Low, each with their own grad students and associates. Work began on IR spectroscopy and a rectified lunar atlas. Kuiper and Johnson started the search for future observatory sites in N. America and Hawaii.

Planets↗

DOE OSTI2020

A Warm Jupiter Transiting an M Dwarf: A TESS Single-transit Event Confirmed with the Habitable-zone Planet Finder

We confirm the planetary nature of a warm Jupiter transiting the early M dwarf TOI-1899 using a combination of available TESS photometry; high-precision, near-infrared spectroscopy with the Habitable-zone Planet Finder; and speckle and adaptive optics imaging. The data reveal a transiting companion on an ∼29 day orbit with a mass and radius of 0.66±0.07 M{sub J} and 1.15{sub −0.05}{sup +0.04} R{sub J}, respectively. The star, TOI-1899, is the lowest-mass star known to host a transiting warm Jupiter, and we discuss the follow-up opportunities afforded by a warm (T{sub eq}∼362 K) gas giant orbiting an M0 star. Our observations reveal that TOI-1899.01 is a puffy warm Jupiter, and we suggest additional transit observations to both refine the orbit and constrain the true dilution observed in TESS.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1987

IRAS and ground-based observations of star formation regions in the Magellanic clouds

The Infrared Astronomy Satellite (IRAS) detected several hundred individual regions of star formation in the Large and Small Magellanic Clouds. Nearly two dozen of the brightest such sources were searched for from the ground at 10 microns; most of these were located and measured at wavelengths from 0.6 to 20 microns. Three principle results emerge from this study: First, the IRAS data show that star formation is considerably less active in the SMC than in the LMC, relative either to mass, luminosity, or H I content. The reduced activity in the SMC is consistent with the smaller amount of molecular material inferred from CO observations. Second, the sizes of the objects range from less than a few arcsecs (objects which look like extremely compact HII regions, with little or no extended radio, optical, or infrared emission) to some tens of arcsecs across (giant HII regions, of which the largest and brightest is 30 Doradus). Third, there are no obvious differences in the characteristics of the central portions of the LMC and SMC sources; all look like Galactic H II regions of similar luminosity.

Elias, Jonathan H.↗

DOE OSTI2022

Probing the Extragalactic Mid-infrared Background with HAWC

The extragalactic background light (EBL) contains all the radiation emitted by nuclear and accretion processes in stars and compact objects since the epoch of recombination. Measuring the EBL density directly is challenging, especially in the near-to-far-infrared wave band, mainly due to the zodiacal light foreground. Instead, gamma-ray astronomy offers the possibility to indirectly set limits on the EBL by studying the effects of gamma-ray absorption in the very high energy (VHE: >100 GeV) spectra of distant blazars. The High Altitude Water Cherenkov Gamma Ray Observatory (HAWC) is one of the few instruments sensitive to gamma rays with energies above 10 TeV. This offers the opportunity to probe the EBL in the near/mid-IR region: λ = 1–100 μm. In this study, we fit physically motivated emission models to Fermi-LAT gigaelectronvolt data to extrapolate the intrinsic teraelectronvolt spectra of blazars. We then simulate a large number of absorbed spectra for different randomly generated EBL model shapes and calculate Bayesian credible bands in the EBL intensity space by comparing and testing the agreement between the absorbed spectra and HAWC extragalactic observations of two blazars. The resulting bands are in agreement with current EBL lower and upper limits, showing a downward trend toward higher wavelength values λ > 10 μm also observed in previous measurements.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1993

Unsteady fluid and optical simulation of transonic aero-windows

The time-varying fluid and optical fields of several cavity configurations have been computed on overset mesh systems using the Reynolds-averaged Navier-Stokes equations and geometric optics. Comparisons between numerical results and Airborne Optical Adjunct (AOA) flight data are made in two-dimensions for a quieted cavity geometry with two lip-blowing rates. In three-dimensions, two proposed aero-window locations for the Stratospheric Observatory For Infrared Astronomy (SOFIA) are discussed. The simulations indicate that convection of large shear layer structures across the aperture cause the blur circle diameter to be three times the diffraction-limited diameter in the near-infrared band.

Atwood, Christopher A.↗