UBVRI Light curves of 44 Type Ia supernovae

We present UBVRI photometry of 44 Type la supernovae (SNe la) observed from 1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The data set comprises 2190 observations and is the largest homogeneously observed and reduced sample of SNe la to date, nearly doubling the number of well-observed, nearby SNe la with published multicolor CCD light curves. The large sample of [U-band photometry is a unique addition, with important connections to SNe la observed at high redshift. The decline rate of SN la U-band light curves correlates well with the decline rate in other bands, as does the U - B color at maximum light. However, the U-band peak magnitudes show an increased dispersion relative to other bands even after accounting for extinction and decline rate, amounting to an additional ∼40% intrinsic scatter compared to the B band

Compound-specific isotope analysis of benzotriazole and its derivatives.

Compound-specific isotope analysis (CSIA) is an important tool for the identification of contaminant sources and transformation pathways, but it is rarely applied to emerging aquatic micropollutants owing to a series of instrumental challenges. Using four different benzotriazole corrosion inhibitors and its derivatives as examples, we obtained evidence that formation of organometallic complexes of benzotriazoles with parts of the instrumentation impedes isotope analysis. Therefore, we propose two strategies for accurate C and N measurements of polar organic micropollutants by gas chromatography isotope ratio mass spectrometry (GC/IRMS). Our first approach avoids metallic components and uses a Ni/Pt reactor for benzotriazole combustion while the second is based on the coupling of online methylation to the established GC/IRMS setup. Method detection limits for on-column injection of benzotriazole, as well as its 1-CH-, 4-CH-, and 5-CH-substituted species were 0.1-0.3 mM and 0.1-1.0 mM for delta C-13 and delta N-15 analysis respectively, corresponding to injected masses of 0.7-1.8 nmol C and 0.4-3.0 nmol N, respectively. The Ni/Pt reactor showed good precision and was very long-lived (1000 successful measurements). Coupling isotopic analysis to offline solid-phase extraction enabled benzotriazole-CSIA in tap water, wastewater treatment effluent, activated sludge, and in commercial dishwashing products. A comparison of C and N values from different benzotriazoles and benzotriazole derivatives, both from commercial standards and in dishwashing detergents, reveals the potential application of the proposed method for source apportionment

ExploreNEOs III: Size, Albedo, And Thermal History Of 58+ Low-deltaV NEOs

Space missions to NEOs are being planned at all major space agencies, and recently President Obama announced the goal of a manned mission to an NEO. Efforts to find and select suitable targets (plus backup targets) are severely hampered by our lack of knowledge on the physical properties of dynamically favorable NEOs. In particular, current mission scenarios tend to favor primitive low-albedo objects. For the vast majority of NEOs the albedo is unknown. We report new constraints on the size and albedo of NEOs with rendezvous deltaV < 7 km/s. Our results are based on thermal flux data obtained in the framework of our ongoing ExploreNEOs survey (Trilling et al., 2010) using NASA's "Warm Spitzer" space telescope. As of this writing, we have results for 253 objects in hand (including the 58 low-deltaV NEOs presented here); before the end of 2011 we expect to have measured the size and albedo of ~700 NEOs (including probably ~160 low-deltaV NEOs). Due to the nature of our observations, our results are generally more accurate for low-albedo objects than for their high-albedo counterparts. While there are reasons to believe that primitive volatile-rich materials are universally low in albedo, the converse need not be true: The orbital evolution of some objects caused them to lose their volatiles by coming too close to the Sun. For all our targets, we give the closest perihelion distance they are likely to have reached (using orbital integrations from Marchi et al., 2009) and corresponding upper limits on the past surface temperature. Low-deltaV objects for which both albedo and thermal history suggest a primitive composition include (162998) 2001 SK162, (68372) 2001 PM9, and (100085) 1992 UY4. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL, Caltech under a contract with NASA

ExploreNEOs: Status and Results from the Warm Spitzer NEO Survey

We are carrying out the Warm Spitzer Near Earth Object Survey "ExploreNEOs." The goals of this project are to determine the albedos and diameters for ~700 NEOs, roughly 10% of all known NEOs, and to explore the history of near-Earth space. By the time of the DPS meeting, we will have observed more than 300 NEOs at 3.6 and 4.5 microns, and produced model-derived albedo and diameter for each target. In this talk we will present the status of our project and highlight some results to date. We find that the distribution of albedos among the NEO population is quite broad, indicating a wide range of compositions among this population. We will present the albedo distribution for low Tisserand objects. We will present a preliminary size distribution for NEOs. We will also show a strong correlation between derived albedo and asteroid taxonomic (spectral) class. Finally, we will present plans for the remainder of the survey and highlight some projects that will be achievable when our entire sample is in hand, by summer, 2011. Support for this work is provided by NASA/JPL/Spitzer Science Center

The Accuracy of the Warm Spitzer Near-Earth Object Survey

We report on observations of near-Earth objects (NEOs) performed with IRAC as part of our on-going (2009-2011) Warm Spitzer NEO survey (“ExploreNEOs”), the primary aim of which is to provide sizes and albedos of some 700 NEOs. The emphasis of the work described here is an assessment of the overall accuracy of our survey results, which are based on a semi-empirical generalized model of asteroid thermal emission. The set of some 170 NEOs in our current Warm Spitzer results catalog contains 28 for which published taxonomic classifications are available, and 14 for which relatively reliable published diameters and albedos are available. From a comparison of the Warm Spitzer results with results expected on the basis of previous observations, we conclude that Warm Spitzer diameters and albedos are accurate to about 25% and 50%, respectively. Cases in which agreement with results from the literature is worse than expected are highlighted and discussed; these include the potential spacecraft target 138911 2001 AE2. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA

ExploreNEOs: Average albedo by taxonomic complex in the near-Earth asteroid population

Understanding the albedo distribution of the near-Earth object (NEO) population allows for a better understanding of the relationship between absolute magnitude and size, which impacts calculations of size-frequency distribution and impact hazards. Examining NEO albedos also sheds light on the differences between the NEO and Main-Belt populations. We combine albedo results from the ExploreNEOs Warm Spitzer Exploration Science program with taxonomic classifications from the literature, publicly available datasets, and new observations from our concurrent spectral survey to derive the average albedos for C-, D-, Q-, S-, V- and X-complex NEOs

ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population

Examining the albedo distribution of the near-Earth object (NEO) population allows for a better understanding of the relationship between absolute (H) magnitude and size, which impacts calculations of the size frequency distribution and impact hazards. Examining NEO albedos also sheds light on the differences between the NEO and Main Belt populations. We combine albedo results from the ExploreNEOs Warm Spitzer Exploration Science program with taxonomic classifications from the literature, publicly available data sets, and new observations from our concurrent spectral survey to derive the average albedos for C-, D-, Q-, S-, V-, and X-complex NEOs. Using a sample size of 118 NEOs, we calculate average albedos of 0.29+0.05 –0.04, 0.26+0.04 –0.03, and 0.42+0.13 –0.11 for the Q-, S-, and V-complexes, respectively. The averages for the C- and D-complexes are 0.13+0.06 –0.05 and 0.02+0.02 –0.01, but these averages are based on a small number of objects (five and two, respectively) and will improve with additional observations. We use albedos to assign X-complex asteroids to one of the E-, M-, or P-types. Our results demonstrate that the average albedos for the C-, S-, V-, and X-complexes are higher for NEOs than the corresponding averages observed in the Main Belt

ExploreNEOs: The Warm Spitzer near Earth object survey

We are carrying out the ExploreNEOs project in which we observe more than 600 near Earth Objects (NEOs) at 3.6 and 4.5 microns with Warm Spitzer. For each NEO we derive diameter and albedo. We present our results to date, which include studies of individual objects, results for our entire observed sample, and, by extrapolation, results for the entire NEO population. We also present several avenues of future work

The Near-Earth Object Surveyor Mission

The Near-Earth Object (NEO) Surveyor mission is a NASA Observatory designed to discover and characterize asteroids and comets. The mission’s primary objective is to find the majority of objects large enough to cause severe regional impact damage (>140 m in effective spherical diameter) within its 5 yr baseline survey. Operating at the Sun-Earth L1 Lagrange point, the mission will survey to within 45° of the Sun in an effort to find objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard reliably. Over the course of its survey, NEO Surveyor will discover ∼200,000-300,000 new NEOs down to sizes as small as ∼10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]