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NEO Surveyor will detect asteroids and comets using mid-infrared thermal emission, however ground-based followup resources will require knowledge of the expected visible light brightness in order to plan characterization observations. Here we describe the range of visual-to-infrared colors that the NEOs detected by Surveyor will span, and demonstrate that for objects that have no previously reported Visual band observations, estimates of the Johnson Visual-band brightness based on infrared flux alone will have significant uncertainty. Incidental or targeted photometric followup of objects discovered by Surveyor enables predictions of the fraction of reflected light visible and near-infrared wavelengths, supporting additional detailed characterization., Comment: 12 pages, 5 figures. Accepted for publication in PSJ

The reactivated Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE-R) serendipitously caught the Type II supernova SN 2023ixf in Messier 101 on the rise, starting day 3.6 through day 10.9, and on the late-time decline from days 211 through 213 and days 370 through 372. We have considered these mid-infrared (mid-IR) data together with observations from the ultraviolet (UV) through the near-IR, when possible. At day 3.6 we approximated the optical emission with a hot, ~26,630 K blackbody, with a notable UV excess likely from strong SN shock interaction with circumstellar matter (CSM). In the IR, however, a clear excess is also obvious, and we fit it with a cooler, ~1,620 K blackbody with radius of ~2.6 x 10^{15} cm, consistent with dust in the progenitor's circumstellar shell likely heated by the UV emission from the CSM interaction. On day 10.8, the light detected was consistent with SN ejecta-dominated emission. At late times we also observed a clear NEOWISE-R excess, which could arise either from newly formed dust in the inner ejecta or in the contact discontinuity between the forward and reverse shocks, or from more distant pre-existing dust grains in the SN environment. Furthermore, the large 4.6 micron excess at late times can also be explained by the emergence of the carbon monoxide 1--0 vibrational band. SN 2023ixf is the best-observed SN IIP in the mid-IR during the first several days after explosion and one of the most luminous such SNe ever seen., Comment: 22 pages, 8 figures, submitted to AAS Journals

Asteroids with low orbital perihelion distances experience extreme heating from the Sun that can modify their surfaces and trigger non-typical activity mechanisms. These objects are generally difficult to observe from ground-based telescopes due to their frequent proximity to the Sun. The Near Earth Object Surveyor mission, however, will regularly survey down to Solar elongations of 45 degrees and is well-suited for the detection and characterization of low-perihelion asteroids. Here, we use the survey simulation software tools developed for mission verification to explore the expected sensitivity of NEO Surveyor to these objects. We find that NEO Surveyor is expected to be >90% complete for near-Sun objects larger than D~300 m. Additionally, if the asteroid (3200) Phaethon underwent a disruption event in the past to form the Geminid meteor stream, Surveyor will be >90% complete to any fragments larger than D~200 m. For probable disruption models, NEO Surveyor would be expected to detect dozens of objects on Phaethon-like orbits, compared to a predicted background population of only a handful of asteroids, setting strong constraints on the likelihood of this scenario., Comment: 13 pages, accepted for publication in PSJ

Hyperactive comet activity typically becomes evident beyond the frost line (3 to 4 au) where it becomes too cold for water-ice to sublimate. If carbon monoxide (CO) and carbon dioxide (CO2) are the species that drive activity at sufficiently large distances, then detailed studies on the production rates of these species are extremely valuable to examine the formation of the solar system because these two species (beyond water) are next culpable for driving cometary activity. The NEOWISE reactivated mission operates at two imaging bandpasses, W1 and W2 at 3.4 and 4.6 microns, respectively, with the W2 channel being fully capable of detecting CO and CO2 at 4.67 and 4.23 microns in the same bandpass. It is extremely difficult to study CO2 from the ground due to contamination in Earth's atmosphere. We present our W1 and W2 photometry, dust measurements, and findings for comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini), hereafter, B1, K2, and U3, respectively. Our results assess CO and CO2 gas production rates observed by NEOWISE. We have determined: (1) comets B1 and K2 have CO2 and CO gas production rates of 1e27 and 1e29 molecules per second, respectively, if one assumes the excess emission is attributed to either all CO or all CO2; (2) B1 and K2 are considered hyperactive in that their measured AfRho dust production values are on the order of greater than or equal to 1e3 cm; and (3) the CO and CO2 production rates do not always follow the expected convention of increasing with decreased heliocentric distance, while B1 and K2 exhibit noticeable dust activity on their inbound leg orbits.

The known near-Earth object (NEO) population consists of over 32,000 objects, with a yearly discovery rate of over 3000 NEOs per year. An essential component of the next generation of NEO surveys is an understanding of the population of known objects, including an accounting of the discovery rate per year as a function of size. Using a near-Earth asteroid (NEA) reference model developed for NASA's NEO Surveyor (NEOS) mission and a model of the major current and historical ground-based surveys, an estimate of the current NEA survey completeness as a function of size and absolute magnitude has been determined (termed the Known Object Model; KOM). This allows for understanding of the intersection of the known catalog of NEAs and the objects expected to be observed by NEOS. The current NEA population is found to be $\sim38\%$ complete for objects larger than 140m, consistent with estimates by Harris & Chodas (2021). NEOS is expected to catalog more than two thirds of the NEAs larger than 140m, resulting in $\sim76\%$ of NEAs cataloged at the end of its 5 year nominal survey (Mainzer et al, 2023}, making significant progress towards the US Congressional mandate. The KOM estimates that $\sim77\%$ of the currently cataloged objects will be detected by NEOS, with those not detected contributing $\sim9\%$ to the final completeness at the end its 5 year mission. This model allows for placing the NEO Surveyor mission in the context of current surveys to more completely assess the progress toward the goal of cataloging the population of hazardous asteroids., Comment: 27 pages, 18 figures, 3 tables. Accepted for publication in Planetary Science Journal (PSJ)

The Near-Earth Object (NEO) Surveyor mission is a NASA observatory designed to discover and characterize near-Earth 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 five-year baseline survey. Operating at the Sun-Earth L1 Lagrange point, the mission will survey to within 45 degrees of the Sun in an effort to find the objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to reliably distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard. Over the course of its survey, NEO Surveyor will discover $\sim$200,000 - 300,000 new NEOs down to sizes as small as $\sim$10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century., Comment: accepted to PSJ

The Near Earth Object Surveyor mission has a requirement to find two-thirds of the potentially hazardous asteroids larger than 140 meters in size. In order to determine the mission's expected progress toward this goal during design and testing, as well as the actual progress during the survey, a simulation tool has been developed to act as a consistent and quantifiable yardstick. We test that the survey simulation software is correctly predicting on-sky positions and thermal infrared fluxes by using it to reproduce the published measurements of asteroids from the NEOWISE mission. We then extended this work to find previously unreported detections of known near Earth asteroids in the NEOWISE data archive, a search that resulted in 21,661 recovery detections, including 1,166 objects that had no previously reported NEOWISE observations. These efforts demonstrate the reliability of the NEOS Survey Simulator tool, and the perennial value of searchable image and source catalog archives for extending our knowledge of the small bodies of the Solar System., Comment: 19 pages, 6 figures, accepted for publication in PSJ

We present X-ray polarimetry observations from the Imaging X-ray Polarimetry Explorer (IXPE) of three low spectral peak and one intermediate spectral peak blazars, namely 3C 273, 3C 279, 3C 454.3, and S5 0716+714. For none of these objects was IXPE able to detect X-ray polarization at the 3$\sigma$ level. However, we placed upper limits on the polarization degree at $\sim$10-30\%. The undetected polarizations favor models where the X-ray band is dominated by unpolarized photons upscattered by relativistic electrons in the jets of blazars, although hadronic models are not completely eliminated. We discuss the X-ray polarization upper limits in the context of our contemporaneous multiwavelength polarization campaigns., Comment: 19 pages, 10 figures, 6 tables; submitted to the Astrophysical Journal

Probing small main-belt asteroids provides insight into their formation and evolution through multiple dynamical and collisional processes. These asteroids also overlap in size with the potentially hazardous near-earth object population and supply the majority of these objects. The Lucy mission will provide an opportunity for study of a small main-belt asteroid, (152830) Dinkinesh. The spacecraft will perform a flyby of this object on November 1, 2023, in preparation for its mission to the Jupiter Trojan asteroids. We employed aperture photometry on stacked frames of Dinkinesh obtained by the Wide-field-Infrared Survey Explorer and performed thermal modeling on a detection at 12 $\mu$m to compute diameter and albedo values. Through this method, we determined Dinkinesh has an effective spherical diameter of $0.76^{+0.11}_{-0.21}$ km and a visual geometric albedo of $0.27^{+0.25}_{-0.06}$ at the 16th and 84th percentiles. This albedo is consistent with typical stony (S-type) asteroids., Comment: Submitted to Astrophysical Journal Letters

Polarization phase-curve measurements provide a unique constraint on the surface properties of asteroids that are complementary to those from photometry and spectroscopy, and have led to the identification of the ``Barbarian'' asteroids as a class of objects with highly unusual surfaces. We present new near-infrared polarimetric observations of six Barbarian asteroids obtained with the WIRC+Pol instrument on the Palomar Hale telescope. We find a dramatic change in polarimetric behavior from visible to near-infrared for these objects, including a change in the polarimetric inversion angle that is tied to the index of refraction of the surface material. Our observations support a two-phase surface composition consisting of high albedo, high index of refraction inclusions with a small optical size scale embedded in a dark matrix material more closely related to C-complex asteroids. These results are consistent with the interpretation that the Barbarians are remnants of a population of primitive bodies that formed shortly after CAIs. Near-infrared polarimetry provides a direct test of the constituent grains of asteroid surfaces., Comment: 13 pages, 3 figures, accepted for publication in PSJ

Blazars are a class of jet-dominated active galactic nuclei with a typical double-humped spectral energy distribution. It is of common consensus the Synchrotron emission to be responsible for the low frequency peak, while the origin of the high frequency hump is still debated. The analysis of X-rays and their polarization can provide a valuable tool to understand the physical mechanisms responsible for the origin of high-energy emission of blazars. We report the first observations of BL Lacertae performed with the Imaging X-ray Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization degree $\Pi_X<$12.6\% was found in the 2-8 keV band. We contemporaneously measured the polarization in radio, infrared, and optical wavelengths. Our multiwavelength polarization analysis disfavors a significant contribution of proton synchrotron radiation to the X-ray emission at these epochs. Instead, it supports a leptonic origin for the X-ray emission in BL Lac., Comment: 17 pages, 5 figures, accepted for publication in ApJL

We report our new analysis of Oort-cloud comet C/2020 T2 (Palomar) (T2) observed at 2.06 au from the Sun (phase angle of 28.5 deg) about two weeks before perihelion. T2 lacks a significant dust tail in scattered light, showing a strong central condensation of the coma throughout the apparition, reminiscent of so-called Manx comets. Its spectral slope of polarized light increases and decreases in the J (1.25 um) and H (1.65 um) bands, respectively, resulting in an overall negative (blue) slope (-0.31+/-0.14 % um^-1) in contrast to the red polarimetric color of active comets observed at similar geometries. The average polarization degree of T2 is 2.86+/-0.17 % for the J and 2.75+/-0.16 % for the H bands. Given that near-infrared wavelengths are sensitive to the intermediate-scale structure of cometary dust (i.e., dust aggregates), our light-scattering modeling of ballistic aggregates with different porosities and compositions shows that polarimetric properties of T2 are compatible with low-porosity (~66 %), absorbing dust aggregates with negligible ice contents on a scale of 10--100 um (density of ~652 kg m^-3). This is supported by the coma morphology of T2 which has a viable beta (the relative importance of solar radiation pressure on dust) range of <~10^-4. Secular evolution of the r-band activity of T2 from archival data reveals that the increase in its brightness accelerates around 2.4 au pre-perihelion, with its overall dust production rate ~100 times smaller than those of active Oort-cloud comets. We also found an apparent concentration of T2 and Manx comets toward ecliptic orbits. This paper underlines the heterogeneous nature of Oort-cloud comets which can be investigated in the near future with dedicated studies of their dust characteristics., Comment: Accepted for publication in Astronomy & Astrophysics

Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to $\sim 1$ TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization - the only range available until now - probe extended regions of the jet containing particles that left the acceleration site days to years earlier (Jorstad et al., 2005; Marin et al., 2018; Blinov et al., 2021), and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian~501 (Mrk~501). We measure an X-ray linear polarization degree $\Pi_X \sim10\%$, a factor of $\sim2$ higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration, and also implies that the plasma becomes increasingly turbulent with distance from the shock., Comment: 34 pages, 4 figures, 4 tables

We present space-based thermal infrared observations of the presumably Geminid-associated asteroids: (3200)Phaethon, 2005 UD and 1999 YC using WISE/NEOWISE. The images were taken at the four wavelength bands 3.4$\mu$m(W1),4.6$\mu$m(W2),12$\mu$m(W3),and 22$\mu$m(W4). We find no evidence of lasting mass-loss in the asteroids over the decadal multi-epoch datasets. We set an upper limit to the mass-loss rate in dust of Q<2kg s$^{-1}$ for Phaethon and <0.1kg s$^{-1}$ for both 2005 UD and 1999 YC, respectively, with little dependency over the observed heliocentric distances of R=1.0$-$2.3au. For Phaethon, even if the maximum mass-loss was sustained over the 1000(s)yr dynamical age of the Geminid stream, it is more than two orders of magnitude too small to supply the reported stream mass (1e13$-$14kg). The Phaethon-associated dust trail (Geminid stream) is not detected at R=2.3au, corresponding an upper limit on the optical depth of $\tau$<7e-9. Additionally, no co-moving asteroids with radii r<650m were found. The DESTINY+ dust analyzer would be capable of detecting several of the 10$\mu$m-sized interplanetary dust particles when at far distances(>50,000km) from Phaethon. From 2005 UD, if the mass-loss rate lasted over the 10,000yr dynamical age of the Daytime Sextantid meteoroid stream, the mass of the stream would be ~1e10kg. The 1999 YC images showed neither the related dust trail ($\tau$<2e-8) nor co-moving objects with radii r<170m at R=1.6au. Estimated physical parameters from these limits do not explain the production mechanism of the Geminid meteoroid stream. Lastly, to explore the origin of the Geminids, we discuss the implications for our data in relation to the possibly sodium (Na)-driven perihelion activity of Phaethon., Comment: Accepted for publication in The Astronomical Journal, 8 tables, 7 figures

Large potentially hazardous asteroids (PHAs) are capable of causing a global catastrophe in the event of a planetary collision. Thus, rapid assessment of such an object's physical characteristics is crucial for determining its potential risk scale. We treated the near-Earth asteroid (99942) Apophis as a newly discovered object during its 2020-2021 close-approach as part of a mock planetary defense exercise. The object was detected by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), and data collected by the two active bands (3.4 ${\mu}$m and 4.6 ${\mu}$m) were analyzed using thermal and thermophysical modeling. Our results indicate that Apophis is an elongated object with an effective spherical diameter D$_{eff}$ = 340 $\pm$ 70 m, a geometric visual albedo p$_{V}$ = 0.31 $\pm$ 0.09, and a thermal inertia $\Gamma$ $\sim$ 150 - 2850 Jm$^{-2}$s$^{-0.5}$K$^{-1}$ with a best-fit value of 550 Jm$^{-2}$s$^{-0.5}$K$^{-1}$. NEOWISE "discovery" observations reveal that (99942) Apophis is a potentially hazardous asteroid that would likely cause damage at a regional level and not a global one., Comment: 19 Pages, 6 Figures, Accepted for publication in PSJ

We present the first results of our survey of asteroid polarization-phase curves in the near-infrared J and H bands using the WIRC+Pol instrument on the Palomar 200-inch telescope. We confirm through observations of standard stars that WIRC+Pol can reach the 0.1% precision needed for asteroid phase curve characterization, and show that C-complex asteroids could act as an alternate calibration source as they show less wavelength variation than stellar polarized standards. Initial polarization-phase curve results for S-complex asteroids show a shift in behavior as a function of wavelength from visible to near-infrared bands, extending previously observed trends. Full near-infrared polarization-phase curve characterization of individual asteroids will provide a unique constraint on surface composition of these objects by probing the wavelength dependence of albedo and index of refraction of the surface material., Comment: 17 pages, 5 figures. Accepted for publication in PSJ

We present new thermophysical model (TPM) fits of 1,847 asteroids, deriving thermal inertia, diameter, and Bond and visible geometric albedo. We use thermal flux measurements obtained by the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010; Mainzer et al. 2011) during its fully cryogenic phase, when both the 12$\mu$m (W3) and 22$\mu$m (W4) bands were available. We take shape models and spin information from the Database of Asteroid Models from Inversion Techniques (DAMIT; \v{D}urech et al. 2010) and derive new shape models through lightcurve inversion and combining WISE photometry with existing DAMIT lightcurves. When we limit our sample to the asteroids with the most reliable shape models and thermal flux measurements, we find broadly consistent thermal inertia relations with recent studies. We apply fits to the diameters $D$ (km) and thermal inertia $\Gamma$ (J m$^{-2}$ s$^{-0.5}$ K$^{-1}$) normalized to 1 au with a linear relation of the form $\log[\Gamma]=\alpha+\beta\log[D]$, where we find $\alpha = 2.667 \pm 0.059$ and $\beta = -0.467 \pm 0.044$ for our sample alone and $\alpha = 2.509 \pm 0.017$ and $\beta = -0.352 \pm 0.012$ when combined with other literature estimates. We find little evidence of any correlation between rotation period and thermal inertia, owing to the small number of slow rotators to consider in our sample. While the large uncertainties on the majority of our derived thermal inertia only allow us to identify broad trends between thermal inertia and other physical parameters, we can expect a significant increase in high-quality thermal flux measurements and asteroid shape models with upcoming infrared and wide-field surveys, enabling even more thermophysical modeling of higher precision in the future., Comment: 86 pages, 17 figures, 6 tables, accepted by PSJ with proof corrections. Table 5, now corrected, was erroneously published with a different definition for "dense lightcurve", using 15 data points as a minimum rather than 30, so several asteroids had higher numbers of dense lightcurves than presented elsewhere in the paper

Solar system bodies with surface and sub-surface volatiles will show observational evidence of activity when they reach a temperature where those volatiles change from solid to gas and are released. This is most frequently seen in comets, where activity is driven by the sublimation of water, carbon dioxide, or carbon monoxide ices. However, some bodies (notably the asteroid (3200) Phaethon) show initiation of activity at very small heliocentric distances, long after they have reached the sublimation temperatures of these ices. We investigate whether the sodium present in the mineral matrix could act as the volatile element responsible for this activity. We conduct theoretical modeling which indicates that sodium has the potential to sublimate in the conditions that Phaethon experiences, depending on the mineral phase it is held in. To test this, we then exposed samples of the carbonaceous chondrite Allende to varying heating events similar to what would be experienced by low perihelion asteroids. We measured the change in sodium present in each sample, and find that the highest temperature samples show a significant loss of sodium from specific mineral phases over a single heating event, comparable to a day on the surface of Phaethon. Under specific thermal histories possible for Phaethon, this outgassing could be sufficient to explain this object's observed activity. This effect would also be expected to be observed for other low-perihelia asteroids as well, and may act as a critical step in the process of disrupting small low-albedo asteroids., Comment: Published in PSJ with interactive figures

We present diameters and albedos computed for the near-Earth and Main Belt asteroids observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of $199$ NEOs and $5851$ MBAs detected during the sixth year of the survey, and $175$ NEOs and $5861$ MBAs from the seventh year. Comparisons of the near-Earth object diameters derived from Reactivation data with those derived from the WISE cryogenic mission data show a $\sim30\%$ relative uncertainty. This larger uncertainty compared to data from the cryogenic mission is due to the need to assume a beaming parameter for the fits to the shorter wavelength data that the Reactivation mission is limited to. We also present an analysis of the orbital parameters of the Main Belt asteroids that have been discovered by NEOWISE during Reactivation, finding that these objects tend to be on orbits that result in their perihelia being far from the ecliptic, and thus missed by other surveys. To date, the NEOWISE Reactivation survey has provided thermal fits of $1415$ unique NEOs. Including the mission phases before spacecraft hibernation increases the count of unique NEOs characterized to $1845$ from WISE's launch to the present., Comment: Accepted to PSJ

We present an analysis of the accuracy of geometric albedos determined for asteroids through the modeling of observed thermal infrared radiation. We show that albedo uncertainty is dominated by the uncertainty on the measured $H_V$ absolute magnitude, and that any analysis using albedos in a statistical application will also be dominated by this source of uncertainty. For all but the small fraction of asteroids with a large amount of characterization data, improved knowledge of the $H_V$ magnitude will be fundamentally limited by incomplete phase curve coverage, incomplete light curve knowledge, and the necessary conversion from the observed band to the $V$ band. Switching the absolute magnitude standard to a different band such a $r'$ would mitigate the uncertainty due to band conversion for many surveys, but this only represents a small component of the total uncertainty. Therefore, techniques making use of these albedos must ensure that their uncertainties are being properly accounted for., Comment: 10 pages, 1 figure. Accepted to the Planetary Science Journal

Thermal infrared measurements of near-Earth objects provide critical data for constraining their physical properties such as size. The NEOWISE mission has been conducting an all-sky infrared survey to gather such data and improve our understanding of this population. While automated routines are employed to identify the majority of moving objects detected by NEOWISE, a subset of objects will have dynamical properties that fall outside the window detectable to these routines. Using the population of known near-Earth objects, we have conducted a manual search for detections of these objects that were previously unreported. We report 303 new epochs of observations for 299 unique near-Earth objects of which 239 have no previous physical property characterization from the NEOWISE Reactivation mission. As these objects are drawn from a list with inherent optical selection biases, the distribution of measured albedos is skewed to higher values than is seen for the diameter-selected population detected by the automated routines. These results demonstrate the importance and benefit of periodic searches of the archival NEOWISE data., Comment: Accepted for publication to the AAS Planetary Science Journal

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft has been conducting a two-band thermal infrared survey to detect and characterize asteroids and comets since its reactivation in Dec 2013. Using the observations collected during the fourth and fifth years of the survey, our automated pipeline detected candidate moving objects which were verified and reported to the Minor Planet Center. Using these detections, we perform thermal modeling of each object from the near-Earth object and Main Belt asteroid populations to constrain their sizes. We present thermal model fits of asteroid diameters for 189 NEOs and 5831 MBAs detected during the fourth year of the survey, and 185 NEOs and 5776 MBAs from the fifth year. To date, the NEOWISE Reactivation survey has provided thermal model characterization for 957 unique NEOs. Including all phases of the original WISE survey brings the total to 1473 unique NEOs that have been characterized between 2010 and the present., Comment: Accepted for publication in the AAS Planetary Science Journal

Thermophysical models allow for improved constraints on the physical and thermal surface properties of asteroids beyond what can be inferred from more simple thermal modeling, provided a sufficient number of observations is available. We present thermophysical modeling results of observations from the NEOWISE mission for two near-Earth asteroids which are the targets of the DESTINY+ flyby mission: (3200) Phaethon and (155140) 2005 UD. Our model assumes a rotating, cratered, spherical surface, and employs a Monte Carlo Markov Chain to explore the multi-dimensional parameter space of the fit. We find an effective spherical diameter for Phaethon of $4.6^{+0.2}_{-0.3}~$km, a geometric albedo of $p_V=0.16\pm0.02$, and a thermal inertia $\Gamma=880$ $^{+580}_{-330}$, using five epochs of NEOWISE observations. The best model fit for (155140) 2005 UD was less well constrained due to only having two NEOWISE observation epochs, giving a diameter of $1.2\pm0.4~$km and a geometric albedo of $p_V=0.14\pm0.09$., Comment: Accepted for publication in AJ

Automated asteroid detection routines set requirements on the number of detections, signal-to-noise ratio, and the linearity of the expected motion in order to balance completeness, reliability, and time delay after data acquisition when identifying moving object tracklets. However, when the full-frame data from a survey are archived, they can be searched later for asteroids that were below the initial detection thresholds. We have conducted such a search of the first three years of the reactivated NEOWISE data, looking for near-Earth objects discovered by ground-based surveys that have previously unreported thermal infrared data. Using these measurements, we can then perform thermal modeling to measure the diameters and albedos of these objects. We present new physical properties for 116 Near-Earth Objects found in this search., Comment: Accepted for publication in AJ

Quantifying the accuracy with which physical properties of asteroids can be determined from thermal modeling is critical to measuring the impact of infrared data on our understanding of asteroids. Previous work (Mainzer et al. 2011b) has used independently-derived diameters (from asteroid radar, occultations, and spacecraft visits) to test the accuracy of the NEOWISE diameter determinations. Here, we present a new and different method for bounding the actual NEOWISE diameter errors in the Main Belt based on our knowledge of the albedos of asteroid families. We show the 1 sigma relative diameter error for the Main Belt population must be less than 17.5% for the vast majority of objects. For a typical uncertainty on H magnitude of 0.2 mag, the relative error on diameter for the population would be ~10%., Comment: Accepted for publication to AJ

From the entire dataset of comets observed by NEOWISE, we have analyzed 11 different Halley-Type Comets (HTCs) for dust production rates, CO+CO2 production rates, and nucleus sizes. Incorporating HTCs from previous studies and multiple comet visits we have a total of 21 stacked visits, 13 of which are active and 8 for which we calculated upper limits of production. We determined the nucleus sizes of 27P, P/2006 HR30, P/2012 NJ, and C/2016 S1. Furthermore, we analyzed the relationships between dust production and heliocentric distance, and gas production and heliocentric distance. We concluded that for this population of HTCs, ranging in heliocentric distance from 1.21 AU to 2.66 AU, there was no significant correlation between dust production and heliocentric distance, nor gas production and heliocentric distance.

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process., Comment: 19 pages, 8 figures, accepted for publication in ApJL

The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 um and 4.6 um of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper we present thermal model fits of asteroid diameters for 170 NEOs and 6110 MBAs detected during the third year of the survey, as well as the associated optical geometric albedos. We compare our results with previous thermal model results from NEOWISE for overlapping sample sets, as well as diameters determined through other independent methods, and find that our diameter measurements for NEOs agree to within 26% (1-sigma) of previously measured values. Diameters for the MBAs are within 17% (1-sigma). This brings the total number of unique near-Earth objects characterized by the NEOWISE survey to 541, surpassing the number observed during the fully cryogenic mission in 2010., Comment: Accepted for publication in AJ

The 163 comets observed during the WISE/NEOWISE prime mission represent the largest infrared survey to date of comets, providing constraints on dust, nucleus sizes, and CO+CO2 production. We present detailed analyses of the WISE/NEOWISE comet discoveries, and discuss observations of the active comets showing 4.6 $\mu$m band excess. We find a possible relation between dust and CO+CO2 production, as well as possible differences in the sizes of long and short period comet nuclei., Comment: 67 pages, 10 figures, 6 Tables; Accepted by The Astrophysical Journal

We present visible spectroscopic and albedo data of the 2.3 Gyr old Themis family and the <10 Myr old Beagle sub-family. The slope and albedo variations between these two families indicate C-complex asteroids become redder and darker in response to space weathering. Our observations of Themis family members confirm previously observed trends where phyllosilicate absorption features are less common among small diameter objects. Similar trends in the albedos of large (> 15 km) and small (< 15 km) Themis members suggest these phyllosilicate feature and albedo trends result from regolith variations as a function of diameter. Observations of the Beagle asteroids show a small, but notable fraction of members with phyllosilicate features. The presence of phyllosilicates and the dynamical association of the main-belt comet 133P/Elst-Pizarro with the Beagle family imply the Beagle parent body was a heterogenous mixture of ice and aqueously altered minerals., Comment: 22 pages, 7 figures, accepted for publication in Icarus

The Euphrosyne asteroid family is uniquely situated at high inclination in the outer Main Belt, bisected by the nu_6 secular resonance. This large, low albedo family may thus be an important contributor to specific subpopulations of the near-Earth objects. We present simulations of the orbital evolution of Euphrosyne family members from the time of breakup to the present day, focusing on those members that move into near-Earth orbits. We find that family members typically evolve into a specific region of orbital element-space, with semimajor axes near ~3 AU, high inclinations, very large eccentricities, and Tisserand parameters similar to Jupiter family comets. Filtering all known NEOs with our derived orbital element limits, we find that the population of candidate objects is significantly lower in albedo than the overall NEO population, although many of our candidates are also darker than the Euphrosyne family, and may have properties more similar to comet nuclei. Followup characterization of these candidates will enable us to compare them to known family properties, and confirm which ones originated with the breakup of (31) Euphrosyne., Comment: Accepted for publication in ApJ