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Joseph Masiero

Publications and source records attributed to Joseph Masiero.

At least 19 recordsLinked to original sources
arXiv2026

The Polana-Eulalia Complex with JWST NIRSpec: Connections to Bennu, Ryugu, and Outer Solar System Bodies

Carbon rich [C complex] asteroids provide insight into the early Solar System, and families of C complex asteroids serve as robust samples for learning about the internal structure of planetesimals and the materials of the protoplanetary disk. This work investigates the compositions of asteroids within the Polana Eulalia Complex [PEC] through analyses of JWST NIRSpec. Obtained as part of the Spectral Analysis of Main Belt Asteroids in the 3 um Region [SAMBA3] project. NIRSpec observations were conducted for the namesake asteroid of the Eulalia family, [495] Eulalia, as well as three members from the Polana family: [2441] Hibbs, [6712] Hornstein, and [6769] Brokoff. Analyses of the 2.7 um region demonstrate that PEC asteroids exhibit absorptions associated with Mg rich phyllosilicates, in turn underscoring high, though incomplete, degrees of aqueous alteration in the past for both PEC families. Although consistent in regard to composition, [142] Polana and [495] Eulalia show deeper 2.7 um bands than the Polana family asteroids, suggesting slight differences in the degrees of aqueous alteration between large and small PEC asteroids. Minor absorptions from 3.0 to 4.0 um indicate that [495] Eulalia's surface may contain more carbonates than [142] Polana, which potentially highlights slight differences between each family's formation and evolution. Additionally, PEC asteroids also show spectral consistency with Bennu and Ryugu, reinforcing their shared origin in the PEC. Minor absorptions in PEC asteroid spectra also connect to small bodies within and beyond the Main Belt, providing further evidence of outer Solar System formation for the PEC parent bodies.

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arXiv2025

Compositional characterisation of asteroid (84) Klio with JWST

The analysis of the composition of primitive C$-$complex asteroids is essential to understand the distribution of volatiles in the Solar System since its formation. Primitive low-albedo families within the inner main asteroid belt are of particular interest because they are a significant source of carbonaceous near-Earth asteroids, such as Ryugu and Bennu. This study, part of the JWST SAMBA3 project (Spectral Analysis of Main Belt Asteroids in the 3 $\mu$m region), report the first spectroscopic analysis of asteroid (84) Klio in the 3 $\mu$m region, in order to better constrain its composition. We analysed the infrared (0.97$-$5.10 $\mu$m) Spectrum of Klio measured by the NIRSpec instrument on board JWST. We used the NEATM thermal model to extract the reflectance spectrum of the asteroid. Several spectral features were then analysed in the 2.8, 3.4, and 3.9 $\mu$m regions by different Gaussian fitting. The Spectrum of Klio shows an absorption band at 2.776 $\pm$ 0.001 $\mu$m that we attributed to phyllosilicates. We compared the position and shape of the feature with that observed in primitive materials such as carbonaceous chondrites and returned samples from Ryugu and Bennu. The position and shape of the 2.8 $\mu$m band, as well as the presence of a 0.7 $\mu$m band in the visible, suggest that Klio's spectrum is similar to certain CM2 meteorites. We observed an absorption band around 3.9 $\mu$m, with a depth of $0.020 \pm 0.001$ that could be attributed to carbonates. We could not clearly detect any absorption associated with organics at 3.4 $\mu$m.

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arXiv2025

Technical Memo: The impact of Nancy Grace Roman Telescope's default image processing on the detectability of moving Solar system objects

The Nancy Grace Roman Telescope is scheduled to launch in 2026 to conduct a wide-field survey of the sky at near-infrared wavelengths. Although Roman is unable to track objects moving at non-sidereal rates, there is recent interest in the potential capability of the telescope to support planetary defense by tracking and characterizing asteroids and comets (Holler et al, 2025, arXiv:2508.14412). However, the standard pipeline image processing scheme that the mission is planning to implement for the majority of its survey data will preferentially reject flux from all moving objects during the process of cosmic ray rejection. Here we describe the impact of the default Wide Field Imager (WFI) processing on moving object detection, and possible mitigations that could be employed to recover moving object observations.

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arXiv2025

Deep learning to improve the discovery of near-Earth asteroids in the Zwicky Transient Facility

We present a novel pipeline that uses a convolutional neural network (CNN) to improve the detection capability of near-Earth asteroids (NEAs) in the context of planetary defense. Our work aims to minimize the dependency on human intervention of the current approach adopted by the Zwicky Transient Facility (ZTF). The target NEAs have a high proper motion of up to tens of degrees per day and thus appear as streaks of light in the images. We trained our CNNs to detect these streaks using three datasets: a set with real asteroid streaks, a set with synthetic (i.e., simulated) streaks and a mixed set, and tested the resultant models on real survey images. The results achieved were almost identical across the three models: $0.843\pm0.005$ in completeness and $0.820\pm0.025$ in precision. The bias on streak measurements reported by the CNNs was $1.84\pm0.03$ pixels in streak position, $0.817\pm0.026$ degrees in streak angle and $-0.048\pm0.003$ in fractional bias in streak length (computed as the absolute length bias over the streak length, with the negative sign indicating an underestimation). We compared the performance of our CNN trained with a mix of synthetic and real streaks to that of the ZTF human scanners by analyzing a set of 317 streaks flagged as valid by the scanners. Our pipeline detected $80~\%$ of the streaks found by the scanners and 697 additional streaks that were subsequently verified by the scanners to be valid streaks. These results suggest that our automated pipeline can complement the work of the human scanners at no cost for the precision and find more objects than the current approach. They also prove that the synthetic streaks were realistic enough to be used for augmenting training sets when insufficient real streaks are available or exploring the simulation of streaks with unusual characteristics that have not yet been detected.

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arXiv2025

Joint Survey Processing. III. Compact Oddballs in the COSMOS Field -- Little Red Dots and Transients

We present the HST ACS G800L grism spectroscopy observation of the faint active galactic nuclei (AGN) candidates in the COSMOS field at redshift of 6 selected by the point-source morphology and the photometry drop-off at 8000\AA. Among the sample of 7 objects, only one is detected by multiple bands, and has similar shape of spectral energy distribution as the so-called ``little red dots'' JWST selected AGN candidates, but our object is 3 magnitude brighter than the JWST sample. We draw the upper limit of the AGN luminosity function $\Phi=1.1\times 10^{-7}$Mpc$^3$ mag$^{-1}$ for $M_{UV}$=$-21$ at redshift of 6. The rest of the sample shows inconsistent flux density when comparing magnitudes of HST ACS F814W to the Subaru $i$-band and $z$-band magnitudes combined. The HST ACS G800L grism observation shows that this inconsistency cannot be created from an emission line. Therefore, we speculate that these objects are transients with the light curve decay timescale at most 6 years in observed frame.

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arXiv2024

Two Distinct Populations of Dark Comets Delineated by Orbits and Sizes

Small bodies are capable of delivering essential prerequisites for the development of life, such as volatiles and organics, to the terrestrial planets. For example, empirical evidence suggests that water was delivered to the Earth by hydrated planetesimals from distant regions of the Solar System. Recently, several morphologically inactive near-Earth objects (NEOs) were reported to experience significant nongravitational accelerations inconsistent with radiation-based effects, and possibly explained by volatile-driven outgassing. However, these "dark comets" display no evidence of comae in archival images, which are the defining feature of cometary activity. Here we report detections of nongravitational accelerations on seven additional objects previously classified as inactive (doubling the population) that could also be explainable by asymmetric mass loss. A detailed search of archival survey and targeted data rendered no detection of dust activity in any of these objects in individual or stacked images. We calculate dust production limits of $\sim10$, $0.1$, and $0.1$ kg s$^{-1}$ for 1998 FR$_{11}$, 2001 ME$_{1}$, and 2003 RM with these data, indicating little or no dust surrounding the objects during the observations. This set of dark comets reveals the delineation between two distinct populations: larger, "outer" dark comets on eccentric orbits that are end members of a continuum in activity level of comets, and smaller, "inner" dark comets on near-circular orbits that could signify a new population. These objects may trace various stages in the life cycle of a previously undetected, but potentially numerous, volatile-rich population that may have provided essential material to the Earth.

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arXiv2023

A planetary collision afterglow and transit of the resultant debris cloud

Planets grow in rotating disks of dust and gas around forming stars, some of which can subsequently collide in giant impacts after the gas component is removed from the disk. Monitoring programs with the warm Spitzer mission have recorded significant and rapid changes in mid-infrared output for several stars, interpreted as variations in the surface area of warm dusty material ejected by planetary-scale collisions and heated by the central star: e.g., NGC 2354-ID8, HD 166191 and V844 Persei. Here we report combined observations of the young (about 300 Myr), solar-like star ASASSN-21qj: an infrared brightening consistent with a blackbody temperature of 1000 K and a luminosity of 4 percent of that of the star lasting for about 1000 days, partially overlapping in time with a complex and deep wavelength-dependent optical eclipse that lasted for about 500 days. The optical eclipse started 2.5 years after the infrared brightening, implying an orbital period of at least that duration. These observations are consistent with a collision between two exoplanets of several to tens of Earth masses at 2 to 16 au from the central star. Such an impact produces a hot, highly-extended post-impact remnant with sufficient luminosity to explain the infrared observations. Transit of the impact debris, sheared by orbital motion into a long cloud, causes the subsequent complex eclipse of the host star.

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arXiv2018

Response to "An empirical examination of WISE/NEOWISE asteroid analysis and results"

We show that a number of claims made in Myhrvold (2018) (hereafter M2018b) regarding the WISE data and thermal modeling of asteroids are incorrect. That paper provides thermal fit parameter outputs for only two of the about 150,000 object dataset and does not make a direct comparison to asteroids with diameters measured by other means to assess the quality of that work's thermal model. We are unable to reproduce the results for the two objects for which M2018b published its own thermal fit outputs, including diameter, albedo, beaming, and infrared albedo. In particular, the infrared albedos published in M2018b are unphysically low. [...] While there were some minor issues with consistency between tables due to clerical errors in the WISE/NEOWISE team's various papers and data release in the Planetary Data System, and a software issue that slightly increased diameter uncertainties in some cases, these issues do not substantially change the results and conclusions drawn from the data. We have shown in previous work and with updated analyses presented here that the effective spherical diameters for asteroids published to date are accurate to within the previously quoted minimum systematic 1-sigma uncertainty of about 10 percent when data of appropriate quality and quantity are available. Moreover, we show that the method used by M2018b to compare diameters between various asteroid datasets is incorrect and overestimates their differences. In addition, among other misconceptions in M2018b, we show that the WISE photometric measurement uncertainties are appropriately characterized and used by the WISE data processing pipeline and NEOWISE thermal modeling software. We show that the Near-Earth Asteroid Thermal Model (Harris 1998) employed by the NEOWISE team is a very useful model for analyzing infrared data to derive diameters and albedos when used properly.

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arXiv2017

Palomar Optical Spectrum of Hyperbolic Near-Earth Object A/2017 U1

We present optical spectroscopy of the recently discovered hyperbolic near-Earth object A/2017 U1, taken on 25 Oct 2017 at Palomar Observatory. Although our data are at a very low signal-to-noise, they indicate a very red surface at optical wavelengths without significant absorption features.

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arXiv2016

The Albedo Distribution of Near Earth Asteroids

The cryogenic WISE mission in 2010 was extremely sensitive to asteroids and not biased against detecting dark objects. The albedos of 428 Near Earth Asteroids (NEAs) observed by WISE during its fully cryogenic mission can be fit quite well by a 3 parameter function that is the sum of two Rayleigh distributions. The Rayleigh distribution is zero for negative values, and follows $f(x) = x \exp[-x^2/(2σ^2)]/σ^2$ for positive x. The peak value is at x=σ, so the position and width are tied together. The three parameters are the fraction of the objects in the dark population, the position of the dark peak, and the position of the brighter peak. We find that 25.3% of the NEAs observed by WISE are in a very dark population peaking at $p_V = 0.03$, while the other 74.7% of the NEAs seen by WISE are in a moderately dark population peaking at $p_V = 0.168$. A consequence of this bimodal distribution is that the Congressional mandate to find 90% of all NEAs larger than 140 m diameter cannot be satisfied by surveying to H=22 mag, since a 140 m diameter asteroid at the very dark peak has H=23.7 mag, and more than 10% of NEAs are darker than p_V = 0.03.

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arXiv2016

Forming Chondrites in a Solar Nebula with Magnetically Induced Turbulence

Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is $\le 5$ times more massive than the minimum-mass solar nebula at $a \simeq 2-3$ AU and parent bodies of chondrites are $\le 10^{24}$ g ($\le$ 500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number of properties of the meteoritic data. The properties include the present asteroid belt mass, the formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies' masses leads to the following implications: primordial asteroids that were originally $\ge 10^{24}$ g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into the origins of the solar system.

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arXiv2015

Asteroid Family Physical Properties

An asteroid family is typically formed when a larger parent body undergoes a catastrophic collisional disruption, and as such family members are expected to show physical properties that closely trace the composition and mineralogical evolution of the parent. Recently a number of new datasets have been released that probe the physical properties of a large number of asteroids, many of which are members of identified families. We review these data sets and the composite properties of asteroid families derived from this plethora of new data. We also discuss the limitations of the current data, and the open questions in the field.

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arXiv2009

Albedo heterogeneity on the surface of (1943) Anteros

We have investigated the effect of rotation on the polarization of scattered light for the near-Earth asteroid (1943) Anteros using the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope. Anteros is an L-type asteroid that has not been previously observed polarimetrically. We find weak but significant variations in the polarization of Anteros as a function of rotation, indicating albedo changes across the surface. Specifically, we find that Anteros has a background albedo of p_v = 0.18 +/- 0.02 with a dark spot of p_v < 0.09 covering < 2% of the surface.

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arXiv2009

The effect of the dust size distribution on asteroid polarization

We have developed a theoretical description of how of an asteroid's polarization-phase curve will be affected by the removal of the dust from the surface due to a size-dependent phenomenon such as radiation pressure-driven escape of levitated particles. We test our calculations against new observations of four small (D ~ 1 km) near-Earth asteroids [(85236), (142348), (162900) and 2006 SZ_217] obtained with the Dual Beam Imaging Polarimeter on the University of Hawaii's 2.2 m telescope, as well as previous observations of (25143) Itokawa and (433) Eros. We find that the polarization of the light reflected from an asteroid is controlled by the mineralogical and chemical composition of the surface and is independent of dust particle. The relation between the slope of the polarization-phase curve beyond the inversion angle and the albedo of an asteroid is thus independent of the surface regolith size distribution and is valid for both Main Belt and Near-Earth asteroids.

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arXiv2009

GRB 090426: The Environment of a Rest-Frame 0.35-second Gamma-Ray Burst at Redshift z=2.609

We present the discovery of an absorption-line redshift of z = 2.609 for GRB 090426, establishing the first firm lower limit to a redshift for a gamma-ray burst with an observed duration of <2 s. With a rest-frame burst duration of T_90z = 0.35 s and a detailed examination of the peak energy of the event, we suggest that this is likely (at >90% confidence) a member of the short/hard phenomenological class of GRBs. From analysis of the optical-afterglow spectrum we find that the burst originated along a very low HI column density sightline, with N_HI < 3.2 x 10^19 cm^-2. Our GRB 090426 afterglow spectrum also appears to have weaker low-ionisation absorption (Si II, C II) than ~95% of previous afterglow spectra. Finally, we also report the discovery of a blue, very luminous, star-forming putative host galaxy (~2 L*) at a small angular offset from the location of the optical afterglow. We consider the implications of this unique GRB in the context of burst duration classification and our understanding of GRB progenitor scenarios.

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arXiv2009

The Thousand Asteroid Light Curve Survey

We present the results of our Thousand Asteroid Light Curve Survey (TALCS) conducted with the Canada-France-Hawaii Telescope in September 2006. Our untargeted survey detected 828 Main Belt asteroids to a limiting magnitude of g'~22.5 corresponding to a diameter range of 0.4 km <= D <= 10 km. Of these, 278 objects had photometry of sufficient quality to perform rotation period fits. We debiased the observations and light curve fitting process to determine the true distribution of rotation periods and light curve amplitudes of Main Belt asteroids. We confirm a previously reported excess in the fraction of fast rotators but find a much larger excess of slow rotating asteroids (~15% of our sample). A few percent of objects in the TALCS size range have large light curve amplitudes of ~1 mag. Fits to the debiased distribution of light curve amplitudes indicate that the distribution of triaxial ellipsoid asteroid shapes is proportional to the square of the axis-ratio, (b/a)^2, and may be bi-modal. Finally, we find six objects with rotation periods that may be less than 2 hours with diameters between 400 m and 1.5 km, well above the break-up limit for a gravitationally-bound aggregate. Our debiased data indicate that this population represents <4% of the Main Belt in the 1-10 km size range.

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