- ID:
- ivo://CDS.VizieR/J/AJ/133/26
- Title:
- Solar phase curves of distant icy bodies
- Short Name:
- J/AJ/133/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured the solar phase curves in B, V, and I for 18 trans-Neptunian objects (TNOs), 7 Centaurs, and Nereid and determined the rotation curves for 10 of these targets. For each body we have made ~100 observations uniformly spread over the entire visible range. We find that all the targets except Nereid have linear phase curves at small phase angles (0.1{deg}-2.0{deg}) with widely varying phase coefficients (0.0-0.4mag/deg). At phase angles of 2{deg}-3{deg}, the Centaurs (54598) Bienor and (32532) Thereus have phase curves that flatten. The recently discovered Pluto-scale bodies (2005 FY9, 2003 EL61, and 2003 UB313 now known as 136199 Eris), like Pluto, have neutral colors compared to most TNOs and small phase coefficients (~0.1mag/deg). Together, these two properties are a likely indication of large TNOs with high-albedo, freshly coated icy surfaces. We find several bodies with significantly wavelength-dependent phase curves. The TNOs (50000) Quaoar, (120348) 2004 TY364, and (47932) 2000 GN171 have unusually high I-band phase coefficients and much lower coefficients in the B and V bands. Their phase coefficients increase in proportion to wavelength by 0.5-0.8mag/deg/um. The phase curves for TNOs with small B-band phase coefficients (<0.1mag/deg) have a similar but weaker wavelength dependence. Coherent backscatter is the likely cause for the wavelength dependence for all these bodies. We see no such dependence for the Centaurs, which have visual albedos of ~0.05.
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- ID:
- ivo://CDS.VizieR/J/AJ/133/1247
- Title:
- Solar system survey with Spacewatch
- Short Name:
- J/AJ/133/1247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have completed a low-inclination ecliptic survey for distant and slow-moving bright objects in the outer solar system. This survey used data taken over 34 months by the University of Arizona's Spacewatch Project based at Steward Observatory, Kitt Peak. Spacewatch revisits the same sky area every three to seven nights in order to track cohorts of main-belt asteroids. This survey used a multiple-night detection scheme to extend our rate sensitivity to as low as 0.012"/hr. When combined with our plate scale and flux sensitivity (V~21), this survey was sensitive to Mars-sized objects out to 300AU and Jupiter-sized planets out to 1200AU. The survey covered approximately 8000deg^2^ of raw sky, mostly within 10{deg} of the ecliptic but away from the Galactic center. An automated motion detection program was modified for this multinight search and processed approximately 2 terabytes of imagery into motion candidates. This survey discovered 2003 MW12, currently the tenth largest classical Kuiper Belt object. In addition, several known large Kuiper Belt objects and Centaurs were detected, and the detections were used with a model of our observational biases to make population estimates as a check on our survey efficiency. We found no large objects at low inclinations despite having sufficient sensitivity in both flux and rate to see them out as far as 1200AU. For low inclinations, we can rule out more than one to two Pluto-sized objects out to 100AU and one to two Mars-sized objects to 200AU.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A141
- Title:
- Spectra of 73 asteroids
- Short Name:
- J/A+A/630/A141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Several primitive families in the inner region of the main asteroid belt were identified as potential sources for two near-Earth asteroids (NEAs), (101955) Bennu and (162173) Ryugu, targets of the sample-return missions OSIRIS-REx and Hayabusa2, respectively. Four of the families, located at high proper inclinations (i>10{deg}), have not yet been compositionally studied: Klio, Chaldaea, Chimaera, and Svea. We want to characterize and analyze these families within the context of our PRIMitive Asteroid Spectroscopic Survey (PRIMASS), in order to complete the puzzle of the origins of the two NEAs. We obtained visible spectra (0.5-0.9um) of a total of 73 asteroids within the Klio, Chaldaea, Chimaera, and Svea collisional families, using the instrument OSIRIS at the 10.4m Gran Telescopio Canarias. We performed a taxonomical classification of these objects, and an analysis of the possible presence of absorption bands related to aqueous alterations, comparing the results with already studied primitive families in the inner main belt. We present here reflectance spectra for 30 asteroids in the Klio family, 15 in Chaldaea, 20 in Chimaera, and 8 in Svea. We show that Klio, Chaldaea, and Chimaera members have moderately red spectral slopes, with aqueous alteration absorption bands centered around 0.7um, characteristic of the group of primitive families known as Erigone-like. In contrast, Svea shows no 0.7um features, and neutral and blue spectral slopes, and thus is a Polana-like family. While all four families might be related to (162173) Ryugu, the only family studied in this work that might be related to (101955) Bennu is Svea.
- ID:
- ivo://CDS.VizieR/J/AJ/152/54
- Title:
- Spectroscopy of main-belt Ch/Cgh-type asteroids
- Short Name:
- J/AJ/152/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CM chondrites are the most common type of hydrated meteorites, making up ~1.5% of all falls. Whereas most CM chondrites experienced only low-temperature (~0{deg}C-120{deg}C) aqueous alteration, the existence of a small fraction of CM chondrites that suffered both hydration and heating complicates our understanding of the early thermal evolution of the CM parent body(ies). Here, we provide new constraints on the collisional and thermal history of CM-like bodies from a comparison between newly acquired spectral measurements of main-belt Ch/Cgh-type asteroids (70 objects) and existing laboratory spectral measurements of CM chondrites. It first appears that the spectral variation observed among CM-like bodies is essentially due to variations in the average regolith grain size. Second, the spectral properties of the vast majority (unheated) of CM chondrites resemble both the surfaces and the interiors of CM-like bodies, implying a "low" temperature (<300{deg}C) thermal evolution of the CM parent body(ies). It follows that an impact origin is the likely explanation for the existence of heated CM chondrites. Finally, similarly to S-type asteroids and (2) Pallas, the surfaces of large (D>100km) - supposedly primordial - Ch/Cgh-type main-belt asteroids likely expose the interiors of the primordial CM parent bodies, a possible consequence of impacts by small asteroids (D<10km) in the early solar system.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A129
- Title:
- SPHERE (87) Sylvia images
- Short Name:
- J/A+A/650/A129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dynamical models of Solar System evolution have suggested that the so-called P- and D-type volatile-rich asteroids formed in the outer Solar System beyond Neptune's orbit and may be genetically related to the Jupiter Trojans, comets, and small Kuiper belt objects (KBOs). Indeed, the spectral properties of P- and D-type asteroids resemble that of anhydrous cometary dust. We aim to gain insights into the above classes of bodies by characterizing the internal structure of a large P- and D-type asteroid. We report high-angular-resolution imaging observations of the P-type asteroid (87) Sylvia with the the Very Large Telescope (VLT) Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. These images were used to reconstruct the 3D shape of Sylvia. Our images together with those obtained in the past with large ground-based telescopes were used to study the dynamics of its two satellites. We also modeled Sylvia's thermal evolution. The shape of Sylvia appears flattened and elongated (a/b~1.45; a/c~1.84). We derive a volume-equivalent diameter of 271+/-5km and a low density of 1378+/-45kg/m^3^. The two satellites orbit Sylvia on circular, equatorial orbits. The oblateness of Sylvia should imply a detectable nodal precession which contrasts with the fully-Keplerian dynamics of its two satellites. This reveals an inhomogeneous internal structure, suggesting that Sylvia is differentiated. Sylvia's low density and differentiated interior can be explained by partial melting and mass redistribution through water percolation. The outer shell should be composed of material similar to interplanetary dust particles (IDPs) and the core should be similar to aqueously altered IDPs or carbonaceous chondrite meteorites such as the Tagish Lake meteorite. Numerical simulations of the thermal evolution of Sylvia show that for a body of such a size, partial melting was unavoidable due to the decay of long-lived radionuclides. In addition, we show that bodies as small as 130-150km in diameter should have followed a similar thermal evolution, while smaller objects, such as comets and the KBO Arrokoth, must have remained pristine, which is in agreement with in situ observations of these bodies. NASA Lucy mission target (617) Patroclus (diameter ~140km) may, however, be differentiated.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A132
- Title:
- SPHERE/ZIMPOL (41) Daphne images
- Short Name:
- J/A+A/623/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy (Vernazza et al., 2016AJ....152..154G) and numerical modeling of their early thermal evolution (Bland & Travis, 2017, Sci. Adv. 3, e1602514). Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite. We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera (ID 199.C-0074, PI P. Vernazza) and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3-D shape, using our ADAM shape modeling algorithm. The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77+/-0.26g/cm^3^ (3{sigma}). This density is consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (~17%). Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A154
- Title:
- SPHERE/ZIMPOL (89) Julia images
- Short Name:
- J/A+A/618/A154
- Date:
- 23 Mar 2022 16:27:22
- Publisher:
- CDS
- Description:
- The vast majority of the geophysical and geological constraints (e.g., internal structure, cratering history) for main-belt asteroids have so far been obtained via dedicated interplanetary missions (e.g., ESA Rosetta, NASA Dawn). The high angular resolution of SPHERE/ZIMPOL, the new-generation visible adaptive-optics camera at ESO VLT, implies that these science objectives can now be investigated from the ground for a large fraction of D>=100km main-belt asteroids. The sharp images acquired by this instrument can be used to accurately constrain the shape and thus volume of these bodies (hence density when combined with mass estimates) and to characterize the distribution and topography of D>=30km craters across their surfaces. Here, via several complementary approaches, we evaluated the recently proposed hypothesis that the S-type asteroid (89) Julia is the parent body of a small compact asteroid family that formed via a cratering collisional event. We observed (89) Julia with VLT/SPHERE/ZIMPOL throughout its rotation, derived its 3D shape, and performed a reconnaissance and characterization of the largest craters. We also performed numerical simulations to first confirm the existence of the Julia family and to determine its age and the size of the impact crater at its origin. Finally, we utilized the images/3D shape in an attempt to identify the origin location of the small collisional family. On the one hand, our VLT/SPHERE observations reveal the presence of a large crater (D~75km) in Julia's southern hemisphere. On the other hand, our numerical simulations suggest that (89) Julia was impacted 30-120Myrs ago by a D~8km asteroid, thereby creating a D>=60km impact crater at the surface of Julia. Given the small size of the impactor, the obliquity of Julia and the particular orientation of the family in the (a,i) space, the imaged impact crater is likely to be the origin of the family. New doors into ground-based asteroid exploration, namely, geophysics and geology, are being opened thanks to the unique capabilities of VLT/SPHERE. Also, the present work may represent the beginning of a new era of asteroid-family studies. In the fields of geophysics, geology, and asteroid family studies, the future will only get brighter with the forthcoming arrival of 30-40m class telescopes like ELT, TMT, and GMT.
- ID:
- ivo://CDS.VizieR/J/AJ/159/230
- Title:
- Stellar occultation by (541132) Leleakuhonua
- Short Name:
- J/AJ/159/230
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132)-Leleakuhonua (also known by the provisional designation of 2015TG_387_) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network (RECON) on 2018-October-20-UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is r=110_-10_^+14^km, corresponding to a geometric albedo p_V_=0.21_-0.05_^+0.03^, for an adopted absolute magnitude of HV=5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
- ID:
- ivo://CDS.VizieR/J/ApJ/882/L22
- Title:
- Subaru obs. of Vesta in MIR spectral range
- Short Name:
- J/ApJ/882/L22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Plagioclase feldspars are among the most prevalent minerals in the solar system, and are present in many chondritic and achondritic meteorite families. Nevertheless, spectral features of plagioclases have never been unambiguously and directly observed in remote observations of asteroids. We report here the detection of an absorption band at 12.2{mu}m on Vesta spectra provided by ground-based spectral observations at the Subaru Telescope. This signature represents the first direct evidence of a widespread presence of crystalline Ca-rich plagioclase on Vesta and reveals that its regolith is comminuted to a very fine grain size, smaller than a few tens of microns, indicating that the mechanical brecciation process has been very effective. The crystalline nature of plagioclase strongly suggests that impacts alone cannot be the sole mechanism for regolith formation on Vesta and a milder process, such as thermal fatigue, should be invoked as an important and concomitant process Thermal fatigue should be considered a very effective process in regolith production and rejuvenation not only for near-Earth asteroids but even for large asteroids located in the main belt.
- ID:
- ivo://CDS.VizieR/J/A+A/610/A25
- Title:
- Sulamitis and Clarissa asteroids spectra
- Short Name:
- J/A+A/610/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The low-inclination (i<80{deg}) primitive asteroid families in the inner main belt, that is, Polana-Eulalia, Erigone, Sulamitis, and Clarissa, are considered to be the most likely sources of near-Earth asteroids (101955) Bennu and (162173) Ryugu. These two primitive NEAs will be visited by NASA OSIRIS-REx and JAXA Hayabusa 2 missions, respectively, with the aim of collecting samples of material from their surfaces and returning them back to Earth. In this context, the Primitive Asteroid Spectroscopic Survey (PRIMASS) was born, with the main aim to characterize the possible origins of these NEAs and constrain their dynamical evolution. As part of the PRIMASS survey we have already studied the Polana and Erigone collisional families in previously published works. The main goal of the work presented here is to compositionally characterize the Sulamitis and Clarissa families using visible spectroscopy. We have observed 97 asteroids (64 from Sulamitis and 33 from Clarissa) with the OSIRIS instrument (0.5-0.9um) at the 10.4m Gran Telescopio Canarias (GTC). We found that about 60% of the sampled asteroids from the Sulamitis family show signs of aqueous alteration on their surfaces. We also found that the majority of the Clarissa members present no signs of hydration. The results obtained here show similarities between Sulamitis-Erigone, and Clarissa-Polana collisional families.
