- ID:
- ivo://CDS.VizieR/J/A+A/631/A2
- Title:
- List of new asteroid models
- Short Name:
- J/A+A/631/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rotation properties (spin-axis direction and rotation period) and coarse shape models of asteroids can be reconstructed from their disk-integrated brightness when measured from various viewing geometries. These physical properties are essential for creating a global picture of structure and dynamical evolution of the main belt. The number of shape and spin models can be increased not only when new data are available, but also by combining independent data sets and inverting them together. Our aim was to derive new asteroid models by processing readily available photometry. We used asteroid photometry compiled in the Lowell Observatory photometry database with photometry from the Gaia Data Release 2. Both data sources are available for about 5400 asteroids. In the framework of the Asteroids@home distributed computing project, we applied the light curve inversion method to each asteroid to find its convex shape model and spin state that fits the observed photometry. Due to the limited number of Gaia DR2 data points and poor photometric accuracy of Lowell data, we were able to derive unique models for only ~1100 asteroids. Nevertheless, 762 of these are new models that significantly enlarge the current database of about 1600 asteroid models. Our results demonstrate the importance of a combined approach to inversion of asteroid photometry. While our models in general agree with those obtained by separate inversion of Lowell and Gaia data, the combined inversion is more robust, model parameters are more constrained, and unique models can be reconstructed in many cases when individual data sets alone are not sufficient.
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- ID:
- ivo://CDS.VizieR/J/A+A/587/A48
- Title:
- Lowell Photometric Database asteroid models
- Short Name:
- J/A+A/587/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information about shapes and spin states of individual asteroids is important for the study of the whole asteroid population. For asteroids from the main belt, most of the shape models available now have been reconstructed from disk-integrated photometry by the lightcurve inversion method. We want to significantly enlarge the current sample (~350) of available asteroid models. We use the lightcurve inversion method to derive new shape models and spin states of asteroids from the sparse-in-time photometry compiled in the Lowell Photometric Database. To speed up the time-consuming process of scanning the period parameter space through the use of convex shape models, we use the distributed computing project Asteroids@home, running on the Berkeley Open Infrastructure for Network Computing (BOINC) platform. This way, the period-search interval is divided into hundreds of smaller intervals. These intervals are scanned separately by different volunteers and then joined together. We also use an alternative, faster, approach when searching the best-fit period by using a model of triaxial ellipsoid. By this, we can independently confirm periods found with convex models and also find rotation periods for some of those asteroids for which the convex-model approach gives too many solutions.
- ID:
- ivo://CDS.VizieR/J/A+A/617/A57
- Title:
- Lowell Photometric Database asteroid models. II.
- Short Name:
- J/A+A/617/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Information about the spin state of asteroids is important for our understanding of the dynamical processes affecting them. However, spin properties of asteroids are known for only a small fraction of the whole population. To enlarge the sample of asteroids with a known rotation state and basic shape properties, we combined sparse-in-time photometry from the Lowell Observatory Database with flux measurements from NASA's WISE satellite. We applied the light curve inversion method to the combined data. The thermal infrared data from WISE were treated as reflected light because the shapes of thermal and visual light curves are similar enough for our purposes. While sparse data cover a wide range of geometries over many years, WISE data typically cover an interval of tens of hours, which is comparable to the typical rotation period of asteroids. The search for best-fitting models was done in the framework of the Asteroids@home distributed computing project. By processing the data for almost 75000 asteroids, we derived unique shape models for about 900 of them. Some of them were already available in the DAMIT database and served us as a consistency check of our approach. In total, we derived new models for 662 asteroids, which significantly increased the total number of asteroids for which their rotation state and shape are known. For another 789 asteroids, we were able to determine their sidereal rotation period and estimate the ecliptic latitude of the spin axis direction. We studied the distribution of spins in the asteroid population. Apart from updating the statistics for the dependence of the distribution on asteroid size, we revealed a significant discrepancy between the number of prograde and retrograde rotators for asteroids smaller than about 10km. Combining optical photometry with thermal infrared light curves is an efficient approach to obtaining new physical models of asteroids. The amount of asteroid photometry is continuously growing and joint inversion of data from different surveys could lead to thousands of new models in the near future.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/29
- Title:
- Main-belt asteroid photometry from TESS
- Short Name:
- J/ApJS/245/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) searches for planets transiting bright and nearby stars using high-cadence, large-scale photometric observations. Full frame images provided by the TESS mission include a large number of serendipitously observed main-belt asteroids (MBAs). Due to the cadence of the published full frame images, we are sensitive to periods as long as of order tens of days, a region of phase space that is generally not accessible through traditional observing. This work represents a much less biased measurement of the period distribution in this period range. We have derived rotation periods for 300 MBAs and have partial lightcurves for a further 7277 asteroids, including 43 with periods of P>100hr; this large number of slow rotators is predicted by theory. Of these slow rotators we find none requiring significant internal strength to resist rotational reshaping. We find our derived rotation periods to be in excellent agreement with results in the Lightcurve Database for the 55 targets that overlap. Over the nominal two-year lifetime of the mission, we expect the detection of around 85,000 unique asteroids with rotation period solutions for around 6000 asteroids. We project that the systematic analysis of the entire TESS data set will increase the number of known slow-rotating asteroids (period >100hr) by a factor of 10. Comparing our new period determinations with previous measurements in the literature, we find that the rotation period of asteroid (2320) Blarney has decreased by at least 20% over the past decade, potentially due to surface activity or subcatastrophic collisions.
- ID:
- ivo://CDS.VizieR/J/AJ/156/139
- Title:
- Main belt asteroid shape distrib. from Gaia DR2
- Short Name:
- J/AJ/156/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gaia Data Release 2 (Cat. I/345) includes observational data for 14099 pre-selected asteroids. From the sparsely sampled G-band photometry, we derive lower-limit light curve amplitudes for 11665 main belt asteroids (MBA) in order to provide constraints on the distribution of shapes in the asteroid main belt. Assuming a triaxial shape model for each asteroid, defined through the axial aspect ratios a>b and b=c, we find an average b/a=0.80+/-0.04 for the ensemble, which is in agreement with previous results. By combining the Gaia data with asteroid properties from the literature, we investigate possible correlations of the aspect ratio with size, semimajor axis, geometric albedo, and intrinsic color. Based on our model simulations, we find that MBAs greater than 50 km in diameter on average have higher b/a aspect ratios (are rounder) than smaller asteroids. We furthermore find significant differences in the shape distribution of MBAs as a function of the other properties that do not affect the average aspect ratios. We conclude that a more detailed investigation of shape distribution correlations requires a larger data sample than is provided in Gaia Data Release 2.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A42
- Title:
- Main Belt asteroids observed by Spitzer
- Short Name:
- J/A+A/578/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multi-epoch Spitzer Space Telescope 24um data is utilized from the MIPSGAL and Taurus Legacy surveys to detect asteroids based on their relative motion. Infrared detections are matched to known asteroids and average diameters and albedos are derived using the Near Earth Asteroid Model (NEATM) for 1865 asteroids ranging in size from 0.2 to 169km. A small subsample of these objects was also detected by IRAS or MSX and the single wavelength albedo and diameter fits derived from these data are within the uncertainties of the IRAS and/or MSX derived albedos and diameters and available occultation diameters, which demonstrates the robustness of our technique. The mean geometric albedo of the small Main Belt asteroids in this sample is p_V_=0.134 with a sample standard deviation of 0.106. The albedo distribution of this sample is far more diverse than the IRAS or MSX samples. The cumulative size-frequency distribution of asteroids in the Main Belt at small diameters is directly derived and a 3{sigma} deviation from the fitted size-frequency distribution slope is found near 8km. Completeness limits of the optical and infrared surveys are discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A40
- Title:
- Main-belt asteroids optical light curves
- Short Name:
- J/A+A/596/A40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Because the second reaction wheel failed, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 mission, the telescope is staring at the plane of the Ecliptic. Thousands of solar system bodies therefore cross the K2 fields and usually cause additional noise in the highly accurate photometric data. We here follow the principle that some person's noise is another person's signal and investigate the possibility of deriving continuous asteroid light curves. This is the first such endeavor. In general, we are interested in the photometric precision that the K2 mission can deliver on moving solar system bodies. In particular, we investigate space photometric optical light curves of main-belt asteroids. We studied the K2 superstamps that cover the fields of M35, and Neptune together with Nereid, which were observed in the long-cadence mode (29.4min sampling). Asteroid light curves were generated by applying elongated apertures. We used the Lomb-Scargle method to determine periodicities that are due to rotation.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A115
- Title:
- Main-belt asteroids polarimetric survey. II.
- Short Name:
- J/A+A/539/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico el Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. The data were obtained with the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A11
- Title:
- Main-belt asteroids polarimetry. III
- Short Name:
- J/A+A/542/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties.
- ID:
- ivo://CDS.VizieR/J/A+A/569/A122
- Title:
- Main-belt asteroids polarimetry. IV
- Short Name:
- J/A+A/569/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. The data were obtained using the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation.
