The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

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 and 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 calcium-aluminum-rich inclusion (CAIs). Near-infrared polarimetry provides a direct test of the constituent grains of asteroid surfaces

The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

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 PS

Polarimetry as a tool for physical characterization of potentially hazardous NEOs

International audienceThe degree of linear polarization of sunlight scattered by an asteroid contains valuable information for rapid characterization of the surface properties of Near-Earth objects (NEOs). In the case of atmosphereless bodies the state of linear polarization varies as a function of the phase angle (α) and is described using the so-called Pr parameter [1]. The properties of the phase-polarization curve of an asteroid are mostly defined by its albedo (pV). Numerous calibrations between polarization and pV have been proposed for main-belt asteroids [2, 3]. However, main-belt asteroids rarely exceed phase angle > 30° while near Earth objects can be observed at phase angle as large as 100°[4]. These observations at higher phase angles allow for deeper characterization of the observed object, but there is currently a lack of observations of NEOs in polarimetry to accurately calibrate the albedo-polarization relationship at high phase angles. We recently started a survey of Near-earth Objects in polarimetry to characterize their phase-polarization curve at high phase angle in order to calibrate the relation between polarization and albedo. These polarimetric observations are complemented with visible photometry, thermal infra-red, spectroscopy, and/or radar observations to obtain independent characterization of the size, shape, albedo, and other surface properties of the objects observed in polarimetry. In this presentation, we will present the polarimetric observations obtained so far. We describe the large variety variety of polarimetric response at high phase angle with polarization ranging from 1 to 50% when observed at the same phase angle. We also discuss the first results using physical characterization using radar, photometric, and thermal observations and how these can be used to calibrate the relation existing between polarimetry and albedo. [1] I. Belskaya, A. Cellino, R. Gil-Hutton, et al., Asteroid Polarimetry, Asteroid IV, (2015) 151-163 [2] A. Cellino, R. Gil-Hutton, A. Dell'Oro, et al. A new calibration of the albedo-polarization relation for the asteroids, JQSRT 113 (2012) 2552–2560. [3] A. Cellino, S. Bagnulo, R. Gil-Hutton, et al., On the calibration of the relation between geometric albedo and polarimetric properties for the asteroids, MNRAS 451 (2015) 3473–3488. [4] M. Devogele, A. Cellino, G. Borisov, et al. The phase-polarization curve of asteroid (3200) Phaethon, MNRAS, 479 (2018) 3498-350

Polarimetry as a tool for physical characterization of potentially hazardous NEOs

International audienceThe degree of linear polarization of sunlight scattered by an asteroid contains valuable information for rapid characterization of the surface properties of Near-Earth objects (NEOs). In the case of atmosphereless bodies the state of linear polarization varies as a function of the phase angle (α) and is described using the so-called Pr parameter [1]. The properties of the phase-polarization curve of an asteroid are mostly defined by its albedo (pV). Numerous calibrations between polarization and pV have been proposed for main-belt asteroids [2, 3]. However, main-belt asteroids rarely exceed phase angle > 30° while near Earth objects can be observed at phase angle as large as 100°[4]. These observations at higher phase angles allow for deeper characterization of the observed object, but there is currently a lack of observations of NEOs in polarimetry to accurately calibrate the albedo-polarization relationship at high phase angles. We recently started a survey of Near-earth Objects in polarimetry to characterize their phase-polarization curve at high phase angle in order to calibrate the relation between polarization and albedo. These polarimetric observations are complemented with visible photometry, thermal infra-red, spectroscopy, and/or radar observations to obtain independent characterization of the size, shape, albedo, and other surface properties of the objects observed in polarimetry. In this presentation, we will present the polarimetric observations obtained so far. We describe the large variety variety of polarimetric response at high phase angle with polarization ranging from 1 to 50% when observed at the same phase angle. We also discuss the first results using physical characterization using radar, photometric, and thermal observations and how these can be used to calibrate the relation existing between polarimetry and albedo. [1] I. Belskaya, A. Cellino, R. Gil-Hutton, et al., Asteroid Polarimetry, Asteroid IV, (2015) 151-163 [2] A. Cellino, R. Gil-Hutton, A. Dell'Oro, et al. A new calibration of the albedo-polarization relation for the asteroids, JQSRT 113 (2012) 2552–2560. [3] A. Cellino, S. Bagnulo, R. Gil-Hutton, et al., On the calibration of the relation between geometric albedo and polarimetric properties for the asteroids, MNRAS 451 (2015) 3473–3488. [4] M. Devogele, A. Cellino, G. Borisov, et al. The phase-polarization curve of asteroid (3200) Phaethon, MNRAS, 479 (2018) 3498-350

Polarimetry as a tool for physical characterization of potentially hazardous NEOs

The degree of linear polarization of sunlight scattered by an asteroid contains valuable information for rapid characterization of the surface properties of Near-Earth objects (NEOs). In the case of atmosphereless bodies the state of linear polarization varies as a function of the phase angle (α) and is described using the so-called Pr parameter [1]. The properties of the phase-polarization curve of an asteroid are mostly defined by its albedo (pV). Numerous calibrations between polarization and pV have been proposed for main-belt asteroids [2, 3]. However, main-belt asteroids rarely exceed phase angle > 30° while near Earth objects can be observed at phase angle as large as 100°[4]. These observations at higher phase angles allow for deeper characterization of the observed object, but there is currently a lack of observations of NEOs in polarimetry to accurately calibrate the albedo-polarization relationship at high phase angles. We recently started a survey of Near-earth Objects in polarimetry to characterize their phase-polarization curve at high phase angle in order to calibrate the relation between polarization and albedo. These polarimetric observations are complemented with visible photometry, thermal infra-red, spectroscopy, and/or radar observations to obtain independent characterization of the size, shape, albedo, and other surface properties of the objects observed in polarimetry. In this presentation, we will present the polarimetric observations obtained so far. We describe the large variety variety of polarimetric response at high phase angle with polarization ranging from 1 to 50% when observed at the same phase angle. We also discuss the first results using physical characterization using radar, photometric, and thermal observations and how these can be used to calibrate the relation existing between polarimetry and albedo

SNEWPY: A Data Pipeline from Supernova Simulations to Neutrino Signals

International audienceCurrent neutrino detectors will observe hundreds to thousands of neutrinos from a Galacticsupernova, and future detectors will increase this yield by an order of magnitude or more.With such neutrino data sets, the next Galactic supernova will significantly increase our un-derstanding of the explosions of massive stars, nuclear physics under extreme conditions, andthe fundamental properties of neutrinos. However, there is a gulf between supernova simu-lations and the corresponding signals in detectors, making comparisons between theory andobservation, as well as between different detectors, very difficult. SNEWPY offers a unifiedinterface for hundreds of supernova simulations, a large library of flux transformations on theway towards the detector, and an interface to SNOwGLoBES (Scholberg & SNOwGLoBESContributors, 2021), allowing users to easily calculate and compare expected event rates frommany supernova models in many different neutrino detectors

SNEWPY: A Data Pipeline from Supernova Simulations to Neutrino Signals

International audienceCurrent neutrino detectors will observe hundreds to thousands of neutrinos from a Galactic supernovae, and future detectors will increase this yield by an order of magnitude or more. With such a data set comes the potential for a huge increase in our understanding of the explosions of massive stars, nuclear physics under extreme conditions, and the properties of the neutrino. However, there is currently a large gap between supernova simulations and the corresponding signals in neutrino detectors, which will make any comparison between theory and observation very difficult. SNEWPY is an open-source software package which bridges this gap. The SNEWPY code can interface with supernova simulation data to generate from the model either a time series of neutrino spectral fluences at Earth, or the total time-integrated spectral fluence. Data from several hundred simulations of core-collapse, thermonuclear, and pair-instability supernovae is included in the package. This output may then be used by an event generator such as sntools or an event rate calculator such as SNOwGLoBES. Additional routines in the SNEWPY package automate the processing of the generated data through the SNOwGLoBES software and collate its output into the observable channels of each detector. In this paper we describe the contents of the package, the physics behind SNEWPY, the organization of the code, and provide examples of how to make use of its capabilities