54 research outputs found
Ensemble Properties of Comets in the Sloan Digital Sky Survey
We present the ensemble properties of 31 comets (27 resolved and 4
unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of
comets represents about 1 comet per 10 million SDSS photometric objects.
Five-band (u,g,r,i,z) photometry is used to determine the comets' colors,
sizes, surface brightness profiles, and rates of dust production in terms of
the Af{\rho} formalism. We find that the cumulative luminosity function for the
Jupiter Family Comets in our sample is well fit by a power law of the form N(<
H) \propto 10(0.49\pm0.05)H for H < 18, with evidence of a much shallower fit
N(< H) \propto 10(0.19\pm0.03)H for the faint (14.5 < H < 18) comets. The
resolved comets show an extremely narrow distribution of colors (0.57 \pm 0.05
in g - r for example), which are statistically indistinguishable from that of
the Jupiter Trojans. Further, there is no evidence of correlation between color
and physical, dynamical, or observational parameters for the observed comets.Comment: 19 pages, 8 tables, 11 figures, to appear in Icaru
Photometry of the Didymos System across the DART Impact Apparition
On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite’s orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ∼1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG 1 G 2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact
Clientes en Contexto: Los Impactos de las Microfinanzas en Tres Países
Las microfinanzas constituyen una atractiva estrategia de desarrollo para un amplio espectro de actores, pues combinan los valores de la prestación de servicios orientada por el mercado, el espíritu empresarial, la autoayuda y la asistencia a los pobres
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