arXiv subjects

Michele Maris

Publications and source records attributed to Michele Maris.

24 records · Page 2Linked to original sources

arXiv2008

Constraints to Uranus' Great Collision. IV. The Origin of Prospero

It is widely accepted that the large obliquity of Uranus is the result of a great tangential collision (GC) with an Earth size proto-planet at the end of the accretion. We attempt to constraint the GC scenario as the cause of Uranus' obliquity as well as on the mechanisms able to give origin to the Uranian irregulars. Different capture mechanisms for irregulars operate at different stages on the giant planets formation process. The mechanisms able to capture the uranian irregulars before and after the GC are analysed. Assuming that they were captured before the GC, we calculate the orbital transfer of the nine irregulars by the impulse imparted by the GC. If their orbital transfer results dynamically implausible, they should have originated after the GC. We investigate and discuss the dissipative mechanisms able to operate later. In particular Prospero could not exist at the time of the GC. Different capture mechanisms for Prospero after the GC are investigated. Gas drag by Uranus'envelope and pull-down capture are not plausible mechanisms. Capture of Prospero through a collisionless interaction seems to be difficult. The GC itself provides a mechanism of permanent capture. However, the capture of Prospero by the GC is a low probable event. Catastrophic collisions could be a possible mechanism for the birth of Prospero and the other irregulars after the GC. Orbital and physical clusterings should then be expected. Either Prospero had to originate after the GC or the GC did not occur. In the former case, the mechanism for the origin of Prospero after the GC remains an open question. In the latter case, another theory to account for Uranus' obliquity and the formation of the Uranian regular satellites on the equatorial plane of the planet would be needed.

astro-ph↗

arXiv2007

Light curves and colours of the faint Uranian irregular satellites Sycorax, Prospero, Stephano, Setebos and Trinculo

After the work of Gladman et al. (1998), it is now assessed that many irregular satellites are orbiting around Uranus. Despite many studies have been performed in past years, very few is know for the light-curves of these objects and inconsistencies are present between colours derived by different authors. This situation motivated our effort to improve both the knowledge of colours and light curves. We present and discuss time series observations of Sycorax, Prospero, Stephano, Setebos and Trinculo, five faint irregular satellites of Uranus, carried out at VLT, ESO Paranal (Chile) in the nights between 29 and 30 July, 2005 and 25 and 30 November, 2005. We derive light curves for Sycorax and Prospero and colours for all of these these bodies. For Sycorax we obtain colours B-V =0.839 +/- 0.014, V-R = 0.531 +/- 0.005 and a light curve which is suggestive of a periodical variation with period about 3.6 hours and amplitude about 0.067 +/- 0.004 mag. The periods and colours we derive for Sycorax are in agreement with our previous determination in 1999 using NTT. We derive also a light-curve for Prospero which suggests an amplitude of about 0.2 mag and a periodicity of about 4 hours. However, the sparseness of our data, prevents a more precise characterization of the light-curves, and we can not determine wether they are one-peaked or two-peaked. Hence, these periods and amplitudes have to be considered preliminary estimates. As for Setebos, Stephano and Trinculo the present data do not allow to derive any unambiguous periodicity, despite Setebos displays a significant variability with amplitude about as large as that of Prospero. Colours for Prospero, Setebos, Stephano and Trinculo are in marginal agreement with the literature.

astro-ph↗

arXiv2006

Time series photometry of the dwarf planet ERIS (2003 UB313)

The dwarf planet Eris (2003 UB313, formerly known also as ``Xena'') is the largest KBO up to now discovered. Despite being larger than Pluto and bearing many similarities with it, it has not been possible insofar to detect any significant variability in its light curve, preventing the determination of its period and axial ratio. We attempt to assess the level of variability of the Eris light curve by determining its BVRI photometry with a target accuracy of 0.03 mag/frame in R and a comparable or better stability in the calibration. Eris has been observed between November $30^\mathrm{th}$ and December $5^\mathrm{th}$ 2005 with the Y4KCam on-board the 1.0m Yale telescope at Cerro Tololo Interamerican Observatory, Chile in photometric nights. We obtain 7 measures in B, 23 in V, 62 in R and 20 in I. Averaged B, V, and I magnitudes as colors are in agreement within $\approx 0.03$ mag with measures from Rabinowitz et al. (2006) taken in the same nights. Night-averaged magnitudes in R shows a statistically significant variability over a range of about $0.05\pm0.01$ mag. This can not be explained by known systematics, background objects or some periodical variation with periods less than two days in the light-curve. The same applies to B, V and to less extent to I due to larger errors. In analogy with Pluto and if confirmed by future observations, this ``long term'' variability might be ascribed to a slow rotation of Eris, with periods longer than 5 days, or to the effect of its unresolved satellite ``Dysnomea'' which may contribute for $\approx0.02$ mag to the total brightness.

astro-ph↗

arXiv2006

Simulating the Zody Emission in the Planck Mission

The increasing sensitivity of cosmic microwave background (CMB) missions will require to significantly improve the accuracy in the subtraction of the various sources of Galactic foreground, from the most relevant components (synchrotron, dust and free-free emission) to those usually considered of minor relevance in CMB experiments. With respect to other Galactic diffuse components, the Zodiacal Light Emission (ZLE) is peculiar, depending not only on the observing direction but also on the location of the observer within the Solar System: ZLE behaves then as a large scale, time-dependent foreground. Starting from the existing far-infrared ZLE models, we discuss the impact of ZLE contribution in CMB maps and the level of contamination in time ordered data and maps expected from the forthcoming Planck space mission as well as the Planck capability to increase our knowledge of the ZLE properties.

astro-ph↗

arXiv2001

Multicolor Photometry of the Uranus Irregular Satellites Sycorax and Caliban

We report on accurate BVRI photometry for the two Uranus irregular satellites Sycorax and Caliban. We derive colours, showing that Sycorax is bluer than Caliban. Our data allows us to detect a significant variability in the Caliban's light-curve, which suggests an estimated period of about 3 hours. Despite it is the brighter of the two bodies, Sycorax does not display a strong statistically significant variability. However our data seem to suggest a period of about 4 hours

astro-ph↗

arXiv1997

Comprehensive Study of the Possibility of Day - Night Effect Enhancement

A set of quantitative predictions for the day-night asymmetry in the Super - Kamiokande detector is presented. For these predictions, neutrino events are collected in ``samples'' defined by the trajectories in the Earth of the corresponding solar neutrinos. The more important samples considered here are: the full sample of neutrinos detected at night, the sample of night neutrinos which cross the Earth core and the sample of night neutrinos which does not cross the Earth core. For energy integrated event rates, the day-night asymmetry for core crossing neutrinos is up to six times bigger than the day-night asymmetry for the full sample of night neutrinos. When the reduction in statistics is considered, an effective enhancement up to a factor $\approx 2.3$ is obtained. The selection of core crossing neutrinos may be relevant for the recoil - $e^-$ spectra too. From these results it is reasonable to expect the Super Kamiokande detector be able to constrain the small mixing angle solution of the solar neutrino problem ($\sin^2 2 θ_v \leq 0.01$) through the day-night effect. Furthermore, it is proposed that the day-night effect may limits the total flux of 8B neutrino produced in the Sun. At last, the sensitivity of these predictions to the Earth model uncertainties is quantitatively discussed.

hep-ph↗