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X-WR-CALDESC:Eventi per Osservatorio Astronomico di Roma
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BEGIN:VEVENT
DTSTART;TZID=Europe/Rome:20230307T113000
DTEND;TZID=Europe/Rome:20230307T123000
DTSTAMP:20260405T015717
CREATED:20230217T061831Z
LAST-MODIFIED:20230223T160230Z
UID:11309-1678188600-1678192200@www.oa-roma.inaf.it
SUMMARY:VVV Microlensing events as tracers of Galactic structure and kinematics
DESCRIPTION:We report the discovery of ~1\,000 microlensing events within an area covering 20.68 deg^2 between 2010 and 2015 in the zero-latitude region of the Galactic bulge using the VVV Survey near-IR data. We used the near-IR Color-Magnitude and Color-Color Diagram to analyze the extinction properties of the sample in the central region of the Galactic plane. We study the Einstein ring crossing time distribution as a strong dark mass indicator and study features of the Galactic structure. We found 20 distant microlensing events probably located in the far disk of the Galaxy. This is the first time a population of events has been discovered\, allowing us to study the other side of the Milky Way. We also examine specific events\, such as the long timescale events showing parallax that favor the presence of dark stellar remnants such as black holes and neutron stars\, which are essential ingredients in our understanding of stellar evolution and mass distribution\, galaxy evolution and structure\, dark matter balance\, etc.
URL:https://www.oa-roma.inaf.it/event/colloquium-gabriela-navarro/
LOCATION:Aula Gratton
CATEGORIES:Seminari
ORGANIZER;CN="Flavia Dell'Agli":MAILTO:flavia.dellagli@inaf.it
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BEGIN:VEVENT
DTSTART;TZID=Europe/Rome:20230321T113000
DTEND;TZID=Europe/Rome:20230321T123000
DTSTAMP:20260405T015717
CREATED:20230210T063937Z
LAST-MODIFIED:20230313T064314Z
UID:11276-1679398200-1679401800@www.oa-roma.inaf.it
SUMMARY:colloquium - Sonia Fornasier: Latest results on 67P/Churyumov-Gerasimenko comet from the OSIRIS instrument onboard the ROSETTA mission
DESCRIPTION:The Rosetta space mission of the European Space Agency Rosetta has observed comet 67P/Churyumov-Gerasimenko for about 2 years\, delivering the lander Philae on the comet surface for the first time in the history of the space exploration.  Ended in September 2016\, the Rosetta/Philae mission\, acquired an incredible amount of unique data of comet 67P\, allowing the most detailed study ever attempted of a comet.\nRosetta had a large complement of scientific experiments including the OSIRIS imaging system which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). More than 80000 images were acquired with the OSIRIS imaging system with spatial resolution ranging from several meters to a few centimeters per pixel during Rosetta’s descent to the comet in late September 2016.  In particular\, the high dynamics of the cameras detectors permitted to distinguish morphological structures on shadowed areas as well as frost layers\, and to monitor at the same time the very dark surface\, faint jets (with lifetimes shorter than a few minutes)\, and ices exposures.\nAn extensive catalogue of volatiles exposure was recently created permitting to investigate the link between composition\, morphology and activity. It also indicates that ices exposures are typically sub-meter sized\, information which is relevant for cometary models.\nDetailed analysis of highly active regions revealed that the small lobe has different physical and mechanical properties than the big one and a lower volatile content\, at least in its uppermost layers. These findings support the hypothesis that comet 67P originated from the merging of two distinct bodies in the early Solar System\, as previously suggested by the geomorphological analyses of the comet terrains.\nFinally\, the reconstructed Philae orbit revealed that it had a second landing site located only 30 m apart from the final one. Philae stamped within a boulder for 25 cm depth\, indicating that the cometary material is extremely soft and highly porous. This collision exposed the primordial water ice embedded within the boulder\, providing an accurate measurement of the refractory to volatile ratio in comet 67P.
URL:https://www.oa-roma.inaf.it/event/colloquium-sonia-fornasier-3/
LOCATION:Aula Gratton
CATEGORIES:Seminari
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Rome:20230328T113000
DTEND;TZID=Europe/Rome:20230328T123000
DTSTAMP:20260405T015717
CREATED:20230210T064046Z
LAST-MODIFIED:20230325T095723Z
UID:11279-1680003000-1680006600@www.oa-roma.inaf.it
SUMMARY:colloquium - Giulia De Somma: The classical Cepheids modelling in the Gaia Era
DESCRIPTION:Classical Cepheids are the most used primary distance indicators to calibrate\nthe cosmic distance ladder and reliable stellar population tracers. These stars\nhave been adopted to probe galactic evolution and star formation\, thanks to\ntheir intrinsic variability and the link between pulsation properties and\nevolutionary parameters. A theoretical approach to the study of these objects\nis crucial to interpret observed behaviors and fully exploiting the accuracy of\nobserved oscillation characteristics in terms of stellar properties and distances.\nBy using the Stellingwerf hydrodynamical code\, we recently provided detailed\nhomogeneous nonlinear Classical Cepheid pulsation models. We take into\naccount variations of chemical composition\, mass-luminosity (ML) relation\, and\nefficiency of super-adiabatic convection.\nThe predicted pulsation observables included the instability strips\, multi-filter\nlight curves\, and the corresponding mean magnitudes and colors.\nWe used these quantities to derive metal-dependent period-luminosity-color\n(PLC) and period-Wesenheit (PW) relations. The latter were applied to a\nsample of Gaia Early Data Release 3 (DR3) Galactic Cepheids. The inferred\ntheoretical parallaxes were tested against Gaia astrometric results. By\ncombining this pulsational scenario with updated stellar evolution\npredictions and using the BASTI code\, we derived new and accurate metal-\ndependent Period-Age and Period-Age-Color relations\, which were applied to\nthe same sample of Galactic Cepheids in the Gaia DR3 to constrain their age\ndistribution. These results are all discussed in view of the incoming SPECTRUM\nproject that will represent the first attempt to systematically compute\nnonlinear convective pulsation models along stellar evolutionary tracks.
URL:https://www.oa-roma.inaf.it/event/colloquium-giulia-de-somma/
LOCATION:Aula Gratton
CATEGORIES:Seminari
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