430 research outputs found
Star-planet interactions: I. Stellar rotation and planetary orbits
Context. As a star evolves, the planet orbits change with time due to tidal
interactions, stellar mass losses, friction and gravitational drag forces, mass
accretion and evaporation on/by the planet. Stellar rotation modifies the
structure of the star and therefore the way these different processes occur.
Changes of the orbits, at their turn, have an impact on the rotation of the
star.
Aims. Models accounting in a consistent way for these interactions between
the orbital evolution of the planet and the evolution of the rotation of the
star are still missing. The present work is a first attempt to fill this gap.
Methods. We compute the evolution of stellar models including a comprehensive
treatment of rotational effects together with the evolution of planetary
orbits, so that the exchanges of angular momentum between the star and the
planetary orbit are treated in a self-consistent way. The evolution of the
rotation of the star accounts for the angular momentum exchange with the planet
and also follows the effects of the internal transport of angular momentum and
chemicals.
Results. We show that rotating stellar models without tidal interactions can
well reproduce the surface rotations of the bulk of the red giants. However,
models without any interactions cannot account for fast rotating red giants in
the upper part of the red giant branch, where, such models, whatever the
initial rotation considered on the ZAMS, always predict very low velocities.
For those stars some interaction with a companion is highly probable and the
present rotating stellar models with planets confirm that tidal interaction can
reproduce their high surface velocities. We show also that the minimum distance
between the planet and the star on the ZAMS that will allow the planet to avoid
engulfment and survive is decreased around faster rotating stars. [abridged]Comment: 14 pages, abstract abridged for arXiv submission, accepted for
publication in Astronomy & Astrophysic
Star-planet interactions. IV. Possibility of detecting the orbit-shrinking of a planet around a red giant
The surface rotations of some red giants are so fast that they must have been
spun up by tidal interaction with a close companion, either another star, a
brown dwarf, or a planet. We focus here on the case of red giants that are spun
up by tidal interaction with a planet. When the distance between the planet and
the star decreases, the spin period of the star decreases, the orbital period
of the planet decreases, and the reflex motion of the star increases. We study
the change rate of these three quantities when the circular orbit of a planet
of 15 M that initially orbits a 2 M star at 1 au shrinks under
the action of tidal forces during the red giant phase. We use stellar evolution
models coupled with computations of the orbital evolution of the planet, which
allows us to follow the exchanges of angular momentum between the star and the
orbit in a consistent way. We obtain that the reflex motion of the red giant
star increases by more than 1 m s per year in the last 40 years
before the planet engulfment. During this phase, the reflex motion of the star
is between 660 and 710 m s. The spin period of the star increases by
more than about 10 minutes per year in the last 3000 y before engulfment.
During this period, the spin period of the star is shorter than 0.7 year.
During this same period, the variation in orbital period, which is shorter than
0.18 year, is on the same order of magnitude. Changes in reflex-motion and spin
velocities are very small and thus most likely out of reach of being observed.
The most promising way of detecting this effect is through observations of
transiting planets, that is, through{\it } changes of the beginning or end of
the transit. A space mission like PLATO might be of great interest for
detecting planets that are on the verge of being engulfed by red giants.Comment: 4 pages, 4 figure
Impact of rotation on stellar models
After a brief recall of the main impacts of stellar rotation on the structure
and the evolution of stars, four topics are addressed: 1) the links between
magnetic fields and rotation; 2) the impact of rotation on the age
determination of clusters; 3) the exchanges of angular momentum between the
orbit of a planet and the star due to tides; 4) the impact of rotation on the
early chemical evolution of the Milky Way and the origin of the
Carbon-Enhanced-Metal-Poor stars.Comment: 5 pages, 2 figures, To appear in Astronomische Nachrichten, special
issue "Reconstruction the Milky Way's History: Spectroscopic surveys,
Asteroseismology and Chemo-dynamical models", Guest Editors C. Chiappini, J.
Montalban, and M. Steffen, AN 2016 (in press
Antiangiogenic Therapy in the Treatment of Recurrent Medulloblastoma in the Adult: Case Report and Review of the Literature
Medulloblastoma is a rare tumor in central nervous system, with an even rarer occurrence in adulthood. The management of a recurrent disease is a medical challenge; chemotherapy has been used as the treatment of choice, while reirradiation has been employed in selected cases. We report the case of a 51-year-old man with recurrent medulloblastoma. He was treated with local reirradiation, chemotherapy, and antiangiogenic drug, with the latter giving the longer progression-free interval. The aim of this report is to show that recurrent medulloblastoma in adults can be approached with a multimodality treatment and that antiangiogenic therapy should have a role in the management of this disease
Etna International Training School of Geochemistry. Science meets Practice
Also this year, the “Etna International Training School of Geochemistry. Science meets practice” took place at Mt. Etna, now in its fourth edition. The school was hosted in the historical Volcanological Observatory “Pizzi Deneri”, one of the most important sites of the INGV - Osservatorio Etneo for geochemical and geophysical monitoring. Mount Etna, located in eastern Sicily, is the largest active volcano in Europe and one of the most intensely degassing volcanoes of the world [Allard et al., 1991; Gerlach, 1991]. Mt Etna emits about 1.6 % of global H2O fluxes from arc volcanism [Aiuppa et al., 2008] and 10 % of global average volcanic emission of CO2 and SO2 [D’Alessandro et al., 1997; Caltabiano et al., 2004; Aiuppa et al., 2008; Carn et al., 2017]. Furthermore, Gauthier and Le Cloarec, [1998] underscored that Mt. Etna is an important source of volcanic particles, having a mass flux of particle passively released from the volcano during non-eruptive period estimated between 7 to 23 tons/day [Martin et al., 2008; Calabrese et al., 2011]. In general, Etna is considered to be still under evolution and rather ‘friendly’, which, along with the above, makes it a favorable natural laboratory to study volcanic geochemistry. The Observatory Pizzi Deneri was sponsored by Haroun Tazieff, and it was built in 1978 by the CNR - International Institute of Volcanology under the direction of Prof. Letterio Villari. It is located at the base of the North-East crater (2,850 m a.s.l.), near the Valle del Leone and it was built on the rim of the Ellittico caldera. A picturesque building, consisting of two characteristics domes in front of the breath-taking panorama of the summit craters. Even though it is quite spartan as an accommodation facility, the dormitories, kitchen, seminar room and laboratory are well equipped. In other words, the Pizzi Deneri observatory is a unique place close to the top of the most active volcano of Europe. The observatory lies in a strategic location making it one of the most important sites for monitoring, research and dissemination of the scientific culture. After six field multidisciplinary campaigns (2010-2015) organized by a group of researchers of several institutions (INGV of Palermo, Catania, Naples, Bologna; Universities of Palermo, Florence, Mainz, Heidelberg), the idea of sharing and passing on the experience to the new generation of students has materialized, and the “Etna International Training School of Geochemistry. Science meets practice” was born in 2016. The four editions of the school were partially funded by INGV of Palermo and Catania, European Geoscience Union (EGU), Società Geochimica Italiana (SoGeI) and Associazione Naturalistica Geode. The conceptual idea of the school is to share scientific knowledge and experiences in the geochemical community, using local resources with a low-cost organization in order to allow as many students as possible access to the school. The “Etna International Training School of Geochemistry. Science meets practice” is addressed to senior graduate students, postdoctoral researchers, fellows, and newly appointed assistant professors, aiming to bring together the next generation of researchers active in studies concerning the geochemistry and the budget of volcanic gases. Introduce the participants with innovative direct sampling and remote sensing techniques. Furthermore, it gives young scientists an opportunity to experiment and evaluate new protocols and techniques to be used on volcanic fluid emissions covering a broad variety of methods. The teaching approach includes theoretical sessions (lectures), practical demonstrations and field applications, conducted by international recognized geochemists. We thank all the teachers who helped to make the school possible, among these: Tobias Fischer (University of New Mexico Albuquerque), Jens Fiebig (Institut für Geowissenschaften Goethe-Universität Frankfurt am Main), Andri Stefansson (University of Iceland, Institute of Earth Sciences), Mike Burton (University of Manchester), Nicole Bobrowski (Universität Heidelberg Institute of Environmental Physics and Max Planck Institute for Chemistry), Alessandro Aiuppa (Università di Palermo), Franco Tassi (Università di Firenze), Walter D’Alessandro (INGV of Palermo), Fatima Viveiros (University of the Azores). Direct sampling of high-to-low temperature fumaroles, plume measurement techniques (using CO2/SO2 sensors such as Multi-GAS instruments, MAX-DOAS instruments and UV SO2 cameras, alkaline traps and particle filters), measurement of diffuse soil gas fluxes of endogenous gases (CO2, Hg0, CH4 and light hydrocarbons), sampling of mud volcanoes, groundwaters and bubbling gases. Sampling sites include the active summit craters, eruptive fractures and peripheral areas. The students have shown an active participation both to the lessons and the fieldworks. Most of them describe the school as formative and useful experience for their future researches. Their enthusiasm is the real engine of this school
Etna International Training School of Geochemistry. Science meets Practice
Also this year, the \u201cEtna International Training School of Geochemistry. Science meets practice\u201d took place at Mt. Etna, now in its fourth edition. The school was hosted in the historical Volcanological Observatory \u201cPizzi Deneri\u201d, one of the most important sites of the INGV - Osservatorio Etneo for geochemical and geophysical monitoring. Mount Etna, located in eastern Sicily, is the largest active volcano in Europe and one of the most intensely degassing volcanoes of the world [Allard et al., 1991; Gerlach, 1991]. Mt Etna emits about 1.6 % of global H2O fluxes from arc volcanism [Aiuppa et al., 2008] and 10 % of global average volcanic emission of CO2 and SO2 [D\u2019Alessandro et al., 1997; Caltabiano et al., 2004; Aiuppa et al., 2008; Carn et al., 2017]. Furthermore, Gauthier and Le Cloarec, [1998] underscored that Mt. Etna is an important source of volcanic particles, having a mass flux of particle passively released from the volcano during non-eruptive period estimated between 7 to 23 tons/day [Martin et al., 2008; Calabrese et al., 2011]. In general, Etna is considered to be still under evolution and rather \u2018friendly\u2019, which, along with the above, makes it a favorable natural laboratory to study volcanic geochemistry. The Observatory Pizzi Deneri was sponsored by Haroun Tazieff, and it was built in 1978 by the CNR - International Institute of Volcanology under the direction of Prof. Letterio Villari. It is located at the base of the North-East crater (2,850 m a.s.l.), near the Valle del Leone and it was built on the rim of the Ellittico caldera. A picturesque building, consisting of two characteristics domes in front of the breath-taking panorama of the summit craters. Even though it is quite spartan as an accommodation facility, the dormitories, kitchen, seminar room and laboratory are well equipped. In other words, the Pizzi Deneri observatory is a unique place close to the top of the most active volcano of Europe. The observatory lies in a strategic location making it one of the most important sites for monitoring, research and dissemination of the scientific culture. After six field multidisciplinary campaigns (2010-2015) organized by a group of researchers of several institutions (INGV of Palermo, Catania, Naples, Bologna; Universities of Palermo, Florence, Mainz, Heidelberg), the idea of sharing and passing on the experience to the new generation of students has materialized, and the \u201cEtna International Training School of Geochemistry. Science meets practice\u201d was born in 2016. The four editions of the school were partially funded by INGV of Palermo and Catania, European Geoscience Union (EGU), Societ\ue0 Geochimica Italiana (SoGeI) and Associazione Naturalistica Geode. The conceptual idea of the school is to share scientific knowledge and experiences in the geochemical community, using local resources with a low-cost organization in order to allow as many students as possible access to the school. The \u201cEtna International Training School of Geochemistry. Science meets practice\u201d is addressed to senior graduate students, postdoctoral researchers, fellows, and newly appointed assistant professors, aiming to bring together the next generation of researchers active in studies concerning the geochemistry and the budget of volcanic gases. Introduce the participants with innovative direct sampling and remote sensing techniques. Furthermore, it gives young scientists an opportunity to experiment and evaluate new protocols and techniques to be used on volcanic fluid emissions covering a broad variety of methods. The teaching approach includes theoretical sessions (lectures), practical demonstrations and field applications, conducted by international recognized geochemists. We thank all the teachers who helped to make the school possible, among these: Tobias Fischer (University of New Mexico Albuquerque), Jens Fiebig (Institut f\ufcr Geowissenschaften Goethe-Universit\ue4t Frankfurt am Main), Andri Stefansson (University of Iceland, Institute of Earth Sciences), Mike Burton (University of Manchester), Nicole Bobrowski (Universit\ue4t Heidelberg Institute of Environmental Physics and Max Planck Institute for Chemistry), Alessandro Aiuppa (Universit\ue0 di Palermo), Franco Tassi (Universit\ue0 di Firenze), Walter D\u2019Alessandro (INGV of Palermo), Fatima Viveiros (University of the Azores). Direct sampling of high-to-low temperature fumaroles, plume measurement techniques (using CO2/SO2 sensors such as Multi-GAS instruments, MAX-DOAS instruments and UV SO2 cameras, alkaline traps and particle filters), measurement of diffuse soil gas fluxes of endogenous gases (CO2, Hg0, CH4 and light hydrocarbons), sampling of mud volcanoes, groundwaters and bubbling gases. Sampling sites include the active summit craters, eruptive fractures and peripheral areas. The students have shown an active participation both to the lessons and the fieldworks. Most of them describe the school as formative and useful experience for their future researches. Their enthusiasm is the real engine of this school
Star-planet interactions
When planets are formed from the protoplanetary disk and after the disk has dissipated, the evolution of their orbits is governed by tidal interactions, friction, and gravitational drag, and also by changes in the mass of the star and planet. These interactions may change the initial distribution of the distances between the planets and their host star by expanding the original orbit, by contracting it (which may cause an engulfment of the planet by the star), or by destroying the planet. We study the evolution of the orbit of a planet orbiting its host star under the effects of equilibrium tides, dynamical tides, drag (frictional and gravitational), and stellar mass loss. We used the Geneva stellar evolution code to compute the evolution of stars with initial masses of 1 and 1.5 solar mass with different rotation rates at solar metallicity. The star is evolved from the pre-main-sequence (PMS) up to the tip of the red giant branch. We used these models as input for computing the evolution of the planetary orbits. We explored the effects of changing the planet masses (of 1 Earth mass up to 20 Jupiter masses), the distance between the planet and the star (of 0.015 and more than 3 au), the mass, and the spin of the star. We present results when only the equilibrium tide was accounted for and when both equilibrium and dynamical tides were accounted for. The expression for the dynamical tide is a frequency-averaged dissipation of tidally excited inertial waves, obtained from a piecewise homogeneous two-layer stellar model. Gravity wave damping was neglected. Dynamical tides in convective zones have a significant effect on planetary orbits only during the PMS phase and only for fast-rotating stars. They have no significant effects during the PMS phase for initially slow-rotating stars and during the red giant branch phase, regardless of the initial rotation (abridged)
Switching from IFX originator to biosimilar CT-P13 does not impact effectiveness,safety and immunogenicity in a large cohort of IBD patients
Background: Switching from IFX originator to CT-P13 is safe; however, little data on immunogenicity exists. Research design and methods: Consecutive IBD patients on IFX originator were switched to CT-P13 and followed-up for 12 months. Clinical activity, infliximab trough levels (ITLs), anti-drug antibodies (ATIs), and adverse events were recorded at predefined timepoints (baseline, second CT-P13 infusion, 6 and 12 months). The outcomes investigated were immunogenicity, pharmacokinetics, effectiveness and safety. Results: 119 patients were switched to CT-P13 after a median time with IFX of 5.8 years. No changes in mean ITLs were observed. ATIs were detected in 30 patients (25.2%): 14 before and 16 after switch. Mean persistent ATIs were significantly higher compared to mean transient ones (109.74 ng/mL ±84.70 vs 18.22 ng/mL ±11.37, p < 0.001), with significantly lower ITLs associated (mean 0.32 µg/mL ±0.6 vs 3.08 µg/mL ±3.22, p < 0.001). A significant decrease of patients in steroid-fee clinical remission was observed after the switch (p = 0.004), with subsequent improvement at 6 months (p = 0.005). Eighteen patients (15.1%) discontinued IFX, only 6 (5%) for loss of response. Conclusions: Switching from infliximab originator to CT-P13 seems safe and effective, without differences in immunogenicity. A temporary reduction of clinical benefit after switching could be potentially explained by a ‘nocebo-effect response’
Characterization of seismic signals recorded in Tethys Bay, Victoria Land (Antarctica): data from atmosphere-cryosphere-hydrosphere interaction
In this paper, we analysed 3-component seismic signals recorded during 27 November 2016 - 10 January 2017 by two stations installed in Tethys Bay (Victoria Land, Antarctica), close to Mario Zucchelli Station. Due to the low noise levels , it was possible to identify three different kinds of signals: teleseismic earthquakes, microseisms, and icequakes . We focus on the latter two. A statistically significant relationship was found between microseism amplitude and both wind speed and sea swell. Thus, we suggest that the recorded microseism data are caused by waves at the shore close to the seismic stations rather than in the deep ocean during storms. In addition, w e detected three icequakes , with dominant low frequencies (below 2 Hz), located in the David Glacier area with local magnitude of 2.4-2.6. These events were likely to have been generated at the rock–ice interface under the glacier. This work shows how seismic signals recorded in Antarctica provide insights on the interactions between the atmosphere-cryosphere-hydrosphere. Since climate patterns drive these interactions, investigations on Antarctic seismic signals could serve as a proxy indicator for estimating climate changes
Rotation of planet-harbouring stars
The rotation rate of a star has important implications for the detectability,
characterisation and stability of any planets that may be orbiting it. This
chapter gives a brief overview of stellar rotation before describing the
methods used to measure the rotation periods of planet host stars, the factors
affecting the evolution of a star's rotation rate, stellar age estimates based
on rotation, and an overview of the observed trends in the rotation properties
of stars with planets.Comment: 16 pages, 4 figures: Invited review to appear in 'Handbook of
Exoplanets', Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
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