The Experts below are selected from a list of 19932 Experts worldwide ranked by ideXlab platform
Alessandra Celletti - One of the best experts on this subject based on the ideXlab platform.
-
the effect of poynting robertson drag on the triangular lagrangian points
Icarus, 2015Co-Authors: Christoph Lhotka, Alessandra CellettiAbstract:Abstract We investigate the stability of motion close to the Lagrangian equilibrium points L 4 and L 5 in the framework of the spatial, elliptic, restricted three-body problem, subject to the radial component of Poynting–Robertson drag. For this reason we develop a simplified resonant model, that is based on averaging theory, i.e. averaged over the Mean Anomaly of the perturbing planet. We find temporary stability of particles displaying a tadpole motion in the 1:1 resonance. From the linear stability study of the averaged simplified resonant model, we find that the time of temporary stability is proportional to β a 1 n 1 , where β is the ratio of the solar radiation over the gravitational force, and a 1 , n 1 are the semi-major axis and the Mean motion of the perturbing planet, respectively. We extend previous results (Murray, C.D. [1994]. Icarus 112, 465–484) on the asymmetry of the stability indices of L 4 and L 5 to a more realistic force model. Our analytical results are supported by Means of numerical simulations. We implement our study to Jupiter-like perturbing planets, that are also found in extra-solar planetary systems.
-
The effect of Poynting–Robertson drag on the triangular Lagrangian points
Icarus, 2015Co-Authors: Christoph Lhotka, Alessandra CellettiAbstract:Abstract We investigate the stability of motion close to the Lagrangian equilibrium points L 4 and L 5 in the framework of the spatial, elliptic, restricted three-body problem, subject to the radial component of Poynting–Robertson drag. For this reason we develop a simplified resonant model, that is based on averaging theory, i.e. averaged over the Mean Anomaly of the perturbing planet. We find temporary stability of particles displaying a tadpole motion in the 1:1 resonance. From the linear stability study of the averaged simplified resonant model, we find that the time of temporary stability is proportional to β a 1 n 1 , where β is the ratio of the solar radiation over the gravitational force, and a 1 , n 1 are the semi-major axis and the Mean motion of the perturbing planet, respectively. We extend previous results (Murray, C.D. [1994]. Icarus 112, 465–484) on the asymmetry of the stability indices of L 4 and L 5 to a more realistic force model. Our analytical results are supported by Means of numerical simulations. We implement our study to Jupiter-like perturbing planets, that are also found in extra-solar planetary systems.
Lorenzo Iorio - One of the best experts on this subject based on the ideXlab platform.
-
On the Mean Anomaly and the Mean longitude in tests of post-Newtonian gravity
The European Physical Journal C, 2019Co-Authors: Lorenzo IorioAbstract:The distinction between the Mean Anomaly $\mathcal{M}(t)$ and the Mean Anomaly at epoch $\eta$, and the Mean longitude $l(t)$ and the Mean longitude at epoch $\epsilon$ is clarified in the context of a possible use of such orbital elements in post-Keplerian tests of gravity, both Newtonian and post-Newtonian. In particular, the perturbations induced on $\mathcal{M}(t),\,\eta,\,l(t),\,\epsilon$ by the post-Newtonian Schwarzschild and Lense-Thirring fields, and the classical accelerations due to the atmospheric drag and the oblateness $J_2$ of the central body are calculated for an arbitrary orbital configuration of the test particle and a general orientation of the primary's spin axis $\boldsymbol{\hat{S}}$. They provide us with further observables which could be fruitfully used, e.g., in better characterizing astrophysical binary systems and in more accurate satellite-based tests around major bodies of the Solar System. Some erroneous and misleading claims by Ciufolini and Pavlis appeared in the literature are confuted. In particular, it is shown that there are no net perturbations of the Lense-Thirring acceleration on either the semimajor axis $a$ and the Mean motion $n_\mathrm{b}$. Furthermore, the quadratic signatures on $\mathcal{M}(t)$ and $l(t)$ due to certain disturbing non-gravitational accelerations like the atmospheric drag can be effectively disentangled from the post-Newtonian linear trends of interest provided that a sufficiently extended temporal interval for the data analysis is assumed. A possible use of $\eta$ along with the longitudes of the ascending node $\Omega$ in tests of general relativity with the existing LAGEOS and LAGEOS II satellites is suggested.
-
on the Mean Anomaly and the Mean longitude in tests of post newtonian gravity
European Physical Journal C, 2019Co-Authors: Lorenzo IorioAbstract:The distinction between the Mean Anomaly $${\mathcal {M}}(t)$$ and the Mean Anomaly at epoch $$\eta $$, and the Mean longitude l(t) and the Mean longitude at epoch $$\epsilon $$ is clarified in the context of a their possible use in post-Keplerian tests of gravity, both Newtonian and post-Newtonian. In particular, the perturbations induced on $${\mathcal {M}}(t),\,\eta ,\,l(t),\,\epsilon $$ by the post-Newtonian Schwarzschild and Lense–Thirring fields, and the classical accelerations due to the atmospheric drag and the oblateness $$J_2$$ of the central body are calculated for an arbitrary orbital configuration of the test particle and a generic orientation of the primary’s spin axis $$\varvec{{\hat{S}}}$$. They provide us with further observables which could be fruitfully used, e.g., in better characterizing astrophysical binary systems and in more accurate satellite-based tests around major bodies of the Solar System. Some erroneous claims by Ciufolini and Pavlis appeared in the literature are confuted. In particular, it is shown that there are no net perturbations of the Lense–Thirring acceleration on either the semimajor axis a and the Mean motion $$n_{\mathrm{b}}$$. Furthermore, the quadratic signatures on $${\mathcal {M}}(t)$$ and l(t) due to certain disturbing non-gravitational accelerations like the atmospheric drag can be effectively disentangled from the post-Newtonian linear trends of interest provided that a sufficiently long temporal interval for the data analysis is assumed. A possible use of $$\eta $$ along with the longitudes of the ascending node $$\Omega $$ in tests of general relativity with the existing LAGEOS and LAGEOS II satellites is suggested.
-
The post-Newtonian Mean Anomaly advance as further post-Keplerian parameter in pulsar binary systems
Astrophysics and Space Science, 2007Co-Authors: Lorenzo IorioAbstract:The post-Newtonian gravitoelectric secular rate of the Mean Anomaly M is worked out for a two-body system in the framework of the General Theory of Relativity. The possibility of using such an effect, which is different from the well known decrease of the orbital period due to gravitational wave emission, as a further post-Keplerian parameter in binary systems including one pulsar is examined. The resulting effect is almost three times larger than the periastron advance \dot\omega. E.g., for the recently discovered double pulsar system PSR J0737-3039 A+B it would amount to -47.79 deg yr^-1. This implies that it could be extracted from the linear part of a quadratic fit of the orbital phase because the uncertainties both in the linear drift due to the Mean motion and in the quadratic shift due to the gravitational wave are smaller. The availability of such additional post-Keplerian parameter would be helpful in further constraining the General Theory of Relativity, especially for such systems in which some of the other post-Keplerian parameters can be measured with limited accuracy. Moreover, also certain pulsar-white dwarf binary systems, characterized by circular orbits like PSR B1855+09 and a limited number of measured post-Keplerian parameters, could be used for constraining competing theories of gravity.
-
the post newtonian Mean Anomaly advance as further post keplerian parameter in pulsar binary systems
Astrophysics and Space Science, 2007Co-Authors: Lorenzo IorioAbstract:The post-Newtonian gravitoelectric secular rate of the Mean Anomaly ℳ is worked out for a two-body system in the framework of the General Theory of Relativity. The possibility of using such an effect, which is different from the well known decrease of the orbital period due to gravitational wave emission, as a further post-Keplerian parameter in binary systems including at least one pulsar is examined. The resulting effect is almost three times larger than the periastron advance \(\dot{\omega}\) . E.g., for the recently discovered double pulsar system PSR J0737-3039 A+B it would amount to −47.79 deg yr−1. This implies that it could be extracted from the linear part of a quadratic fit of the orbital phase because the uncertainties both in the linear drift due to the Mean motion and in the quadratic shift due to the gravitational wave are smaller. The availability of such additional post-Keplerian parameter would be helpful in further constraining the General Theory of Relativity, especially for such systems in which some of the other post-Keplerian parameters can be measured with limited accuracy. Moreover, also certain pulsar-white dwarf binary systems, characterized by circular orbits like PSR B1855+09 and a limited number of measured post-Keplerian parameters, could be used for constraining competing theories of gravity.
-
On the Mean Anomaly and the Lense-Thirring effect
arXiv: General Relativity and Quantum Cosmology, 2006Co-Authors: Lorenzo IorioAbstract:In this brief note we reply to the authors of a recent preprint in which an alleged explicit proposal of using the Mean Anomaly of the LAGEOS satellites to measure the general relativistic Lense-Thirring effect in the gravitational field of the Earth is attributed to the present author.
Christoph Lhotka - One of the best experts on this subject based on the ideXlab platform.
-
the effect of poynting robertson drag on the triangular lagrangian points
Icarus, 2015Co-Authors: Christoph Lhotka, Alessandra CellettiAbstract:Abstract We investigate the stability of motion close to the Lagrangian equilibrium points L 4 and L 5 in the framework of the spatial, elliptic, restricted three-body problem, subject to the radial component of Poynting–Robertson drag. For this reason we develop a simplified resonant model, that is based on averaging theory, i.e. averaged over the Mean Anomaly of the perturbing planet. We find temporary stability of particles displaying a tadpole motion in the 1:1 resonance. From the linear stability study of the averaged simplified resonant model, we find that the time of temporary stability is proportional to β a 1 n 1 , where β is the ratio of the solar radiation over the gravitational force, and a 1 , n 1 are the semi-major axis and the Mean motion of the perturbing planet, respectively. We extend previous results (Murray, C.D. [1994]. Icarus 112, 465–484) on the asymmetry of the stability indices of L 4 and L 5 to a more realistic force model. Our analytical results are supported by Means of numerical simulations. We implement our study to Jupiter-like perturbing planets, that are also found in extra-solar planetary systems.
-
The effect of Poynting–Robertson drag on the triangular Lagrangian points
Icarus, 2015Co-Authors: Christoph Lhotka, Alessandra CellettiAbstract:Abstract We investigate the stability of motion close to the Lagrangian equilibrium points L 4 and L 5 in the framework of the spatial, elliptic, restricted three-body problem, subject to the radial component of Poynting–Robertson drag. For this reason we develop a simplified resonant model, that is based on averaging theory, i.e. averaged over the Mean Anomaly of the perturbing planet. We find temporary stability of particles displaying a tadpole motion in the 1:1 resonance. From the linear stability study of the averaged simplified resonant model, we find that the time of temporary stability is proportional to β a 1 n 1 , where β is the ratio of the solar radiation over the gravitational force, and a 1 , n 1 are the semi-major axis and the Mean motion of the perturbing planet, respectively. We extend previous results (Murray, C.D. [1994]. Icarus 112, 465–484) on the asymmetry of the stability indices of L 4 and L 5 to a more realistic force model. Our analytical results are supported by Means of numerical simulations. We implement our study to Jupiter-like perturbing planets, that are also found in extra-solar planetary systems.
Bruno Sanso - One of the best experts on this subject based on the ideXlab platform.
-
a spatio temporal model for Mean Anomaly and trend fields of north atlantic sea surface temperature
Journal of the American Statistical Association, 2009Co-Authors: Ricardo T Lemos, Bruno SansoAbstract:We consider the problem of fitting a statistical model to 30 years of sea surface temperature records collected over a large portion of the Northern Atlantic. The observations were collected sparsely in space and time with different levels of accuracy. The purpose of the model is to produce an atlas of oceanic properties, including climatological Mean fields, estimates of historical trends, and a spatio-temporal reconstruction of the anomalies, i.e., the transient deviations from the climatological Mean. These products are of interest to climate change and climate variability research, numerical modeling, and remote sensing analyses. Our model improves upon the current tools used by oceanographers in that it constructs instantaneous temperature fields before averaging them into the climatology, thus giving equal weight to all years in the time frame, regardless of the temporal distribution of data. It also accounts for nonisotropic and nonstationary space and time dependencies, owing to its use of discret...
Ricardo T Lemos - One of the best experts on this subject based on the ideXlab platform.
-
a spatio temporal model for Mean Anomaly and trend fields of north atlantic sea surface temperature
Journal of the American Statistical Association, 2009Co-Authors: Ricardo T Lemos, Bruno SansoAbstract:We consider the problem of fitting a statistical model to 30 years of sea surface temperature records collected over a large portion of the Northern Atlantic. The observations were collected sparsely in space and time with different levels of accuracy. The purpose of the model is to produce an atlas of oceanic properties, including climatological Mean fields, estimates of historical trends, and a spatio-temporal reconstruction of the anomalies, i.e., the transient deviations from the climatological Mean. These products are of interest to climate change and climate variability research, numerical modeling, and remote sensing analyses. Our model improves upon the current tools used by oceanographers in that it constructs instantaneous temperature fields before averaging them into the climatology, thus giving equal weight to all years in the time frame, regardless of the temporal distribution of data. It also accounts for nonisotropic and nonstationary space and time dependencies, owing to its use of discret...