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Lorenzo Iorio

Publications and source records attributed to Lorenzo Iorio.

At least 91 records · Page 5Linked to original sources
arXiv2015

The impact of the orbital decay of the LAGEOS satellites on the frame-dragging tests

The laser-tracked geodetic satellites LAGEOS, LAGEOS II and LARES are currently employed, among other things, to measure the general relativistic Lense-Thirring effect in the gravitomagnetic field of the spinning Earth with the hope of providing a more accurate test of such a prediction of the Einstein's theory of gravitation than the existing ones. The secular decay $\dot a$ of the semimajor axes $a$ of such spacecrafts, recently measured in an independent way to a $σ_{\dot a}\approx 0.1-0.01$ m yr$^{-1}$ accuracy level, may indirectly impact the proposed relativistic experiment through its connection with the classical orbital precessions induced by the Earth's oblateness $J_2$. \textcolor{black}{Indeed,} the systematic bias due to the current measurement errors $σ_{\dot a}$ is of the same order of magnitude of, or even larger than, the expected relativistic signal itself; moreover, it grows linearly with the time span $T$ of the analysis. \textcolor{black}{Therefore, the parameter-fitting algorithms must be properly updated in order to suitably cope with such a new source of systematic uncertainty. Otherwise,} an improvement of one-two orders of magnitude in measuring the orbital decay of the satellites of the LAGEOS family would be required to reduce this source of systematic uncertainty to a percent fraction of the Lense-Thirring signature.

gr-qc↗
arXiv2015

Orbital effects due to gravitational induction

We study the motion of test particles in the metric of a localized and slowly rotating astronomical source, within the framework of linear gravitoelectromagnetism, grounded on a Post-Minkowskian approximation of general relativity. Special attention is paid to gravitational inductive effects due to time-varying gravitomagnetic fields. We show that, within the limits of the approximation mentioned above, there are cumulative effects on the orbit of the particles either for planetary sources or for binary systems. They turn out to be negligible.

gr-qc↗
arXiv2015

Accurate characterization of the stellar and orbital parameters of the exoplanetary system WASP-33 b from orbital dynamics

By using the most recently published Doppler tomography measurements and accurate theoretical modeling of the oblateness-driven orbital precessions, we tightly constrain some of the physical and orbital parameters of the planetary system hosted by the fast rotating star WASP-33. In particular, the measurements of the orbital inclination $i_{\rm p}$ to the plane of the sky and of the sky-projected spin-orbit misalignment $λ$ at two epochs about six years apart allowed for the determination of the longitude of the ascending node $Ω$ and of the orbital inclination $I$ to the apparent equatorial plane at the same epochs. As a consequence, average rates of change $\dotΩ_{\rm exp},~\dot I_{\rm exp}$ of this two orbital elements, accurate to a $\approx 10^{-2}~{\rm deg}~{\rm yr}^{-1}$ level, were calculated as well. By comparing them to general theoretical expressions $\dotΩ_{J_2},~\dot I_{J_2}$ for their precessions induced by an oblate star whose symmetry axis is arbitrarily oriented, we were able to determine the angle $i^{\star}$ between the line of sight the star's spin $S^{\star}$ and its first even zonal harmonic $J_2^{\star}$ obtaining $i^{\star} = 142^{+10}_{-11}~{\rm deg},~J_2^{\star} = (2.1^{+0.8}_{-0.5})\times 10^{-4}.$ As a by-product, the angle between $S^{\star}$ and the orbital angular momentum $L$ is as large as about $ψ\approx 100$ deg $(ψ^{2008} = 99^{+5}_{-4}~{\rm deg},~ψ^{2014} = 103^{+5}_{-4}~{\rm deg})$, and changes at a rate $\dotψ= 0.7^{+1.5}_{-1.6}~{\rm deg}~{\rm yr}^{-1}$. The predicted general relativistic Lense-Thirring precessions, or the order of $\approx 10^{-3}~{\rm deg}~{\rm yr}^{-1}$, are, at present, about one order of magnitude below the measurability threshold.

gr-qc↗
arXiv2015

Constraining f(T) gravity in the Solar System

In the framework of $f(T)$ theories of gravity, we solve the field equations for $f(T)=T+αT^{n}$, in the weak-field approximation and for spherical symmetry spacetime. Since $f(T)=T$ corresponds to Teleparallel Gravity, which is equivalent to General Relativity, the non linearity of the Lagrangian are expected to produce perturbations of the general relativistic solutions, parameterized by $α$. Hence, we use the $f(T)$ solutions to model the gravitational field of the Sun, and exploit data from accurate tracking of spacecrafts orbiting Mercury and Saturn to infer preliminary insights on what could be obtained about the model parameter $α$ and the cosmological constant $Λ$. It turns out that improvements of about one-three orders with respect to the present-day constraints in the literature of magnitude seem possible.

gr-qc↗
arXiv2015

Editorial for the Special Issue 100 Years of Chronogeometrodynamics: The Status of the Einstein's Theory of Gravitation in Its Centennial Year

The present Editorial introduces the Special Issue dedicated by the journal Universe to the General Theory of Relativity, the beautiful theory of gravitation of Einstein, a century after its birth. It reviews some of its key features in a historical perspective, and, in welcoming distinguished researchers from all over the world to contribute it, some of the main topics at the forefront of the current research are outlined.

gr-qc↗
arXiv2015

Gravitational Anomalies in the Solar System?

Mindful of the anomalous perihelion precession of Mercury discovered by U. Le Verrier in the second half of the nineteenth century and its successful explanation by A. Einstein with his General Theory of Relativity in the early years of the twentieth century, discrepancies among observed effects in our Solar system and their theoretical predictions on the basis of the currently accepted laws of gravitation applied to known bodies have the potential of paving the way for remarkable advances in fundamental physics. This is particularly important now more than ever, given that most of the Universe seems to be made of unknown substances dubbed Dark Matter and Dark Energy. Should this not be directly the case, Solar system's anomalies could anyhow lead to advancements in cumulative science, as shown to us by the discovery of Neptune in the first half of the nineteenth century. Moreover, investigations in one of such directions can serendipitously enrich the other one as well. The current status of some alleged gravitational anomalies in the Solar system is critically reviewed. They are: a) Possible anomalous advances of planetary perihelia; b) Unexplained orbital residuals of a recently discovered moon of Uranus (Mab); c) The lingering unexplained secular increase of the eccentricity of the orbit of the Moon; d) The so-called Faint Young Sun Paradox; e) The secular decrease of the mass parameter of the Sun; f) The Flyby Anomaly; g) The Pioneer Anomaly; and h) The anomalous secular increase of the astronomical unit

gr-qc↗
arXiv2014

Orbital effects of a monochromatic plane gravitational wave with ultra-low frequency incident on a gravitationally bound two-body system

We analytically compute the long-term orbital variations of a test particle orbiting a central body acted upon by an incident monochromatic plane gravitational wave. We assume that the characteristic size of the perturbed two-body system is much smaller than the wavelength of the wave. Moreover, we also suppose that the wave's frequency is much smaller than the particle's orbital one. We make neither a priori assumptions about the direction of the wavevector nor on the orbital geometry of the planet. We find that, while the semi-major axis is left unaffected, the eccentricity, the inclination, the longitude of the ascending node, the longitude of pericenter and the mean anomaly undergo non-vanishing long-term changes. They are not secular trends because of the slow modulation introduced by the tidal matrix coefficients and by the orbital elements themselves. They could be useful to indepenedently constrain the ultra-low frequency waves which may have been indirectly detected in the BICEP2 experiment. Our calculation holds, in general, for any gravitationally bound two-body system whose characteristic frequency is much larger than the frequency of the external wave. It is also valid for a generic perturbation of tidal type with constant coefficients over timescales of the order of the orbital period of the perturbed particle.

gr-qc↗
arXiv2014

Orbital motions and the conservation-law/preferred-frame $α_3$ parameter

We analytically calculate some orbital effects induced by the Lorentz-invariance/momentum-conservation PPN parameter $α_3$ in a gravitationally bound binary system made of a compact primary orbited by a test particle. We neither restrict ourselves to any particular orbital configuration nor to specific orientations of the primary's spin axis $\boldsymbol{\hatψ}$. We use our results to put preliminary upper bounds on $α_3$ in the weak-field regime by using the latest data from Solar System's planetary dynamics. By linearly combining the supplementary perihelion precessions $Δ\dot\varpi$ of the Earth, Mars and Saturn, determined with the EPM2011 ephemerides, we infer $|α_3|\lesssim 6\times 10^{-10}$. Our result is about 3 orders of magnitude better than the previous weak-field constraints existing in the literature, and of the same order of magnitude of the bound expected from the future BepiColombo mission to Mercury. It is, by construction, independent of the other preferred-frame PPN parameters $α_1,α_2$, both preliminarily constrained down to a $\approx 10^{-6}$ level. The wide pulsar-white dwarf binary PSR J0407+1607 yields a preliminary upper bound on the strong-field version $\hatα_3$ of the Lorentz-invariance/momentum-conservation PPN parameter of the order of $3\times 10^{-17}$. It relies upon certain assumptions on the unknown values of the pulsar's spin axis orientation $\boldsymbol{\hatψ}$, the orbital node $Ω$ and the inclination $I$. Neither the pulsar's proper motion, still undetected, nor a possible value of the pulsar's mass $m_{\rm p}$ up to two solar masses substantially affect our result.

gr-qc↗
arXiv2014

Orbital motions as gradiometers for post-Newtonian tidal effects

The direct long-term changes occurring in the orbital dynamics of a local gravitationally bound binary system $S$ due to the post-Newtonian tidal acceleration caused by an external massive source are investigated. A class of systems made of a test particle $m$ rapidly orbiting with orbital frequency $n_{\rm b}$ an astronomical body of mass $M$ which, in turn, slowly revolves around a distant object of mass $M^{'}$ with orbital frequency $n_{\rm b}^{'}\ll n_{\rm b}$ is considered. The characteristic frequencies of the non-Keplerian orbital variations of $m$ and of $M$ itself are assumed to be negligible with respect to both $n_{\rm b}$ and $n_{\rm b}^{'}$. General expressions for the resulting Newtonian and post-Newtonian tidal orbital shifts of $m$ are obtained. The future missions BepiColombo and JUICE to Mercury and Ganymede, respectively, are considered in view of a possible detection. The largest effects, of the order of $\approx 0.1-0.5$ milliarcseconds per year (mas yr$^{-1}$), occur for the Ganymede orbiter of the JUICE mission. Although future improvements in spacecraft tracking and orbit determination might, perhaps, reach the required sensitivity, the systematic bias represented by the other known orbital perturbations of both Newtonian and post-Newtonian origin would be overwhelming. The realization of a dedicated artificial mini-planetary system to be carried onboard and Earth-orbiting spacecraft is considered as well. Post-Newtonian tidal precessions as large as $\approx 1-10^2$ mas yr$^{-1}$ could be obtained, but the quite larger Newtonian tidal effects would be a major source of systematic bias because of the present-day percent uncertainty in the product of the Earth's mass times the Newtonian gravitational parameter.

gr-qc↗
arXiv2014

Planet X revamped after the discovery of the Sedna-like object 2012 VP$_{113}$?

The recent discovery of the Sedna-like dwarf planet 2012 VP$_{\rm 113}$ by Trujillo and Sheppard has revamped the old-fashioned hypothesis that a still unseen trans-Plutonian object of planetary size, variously dubbed over the years as Planet X, Tyche, Thelisto, may lurk in the distant peripheries of the Solar System. This time, the presence of a super-Earth with mass $m_{\rm X} = 2-15m_{\oplus}$ at a distance $d_{\rm X}\approx 200-300$ astronomical units (AU) was proposed to explain the observed clustering of the arguments of perihelion $ω$ near $ω\approx 0^{\circ}$ but not $ω\approx 180^{\circ}$ for Sedna, 2012 VP$_{\rm 113}$ and other minor bodies of the Solar System with perihelion distances $q>30$ AU and semimajor axes $a>150$ AU. Actually, such a scenario is strongly disfavored by the latest constraints $Δ\dot\varpi$ on the anomalous perihelion precessions of some Solar System's planets obtained with the INPOP and EPM ephemerides. Indeed, they yield $d_{\rm X}\gtrsim 496-570$ AU ($m_{\rm X}=2m_{\oplus}$), and $d_{\rm X}\gtrsim 970-1111$ AU ($m_{\rm X} = 15 m_{\oplus}$). Much tighter constraints could be obtained in the near future from the New Horizons mission to Pluto.

astro-ph.EP↗
arXiv2014

A flyby anomaly for Juno? Not from standard physics

An empirical formula recently appeared in the literature to explain the observed anomalies of about $Δ\dotρ\approx 1-10$ mm s$^{-1}$ in the geocentric range-rates $\dotρ$ of the Galileo, NEAR and Rosetta spacecraft at some of their past perigee passages along unbound, hyperbolic trajectories. It predicts an anomaly of the order of $6$ mm s$^{-1}$ for the recent flyby of Juno, occurred on 9 October 2013. Data analyses to confirm or disproof it are currently ongoing. We numerically calculate the impact on the geocentric Juno's range rate of some classical and general relativistic dynamical effects which are either unmodelled or mismodelled to a certain level in the software used to process the data. They are: a) The first even zonal harmonic coefficient $J_2$ of the multipolar expansion of the terrestrial gravitational potential causing orbital perturbations both at the $\left.{\rm a}^{'}\right)$ Newtonian ($J_2$) and at the $\left. {\rm a}^{''}\right)$ first post-Newtonian level ($J_2 c^{-2}$) b) The post-Newtonian gravitoelectric (GE) Schwarschild-like component of the Earth's gravitational field c) The post-Newtonian gravitomagnetic (GM) Lense-Thirring effect. The magnitudes of their mismodeled and nominal range-rate signatures are: $\left. {\rm a}^{'}\right)$ $Δ\dotρ_{σ_{J_2}} \approx 1$ $μ$m s$^{-1}$ $\left. {\rm a}^{''}\right)$ $Δ\dotρ_{J_2 c^{-2}} \approx 0.015$ $μ$m s$^{-1}$ b) $Δ\dotρ_{\rm GE} \approx 25$ $μ$m s$^{-1}$ c) $Δ\dotρ_{\rm GM} \approx 0.05$ $μ$m s$^{-1}$. If a flyby anomaly as large as a few mm s$^{-1}$ will be finally found also for Juno, it will not be due to any of these standard gravitational effects. (Abridged)

gr-qc↗
arXiv2014

The lingering anomalous secular increase of the eccentricity of the orbit of the Moon: further attempts of explanation of cosmological origin

A new analysis of extended data records collected with the Lunar Laser Ranging (LLR) technique performed with improved tidal models was not able to resolve the issue of the anomalous rate $\dot e$ of the eccentricity $e$ of the orbit of the Moon, which is still in place with a magnitude of $\dot e=(5\pm 2)\times 10^{-12}$ yr$^{-1}$. Some possible cosmological explanations are offered in terms of the post-Newtonian effects of the cosmological expansion, and of the slow temporal variation of the relative acceleration rate $\ddot{S} S^{-1}$ of the cosmic scale factor $S$. None of them is successful since their predicted secular rates of the lunar eccentricity are too small by several orders of magnitude.

gr-qc↗
arXiv2014

Modified theories of gravity with nonminimal coupling and orbital particle dynamics

We consider a non-rotating, massive test particle acted upon by a "pressure"-type, non-geodesic acceleration arising from a certain general class of gravitational theories with nonminimal coupling between the matter and the metric. The resulting orbital perturbations for a two-body system are investigated both analytically and numerically. Among the other long-term effects, a secular increase of the two-body relative distance occurs. In principle, it may yield a physical mechanism for the steady recession of the Earth from the Sun recently proposed to explain the Faint Young Sun Paradox in the Archean eon. At present, the theorists have not yet derived explicit expressions for some of the key parameters of the model, such as the integrated "charge" $ξ$, depending on the matter distribution of the system, and the 4-vector $K^μ=\{K^0,\boldsymbol{K}\}$ connected with the nonminimal function $F$. Thus, we phenomenologically treat them as free parameters, and preliminarily infer some indications on their admissible values according to the most recent Solar System's planetary ephemerides. From the latest determinations of the corrections $Δ\dot\varpi$ to the standard perihelion precessions, estimated by the astronomers who produced the EPM2011 ephemerides without modeling the theory considered here, we preliminarily obtain $|ξK|\lesssim 0.1$ kg s$^{-1}$ for Mars. From guesses on what could be the current bounds on the secular rates of change of the planetary semimajor axes, we get $|ξK^0|\lesssim 1249$ kg s$^{-1}$ for Mars. More effective constraints could be posed by reprocessing the same planetary data sets with dedicated dynamical models including the effects studied here, and explicitly estimating the associated parameters. COBE and GP-B terrestrial satellites yield $|ξK|\lesssim 2\times 10^{-4}$ kg s$^{-1}$ and $|ξK_0|\lesssim 2\times 10^{-10}$ kg s$^{-1}$.

gr-qc↗
arXiv2014

Constraining the Preferred-Frame $α_1$, $α_2$ parameters from Solar System planetary precessions

Analytical expressions for the orbital precessions affecting the relative motion of the components of a local binary system induced by Lorentz-violating Preferred Frame Effects (PFE) are explicitly computed in terms of the PPN parameters $α_1$, $α_2$. A linear combination of the supplementary perihelion precessions of all the inner planets of the Solar System, able to remove the a-priori bias of unmodelled/mismodelled standard effects such as the general relativistic Lense-Thirring precessions and the classical rates due to the Sun's oblateness $J_2$, allows to infer $|α_1| \leq 6\times 10^{-6}, |α_2| \leq 3.5\times 10^{-5}$. Such bounds should be improved in the near future after processing the data that are being collected by the MESSENGER spacecraft, currently orbiting Mercury. Further improvements may come in the mid-future from the approved BepiColombo mission to Mercury. The constraint $|α_2|\leq 10^{-7}$ existing in the literature is critically discussed (Abridged).

gr-qc↗
arXiv2014

Two-body orbit expansion due to time-dependent relative acceleration rate of the cosmological scale factor

By phenomenologically assuming a slow temporal variation of the percent acceleration rate $\ddot S S^{-1}$ of the cosmic scale factor $S(t)$, it is shown that the orbit of a local binary undergoes a secular expansion. To first order in the power expansion of $\ddot S S^{-1}$ around the present epoch $t_0$, a non-vanishing shift per orbit $\left\langleΔr\right\rangle$ of the two-body relative distance $r$ occurs for eccentric trajectories. A general relativistic expression, which turns out to be cubic in the Hubble parameter $H_0$ at the present epoch, is explicitly calculated for it in the case of matter-dominated epochs with Dark Energy. For a highly eccentric Oort comet orbit with period $P_{\rm b}\approx 31$ Myr, the general relativistic distance shift per orbit turns out to be of the order of $\left\langleΔr\right\rangle\approx 70$ km. For the Large Magellanic Cloud, assumed on a bound elliptic orbit around the Milky Way, the shift per orbit is of the order of $\left\langleΔr\right\rangle\approx 2-4$ pc. Our result has a general validity since it holds in any cosmological model admitting the Hubble law and a slowly varying $\ddot S S^{-1}(t)$. More generally, it is valid for an arbitrary Hooke-like extra-acceleration whose \virg{elastic} parameter $\mathcal{K}$ is slowly time-dependent, irrespectively of the physical mechanism which may lead to it. The coefficient $\mathcal{K}_1$ of the first-order term of the power expansion of $\mathcal{K}(t)$ can be preliminarily constrained in a model-independent way down to a $\mathcal{K}_1\lesssim 2\times 10^{-13}$ yr$^{-3}$ level from latest Solar System's planetary observations. The radial velocities of the double lined spectroscopic binary $α$ Cen AB yield $\mathcal{K}_1\lesssim 10^{-8}$ yr$^{-3}$.

gr-qc↗
arXiv2014

On a recent preliminary study for the measurement of the Lense-Thirring effect with the Galileo satellites

It has been recently proposed to combine the node drifts of the future constellation of 27 Galileo spacecraft together with those of the existing LAGEOS-type satellites to improve the accuracy of the past and ongoing tests of the Lense-Thirring (LT) effect by removing the bias of a larger number of even zonal harmonics $J_{\ell}$ than either done or planned so far. Actually, it seems a difficult goal to be realistically achieved for a number of reasons. First, the LT range signature of a Galileo-type satellite is as little as $0.5$ mm over 3-days arcs, corresponding to a node rate of just $\dotΩ_{\rm LT}=2$ milliarcseconds per year (mas yr$^{-1}$). Some tesseral and sectorial ocean tides such as $K_1,K_2$ induce long-period harmonic node perturbations with frequencies which are integer multiples of the extremely slow Galileo's node rate $\dotΩ$ completing a full cycle in about 40 yr. Thus, over time spans $T$ of some years they would act as superimposed semi-secular aliasing trends. Since the coefficients of the $J_{\ell}$-free multisatellite linear combinations are determined only by the semimajor axis $a$, the eccentricity $e$ and the inclination $I$, which are nominally equal for all the Galileo satellites, it is not possible to include all of them. Even by using only one Galileo spacecraft together with the LAGEOS family would be unfeasible because the resulting Galileo coefficient would be $\gtrsim 1$, thus enhancing the aliasing impact of the uncancelled non-conservative and tidal perturbations.

gr-qc↗
arXiv2013

Commentary to "LARES successfully launched in orbit: Satellite and mission description" by A. Paolozzi and I. Ciufolini

We comment on some statements in a recent paper by Paolozzi and Ciufolini concerning certain remarks raised by us on the realistic accuracy obtainable in testing the general relativistic Lense-Thirring effect in the gravitational field of the Earth with the newly launched LARES satellite together with the LAGEOS and LAGEOS II spacecraft in orbit for a long time. The orbital configuration of LARES is different from that of the originally proposed LAGEOS-3. Indeed, while the latter one should have been launched to the same altitude of LAGEOS (i.e. about $h_{\rm L}=5890$ km) in an orbital plane displaced by $180$ deg with respect to that of LAGEOS ($I_{\rm L}=110$ deg, $I_{\rm L3}=70$ deg), LARES currently moves at a much smaller altitude (about $h_{\rm LR}=1440$ km) and at a slightly different inclination ($I_{\rm LR} = 69.5$ deg). As independently pointed out in the literature by different authors, the overall accuracy of a LARES-LAGEOS-LAGEOS II Lense-Thirring test may be unfavorably \textcolor{black}{impacted} by the lower altitude of LARES with respect to the expected $\approx 1%$ level claimed by Ciufolini \textit{et al.} because of an enhanced sensitivity to the low-degree even zonal geopotential coefficients inducing orbital precessions competing with the relativistic ones. Concerning the previous tests performed with the combined nodes of only LAGEOS and LAGEOS II, an independent analysis recently appeared in the literature indirectly confirms that the total uncertainty in them is likely far from being as little as $10%$.

gr-qc↗