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Lorenzo Iorio

Publications and source records attributed to Lorenzo Iorio.

At least 199 records · Page 11Linked to original sources
arXiv2008

Prospects for measuring the moment of inertia of pulsar PSR J0737-3039A

Here we consider the possibility of measuring at 10% or better the moment of inertia I of the J0737-3039A via the gravitomagnetic spin-orbit periastron precession. It turns out that the prospect of measuring the moment of inertia of PSR J0737-3039A at 10% accuracy or better seems unlikely given the limitations to the precision with which the system's basic binary and post-Keplerian parameters can be measured via radio timing.

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arXiv2008

Solar System motions and the cosmological constant: a new approach

We use the corrections to the Newton-Einstein secular precessions of the longitudes of perihelia of some planets (Mercury, Earth, Mars, Jupiter, Saturn) of the Solar System, phenomenologically estimated as solve-for parameters by the Russian astronomer E.V. Pitjeva in a global fit of almost one century of data with the EPM2004 ephemerides, in order to put on the test the expression for the perihelion precession induced by an uniform cosmological constant Lambda in the framework of the Schwarzschild-de Sitter (or Kottler) space-time. We compare such an extra-rate to the estimated corrections to the planetary perihelion precessions by taking their ratio for different pairs of planets instead of using one perihelion at a time for each planet separately, as done so far in literature. The answer is neatly negative, even by further re-scaling by a factor 10 (and even 100 for Saturn) the errors in the estimated extra-precessions of the perihelia released by Pitjeva. Our conclusions hold also for any other metric perturbation having the same dependence on the spatial coordinates, as those induced by other general relativistic cosmological scenarios and by many modified models of gravity. Currently ongoing and planned interplanetary spacecraft-based missions should improve our knowledge of the planets' orbits allowing for more stringent constraints.

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arXiv2008

Constraining MOND with Solar System dynamics

In this letter we investigate the deep Newtonian regime of the MOND paradigm from a purely phenomenological point of view by exploiting the least-square estimated corrections to the secular rates of the perihelia of the inner and of some of the outer planets of the Solar System by E.V. Pitjeva with the EPM2004 ephemerides. By using $μ(x)\approx 1-k_0(1/x)^n$ for the interpolating MONDian function, and by assuming that $k_0$, considered body-independent so to avoid violations of the equivalence principle, experiences no spatial variations throughout the Solar System we tightly constrain $n$ with the ratios of the perihelion precessions for different pairs of planets. We find that the range $1\leq n\leq 2$ is neatly excluded at much more than $3-σ$ level. Such a test would greatly benefit from the use of extra-precessions of perihelia independently estimated by other groups as well.

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arXiv2008

Determination of tidal distortion in the eclipsing binary system V621 Cen by means of deviations from the third Kepler law

In this paper we determine the tidal distortion parameter k_m of the secondary partner (mass loser) of the semi-detached eclipsing binary system V621 Cen by comparing the phenomenologically determined orbital period P_b=3.683549(11) d to the Keplerian one P^Kep computed with the values of the relevant system's parameters determined independently of the third Kepler law itself. Our result is k_m = -1.5 +/- 0.6. Using the periastron precession, as traditionally done with other eclipsing binaries in eccentric orbits, would have not been possible because of the circularity of the V621 Cen path.

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arXiv2007

Jupiter, Saturn and the Pioneer anomaly: a planetary-based independent test

In this paper we use the ratio of the corrections to the standard Newtonian/Einsteinian secular precessions of the longitudes of perihelia of Jupiter and Saturn, recently estimated by the Russian astronomer E.V. Pitjeva by fitting almost one century of data with the EPM ephemerides, to make an independent, planetary-based test of the hypothesis that the Pioneer anomaly (PA), as it is presently known in the 5-10 AU region, is of gravitational origin. Accounting for the errors in the determined apsidal extra-rates and in the values of the PA acceleration at the orbits of Jupiter and Saturn the answer is negative. If and when the re-analysis of the entire Pioneer 10/11 will be completed more firm conclusions could be reached. Moreover, it would also be important that other teams of astronomers estimate independently their own corrections to the perihelion precessions.

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arXiv2007

Perspectives in measuring the PPN parameters beta and gamma in the Earth's gravitational fields with the CHAMP/GRACE models

The current bounds on the PPN parameters gamma and beta are of the order of 10^-4-10^-5. Various missions aimed at improving such limits by several orders of magnitude have more or less recently been proposed like LATOR, ASTROD, BepiColombo and GAIA. They involve the use of various spacecraft, to be launched along interplanetary trajectories, for measuring the effects of the solar gravity on the propagation of electromagnetic waves. In this paper we investigate what is needed to measure the combination nu=(2+2gamma-beta)/3 of the post-Newtonian gravitoelectric Einstein perigee precession of a test particle to an accuracy of about 10^-5 with a pair of drag-free spacecraft in the Earth's gravitational field. It turns out that the latest gravity models from the dedicated CHAMP and GRACE missions would allow to reduce the systematic error of gravitational origin just to this demanding level of accuracy. In regard to the non-gravitational errors, the spectral noise density of the drag-free sensors required to reach such level of accuracy would amounts to 10^-8-10^-9 cm s^-2 Hz^-1/2 over very low frequencies. Although not yet obtainable with the present technologies, such level of compensation is much less demanding than those required for, e.g., LISA. As a by-product, an independent measurement of the post-Newtonian gravitomagnetic Lense-Thirring effect with a 0.9% accuracy would be possible as well. The forthcoming Earth gravity models from CHAMP and GRACE will further reduce the systematic gravitational errors in both of such tests.

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arXiv2007

The post-Newtonian mean anomaly advance as further post-Keplerian parameter in pulsar binary systems

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 \dotω. 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.

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arXiv2007

Astronomical constraints on some long-range models of modified gravity

In this paper we use the corrections to the usual Newton-Einstein secular precessions of the perihelia of the inner planets of the Solar System, phenomenologically estimated as solve-for parameters by the Russian astronomer E.V. Pitjeva by fitting almost one century of data with the EPM2004 ephemerides, in order to constrain some long-range models of modified gravity recently put forth to address the dark energy and dark matter problems. The models examined here are the four-dimensional ones obtained with the addition of inverse powers and logarithm of some curvature invariants, and the multidimensional braneworld model by Dvali, Gabadadze and Porrati (DGP). After working out the analytical expressions of the secular perihelion precessions induced by the corrections to the Newtonian potential of such models, we compare them to the estimated corrections to the rates of perihelia by taking their ratio for different pairs of planets instead of using one perihelion at a time for each planet separately, as done so far in literature. As a result, the curvature invariants-based models are ruled out, even by re-scaling by a factor 10 the errors in the planetary orbital parameters estimated by Pitjeva. Less neat is the situation for the DGP model. Only the general relativistic Lense-Thirring effect, not included, as the other exotic models considered here, by Pitjeva in the dynamical force models used in the estimation process, passes such a test. It would be important to repeat the present analysis by using corrections to the precessions of perihelia independently estimated by other teams of astronomers as well, but, at present, such rates are not yet available.

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arXiv2007

LARES/WEBER-SAT and the equivalence principle

It has often been claimed that the proposed Earth artificial satellite LARES/WEBER-SAT-whose primary goal is, in fact, the measurement of the general relativistic Lense-Thirring effect at a some percent level-would allow to greatly improve, among (many) other things, the present-day (10^-13) level of accuracy in testing the equivalence principle as well. Recent claims point towards even two orders of magnitude better, i.e. 10^-15. In this note we show that such a goal is, in fact, unattainable by many orders of magnitude being, instead, the achievable level of the order of 10^-9.

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arXiv2007

Constraints on the range lambda of Yukawa-like modifications to the Newtonian inverse-square law of gravitation from Solar System planetary motions

In this paper we use the latest corrections to the Newton-Einstein secular perihelion rates of some planets of the Solar System, phenomenologically estimated with the EPM2004 ephemerides by the Russian astronomer E.V. Pitjeva, to put severe constraints on the range parameter lambda characterizing the Yukawa-like modifications of the Newtonian inverse-square law of gravitation. It turns out that the range cannot exceed about one tenth of an Astronomical Unit. We assumed neither equivalence principle violating effects nor spatial variations of $α$ and $λ$. This finding may have important consequences on all the modified theories of gravity involving Yukawa-type terms with range parameters much larger than the Solar System size. However, caution is advised since we, currently have at our disposal only the periehlion extra-rates estimated by Pitjeva: if and when other groups will estimate their own corrections to the secular motion of perihelia, more robust and firm tests may be conducted.

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arXiv2007

Dynamical constraints on some orbital and physical properties of the WD0137-349 A/B binary system

In this paper I deal with the WD0137-349 binary system consisting of a white dwarf (WD) and a brown dwarf (BD) in a close circular orbit of about 116 min. I, first, constrain the admissible range of values for the inclination i by noting that, from looking for deviations from the third Kepler law, the quadrupole mass moment Q would assume unlikely large values, incompatible with zero at more than 1-sigma level for i < 35 deg and i > 43 deg. Then, by conservatively assuming that the most likely values for i are those that prevent such an anomalous behavior of Q, i.e. those for which the third Kepler law is an adequate modeling of the orbital period, I obtain i=39 +/- 2 deg. Such a result is incompatible with the value i=35 deg quoted in literature by more than 2 sigma. Conversely, it is shown that the white dwarf's mass range obtained from spectroscopic measurements is compatible with my experimental range, but not for i=35 deg. As a consequence, my estimate of $i$ yields an orbital separation of a=(0.59 +/- 0.05)R_Sun and an equilibrium temperature of BD of T_eq=(2087 +/- 154)K which differ by 10% and 4%, respectively, from the corresponding values for i=35 deg.

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arXiv2007

Constraining models of modified gravity with the double pulsar PSR J0737-3039A/B system

In this paper we use Delta P = -1.772341 +/- 13.153788 s between the phenomenologically determined orbital period P_b of the PSR J0737-3039 double pulsar system and the purely Keplerian period P^(0)=2π\sqrt{a^3/G(m_A+m_B)} calculated with the system's parameters, determined independently of the third Kepler law itself, in order to put constraints on some models of modified gravity (f(R), Yukawa-like fifth force, MOND). The major source of error affecting Delta P is not the one in the phenomenologically measured period (δP_b=4 10^-6 s), but the systematic uncertainty δP^(0) in the computed Keplerian one due to the relative semimajor axis a mainly caused, in turn, by the errors in the ratio R of the pulsars' masses and in sin i. We get |κ|< 0.8 10^-26 m^-2 for the parameter that in the f(R) framework is a measure of the non linearity of the theory, |α|< 5.5 10^-4 for the fifth-force strength parameter (for λ\approx a=0.006 AU). The effects predicted by the strong-acceleration regime of MOND are far too small to be constrained with some effectiveness today and in the future as well. In view of the continuous timing of such an important system, it might happen that in the near future it will be possible to obtain somewhat tighter constraints.

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arXiv2007

The impact of the Kuiper Belt Objects and of the asteroid ring on future high-precision relativistic Solar System tests

We preliminarily investigate the impact of the Kuiper Belt Objects (KBOs) and of the asteroid ring on some proposed high-precision tests of Newtonian and post-Newtonian gravity to be performed in the Solar System by means of spacecraft in heliocentric \approx 1 AU orbits and accurate orbit determination of some of the inner planets. It turns out that the Classical KBOSs (CKBOS), which amount to \approx 70% of the observed population of Trans-Neptunian bodies, induce a systematic secular error of about 1 m after one year in the transverse direction T of the orbit of a test particle orbiting at 1 AU from the Sun. For Mercury the ratios of the secular perihelion precessions induced by CKBOs to the ones induced by the general relativity and the solar oblateness J_2 amount to 6 10^-7 and 8 10^-4, respectively. The secular transverse perturbation induced on a \approx 1 AU orbit by the asteroid ring, which globally accounts for the action of the minor asteroids whose mass is about 5 10^-10 solar masses, is 10 m yr^-1; the bias on the relativistic and J_2 Mercury perihelion precessions is 6.1 10^-6 and 1 10^-2, respectively. Given the very ambitious goals of many expensive and complex missions aimed to testing gravitational theories to unprecedented levels of accuracy, these notes may suggest further and more accurate investigations of such sources of potentially insidious systematic bias.

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arXiv2007

Testing frame-dragging with the Mars Global Surveyor spacecraft in the gravitational field of Mars

In this paper we propose an interpretation of the time series of the RMS overlap differences of the out-of-plane part $N$ of the orbit of the Martian polar orbiter Mars Global Surveyor (MGS) over a time span Delta P of about 5 years (14 November 1999-14 January 2005) in terms of the general relativistic gravitomagnetic Lense-Thirring effect. It turns out that the average of such a time series over Delta P, normalized to the predicted Lense-Thirring out-of-plane mean shift over the same time span, is μ= 1.0018 +/- 0.0053. A linear fit of the considered time series over Delta P yields a normalized slope 1.1 +/- 0.3 strengthening our interpretation of the determined MGS out-of-plane features of motion as due to the gravitomagnetic force of Mars.

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arXiv2007

First preliminary tests of the general relativistic gravitomagnetic field of the Sun and new constraints on a Yukawa-like fifth force from planetary data

The general relativistic Lense-Thirring precessions of the perihelia of the inner planets of the Solar System are about 10^-3 arcseconds per century. Recent improvements in planetary orbit determination may yield the first observational evidence of such a tiny effect. Indeed, corrections to the known perihelion rates of -0.0036 +/- 0.0050, -0.0002 +/- 0.0004 and 0.0001 +/- 0.0005 arcseconds per century were recently estimated by E.V. Pitjeva for Mercury, the Earth and Mars, respectively, on the basis of the EPM2004 ephemerides and a set of more than 317,000 observations of various kinds. The predicted relativistic Lense-Thirring precessions for these planets are -0.0020, -0.0001 and -3 10^-5 arcseconds per century, respectively and are compatible with the determined perihelia corrections. The relativistic predictions fit better than the zero-effect hypothesis, especially if a suitable linear combination of the perihelia of Mercury and the Earth, which a priori cancels out any possible bias due to the solar quadrupole mass moment, is considered. However, the experimental errors are still large. Also the latest data for Mercury processed independently by Fienga et al. with the INPOP ephemerides yield preliminary insights about the existence of the solar Lense-Thirring effect. The data from the forthcoming planetary mission BepiColombo will improve our knowledge of the orbital motion of this planet and, consequently, the precision of the measurement of the Lense-Thirring effect. As a by-product of the present analysis, it is also possible to constrain the strength of a Yukawa-like fifth force to a 10^-12-10^-13 level at scales of about one Astronomical Unit (10^11 m).

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arXiv2007

A comment on the paper "On the orbit of the LARES satellite", by I. Ciufolini

In this note we comment on a recent paper by I.Ciufolini about the possibility of placing the proposed terrestrial satellite LARES in a low-altitude, nearly polar orbit in order to measure the general relativistic Lense-Thirring effect with its node. Ciufolini claims that, for a departure of 4 deg in the satellite's inclination $i$ from the ideal polar configuration (i=90 deg), the impact of the errors in the even zonal harmonics of the geopotential, modelled with EIGEN-GRACE02S, would be nearly zero allowing for a few-percent measurement of the Lense-Thirring effect. Instead, we find that, with the same Earth gravity model and for the same values of the inclination, the upper bound of the systematic error due to the mismodelling in the even zonals amounts to 64% of the relativistic effect investigated.

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arXiv2007

Dynamical determination of the quadrupole mass moment of a white dwarf

In this letter we dynamically determine the quadrupole mass moment Q of the magnetic white dwarf WD 0137-349 by analyzing the period of the recently discovered brown dwarf moving around it in a close 2-hr orbit. It turns out that a purely Newtonian model for the orbit of WD 0137-349B, assumed circular and equatorial, is adequate, given the present-day accuracy in knowing the orbital parameters of such a binary system. Our result is Q=(-1.4615 +/- 0.9004) 10^47 kg m^2 for i=35 deg. It is able to accommodate the 3-sigma significant discrepancy of (1.0 +/- 0.3) 10^-8 s^-2 between the inverse square of the phenomenologically determined orbital period and the inverse square of the calculated Keplerian one. The impact of i, for which a range Delta i of possible values close to 35 deg is considered, is investigated as well.

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