Asteroids in the Inner Solar System II - Observable Properties

This paper presents synthetic observations of long-lived, coorbiting asteroids of Mercury, Venus, the Earth and Mars. Our sample is constructed by taking the limiting semimajor axes, differential longitudes and inclinations for long-lived stability provided by simulations. The intervals are randomly populated with values to create initial conditions. These orbits are re-simulated to check that they are stable and then re-sampled every 2.5 years for 1 million years. The Mercurian sample contains only horseshoe orbits, the Martian sample only tadpoles. For both Venus and the Earth, the greatest concentration of objects on the sky occurs close to the classical Lagrange points at heliocentric ecliptic longitudes of 60 and 300 degrees. The distributions are broad especially if horseshoes are present in the sample. The full-width half maximum (FWHM) in heliocentric longitude for Venus is 325 degrees and for the Earth is 328 degrees. The mean and most common velocity of these coorbiting satellites coincides with the mean motion of the parent planet, but again the spread is wide with a FWHM for Venus of 27.8 arcsec/hr and for the Earth of 21.0 arcsec/hr. For Mars, the greatest concentration on the sky occurs at heliocentric ecliptic latitudes of 12 degrees. The peak of the velocity distribution occurs at 65 arcsec/hr, significantly less than the Martian mean motion, while its FWHM is 32.3 arcsec/hr. The case of Mercury is the hardest of all, as the greatest concentration occurs at heliocentric longitudes close to the Sun.Comment: 16 pages, 11 figures, Monthly Notices (in press). Higher quality figures available at http://www-thphys.physics.ox.ac.uk/users/WynEvans/home.htm

Asteroids Observed by The Sloan Digital Sky Survey

We announce the first public release of the SDSS Moving Object Catalog, with SDSS observations for 58,117 asteroids. The catalog lists astrometric and photometric data for moving objects observed prior to Dec 15, 2001, and also includes orbital elements for 10,592 previously known objects. We analyze the correlation between the orbital parameters and optical colors for the known objects, and confirm that asteroid dynamical families, defined as clusters in orbital parameter space, also strongly segregate in color space. Their distinctive optical colors indicate that the variations in chemical composition within a family are much smaller than the compositional differences between families, and strongly support earlier suggestions that asteroids belonging to a particular family have a common origin.Comment: 6 pages, 1 color figure, to be presented at "Astronomical Telescopes & Instrumentation", SPIE 200

Apsidal Alignment in Upsilon Andromedae

One of the parameters fitted by Doppler radial velocity measurements of extrasolar planetary systems is omega, the argument of pericenter of a given planet's orbit referenced to the plane of the sky. Curiously, the omega's of the outer two planets orbiting Upsilon Andromedae are presently nearly identical: Delta-omega = omega_D - omega_C = 4.8 deg +/- 4.8 deg (1 sigma). This observation is least surprising if planets C and D occupy orbits that are seen close to edge-on (sin i_C, sin i_D > 0.5) and whose mutual inclination Theta does not exceed 20 deg. In this case, planets C and D inhabit a secular resonance in which Delta-omega librates about 0 deg with an amplitude of 30 deg and a period of 4000 yr. The resonant configuration spends about one-third of its time with |Delta-omega| 40 deg, either Delta-omega circulates or the system is unstable. This instability is driven by the Kozai mechanism which couples the eccentricity of planet C to Theta to drive the former quantity to values approaching unity. Our expectation that Theta < 20 deg suggests that planets C and D formed in a flattened, circumstellar disk, and may be tested by upcoming astrometric measurements with the FAME satellite.Comment: Refereed version, accepted by AJ, to appear in September 2001 issu

Asteroids in the Inner Solar System I - Existence

Ensembles of in-plane and inclined orbits in the vicinity of the Lagrange points of the terrestrial planets are integrated for up to 100 million years. The integrations incorporate the gravitational effects of Sun and the eight planets (Pluto is neglected). Mercury is the least likely planet, as it is unable to retain tadpole orbits over 100 million year timescales. Both Venus and the Earth are much more promising, as they possess rich families of stable tadpole and horseshoe orbits. Our survey of Trojans in the orbital plane of Venus is undertaken for 25 million years. Some 40% of the survivors are on tadpole orbits. For the Earth, the integrations are pursued for 50 million years. The stable zones in the orbital plane are larger for the Earth than for Venus, but fewer of the survivors are tadpoles. Both Venus and the Earth also have regions in which inclined test particles can endure near the Lagrange points. For Venus, only test particles close to the orbital plane are stable. For the Earth, there are two bands of stability, one at low inclinations (i < 16 degrees) and one at moderate inclinations (between 24 degrees and 34 degrees). The inclined test particles that evade close encounters are primarily moving on tadpole orbits. Our survey of in-plane test particles near the Martian Lagrange points shows no survivors after 60 million years. Low inclination test particles do not persist, as their inclinations are quickly increased until the effects of a secular resonance with Jupiter cause de-stabilisation. Numerical integrations of inclined test particles for timespans of 25 million years show stable zones for inclinations between 14 and 40 degrees.Comment: 20 pages, 21 figures, Monthly Notices (in press

Differential regulation of glucocorticoid receptor messenger RNA (GR-mRNA) by maternal deprivation in immature rat hypothalamus and limbic regions.

Maternal deprivation (MDep) of neonatal rats significantly influences the hypothalamic-pituitary-adrenal (HPA) axis. This study hypothesized that GR-mRNA modulation constituted an early, critical mechanism for the acute effects of MDep on neuroendocrine stress-responses. GR-mRNA hybridization signal in hippocampal CA1, hypothalamic paraventricular nucleus (PVN) and frontal cortex was significantly reduced immediately following 24 h MDep. In amygdala, cingulate cortex, PVN and CA1, apparent gender-dependent MDep effects on GR-mRNA expression were observed, without significant differences in absolute levels. Thus, rapid, region-specific MDep effects on GR-mRNA expression in HPA-regulating areas are shown, consistent with involvement of GR-expression in mechanisms of MDep influence on HPA tone