arXiv subjects

Jason H. Steffen

Publications and source records attributed to Jason H. Steffen.

101 records · Page 6Linked to original sources

arXiv2008

Constraints on chameleons and axion-like particles from the GammeV experiment

We present the most recent results of both aspects of the GammeV experiment. The first aspect is a search for axion-like particles using a variable baseline, "light-shining-through-a-wall" technique. This search excludes the particle interpretation of the PVLAS signal with high confidence. The second aspect of the GammeV experiment is a search for chameleon particles, scalar particles which may be responsible for the dark energy of the universe. This is accomplished by looking for a characteristic afterglow signature from a "particle-in-a-jar" experiment whereby chameleon particles become trapped in a region with a high magnetic field and slowly decay into detectable photons. This is the first use of this experimental technique to probe for these particles. We place interesting limits on a limited range of general chameleon models. These limits are complimentary to other experiments, such as torsion pendulum experiments, which probe for forces that would result from new scalar particles.

hep-ex↗

arXiv2008

A statistical mechanics model for free-for-all airplane passenger boarding

I present and discuss a model for the free-for-all passenger boarding which is employed by some discount air carriers. The model is based on the principles of statistical mechanics where each seat in the aircraft has an associated energy which reflects the preferences of the population of air travelers. As each passenger enters the airplane they select their seats using Boltzmann statistics, proceed to that location, load their luggage, sit down, and the partition function seen by remaining passengers is modified to reflect this fact. I discuss the various model parameters and make qualitative comparisons of this passenger boarding model with models which involve assigned seats. This model can also be used to predict the probability that certain seats will be occupied at different times during the boarding process. These results may be of value to industry professionals as a useful description of this boarding method. However, it also has significant value as a pedagogical tool since it is a relatively unusual application of undergraduate level physics and it describes a situation with which many students and faculty may be familiar.

physics.soc-ph↗

arXiv2008

Transits and secondary eclipses of HD 189733 with Spitzer

We present limits on transit timing variations and secondary eclipse depth variations at 8 microns with the Spitzer Space Telescope IRAC camera. Due to the weak limb darkening in the infrared and uninterrupted observing, Spitzer provides the highest accuracy transit times for this bright system, in principle providing sensitivity to secondary planets of Mars mass in resonant orbits. Finally, the transit data provides tighter constraints on the wavelength- dependent atmospheric absorption by the planet.

astro-ph↗

arXiv2008

Constraints on the angular distribution of satellite galaxies about spiral hosts

We present, using a novel technique, a study of the angular distribution of satellite galaxies around a sample of isolated, blue host galaxies selected from the sixth data release of the Sloan Digital Sky Survey. As a complement to previous studies we subdivide the sample of galaxies into bins of differing inclination and use the systematic differences that would exist between the different bins as the basis for our approach. We parameterize the cumulative distribution function of satellite galaxies and apply a maximum likelihood, Monte-Carlo technique to determine allowable distributions, which we show as an exclusion plot. We find that the allowed distributions of the satellites of spiral hosts are very nearly isotropic. We outline our formalism and our analysis and discuss how this technique may be refined for future studies and future surveys.

astro-ph↗

arXiv2008

Optimal boarding method for airline passengers

Using a Markov Chain Monte Carlo optimization algorithm and a computer simulation, I find the passenger ordering which minimizes the time required to board the passengers onto an airplane. The model that I employ assumes that the time that a passenger requires to load his or her luggage is the dominant contribution to the time needed to completely fill the aircraft. The optimal boarding strategy may reduce the time required to board and airplane by over a factor of four and possibly more depending upon the dimensions of the aircraft. In addition, knowledge of the optimal boarding procedure can inform decisions regarding changes to methods that are employed by a particular carrier. I explore some of the salient features of the optimal boarding method and discuss practical modifications to the optimal. Finally, I mention some of the benefits that could come from implementing an improved passenger boarding scheme.

physics.soc-ph↗

arXiv2007

Detecting and Characterizing Planetary Systems with Transit Timing

In the coming decades, research in extrasolar planets aims to advance two goals: 1) detecting and characterizing low-mass planets increasingly similar to the Earth, and 2) improving our understanding of planet formation. We present a new planet detection method that is capable of making large advances towards both of these objectives and describe a modest network of telescopes that is able to make the requisite observations. In a system where a known planet transits its host star, a second planet in that system will cause the time between transits to vary. These transit timing variations can be used to infer the orbital elements and mass of the perturbing planet even if it has a mass that is smaller than the mass of the Earth. This detection technique complements other techniques because it is most sensitive in mean-motion resonances where, due to degeneracies, other techniques have reduced sensitivity. Small ground-based observatories have already exceeded the photometric precision necessary to detect sub-Earth mass planets. However, TTV planet searches are currently limited by the relatively small number of high-precision transit data and insufficient observing time on existing telescopes. These issues will be compounded as the number of known transiting planets suitable for TTV study will increase substantially in the near future. A relatively modest investment in a ground-based network of small ($\sim 0.5 {\rm m}$ telescopes could provide the needed coverage and so dramatically increase the effectiveness of transit timing observations.

astro-ph↗

arXiv2006

Developments in Planet Detection using Transit Timing Variations

In a transiting planetary system, the presence of a second planet will cause the time interval between transits to vary. These transit timing variations (TTV) are particularly large near mean-motion resonances and can be used to infer the orbital elements of planets with masses that are too small to detect by any other means. I present the results of a study of simulated data where I show the potential that this planet detection technique has to detect and characterize secondary planets in transiting systems. These results have important ramifications for planetary transit searches since each transiting system presents an opportunity for additional discoveries through a TTV analysis. I present such an analysis for 13 transits of the HD 209458 system that were observed with the Hubble Space Telescope. This analysis indicates that a putative companion in a low-order, mean-motion resonance can be no larger than the mass of the Earth and constitutes, to date, the most sensitive probe for extrasolar planets that orbit main sequence stars. The presence or absence of small planets in low-order, mean-motion resonances has implications for theories of the formation and evolution of planetary systems. Since TTV is most sensitive in these regimes, it should prove a valuable tool not only for the detection of additional planets in transiting systems, but also as a way to determine the dominant mechanisms of planet formation and the evolution of planetary systems.

astro-ph↗

arXiv2006

A limit on the presence of Earth-mass planets around a Sun-like star

We present a combined analysis of all publicly available, visible HST observations of transits of the planet HD 209458b. We derive the times of transit, planet radius, inclination, period, and ephemeris. The transit times are then used to constrain the existence of secondary planets in the system. We show that planets near an Earth mass can be ruled out in low-order mean-motion resonance, while planets less than an Earth mass are ruled out in interior, 2:1 resonance. We also present a combined analysis of the transit times and 68 high precision radial velocity measurements of the system. These results are compared to theoretical predictions for the constraints that can be placed on secondary planets.

astro-ph↗

arXiv2006

Detecting New Planets in Transiting Systems

I present an initial investigation into a new planet detection technique that uses the transit timing of a known, transiting planet. The transits of a solitary planet orbiting a star occur at equally spaced intervals in time. If a second planet is present, dynamical interactions within the system will cause the time interval between transits to vary. These transit time variations can be used to infer the orbital elements of the unseen, perturbing planet. I show analytic expressions for the amplitude of the transit time variations in several limiting cases. Under certain conditions the transit time variations can be comparable to the period of the transiting planet. I also present the application of this planet detection technique to existing transit observations of the TrES-1 and HD209458 systems. While no convincing evidence for a second planet in either system was found from those data, I constrain the mass that a perturbing planet could have as a function of the semi-major axis ratio of the two planets and the eccentricity of the perturbing planet. Near low-order, mean-motion resonances (within about 1% fractional deviation), I find that a secondary planet must generally have a mass comparable to or less than the mass of the Earth--showing that these data are the first to have sensitivity to sub Earth-mass planets orbiting main sequence stars. These results show that TTV will be an important tool in the detection and characterization of extrasolar planetary systems.

astro-ph↗

arXiv2005

An analysis of the transit times of TrES-1b

The presence of a second planet in a known, transiting-planet system will cause the time between transits to vary. These variations can be used to constrain the orbital elements and mass of the perturbing planet. We analyse the set of transit times of the TrES-1 system given in Charbonneau et al. (2005). We find no convincing evidence for a second planet in the TrES-1 system from that data. By further analysis, we constrain the mass that a perturbing planet could have as a function of the semi-major axis ratio of the two planets and the eccentricity of the perturbing planet. Near low-order, mean-motion resonances (within ~1% fractional deviation), we find that a secondary planet must generally have a mass comparable to or less than the mass of the Earth--showing that this data is the first to have sensitivity to sub Earth-mass planets. We compare the sensitivity of this technique to the mass of the perturbing planet with future, high-precision radial velocity measurements.

astro-ph↗

arXiv2005

Symmetry in a Perturbed Optical System

This paper investigates the effects that perturbations to an optical system, such as translations or rotations of the optical elements, have on the final location where a light ray strikes a detector. Symmetry arguments are employed to give selection rules for the combinations of those perturbations that can affect the light ray. It is shown that a ``Transverse Parity'' can be assigned to each type of perturbation and that only combinations with an overall odd parity will produce an effect. Some examples of how these results can be applied to undergraduate classroom or laboratory courses are given.

physics.ed-ph↗