arXiv subjects

Darryl Z. Seligman

Publications and source records attributed to Darryl Z. Seligman.

57 records · Page 4Linked to original sources

arXiv2022

The Population of Interstellar Objects Detectable with the LSST and Accessible for $\textit{In Situ}$ Rendezvous with Various Mission Designs

The recently discovered population of interstellar objects presents us with the opportunity to characterize material from extrasolar planetary and stellar systems up close. The forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented increase in sensitivity to these objects compared to the capabilities of currently operational observational facilities. We generate a synthetic population of `Oumuamua-like objects drawn from their galactic kinematics, and identify the distribution of impact parameters, eccentricities, hyperbolic velocities and sky locations of objects detectable with the LSST, assuming no cometary activity. This population is characterized by a clustering of trajectories in the direction of the solar apex and anti-apex, centered at orbital inclinations of $\sim90^\circ$. We identify the ecliptic or solar apex as the optimal sky locations to search for future interstellar objects as a function of survey limiting magnitude. Moreover, we identify the trajectories of detectable objects that will be reachable for \textit{in-situ} rendezvous with a dedicated mission with the capabilities of the forthcoming \textit{Comet Interceptor} or proposed \textit{Bridge} concept. By scaling our fractional population statistics with the inferred spatial number density, we estimate that the LSST will detect of order $\sim 15$ interstellar objects over the course of its $\sim10$ year observational campaign. Furthermore, we find that there should be $\sim1-3$ and $\sim0.0007-0.001$ reachable targets for missions with propulsion capabilities comparable to \textit{Bridge} and \textit{Comet Interceptor}, respectively. These numbers are lower limits, and will be readily updateable when the number density and size frequency distribution of interstellar objects are better constrained.

astro-ph.EP↗

arXiv2022

Testing Self-Organized Criticality Across the Main Sequence using Stellar Flares from TESS

Self-organized criticality describes a class of dynamical systems that maintain themselves in an attractor state with no intrinsic length or time scale. Fundamentally, this theoretical construct requires a mechanism for instability that may trigger additional instabilities locally via dissipative processes. This concept has been invoked to explain nonlinear dynamical phenomena such as featureless energy spectra that have been observed empirically for earthquakes, avalanches, and solar flares. If this interpretation proves correct, it implies that the solar coronal magnetic field maintains itself in a critical state via a delicate balance between the dynamo-driven injection of magnetic energy and the release of that energy via flaring events. All-sky high-cadence surveys like the Transiting Exoplanet Survey Satellite (TESS) provide the necessary data to compare the energy distribution of flaring events in stars of different spectral types to that observed in the Sun. We identified $\sim 10^6$ flaring events on $\sim 10^5$ stars observed by TESS at 2-minute cadence. By fitting the flare frequency distribution for different mass bins, we find that all main sequence stars exhibit distributions of flaring events similar to that observed in the Sun, independent of their mass or age. This may suggest that stars universally maintain a critical state in their coronal topologies via magnetic reconnection events. If this interpretation proves correct, we may be able to infer properties of magnetic fields, interior structure, and dynamo mechanisms for stars that are otherwise unresolved point sources.

astro-ph.SR↗

arXiv2021

A Sublime Opportunity: The Dynamics of Transitioning Cometary Bodies and the Feasibility of $\textit{In Situ}$ Observations of The Evolution of Their Activity

The compositional and morphological evolution of minor bodies in the Solar System is primarily driven by the evolution of their heliocentric distances, as the level of incident solar radiation regulates cometary activity. We investigate the dynamical transfer of Centaurs into the inner Solar System, facilitated by mean motion resonances with Jupiter and Saturn. The recently discovered object, P/2019 LD2, will transition from the Centaur region to the inner Solar System in 2063. In order to contextualize LD2, we perform N-body simulations of a population of Centaurs and JFCs. Objects between Jupiter and Saturn with Tisserand parameter $T_J\sim$3 are transferred onto orbits with perihelia $q<4$au within the next 1000 years with notably high efficiency. Our simulations show that there may be additional LD2-like objects transitioning into the inner Solar System in the near-term future, all of which have low $Δ$V with respect to Jupiter. We calculate the distribution of orbital elements resulting from a single Jovian encounter and show that objects with initial perihelia close to Jupiter are efficiently scattered to $q<4$au. Moreover, approximately $55\%$ of the transitioning objects in our simulated population experience at least 1 Jovian encounter prior to reaching $q<4$au. We demonstrate that a spacecraft stationed near Jupiter would be well-positioned to rendezvous, orbit match, and accompany LD2 into the inner Solar System, providing an opportunity to observe the onset of intense activity in a pristine comet $\textit{in situ}$. Finally, we discuss the prospect of identifying additional targets for similar measurements with forthcoming observational facilities.

astro-ph.EP↗