The Arecibo Observatory is committed to operating as safely as possible during the COVID-19 pandemic and is continuing the AO Seminar Series virtually via Zoom. We encourage you to join our email list to be notified of upcoming seminars here. If you are working with AO data and would like to present your research as a seminar, please contact Maxime Devogele (firstname.lastname@example.org).
1/19/2022 Searching for Pulsars and Fast Radio Bursts: the Legacy of the Arecibo PALFA Survey
1/21/2022 Ices, Organics, and Cryovolcanism in the Outer Solar System
Date Name Affiliation Title Abstract 1/21/2022 Dr. Dale Cruikshank Ices, Organics, and Cryovolcanism in the Outer Solar System View Abstract 1/19/2022 Dr. Emilie Parent Institute of Space Sciences, Barcelona, Spain Searching for Pulsars and Fast Radio Bursts: the Legacy of the Arecibo PALFA Survey View AbstractPulsar astrophysics has greatly impacted a variety of fields in fundamental physics, from gravitational radiation to the extreme states of matter. Conducting large-scale surveys with sensitive radio telescopes to discover more pulsars has been a gateway to new science. One such survey was the Arecibo PALFA survey, the deepest of its kind, which targeted the Galactic plane to discover new radio pulsars and fast transients. In this talk, I will give an overview of PALFA’s most groundbreaking discoveries, which includes relativistic double neutron star systems and the first repeating fast radio burst. I will also present some of the survey’s latest results.
Date Name Affiliation Title Abstract 12/03/21 Dr. Lisa Prato Lowell Observatory Finding the Youngest Exoplanets and Understanding Their Formation View AbstractIn spite of the unexpected configurations of novel planets around stars other than the Sun, such as giant hot Jupiters with periods of days and tightly packed multi-planet systems like the passel of small planets around Trappist-1, astronomers have a lot of theories and ideas about how exoplanets form and arrive in their orbits. However, we are not sure yet about what is actually happening and which processes dominate. In order to decode the planet formation process, we require observations of young planets in the act of forming. I will outline my team’s search for the youngest exoplanets and describe some of our approaches for young planet detection and candidate identification. 10/10/21 Dr. Leonardo Supan Instituto de Astronomía y Física del Espacio CONICET Low-frequency radio observations of Galactic SNRs as indicators of interaction with their environments View AbstractRadio emission at low frequencies (< 100 MHz) from supernova remnants (SNRs) encodes a wealth of information not only about the physical conditions of the expanding shock waves, but also about the local and intervening interstellar medium, notably the ionised component through thermal absorption. This talk presents a recent observational analysis conducted on a set of 14 Galactic SNRs selected from the 74 MHz Very Large Array Low-Frequency Sky Survey Redux (VLSSr). We combine the VLSSr data with measurements, when available, from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey, together with publicly available images and flux estimates at higher radio frequencies. Our analysis reveals extrinsic low-frequency thermal absorption in nine of the 14 SNRs. In five cases the absorption is caused by ionised gas in thermal sources located either along the line of sight (likely from extended HII region envelopes) or in the immediate environment of the S! NR. In th e remaining four cases the absorption occurs in the ionised interface between SNR forward shocks and the surrounding medium, a scenario previously revealed in only a few cases. Our results demonstrate that resolved observations of SNRs at low radio frequencies provide unique ways to detect ionised gas in the interaction zone between the remnants and their environs, and will certainly emerge as a powerful tool as technical capabilities continue to improve sensitivity and angular resolution at long wavelengths. 5/26/21 Dr. Tarek Elgohary University of Central Florida Novel Techniques for Space Situational Awareness: Combining Multi-Node Space-Based Observations with High Fidelity Computations View AbstractIn this talk, novel analytical and computational techniques applied to space situational awareness (SSA) will be presented. First, A new method for inertial orbit estimation of an object, either known or unknown, adaptable to a network of observation satellites is presented. The observation satellites would only require a monocular camera for line of sight measurements. Total system observability is analyzed and the instantaneous observability (per node) is used to remove “bad” measurements from the system. The measurement model is used in an extended Kalman filter framework and the measurement noise nonlinear transformation is addressed. The method is shown to be highly accurate and adaptable to different dynamical models beyond Earth orbits. Second, a Taylor series based technique, Analytic Continuation, is implemented to develop a method for the computation of the gravity and drag perturbed State Transition Tensors incorporating adaptive time steps and expansion order. For the state transition matrix (STM), the method is validated for four types of orbits, LEO, MEO, GTO and HEO for 10 orbit periods. The accuracy of the STM is evaluated via RMS error for the unperturbed cases, symplectic check for the gravity perturbed cases and error propagation for the gravity and drag perturbed orbits. Results are compared against analytical and high order numerical solvers (ODE45, ODE113 and ODE87) in terms of accuracy. The results show that the method maintains double-precision accuracy for all test cases and 1-2 orders of magnitude improvement in linear prediction results compared to ODE87. The present approach is simple, adaptive and is shown to be readily expandable to compute the full spherical harmonics gravity perturb! ations as well as the higher order state transition tensors for both estimation and initial state uncertainty propagation purposes. Finally, a novel approach for accurate uncertainty propagation is presented for the orbit problem. In lieu of Monte Carlo methods, the proposed approach identifies the region of extreme probability at the time of interest, populates that region with structured points, and then identifies the associated probability based on the a-priori probability density function (PDF). This leads to an approximation for the non-linearly distorted non-Gaussian PDF at an arbitrary time t with a rigorous relationship to the a-priori probability density, and therefore doing any probabilistic analysis reduces to operations on simple interpolation functions. The algorithms aim at providing high-fidelity solutions for uncertainty propagation while mitigating the curse of dimensionality that plagues existing approaches. 5/1/21 Dr. Michael Busch University of California Los Angeles An Overview of Radar Speckle Tracking View AbstractRadar images of asteroids and other solar system targets frequently provide only ambiguous information on their spin states. Radar speckle tracking is a technique to obtain unambiguous information on the spins of selected radar targets, by tracking the motion of their radar echoes between multiple receive stations. I will review how radar speckle tracking works, its history using both the Arecibo planetary radar and the Goldstone Solar System Radar, and discuss possibilities for future speckle observations with a focus on near-Earth asteroid targets.