Earth and Planetary Astrophysics (astro-ph.EP)

Abstract: The Virginid meteoroid streams produce a series of meteor showers active annually during February-May. A certain parent comet is not found but a related association of some showers with near-Earth asteroids was previously established and a cometary origin of these asteroids was suggested. We performed a new search for NEAs belonging to the Virginid asteroid-meteoroid complex. On the base of calculation of orbital evolution of a sample of NEAs and determination of theoretical features of related showers a search for observable active showers close to theoretically predicted ones was carried out. As a result, the predicted showers of 29 NEAs were identified with the showers of the Virginid complex. Revealed association points to a cometary nature of NEAs that are moving within the stream and may be considered as extinct fragments of a larger comet-progenitor of the Virginid asteroid-meteoroid complex.

Abstract: The relation between ice composition in the nucleus of comet 67P/Churyumov-Gerasimenko on the one hand and relative abundances of volatiles in the coma on the other hand is important for the interpretation of density measurements in the environment of the cometary nucleus. For the 2015 apparition, in situ measurements from the two ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) sensors COPS (COmet Pressure Sensor) and DFMS (Double Focusing Mass Spectrometer) determined gas densities at the spacecraft position for the 14 gas species H2O, CO2, CO, H2S, O2, C2H6, CH3OH, H2CO, CH4, NH3, HCN, C2H5OH, OCS, and CS2. We derive the spatial distribution of the gas emissions on the complex shape of the nucleus separately for 50 subintervals of the two-year mission time. The most active patches of gas emission are identified on the surface. We retrieve the relation between solar irradiation and observed emissions from these patches. The emission rates are compared to a minimal thermophysical model to infer the surface active fraction of H2O and CO2. We obtain characteristic differences in the ice composition close to the surface between the two hemispheres with a reduced abundance of CO2 ice on the northern hemisphere (locations with positive latitude). We do not see significant differences for the ice composition on the two lobes of 67P/C-G.

Abstract: The Nancy Grace Roman Space Telescope (Roman) is NASA's next astrophysics flagship mission, expected to launch in late 2026. As one of Roman's core community science surveys, the Galactic Bulge Time Domain Survey (GBTDS) will collect photometric and astrometric data for over 100 million stars in the Galactic bulge to search for microlensing planets. To assess the potential with which Roman can detect exoplanets via transit, we developed and conducted pixel-level simulations of transiting planets in the GBTDS. From these simulations, we predict that Roman will find between $\sim$60,000 and $\sim$200,000 transiting planets, over an order of magnitude more planets than are currently known. While the majority of these planets will be giants ($R_p>4R_\oplus$) on close-in orbits ($a<0.3$ au), the yield also includes between $\sim$7,000 and $\sim$12,000 small planets ($R_p<4 R_\oplus$). The yield for small planets depends sensitively on the observing cadence and season duration, with variations on the order of $\sim$10-20% for modest changes in either parameter, but is generally insensitive to the trade between surveyed area and cadence given constant slew/settle times. These predictions depend sensitively on the Milky Way's metallicity distribution function, highlighting an incredible opportunity to understand exoplanet demographics across a comprehensive set of stellar populations and Galactic environments.

Abstract: Of the three space telescopes launched so far to survey transiting extrasolar planets, CoRoT is unique in that it was the only one with spectral resolution, allowing for an extraordinary opportunity to study the reflective properties of exoplanets at different wavelengths. In this work, I present a systematic lightcurve analysis of the white-light and chromatic CoRoT lightcurves of CoRoT-1 in order to search for the secondary eclipse and orbital phase variation of the transiting extrasolar planet CoRoT-1 b, as well at search for any chromatic difference in the aforementioned effects. I manage to detect a significant secondary eclipse in the white lightcurve, and detect the eclipse marginally in all three of the color channels. However I am only able to significantly detect the planetary phase variation in the red channel lightcurve. The retrieved secondary eclipse depth is higher in the blue and green channels compared to the white and red, suggesting that CoRoT-1 b has a higher geometric albedo at shorter wavelengths. I also attempt to detect the secondary eclipse using TESS, but show that the available volume and precision of the data is not high enough to allow detection of the secondary eclipse.

Abstract: Asteroid diameters are traditionally difficult to estimate. When a direct measurement of the diameter cannot be made through either occultation or direct radar observation, the most common method is to approximate the diameter from infrared observations. Once the diameter is known, a comparison with visible light observations can be used to find the visible geometric albedo of the body. One of the largest datasets of asteroid albedos comes from the NEOWISE mission, which measured asteroid albedos both in the visible and infrared. We model these albedos as a function of proper elements available from the Asteroid Families Portal using an ensemble of neural networks. We find that both the visible and infrared geometric albedos are significantly correlated with asteroid position in the belt and occur in both asteroid families and in the background belt. We find that the ensemble's prediction reduces the average error in albedo by about 37% compared to a model that simply adopts an average albedo, with no regard for the dynamical state of the body. We then use this model to predict albedos for the half million main belt asteroids with proper elements available in the Asteroid Families Portal and provide the results in a catalog. Finally, we show that several presently categorized asteroid families exist within much larger groups of asteroids of similar albedos - this may suggest that further improvements in family identification can be made.

Abstract: Warm Jupiters are close-in giant planets with relatively large planet-star separations (i.e., $10< a/R_\star <100$). Given their weak tidal interactions with their host stars, measurements of stellar obliquity may be used to probe the initial obliquity distribution and dynamical history for close-in gas giants. Using spectroscopic observations, we confirm the planetary nature of TOI-1859b and determine the stellar obliquity of TOI-1859 to be $\lambda = 38.9^{+2.8}_{-2.7}\deg$ relative to its planetary companion using the Rossiter-McLaughlin effect. TOI-1859b is a 64-day warm Jupiter orbiting around a late-F dwarf and has an orbital eccentricity of $0.57^{+0.12}_{-0.16}$, inferred purely from transit light curves. The eccentric and misaligned orbit of TOI-1859b is likely an outcome of dynamical interactions, such as planet-planet scattering and planet-disk resonance crossing.