arXiv subjects

Arin M. Avsar

Publications and source records attributed to Arin M. Avsar.

4 recordsLinked to original sources

arXiv2026

Deep HST/STIS Coronagraphic Imaging of the $β$ Pictoris Debris Disk: On the Scattered Light Component of the Cat's Tail

The $β$ Pictoris debris disk is a unique system where mid-infrared coronagraphic imaging with JWST/MIRI revealed a new spatially resolved substructure known as the Cat's Tail. We present deep HST/STIS coronagraphic imaging of $β$ Pic in scattered light, combining six epochs of observations between 2012 and 2025, in search of the scattered light component of the Cat's Tail. We detect the disk out to a projected separation of 500 au for the first time with HST/STIS, achieving SNR > 100 across much of the midplane between 50 and 200 au. We report the detection of the visible/near-infrared scattered light component of the Cat's Tail substructure. We find through injection-recovery analysis that the scattered light component of the Cat's Tail has a total flux of $0.1-0.4\%$ of the MIRI F1550C flux. Using the measured STIS-to-MIRI flux ratio, we model the Cat's Tail grain properties and find that the grains are highly porous and almost entirely composed of organic refractory material, which is in agreement with findings with JWST/MIRI. We use the organics content of Solar System dwarf planets and dust in the local ISM as a proxy to estimate the size of the colliding progenitors that can produce enough organic refractory material seen in the Cat's Tail. We find that each colliding progenitor must have a mass of at least $1-3\times 10^{21}$ kg, comparable to Charon and Makemake in our Kuiper Belt. Additionally, we find a prominent warped morphology and surface brightness asymmetry in the outer dust halo of $β$ Pic. We compare the observed halo morphology and asymmetry to predicted vertical structures, which may arise from planet--disk interactions.

astro-ph.EP↗

arXiv2026

Forecasting Catastrophe: Constraints on the Fomalhaut Main Belt Planetesimal Population from Observed Collisional Remnants

Catastrophic planetesimal disruptions offer a unique opportunity to study and characterize large planetesimal populations in exoplanetary systems that are not currently detectable by modern observatories. The unexpected discovery of a second collision event in the Fomalhaut system raises important questions about the planetesimal population and dynamical state inside the Fomalhaut main belt that led to two collisions in 20 years. We present a statistical model developed and applied to the archetypal Fomalhaut system to provide new constraints on the bulk properties of the planetesimals in Fomalhaut's main belt. Utilizing the constraints provided by the spatially resolved Fomalhaut cs1 and cs2 collision events, we retrieve the belt parameters that best reproduce the observed collision rate while remaining consistent with the system's age and dust mass. Our best-fit model suggests a total main belt mass of 200-360 $M_{\oplus}$, with the transition from a collisionally evolved to a primordial planetesimal population occurring at a radius of $115_{-10}^{+30}$ km and a maximum planetesimal radius of $380_{-202}^{+643}$ km. We estimate a catastrophic collision rate of $0.086_{-0.048}^{+0.067}$ collision events per year for planetesimals with radii $\ge$ 100 km in the region interior to the main belt. Our findings show that further observable collisions are likely, motivating continued monitoring of Fomalhaut and other nearby debris disks.

astro-ph.EP↗

arXiv2024

A Search for Collisions and Planet-Disk Interactions in the Beta Pictoris Disk with 26 Years of High Precision HST/STIS Imaging

Beta Pictoris (Beta Pic)'s well-studied debris disk and two known giant planets, in combination with the stability of HST/STIS (and now also JWST), offers a unique opportunity to test planet-disk interaction models and to observe recent planetesimal collisions. We present HST/STIS coronagraphic imaging from two new epochs of data taken between 2021 and 2023, complementing earlier data taken in 1997 and 2012. This dataset enables the longest baseline and highest precision temporal comparison of any debris disk to date, with sensitivity to temporal surface brightness variations of sub-percentage levels in the midplane of the disk. While no localized surface brightness changes are detected, which would be indicative of a recent planetesimal collision, there is a tentative brightening of the SE side of the disk over the past decade. We link the constraints on surface brightness variations to dynamical models of the planetary system's evolution and to the collisional history of planetesimals. Using a coupled collisional model and injection/recovery framework, we estimate sensitivity to expanding collisional debris down to a Ceres-mass per progenitor in the most sensitive regions of the disk midplane. These results demonstrate the capabilities of long-baseline, temporal studies with HST (and also soon with JWST) for constraining the physical processes occurring within debris disks.

astro-ph.EP↗

arXiv2022

A 16 Hour Transit of Kepler-167 e Observed by the Ground-based Unistellar Telescope Network

More than 5,000 exoplanets have been confirmed and among them almost 4,000 were discovered by the transit method. However, few transiting exoplanets have an orbital period greater than 100 days. Here we report a transit detection of Kepler-167 e, a "Jupiter analog" exoplanet orbiting a K4 star with a period of 1,071 days, using the Unistellar ground-based telescope network. From 2021 November 18 to 20, citizen astronomers located in nine different countries gathered 43 observations, covering the 16 hour long transit. Using a nested sampling approach to combine and fit the observations, we detected the mid-transit time to be UTC 2021 November 19 17:20:51 with a 1$σ$ uncertainty of 9.8 minutes, making it the longest-period planet to ever have its transit detected from the ground. This is the fourth transit detection of Kepler-167 e, but the first made from the ground. This timing measurement refines the orbit and keeps the ephemeris up to date without requiring space telescopes. Observations like this demonstrate the capabilities of coordinated networks of small telescopes to identify and characterize planets with long orbital periods.

astro-ph.EP↗