Additional Event Information

• Special Talks

  Speaker: Sammy Hasler (STScI)
  Title: Entering the Era of Circumplanetary Ring Detection with Direct Imaging
  Abstract: The Nancy Grace Roman Space Telescope will open a new window to nearby planetary systems with its Coronagraph Instrument (CGI), demonstrating the technology needed to directly image giant exoplanets in reflected light. These observations will provide a first opportunity to study Jupiter-like planets and inform future missions such as the Habitable Worlds Observatory (HWO). But what will these planets actually look like? One potentially important and often overlooked feature is circumplanetary rings. I developed a model combining observations of Saturn’s rings with simulations of Jupiter-like planets to investigate how rings alter their appearance. Saturn-like rings can increase peak visible brightness by a factor of 3.1, while more extended rings can produce enhancements exceeding an order of magnitude. However, this effect depends strongly on ring orientation and orbital location, with some configurations making a planet fainter than a ringless planet. These results demonstrate that rings can substantially affect the appearance and interpretation of directly imaged giant planets and should be considered when planning and interpreting future observations.

  Speaker: Sofia Savvidou (STScI)
  Title: Is the Inner Disk Composition Regulated by the Disk and Stellar Properties or the Existence of Substructures?
  Abstract: Prior studies have shown that the chemical composition of the inner protoplanetary disk can be shaped by the inward transport of solids from the outer disk, with volatiles evaporating at their individual icelines and enriching the inner disk gas. Recent JWST observations have also revealed enhanced water abundances in compact, smooth disks compared to extended substructured ones, consistent with efficient volatile delivery by pebble drift in smooth disks. On the other hand, substructures, such as pressure bumps and gaps, could regulate this radial transport by trapping the inwardly drifting dust. The variations in the observed inner disk compositions are often attributed to the disk or stellar properties, however, we aim to determine how strongly these differences are instead shaped by the presence of (even undetected) substructures. We perform numerical simulations probing various stellar masses from 0.1 to 1.3 solar masses to investigate the influence of the stellar properties, varying the disk size, along with the gap depth, the timing for the introduction of the gap, and α-viscosity which affects the accretion rates.

  Speaker: Vishal Tiwari (STScI)
  Title: Radiation Magnetohydrodynamic Simulations of Accretion Flows Around Massive Black Hole Binaries
  Abstract: The recent detection of a gravitational wave (GW) background by Pulsar Timing Arrays (PTAs) provides the first evidence for a population of inspiraling massive black hole binaries (MBHBs). Combining individual GW signals from PTAs and the forthcoming Laser Interferometer Space Antenna (LISA) with their electromagnetic (EM) counterparts is crucial for testing theories of gravity and constraining the universe’s expansion rate. Therefore, theoretical models predicting these EM signatures are needed to pinpoint the source locations, overcoming the poor sky localization of gravitational wave detectors. Calculating these EM signatures from first principles is challenging, requiring a detailed understanding of the gas, radiation, and magnetic fields within the accretion flows around MBHBs. This research directly addresses this challenge by performing global three-dimensional radiation magnetohydrodynamic simulations of the accretion flows around MBHBs to calculate their EM signatures.

  Speaker: Tobin Wainer (STScI)
  Title: The Star Formation History of M31 with HST, and the New World of Roman
  Abstract: We use Hubble Space Telescope optical imaging from the Panchromatic Hubble Andromeda Southern Treasury (PHAST) to measure the spatially resolved recent star formation history (SFH)  of M31 over the last ∼500 Myr. Combining PHAST and PHAT measurements, we now cover two-thirds of M31’s star-forming disk with homogeneous SFHs derived with the same CMD fitting technique, yielding the highest resolution spatially resolved SFHs of M31 measured with resolved stars. The resulting maps show coherent structure that traces the ringed morphology of the disk. We find  a clear global decline in the recent star formation rate (SFR), with a pronounced drop in the last ∼40 Myr that is most evident in the region closest to M32. The observed decline is interpreted to be the late stages of a multi-Gyr wind-down from a previously more active state. Because recent star formation in M31 is concentrated primarily in the rings, the observed global decline is driven mainly by decreasing activity within those features. This resolved star technique of SFH fitting will be widely used in galaxies observed with Roman. My work here at the institute will in part be to test the recovery of synthetic SFHs in realistic mock Roman observations.