Recalibrating SMBH Scaling Relations with UV-Optical SEDs of Reverberation-Mapped AGN

Jodie Kiyokawa

Graduate Student

University of Wisconsin

Wisconsin webpage

Understanding how galaxies form and evolve over cosmic time requires accurate measurements of the supermassive black holes (SMBHs) at their centers. In nearby active galactic nuclei (AGN), reverberation mapping (RM) of the broad line region (BLR) has been used to estimate SMBH masses. In addition, RM studies have established an empirical radius–luminosity (R−L) relation linking optical luminosity to BLR size, which is now widely used to estimate SMBH masses in more distant AGN where direct RM is not feasible. However, mounting evidence suggests that this standard R−L relation does not hold uniformly across all AGN. These deviations likely arise from differences in accretion properties, which affect the connection between the ultraviolet (UV) ionizing continuum and the optical continuum typically used in the R−L relation. To explore this, we use quasi-simultaneous multi-band imaging from the Las Cumbres Observatory Global Telescope network and the Hubble Space Telescope to construct UV–optical spectral energy distributions (SEDs) for a sample of 26 AGN at z ∼ 0.1–1.1 with existing RM measurements. Here, I will present preliminary results indicating a tentative correlation between the UV–optical SED slope and deviations from the R–L relation, with potential implications for correcting the R–L relation and improving SMBH mass measurements.

The EVE Mission: A NASA Small Explorer Concept

Ann Marie Cody & Laura Venuti

SETI Institute

Over the past decade, the Kepler and TESS missions have been a boon for time domain discoveries, from exoplanets to transients, pulsators and more. While the photometric precision and time sampling have proven exquisite, one shortcoming was the lack of multi-band data. We now have a chance to expand the state-of-the-art in space-based time domain monitoring by considering the sky at multiple wavelengths. This Tuesday, NASA released a call for Small Explorer (SMEX) mission proposals, including new space telescopes that could launch on a roughly five-year timescale. Our team led by PI Meredith MacGregor (JHU) has developed a novel SMEX concept focused on the time domain behaviors of thousands of young stars in the near-ultraviolet (200-300nm), optical (500-900nm), and near-infrared (1100-2000nm). With an aim to survey several dozen stellar populations in the 1-100 Myr age range, the Early Evolution Explorer (EVE) would simultaneously monitor fields in these three bands for at least 30 days at a time. In this talk we will outline EVE’s three core science objectives, which focus on the properties of young exoplanets, energetic flares, and interactions between the youngest stars and their protoplanetary disks. If selected, this mission would fill a crucial gap in our knowledge of the origins and early evolution of planetary systems.

A brief history of Herbig (Ae/Be) stars and the current perspective on this population

Miguel Vioque

JAO Fellow

ESO

Personal Website

Intermediate-mass forming stars (Herbig stars, 1.5 to 15 solar-mass young stellar objects) were first characterized as a population by George Herbig in 1960. Now, they are of great importance for planet formation studies, and for linking the low-mass to high-mass star formation regimes. Historically, the study of the general properties of Herbig stars has been limited by the lack of a well-defined sample. In addition, only a few, mostly serendipitously discovered sources were known. However, this has recently changed thanks to the homogeneous discovery of many new stars of the class. In this talk, I provide a brief review of the history of Herbig stars, and describe our current knowledge of this population of stars and their protoplanetary disks, which host key observational features for understanding planet formation and the interaction of young stars with their environment.

Using the heating and cooling of dust grains to study their composition, structure, and size

Adolfo Carvalho

Postdoctoral Fellow

Smithsonian Astrophysical Observatory

Personal Website

In low temperature systems that contain both gas and dust, such as protoplanetary disks, the dust contributes significantly to the heating and cooling of the system. The extent of its contribution depends strongly on the properties of the dust such as the grain size distribution, composition, porosity, and temperature. The best observations with which to probe these properties tend to be spectrophotometry at infrared and millimeter wavelengths but the impact of each is difficult to disentangle in a single observation or even a single broad-band spectrum. The time domain offers an opportunity to instead study the how dust grain properties impact the heating and cooling rates of dust around variable objects. These heating and cooling rates will depend differently on grain properties than the spectrum does, enabling an independent constraint on these important parameters. I will discuss how new models and existing and upcoming millimeter and mid-infrared time domain experiments will open a new direction in the study of interstellar and circumstellar dust.

SN Winny: The First Galaxy-Scale Lensed Supernova Suitable for Cosmology

Christopher Storfer

Graduate Student

IfA

IfA Website

Multiply imaged, gravitationally lensed supernovae (SNe) are rare but powerful probes of cosmological parameters. The relative time delays between the lensed images encode the Hubble constant (H₀) directly and provide a measurement independent of both the local distance ladder and the CMB. To date, the known lensed SNe have either had time delays too short to constrain H₀ or have been found behind complex, cluster-scale lenses, where lens modeling dominates the systematic error budget. SN 2025wny (“SN Winny”) is the first lensed SN with time delays suitable for an H₀ measurement in a system with a galaxy-scale mass distribution.* It is also the first lensed Type I superluminous SN. In this talk, I will present a mass model of the SN Winny system, leveraging AO imaging obtained with Keck/NIRC2, which enables precise astrometry of the multiple SN images. Combined with preliminary analysis of Keck/KCWI spectroscopy and ground-based photometric time series, this model is an essential first step toward an independent measurement of H₀ with this system. Ancillary science cases, including the physics of the first superluminous SN known at z > 2, will follow from the same analyses. SN Winny also serves as a critical end-to-end test run for lensed SN analysis ahead of LSST and Roman, where hundreds of such systems are expected.

Preparing for Habitable Worlds Observatory: Constraining Properties of Potential ExoEarth Host Systems

Caleb Harada

Post-Doctoral Researcher

IfA

Personal Website

Searching for global biospheres on rocky planets in the habitable zones (HZs) of nearby stars is a key goal of future space-based, high-contrast, exoplanet imaging missions such as the Habitable Worlds Observatory (HWO). Maximizing precursor knowledge of potential exo-Earth survey targets for HWO is critical to science and engineering trade studies that weigh the impacts of potential design choices and astrophysical realities on expected planet yields, thereby mitigating potential mission risk. In this talk, I will provide motivation for HWO precursor science investigations and summarize recent and ongoing work to better characterize potential target systems for HWO’s defining exoEarth survey. These efforts aim to optimize HWO’s overall architecture, mitigate the risk of imposter exoEarths, and provide key astrophysical context for interpreting future spectroscopic observations of reflected light from potentially habitable exoplanets.

Are Little Red Dots Quasi-stars?

Earl Bellinger

Assistant Professor

Yale University

Website

The James Webb Space Telescope has discovered an intriguing and unexpected class of high-redshift, morphologically compact, low-temperature objects that have been dubbed “Little Red Dots” (LRDs). Strong-lensing observations of LRDs behind galaxy clusters have revealed two clues that may help discern their true nature. First, LRDs seem to consist of pairs: a compact, luminous red component and a nearby, star-forming blue component. Second, the red component appears to exhibit periodic variability on a timescale of decades. We show that this lends support to the hypothesis that LRDs are quasi-stars: supermassive black holes embedded in a star-like convective envelope. During their formation, the nearby star-forming galaxy dissociates molecular hydrogen in the infalling gas, preventing fragmentation and triggering the formation of a supermassive star. Due to the general-relativistic instability, the supermassive star’s core collapses directly into a black hole and feeds on the envelope, creating a quasi-star. We present the MESA-QUEST toolkit for modelling the evolution of quasi-stars. We show that these models successfully reproduce the observed spectral energy distributions of LRDs, and that their lifetimes are sufficient to account for the observed population. We furthermore present recent developments to the time-dependent convection module of MESA, which enables us to follow the nonlinear hydrodynamic variability of large-amplitude radial pulsators such as Cepheids, RR Lyrae, red supergiants, and quasi-stars, and show that these pulsating quasi-star models are consistent with the variability measurements of lensed LRDs. If confirmed, this interpretation would simultaneously solve two major outstanding problems in astrophysics: the nature of LRDs, and the origin of supermassive black holes in the early universe.