COMO 2025 SCHEDULE
COMO 2025 SCHEDULE
9:00 - 9:20 Breakfast, check-in
9:20 - 9:30 Opening Remarks (COMO Esta!)
Rajib Ganguly, COMO 2025 host
9:30 - 9:40 Radio Observations of Novae with Evolved Companions
Wilhelm Hawes, Michigan State University
Classical novae emit detectable radiation from a range of wavelengths. We can use radio observations to study the physical characteristics of the white dwarf and the eruption. We study multiple novae in radio wavelengths. We plot and analyze their radio light curves, estimate their brightness temperature, plot their spectral index, and compare radio and optical properties. We are able to determine the main source of the radio emission and how quickly the radio light curve declines.
9:41 - 9:51 The Recurrent Nova V3890 Sgr in Radio Wavelengths
Bella Molina, Michigan State University
The recurrent nova V3890Sgr has had three observed eruptions on August 27.9 2019, June 1962 and April 1990 with a recurrence time of about 28 years. This nova consists of a white dwarf and an 5 III giant companion with an estimated white dwarf mass of 1.35M⊙. VLA and VLBA observations were taken of the August 2019 eruption.While the VLA and MeerKat data have been published, the VLBA data have not been published.Here I present VLBA images of the 2019 eruption and radio analysis of this eruption.
9:52 - 10:02 The Dead Stars Society: Enabling Astronomy Research within the Wider Undergraduate Community
Dominic DeYonker, Henry Ford College
The Dead Stars Society (DSS) expands astronomy research opportunities for community college students. DSS members have gained experience in analyzing data from the Chandra X-ray Observatory, the VLA, and NICER. The current DSS project focuses on building a database of temporal information on neutron star low-mass X-ray binaries. I will present the DSS workflow hierarchy and accomplishments that include three published research papers and analysis manuals (Chandra, LSST, and Hubble telescopes).
10:03 - 10:14 Hunting for QPOs in Neutron Star Low-Mass X-ray Binaries
Marie Ismail Fawaz, University of Michigan-Dearborn
Mass accretion onto neutron stars in low-mass X-ray binary systems (NS LMXBs) provides an opportunity to study the behavior of matter in strong gravity. They exhibit diverse temporal variability and quasi-periodic oscillations (QPOs) in their power density spectra. The Dead Star Society is compiling a database of NS LMXBs using NICER archival data for systematic temporal studies. I will present preliminary results from this project for selected systems and interpretation within QPO models.
10:14 - 10:24 A young ultra compact X-ray binary in NGC 1399
Kwangmin Oh, Michigan State University
We present multiwavelength observations of the globular cluster ULX GCU7 in NGC 1399. Its optical spectrum shows only N II and O III lines, indicating H-poor material. The long-term stability of X-ray and optical properties rules out a tidal disruption origin. CLOUDY modeling suggests an ultracompact X-ray binary, with a neutron star accreting super-Eddington material from a helium white dwarf, highlighting rare binary evolutionary phases in extragalactic GCs.
10:40 - 10:50 Characterizing the spectro-temporal behavior of the neutron star low-mass X-ray binary GX 3+1
Malu Sudha, Wayne State University
Neutron star low-mass X-ray binaries show complex spectro-temporal variability. Current existing spectral models are degenerate, making combined spectral and temporal variability studies essential. I present the spectral and temporal analysis of the persistently accreting atoll source GX 3+1 using data obtained from NICER. Results from the reflection spectral modeling of the source, supplemented by the simultaneous timing characteristics in the soft X-ray energy domain will be discussed.
10:51 - 11:01 Using Metastable Fe XXIII as a density diagnostic for LMXB Disk Winds
David Moutard, University of Michigan
Low mass X-ray binaries (LMXBs) occasionally show signs of outflowing material from the accretion disk. Studying these outflows can inform the understanding of the geometry of the systems, as well as the dynamics and energetics of accretion. One key variable for determining the location of these disk winds is the density of the outflowing material. In this study we explore a density diagnostic based upon the absorption of ionizing photons by density-sensitive metastable states of Fe XXIII.
11:02 - 11:12 Comparing Optical Emission Line Features of Transitional Millisecond Pulsars to Accreting White Dwarfs
Rebecca Kyer, Michigan State University
Transitional millisecond pulsars switch between radio pulsar and accretion disk states. In the disk state they show strong X-ray/optical variability. Most candidates are found by optical follow-up of X-ray sources near unassociated Fermi-LAT gamma-ray sources. Classification often relies on X-ray variability, which is often inaccessible for distant systems. We explore using optical spectra to distinguish tMSPs from accreting white dwarfs, enhancing classification and emission line understanding.
11:13 - 11:23 Resolving structure within the iron line profile of Serpens X-1 with XRISM and NuSTAR
Hayden Hall, Wayne State University
Serpens X-1, a persistently accreting neutron star (NS) low-mass X-ray binary (LMXB), was the first NS discovered to have a relatvistically broadened Fe line. Using the superior spectral resolution of XRISM/Resolve, we are able to show structure within the reflection feature itself, allowing for more accurate matching with reflection models and improved precision on system parameter values. The work represents the first joint XRISM/RESOLVE and NuSTAR observation of Serpens X-1.
11:24 - 11:34 Probing the Transient Radio Sky with Student-Built Telescopes and Archival Data
Tim Dolch, Hillsdale College / Eureka Scientific
The Low-Frequency All-Sky Monitor and the Deployable Low-Band Ionosphere and Transient Experiment are radio telescopes with stations in MI, WV, and (yes) OH, undergraduate-built and operated. With these telescopes, we conducted eclipse observations and continue to observe solar radio bursts. They remain sensitive to low-frequency transients such as a future galactic fast radio burst from the magnetar SGR 1935+2154. In a supplemental project, our students searched for point-sources in archival imaging data corresponding to an elusive subset of pulsars.
11:35 - 11:45 Exploring Calcium-Rich Supernovae with Swift telescope
Tianyin Hu, University of Michigan, Ann Arbor
Calcium-rich supernovae are compelling targets for study. They typically exhibit strong Ca II lines and are characterized as faint, fast-evolving explosions with peak luminosities that are intermediate between novae and supernovae. We present data on the newly discovered Ca-rich supernova SN2025coe, with the Swift UVOT telescope. In addition, we summarize observations of other Ca-rich transients from Swift and compare these results to place SN2025coe in a broader context.
11:46 - 11:56 Limits on the Prevalence of Radio Nebulae Around Ultraluminous X-ray Sources
Andrew Harms, Michigan State University
I constrain the prevalence of radio-bright nebulae coincident with ULXs through a systematic search of radio continuum data to build towards a more comprehensive understanding of the population as a whole. I present upper limits for detectability with current and future radio surveys, and the first radio detection of a nebula around NGC 925 ULX-1. I discuss analysis of a new optical spectrum of the shock-ionized nebula.
13:30 - 13:40 Connecting Supernova Theory and Observation: A Physics-motivated Pipeline for 1D Synthetic Supernova Observables
John Delker, Michigan State University
I will discuss our efforts to develop an open-source pipeline for generating synthetic CCSN observables that can be directly compared to observations. Our pipeline starts with a physics-motivated 1D model for CCSN explosions that includes accurate neutrino transport and a model for convection and turbulence which aids explosion and ends with light curves and spectra modeled using Monte Carlo transport code TARDIS. Results also include nucleosynthesis, light curves, and neutrino observables.
13:41 - 13:51 Fast Transients from Magnetic Disks Around Non-Spinning Collapsar Black Holes
Justin Bopp, Michigan State University
We present global 3D GRMHD simulations of collapsing stars that form slowly spinning BHs with accretion disks. As the disk transitions to a magnetically arrested state, it drives mildly relativistic, wobbling, collimated magnetic outflows. Once the outflows emerge from the star, they produce mildly relativistic shock breakout and cooling emission. Our cooling emission estimates an optical signal at absolute magnitude MAB ≈ −16 lasting for several days.
13:52 - 14:02 Gone with the wind: JWST-MIRI Unveils a Strong Outflow from the Quiescent Stellar-Mass Black Hole A0620-00
Zihao Zuo, University of Michigan
We present new JWST/MIRI observations of the black hole X-ray binary A0620–00 in an extremely quiescent state, coordinated with multiwavelength data. The stellar-subtracted MIR spectrum has a spectral index of 0.72 and shows rapid variability, ruling out a circumbinary disk origin. The spectral shape and 7.5 µm emission feature are consistent with thermal bremsstrahlung from a warm wind, indicating much of the donor’s mass is expelled by the wind rather than accreted onto the black hole.
14:03 - 14:13 Finding an intermediate mass needle in a galactic haystack: constraining the presence of IMBHs in M33
Thomas Do, Michigan State University
Intermediate mass black holes (IMBHs) are believed to be a critical step in black hole evolution. To constrain the importance of IMBHs on black hole evolution, we must first constrain their abundance. Some of the best environments to find IMBHs are the massive star clusters of Local Group galaxies. We use VLA data from the Local Group L-Band Survey to search for black hole radio emission in massive M33 star clusters and will discuss constraints on potential M33 IMBHs.
14:14 - 14:24 Central Massive Black Holes Are Not Ubiquitous in Local Low-Mass Galaxies
Fan Zhou, University of Michigan
The black-hole occupation fraction defines the fraction of galaxies hosting central massive black holes (MBHs). I will present the first statistically meaningful constraints on the quantity based on over 20 years of Chandra imaging data for 1600 galaxies within 50 Mpc. Two main conclusions were drawn: (a) the occupation fraction decreases dramatically with decreasing stellar mass; (b) the MBH population accretion-rate distribution peaks around (X-ray luminosity / stellar mass) ~ 1e28 erg/s/Msol.
14:25 - 14:35 Continuum reverberation mapping of the low-mass black hole AGN NGC 4051
Marcin Marculewicz, Wayne State University
We report the results of a two-year, sub-daily, seven-band optical reverberation mapping study of NGC 4051, an AGN powered by a low-mass ($8\times10^5$ M$_\odot$) black hole, using the Las Cumbres Observatory robotic telescope network. The light curves exhibit well-correlated variations, with time lags that increase with wavelength. An asymmetric time-delay distribution, skewed toward positive lags, is evident from a trend of shorter/longer lags for faster/slower variations.
14:36 - 14:46 The Illumination of Galactic Center Molecular Clouds by Sgr A*
Steve DiKerby, Michigan State University Dept of Physics & Astronomy
Though Sgr A* currently appears quiescent, the varying X-ray fluorescence of different galactic center molecular clouds (GCMC) traces out the history of X-ray emission from Sgr A* over the past few centuries. Using XMM-Newton and NuSTAR observations, we can create a centuries-long history of the X-ray output from Sgr A*, and using unprecedented observations by XRISM we have shown how X-ray illumination from Sgr A* can serve as a diagnostic for GCMC composition.
14:47 - 14:57 High-energy X-ray Flares detected by NuSTAR during 2016-2025
Grace Sanger-Johnson, Michigan State University
Sagittarius A* (Sgr A*) exhibits unique flaring activities in sub-millimeter, NIR and X-ray bands. The X-ray luminosity of Sgr A* during these flaring events can increase to up to a few hundred times its quiescent luminosity. Using almost a decade of NuSTAR data, we detect ten Sgr A* flares between 2016-2025, the largest Sgr A* flare sample to date. Here, we present 3-79 keV light curves and spectra of prominent flares and examine the correlation between flare strength and spectral index.
14:58 - 15:08 NuSTAR Detection of a Unique Galactic Center X-ray Filament G0.173-0.413
Alec Deen, Michigan State University
Magnetic filaments are a phenomenon found only in the Galactic Center. To gain insight into the origins of these filaments, we present NuSTAR's detection of a Galactic center filament, G0.173-0.41, a rare filament with both radio and X-ray detections. Its broadband X-ray spectrum is best explained by a thermal plasma model, making this filament the only one detectable above 10 keV with a thermal nature. The unexpected thermal nature of this filament calls for a new model to explain the data.
15:30 - 15:40 XRISM Spectroscopy of Accretion-Driven Wind Feedback in NGC 4151
Xin Xiang, University of Michigan
The hottest, most ionized, and fastest winds driven by accretion onto massive black holes have the potential to reshape their host galaxies. Calorimeter-resolution X-ray spectroscopy is the ideal tool to understand this feedback mode, as it enables accurate estimates of physical characteristics needed to determine the wind's kinetic power. We report on a photoionization analysis of five observations of the Seyfert-1.5 galaxy NGC 4151, obtained with XRISM/Resolve in 2023 and 2024.
15: 41 - 15:51 Insights into SMBH-Galaxy Co-Evolution From the Gravitational Wave Background
Cayenne Matt, University of Michigan
I will describe how I use the gravitational wave background (GWB) to constrain galaxy and black hole co-evolution. Using a semi-analytic model, I infer black hole mass from galaxy mass using the Mbh-Mbulge relation. I have found that the high amplitude of the observed GWB is well described using an Mbh-Mbulge relation with a positively evolving amplitude. This work can be used to inform models for galaxy and black hole growth and what this means for our interpretations for the GWB.
15:52 - 16:02 Multimessenger Constraints on the Supermassive Black Hole Binary Hardening Timescale
CJ Harris, University of Michigan
Supermassive black hole binaries evolve (harden) under three broad phases: dynamical friction, stellar scattering, and gravitational wave emission. Here we present constraints on the supermassive black hole binary hardening timescale using data from HST observations of core galaxies and pulsar timing array measurements of the gravitational wave background.
16:03 - 16:13 5-year Study of Reverberation Lags of AGN MCG+08-11-011
Avital Keeley, Wayne State University
Active galactic nuclei (AGN) are comprised of a supermassive black hole surrounded by an accretion disk (AD). The angular size of an AGN is typically too small for direct imaging, so alternative techniques must be employed. Reverberation mapping (RM) can be used to outline the structure of the AD by measuring time lags. We present an analysis of a 5-year RM campaign on the AGN MCG+08-11-011. Interestingly, we do not observe the expected dependence of the lags on flux for a standard AD.
16:14 - 16:24 Tracing the Evolution of Supermassive Black Hole Mass and Accretion Rates Across the Last 10 Billion Years (z ≲ 2)
Md Mahmudummobe, Wayne State University
Supermassive black holes (SMBHs) reside at the centers of nearly all galaxies, yet their growth and the distribution of surrounding gas remain poorly understood. We study 2,293 X-ray–selected SMBHs from the Stripe82X survey to trace the evolution of mass and accretion rates over the past 10 billion years (z ≲ 2). Using Bayesian modeling, we map their distribution functions, revealing that low-mass SMBHs grew faster at earlier times, while high- and low-mass SMBHs show similar accretion locally.
16:25 - 16:35 Bringing Black Holes out of the Darkness: Tracing X-Ray Flux from NGC 1275's and M87's Supermassive Black Holes
Sarah Ketchum, University of Michigan, Ann Arbor
NGC 1275, situated in the Perseus cluster, has a nucleus that primarily emits X-rays but is obscured by cluster contamination. Using 89 Swift observations (from 2005 until 2025), data was processed with Xspec, linking all parameters except the power-law index, which was allowed to vary by observation. This approach isolates changing flux values from nearby cluster emission. This technique is now being attempted on M87’s central supermassive black hole.
16:36 - 16:46 Variability in the Ionized UV Emission and Absorption of NGC 4151
Doyee Byun, University of Michigan
Simultaneous observations of the Seyfert galaxy NGC 4151 have been made with XRISM and HST to examine the time variability in its emission and absorption features, as well as find correlations between the parameters of features in the UV and X-ray bands. We report the time variability of the ionized emission and absorption features observed by HST/STIS over the course of two weeks.