STEM research and innovations have positively impacted many aspects of our society.  Today, the quality of the STEM enterprise must be elevated if the quality of innovation is to meet an increasing complexity of societal needs; and that elevation is inextricably linked to diversifying STEM disciplines. However, an ongoing challenge to STEM diversification continues to

NICER, the Neutron Star Interior Composition Explorer, is an X-ray telescope that installed on the International Space Station. Its mission is to study the nature of the densest matter in the Universe, found in the cores of neutron stars.  NICER uses Pulse Profile Modeling, where we use relativistic effects on X-rays emitted from the hot magnetic polar

The high-mass X-ray binary system Cygnus X-1 contains one of the first known and best-studied black holes. We recently refined the distance to this important source using astrometric very long baseline interferometry observations. The new distance implied that the masses of the two binary components both needed to be revised upwards, with our modelling showing

A modeler’s approach to visible (and, indeed, also dark) matter in the Universe is to think of it as a fluid, write some version of (magneto)hydrodynamical equations for its density, velocity and temperature, code them up and model away. By and large, this has given us a successful (at least visually) description of many astrophysical

Stellar activity is one of the main limiting factors for exoplanet surveys using the transit and radial velocity (RV) methods. It induces variations in the light and RV curves that can completely overwhelm planetary signals, particularly for young planets orbiting active stars, and for potentially habitable, Earth-like planets. My group use data-driven methods, particularly Gaussian

Binary stars are foundational to modern astrophysics. They underpin precision measurements of stellar structure, age, and composition; they provide the most stringent tests of general relativity, they make possible the study of faint and rare objects such as black holes and neutron stars, and they are the progenitors of gravitational wave sources. The components of binaries often interact,

The merger of a neutron star with a stellar mass black hole is one of the main sources of gravitational waves detectable by current ground-based observatories (LIGO, Virgo, KAGRA). The first two detections of these mergers were in fact just performed in 2020, with more events expected in future observational runs of LIGO/Virgo/KAGRA. If the

Type Ia supernovae involve the thermonuclear detonation of white dwarf stars, and are one tool allowing us to study the Universe on vast scales. However, violent explosions are not the only byproducts of the mergers of the endpoints of stellar binaries. I will discuss the growing number of observational signposts that can distinguish populations of

The study of compact objects such as black holes and neutron stars is an important component of modern astrophysics. Recent detections of astrophysical neutrinos, gamma-rays, ultrahigh-energy cosmic rays, and gravitational waves open up opportunities to study compact objects with multi-messengers. In this talk, we first review the latest progress in Astroparticle Physics, including some surprising

Supermassive black hole (SMBH) binaries are inevitably produced during galaxy formation, but observational evidence for them remains elusive. I will discuss the coupled dynamics of a SMBH binary with a circumbinary gas disk, and the expected characteristics of electromagnetic (EM) emission from such a system.  In particular, the emission is likely time-variable, and contain unique

The present-day population of supermassive black holes in low-mass galaxies offers a window into massive black hole formation in the early universe. While we cannot yet observe the formation of “black hole seeds” at high redshift, the fraction of small galaxies that host a supermassive black hole — and the properties of those black holes

The past 25 years have revealed a diversity of exoplanets far beyond what was imagined from the limited sample in the Solar System. With new and upcoming observing facilities and a rapidly growing number of nearby planets, we are poised to bring this diversity into focus, with detailed follow-up characterization of the planets’ atmospheres. In

The majority of the baryons in galaxies are inferred to comprise the circumgalactic medium (CGM) – gas that is mostly in either a cool (~10^4K) or a hot (10^5-10^6 K) phase. The former has been studied with QSO absorption line studies and the latter using X-ray observations. The observational picture, however, is unsatisfactory because of

Since the detection of the first gravitational wave transient in 2015 there has been a small revolution in our understanding of the mass distribution of black holes. But there are still many unknowns and theory is still struggling to understand how the observed distribution is determined. There are also other windows onto black holes that

Galaxy clusters are the most powerful gravitational lenses in the known Universe. Near the lensing caustics they host some of the most dramatically magnified extragalactic sources ever detected, including extremely magnified individual super-luminous stars, and compact super star clusters. These are systems where small-scale lens substructures strongly couple to the effects from the macroscopic lens

When the universe was merely three billion years old, about half of massive galaxies had already formed the bulk of their stars and new star formation plummeted. How these ‘red and dead’ (quiescent) galaxies quench at such early times remains a puzzle, as their dark matter halos contain large gas reservoirs. This gas should cool

Transmission spectroscopy of transiting exoplanets provides our best opportunity to identify the makeup of planetary atmospheres in the coming decade. However, stellar surface brightness inhomogeneities due to features such as star spots, can impact these measurements and contaminate the observed spectra. I will present the Pandora SmallSat mission that is designed to disentangle star and

In 2019 the Event Horizon Telescope (EHT) collaboration published the first direct image of a black hole shadow. This result signaled the arrival of event horizon scale observations that will allow us to test our knowledge of gravity and plasma physics around compact objects. Although the EHT uses unprecedented resolution, only two potential supermassive black

Tidal disruption events (TDEs) are currently discovered in ever increasing numbers by optical transient surveys. Similarly, the eROSITA and planned Einstein Probe X-ray satellites are expected to discover many TDEs in X-rays. TDEs are one of the most direct and promising routes to study otherwise quiescent supermassive black holes (SMBHs), but also stellar-mass BHs through

Machine learning is presenting new opportunities for astrophysics—and all the natural sciences. The standard machine-learning workflow represents a very different epistemology than that of other kinds of scientific methods. How does that impact our results and beliefs about those results? I’ll discuss the different roles for machine learning in astrophysics and discuss them in terms

Optical transit surveys have been extraordinarily fruitful in the detection and characterization of exoplanets orbiting main-sequence stars. While the bulk of a star’s lifetime is spent undergoing core hydrogen fusion, much can be learned about star-planet systems by turning our gaze away from the main sequence. In this talk, I discuss the observational properties of

The observed number of galaxy clusters provides a sensitive probe of the structure of the Universe by measuring the evolution of the halo mass function.  However, already current cluster surveys are systematically limited by uncertainties in the relation between cluster mass and observables (e.g. the number of galaxies, X-ray luminosity, or the imprint on the

From measurements of its remnant radiation (the cosmic microwave background or CMB), we comprehend more about the primordial universe than one might have guessed possible.  Data  from the Planck satellite have been compressed to a set of six parameters describing initial conditions for its evolution.  Meanwhile, measurements of the present-day universe reveal multiple aspects of

The Milky Way’s Galactic Center black hole Sagittarius A* is the closest to us supermassive black hole. It is an ideal candidate to explore near horizon effects, to test alternative theories of gravity, and to learn the mechanics of black hole feeding, accretion, and feedback — forces shaping galaxies and the Universe as a whole. 

Turbulence and magnetized disk winds are agents that can remove angular momentum and facilitate inflow through accretion disks. Initially considered as largely alternate hypotheses for why disks accrete, current theoretical work suggests that they are linked through the net flux – vertical magnetic field that threads the entire disk. Multiple numerical simulations, and more recently observations

We have recently seen a remarkable convergence in our overall understanding of how galaxies in the universe form, through the collapse of gas in dark matter halos, and growth through star formation and merging over cosmic time. However, many of the key physical processes, such as gas dynamics, feedback, and the growth and impact of

Contrary to what their name suggests, black holes are not empty space; they are the most extreme objects in the universe, so powerful that nothing can escape them, not even light. Filled with an exceptional amount of energy, they can easily destroy entire galaxies. The goal of my work is to understand the most massive black

Innovations in sensor technology, software, optical coatings, and mass production can be coupled to allow powerful wide-field imaging telescopes to be constructed unbelievably quickly and relatively inexpensively. The Dragonfly Telephoto Array (Dragonfly for short) is an example of this kind of thinking, and over the past few years it has ignited interest in the low

Compact objects are among the most inspiring and extreme objects in the Universe, allowing us to probe a range of astrophysical phenomena unattainable on Earth, while offering opportunities to bridge research areas and astrophysics communities. Even more than 50 years into their discovery, neutron stars in particular continue to fascinate and puzzle us. The highly

 I will review ongoing work aimed at understanding when and how the major structural components of our Galaxy came into place.  The H3 Survey is collecting high resolution spectra for 300,000 stars at high latitudes.  In combination with Gaia astrometry, these data are providing a detailed view of the phase space structure of our Galaxy.

M51-ULS1b, the first candidate planet in another galaxy, was discovered because it transited a bright X-ray source in the Whirlpool galaxy, M51.  Searches for other distant planets provide powerful reasons to study the short-time-scale behavior of X-ray sources. Equally important are other classes of short-duration events, including X-ray flares which may be due to either system

The discoveries of thousands of exoplanets have presented a number of puzzles about their properties and origins. Until recently, though, many of the assumptions made by planet formation models could not be examined directly. We have now entered an era where deep, high resolution images of protoplanetary disks at millimeter and infrared wavelengths are yielding a wealth of

With the recent successful launch of JWST, a new window into exoplanet atmospheres is now wide open. Early JWST observations of exoplanet hosting systems have already proven the power of this observatory to provide new and transformational insights into exoplanet atmospheres. Although JWST will provided us with unprecedented looks at exoplanets in the infrared, to

Galaxy growth is a slow but continuous process. The observed properties of galaxies suggest that accretion must continue to support star formation. However, direct observational evidence of gas flows into galaxies have been extremely hard to come by. One of the most promising regions in our search has been the disk-halo interface, where new data

Dwarf galaxies pose strong constraints to the Lambda Cold Dark Matter (LCDM) model, with several outstanding challenges still to be reconciled between theoretical models and observations. I will discuss some of these tensions, including the mapping between stellar mass and halo mass, dark matter cores, morphology of dwarfs and diversity of rotation curves. I will

We have learned that our universe seems to be composed of significant amounts of invisible matter called dark matter and an unexpected dark energy driving the universe’s accelerating expansion. In the last few decades, we have also uncovered large populations of new worlds called exoplanets orbiting the stars of our Galaxy. These discoveries represent just

The Southern Stellar Stream Spectroscopic Survey (S5) is an ongoing spectroscopic program that maps the newly discovered stellar streams with the fiber-fed AAOmega spectrograph on the Anglo-Australian Telescope (AAT). S5 is the first systematic program pursuing a complete census of known streams in the Southern Hemisphere, providing a uniquely powerful sample for understanding the building blocks of

The success of transit and RV surveys have shifted the exoplanet field from pure discovery to a combination of discovery, demographic analysis, and detailed characterization, especially for exoplanet atmospheres. However, even with nearly 5000 exoplanets known, we are still working to understand their origins and evolutionary mechanisms. Using data from NASA’s TESS and Kepler/K2 missions,

Accreting stellar-mass black holes in X-ray binary systems show X-ray variations over a broad range of time-scales, which are generated by mass-accretion fluctuations arising in the turbulent accretion flow.  The variability is noise-like, but with certain plausible assumptions, we can use it to map the emitting regions close to the black hole by studying the response of distinct spectral components: the blackbody-emitting accretion disk

In our LCDM paradigm, galaxies form and reside in dark matter halos. Establishing the (statistical) relation between galaxies and dark matter halos, the `Galaxy-Halo connection’, therefore gives important insight into galaxy formation, and also is a gateway to using the distribution of galaxies to constrain cosmological parameters. After a brief introduction to how clustering and

With the ever-growing role of software development and computer programming in astronomical research, our community is faced with many new challenges in nearly every aspect of our profession. In this talk, I first will describe the various types of software and the many different roles it plays in the research cycle. I will also describe