Search Publications
The Discovery of the First “Changing Look” Quasar: New Insights Into the Physics and Phenomenology of Active Galactic Nucleus
Moran, Edward C.; Myers, Adam D.; Heckman, Timothy M. +6 more
SDSS J015957.64+003310.5 is an X-ray selected, z = 0.31 active galactic nucleus (AGN) from the Stripe 82X survey that transitioned from a Type 1 quasar to a Type 1.9 AGN between 2000 and 2010. This is the most distant AGN, and first quasar, yet observed to have undergone such a dramatic change. We re-observed the source with the double spectrograp…
Compton-thick Accretion in the Local Universe
Bauer, F. E.; Gandhi, P.; Ricci, C. +3 more
Heavily obscured accretion is believed to represent an important stage in the growth of supermassive black holes and to play an important role in shaping the observed spectrum of the cosmic X-ray background. Hard X-ray (E > 10 keV) selected samples are less affected by absorption than samples selected at lower energies, and are therefore one of…
Obscuration-dependent Evolution of Active Galactic Nuclei
Nandra, Kirpal; Aird, James; Liu, Zhu +9 more
We aim to constrain the evolution of active galactic nuclei (AGNs) as a function of obscuration using an X-ray-selected sample of ~2000 AGNs from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS, and XMM-XXL fields. The spectra of individual X-ray sources are analyzed using a Bayesian methodology with a physically realistic model to infe…
Constraining the Milky Way's Hot Gas Halo with O VII and O VIII Emission Lines
Bregman, Joel N.; Miller, Matthew J.
The Milky Way hosts a hot (≈2 × 106 K), diffuse, gaseous halo based on detections of z = 0 O VII and O VIII absorption lines in quasar spectra and emission lines in blank-sky spectra. Here we improve constraints on the structure of the hot gas halo by fitting a radial model to a much larger sample of O VII and O VIII emission line measu…
LoCuSS: The Slow Quenching of Star Formation in Cluster Galaxies and the Need for Pre-processing
Finoguenov, A.; Smith, G. P.; Okabe, N. +8 more
We present a study of the spatial distribution and kinematics of star-forming galaxies in 30 massive clusters at 0.15 < z < 0.30, combining wide-field Spitzer 24 µm and GALEX near-ultraviolet imaging with highly complete spectroscopy of cluster members. The fraction (fSF) of star-forming cluster galaxies rises steadily with …
NuSTAR Spectroscopy of Multi-component X-Ray Reflection from NGC 1068
Hailey, Charles J.; Brandt, William N.; Comastri, Andrea +26 more
We report on high-energy X-ray observations of the Compton-thick Seyfert 2 galaxy NGC 1068 with NuSTAR, which provide the best constraints to date on its >10 keV spectral shape. The NuSTAR data are consistent with those from past and current instruments to within cross-calibration uncertainties, and we find no strong continuum or line variabili…
Accretion-powered Pulsations in an Apparently Quiescent Neutron Star Binary
Deller, Adam T.; Lyne, Andrew G.; Bogdanov, Slavko +10 more
Accreting millisecond X-ray pulsars (AMXPs) are an important subset of low-mass X-ray binaries (LMXBs) in which coherent X-ray pulsations can be observed during occasional, bright outbursts (X-ray luminosity {L}{{X}}∼ {10}36 {erg} {{{s}}}-1). These pulsations show that matter is being channeled onto the neutron sta…
Suppression of Star Formation in NGC 1266
Meier, David S.; Chang, Philip; Martín, Sergio +11 more
NGC 1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicat…
A Very Deep Chandra Observation of the Galaxy Group NGC 5813: AGN Shocks, Feedback, and Outburst History
Simionescu, A.; Giacintucci, S.; David, L. +11 more
We present results from a very deep (650 ks) Chandra X-ray observation of the galaxy group NGC 5813, the deepest Chandra observation of a galaxy group to date. This system uniquely shows three pairs of collinear cavities, with each pair associated with an unambiguous active galactic nucleus (AGN) outburst shock front. The implied mean kinetic powe…
Coordinated X-Ray, Ultraviolet, Optical, and Radio Observations of the PSR J1023+0038 System in a Low-mass X-Ray Binary State
Deller, Adam T.; Lyne, Andrew G.; Bogdanov, Slavko +14 more
The PSR J1023+0038 binary system hosts a neutron star and a low-mass, main-sequence-like star. It switches on year timescales between states as an eclipsing radio millisecond pulsar and a low-mass X-ray binary (LMXB). We present a multi-wavelength observational campaign of PSR J1023+0038 in its most recent LMXB state. Two long XMM-Newton observati…