Neutron stars and black holes. Compact objects such as black holes and neutron stars have extremely high densities that cannot be created in terrestrial laboratories and involve phases of matter that are not well understood. Members of the department are studying the associated highly relativistic phenomena theoretically and observationally. One theoretical focus is understanding the interplay between magnetic and thermal processes for strongly magnetic neutron stars. In addition, just like their stellar precursors, many compact objects occur in binary systems. Members of the department study the origin and evolution of compact X-ray binaries using data from RXTE as well as ASCA and ROSAT and other X-ray data (archives). With the successful launch of Chandra, the Department is in a key position to conduct new high resolution imaging and spectral studies of compact objects in both binaries and AGN. In addition, departmental researchers continue to pursue detailed optical studies of compact objects in binaries to measure masses (of black holes) as well as phenomena associated with the accretion disk.

Accretion Flows. Accretion flows occur in many astrophysical systems and in particular produce much of the observable phenomena associated with compact objects. Departmental members are leaders in the modelling of accretion flows. Model predictions for the spectral features and transient behaviors are compared with observations, from radio to high energy X-rays and gamma rays. Particular interests in the department include flows around supermassive black holes in galaxy centers such as the one in our own galaxy. The observational differences between the flows for neutron stars and black holes are also under study.

Active Galactic Nuclei. Multiwavelength studies of active galactic nuclei (AGN) using all the resources available to CfA scientists such as the Einstein and ROSAT archives and optical and infrared observations from Mt. Hopkins telescopes have begun to unlock the secret of the energy sources in these extremely luminous objects. Theoretical models of AGN X-ray emission are being developed which require strong magnetic fields and relativistic particles, generated near a supermassive black hole. Members of the Department are leaders in the study of the active nucleus of the galaxy NGC 4258. They discovered a thin slightly warped disk inside the nucleus rotating at 1000 km/sec. The multiwavelength and VLBI observations of NGC 4258 have provided the strongest evidence yet that a massive black hole may reside in the galaxy's center. Hard X-ray telescopes and detectors are being developed and utilized by the EXITE project to study neutron stars, black holes and AGN's.

Gamma Ray Bursts. High energy gamma ray bursts are being detected with regularity now, but their nature remains a mystery. Department and CfA researchers are actively involved in modeling these bursts and identifying tests and consequences of suggested mechanisms for a wide array of data sets.

See also the related areas of stellar remnants and supernovae remnants.

Associated Professors and Lecturers

L.Greenhill, J. Grindlay, L. Hernquist, J. Huchra, J. Lee, A. Loeb, J. Moran, R. Narayan,

The International AGN Webwatch

The Chandra Multiwavelength Project , ChaMP

HRC: The High Resolution Camera on Chandra X-Ray Observatory

Very Energetic Radiation Imaging Telescope Array System, VERITAS

Chandra X-Ray Observatory

EXIST Energetic X-Ray Imaging Survey Telescope

EXITE program, including the Harvard balloon-borne Hard X-ray Imaging Telescope

Constellation X, X-Ray mission

High Energy Astrophysics, Optical and Infrared, Radio and Geoastronomy, Theoretical Astrophysics