Search Publications
The Link between Star Formation and Accretion in LINERs: A Comparison with Other Active Galactic Nucleus Subclasses
O'Halloran, B.; Dudik, R. P.; Satyapal, S. +1 more
We present archival high-resolution X-ray imaging observations of 25 nearby LINERs observed by ACIS on board Chandra. This sample builds on our previously published proprietary and archival X-ray observations and includes the complete set of LINERs with published black hole masses and FIR luminosities that have been observed by Chandra. Of the 82 …
Halos of Spiral Galaxies. I. The Tip of the Red Giant Branch as a Distance Indicator
Ferguson, H. C.; Rich, R. M.; Mouhcine, M. +2 more
We have imaged the halo populations of a sample of nearby spiral galaxies using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope with the aim of studying the stellar population properties and relating them to those of the host galaxies. In four galaxies, the red giant branch is sufficiently well populated to measure the magnit…
A Coherent Timing Solution for the Nearby Isolated Neutron Star RX J0720.4-3125
van Kerkwijk, M. H.; Kaplan, D. L.
We present the results of a dedicated effort to measure the spin-down rate of the nearby isolated neutron star RX J0720.4-3125. Comparing arrival times of the 8.39 s pulsations for data from Chandra, we derive an unambiguous timing solution for RX J0720.4-3125 that is accurate to <0.1 cycles over >5 years. Adding data from XMM and ROSAT, the…
Moving Magnetic Features as Prolongation of Penumbral Filaments
Martínez Pillet, V.; Sainz Dalda, A.
A sequence of 633 high spatial resolution magnetograms and continuum images from SOHO MDI of NOAA AR 0330 is used to study moving magnetic feature (MMF) activity in the moat surrounding a mature leader sunspot. The time-averaged frame shows that the moat region is covered by a magnetic field that exhibits the same polarity distribution as that obs…
Variations of the Mid-Infrared Emission Spectrum in Reflection Nebulae
Temi, Pasquale; Bregman, Jesse
Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM, we have observed a shift in the central wavelength of the 7.7 µm band within several reflection nebulae. This band, composed of components at 7.85 and 7.65 µm, shows a centroid shift from 7.75 µm near the edge of the nebulae to 7.65 µm toward the ce…
Detection of Water in the Shocked Gas Associated with IC 443: Constraints on Shock Models
Wang, Z.; Bergin, E. A.; Melnick, G. J. +5 more
We have used the Submillimeter Wave Astronomy Satellite (SWAS) to observe the ground-state 110-->101 transition of ortho-H2O at 557 GHz in three of the shocked molecular clumps associated with the supernova remnant IC 443. We also observed simultaneously the 487 GHz line (3,1-->3,2) of O2, the 492 …
The Hubble Space Telescope View of LINER Nuclei: Evidence for a Dual Population?
Chiaberge, Marco; Capetti, Alessandro; Macchetto, F. Duccio
We study a complete, distance-limited sample of 25 LINERs, 21 of which have been imaged with the Hubble Space Telescope. In nine objects we detect an unresolved nucleus. To study their physical properties, we compare the radio and optical properties of the nuclei of LINERs with those of other samples of local active galactic nuclei (AGNs), namely,…
Repeated X-Ray Flaring Activity in Sagittarius A*
Grosso, N.; Porquet, D.; Ferrando, P. +5 more
Investigating the spectral and temporal characteristics of the X-rays coming from Sagittarius A* (Sgr A*) is essential to our development of a more complete understanding of the emission mechanisms in this supermassive black hole located at the center of our Galaxy. Several X-ray flares with varying durations and spectral features have already bee…
Modeling Complete Distributions with Incomplete Observations: The Velocity Ellipsoid from Hipparcos Data
Hogg, David W.; Johnston, Kathryn V.; Blanton, Michael R. +1 more
An algorithm is developed to model the three-dimensional velocity distribution function of a sample of stars using only measurements of each star's two-dimensional tangential velocity. The algorithm works with ``missing data'': it reconstructs the three-dimensional distribution from data (velocity measurements) that all have one dimension that is …
Discovery of a 105 ms X-Ray Pulsar in Kesteven 79: On the Nature of Compact Central Objects in Supernova Remnants
Gotthelf, E. V.; Halpern, J. P.; Seward, F. D.
We report the discovery of 105 ms X-ray pulsations from the compact central object (CCO) in the supernova remnant Kes 79 using data acquired with the Newton X-Ray Multi-Mirror Mission (XMM-Newton). Two observations of the pulsar taken 6 days apart yield an upper limit on its spin-down rate of P˙<7×10-14 s s-1 and no eviden…