Search Publications
Pushing the ground-based limit: 14-µmag photometric precision with the definitive Whole Earth Telescope asteroseismic data set for the rapidly oscillating Ap star HR1217
Kepler, S. O.; Kawaler, S. D.; Winget, D. E. +43 more
HR1217 is one of the best-studied rapidly oscillating Ap (roAp) stars, with a frequency spectrum of alternating even- and odd-l modes that are distorted by the presence of a strong, global magnetic field. Several recent theoretical studies have found that within the observable atmospheres of roAp stars the pulsation modes are magneto-acoustic with…
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…
Non-parametric mass reconstruction of A1689 from strong lensing data with the Strong Lensing Analysis Package
Diego, J. M.; Broadhurst, T.; Benítez, N. +3 more
We present the mass distribution in the central area of the cluster A1689 by fitting over 100 multiply lensed images with the non-parametric Strong Lensing Analysis Package. The surface mass distribution is obtained in a robust way, finding a total mass of 0.25 × 1015h-1 Msolar within a 70-arcsec circle radius from…
Improved bow shock model with dependence on the IMF strength
Němeček, Z.; Šafránková, J.; Jelínek, K. +2 more
The presence of the bow shock in front of an obstacle immersed into a supersonic flow of collisionless plasma has been theoretically predicted and experimentally confirmed more than 40 years ago. However, in spite of a great effort of theoreticians and experimenters, we are still not able to predict the bow shock location under varying upstream co…
Quasi-monochromatic ULF foreshock waves as observed by the four-spacecraft Cluster mission: 1. Statistical properties
Balogh, A.; Dandouras, I.; Eastwood, J. P. +2 more
Cluster data are used to study the statistics of a particular type of foreshock wave: quasi-monochromatic ultra-low-frequency (ULF) waves with characteristic periods of 30 s in the spacecraft frame. On the basis of a large set of foreshock observations made in 2001 with spacecraft separations ∼600 km, the intrinsic properties of the waves are foun…
Thick disks and halos of spiral galaxies M 81, NGC 55 and NGC 300
Tikhonov, N. A.; Galazutdinova, O. A.; Drozdovsky, I. O.
By using images from the HST/WFPC2/ACS archive, we have analyzed the spatial distribution of the AGB and RGB stars along the galactocentric radius of nearby spiral galaxies M 81, NGC 300 and NGC 55. Examining color-magnitude diagrams and stellar luminosity functions, we gauge the stellar contents of the surroundings of the three galaxies. The red …
Gemini Near Infrared Spectrograph Observations of the Central Supermassive Black Hole in Centaurus A
Gebhardt, Karl; Richstone, Douglas; Bergmann, Marcel +1 more
The Gemini Near Infrared Spectrograph on Gemini South unlocks new possibilities to study the central black holes (BHs) in dusty galaxies that have been inaccessible to previous BH studies. We exploit good near-infrared seeing to measure the central BH of Centaurus A (NGC 5128). We measure the stellar kinematics of NGC 5128 using the region around …
Revealing the Interaction between the X-Ray Gas of Starburst Galaxy UGC 6697 and the Hot Intracluster Medium of A1367
Vikhlinin, A.; Sun, M.
We present the result from a Chandra observation of an X-ray-luminous starburst galaxy, UGC 6697, which is embedded in the northwest hot region of A1367 (5-6 keV). A very sharp X-ray edge (~13-fold surface brightness jump) at the southeast and a long tail (at least 60 kpc from the nucleus) at the northwest of the galaxy are detected, as expected i…
Integral field spectroscopy of the ultraluminous X-ray source Holmberg II X-1
Greiner, J.; Costantini, E.; Roth, M. +10 more
We present optical integral field observations of the H II region containing the ultraluminous X-ray source Holmberg II X-1. We confirm the existence of an X-ray ionized nebula as the counterpart of the source owing to the detection of an extended He II λ4686 region (21× 47 pc) at the Chandra ACIS-S position. An extended blue object with a size of…