Search Publications
Clusters in the inner spiral arms of M 51: The cluster IMF and the formation history
Panagia, N.; Bastian, N.; Bik, A. +2 more
We present the results of an analysis of the HST-WFPC2 observations of the interacting galaxy M 51. From the observations in 5 broadband filters (UBVRI) and two narrowband filters (Hα and [OIII]) we study the cluster population in a region of 3.2 x 3.2 kpc2 in the inner spiral arms of M 51, at a distance of about 1 to 3 kpc from the nuc…
X-ray continuum variability of MCG-6-30-15
Nandra, K.; Vaughan, S.; Fabian, A. C.
This paper presents a comprehensive examination of the X-ray continuum variability of the bright Seyfert 1 galaxy MCG-6-30-15. The source clearly shows the strong, linear correlation between rms variability amplitude and flux first seen in Galactic X-ray binaries. The high-frequency power spectral density (PSD) of MCG-6-30-15 is examined in detail…
A Dynamical Model for the Globular Cluster G1
Baumgardt, Holger; Makino, Junichiro; Hut, Piet +2 more
We present a comparison between the observational data on the kinematical structure of G1 in M31, obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 and Space Telescope Imaging Spectrograph instruments, and the results of dynamical simulations carried out using the special purpose computer GRAPE-6. We have obtained good fits fo…
Radio Emission from an Ultraluminous X-ray Source
Kaaret, Philip; Zezas, Andreas; Corbel, Stephane +1 more
The physical nature of ultraluminous x-ray sources is uncertain. Stellar-mass black holes with beamed radiation and intermediate black holes with isotropic radiation are two plausible explanations. We discovered radio emission from an ultraluminous x-ray source in the dwarf irregular galaxy NGC 5408. The x-ray, radio, and optical fluxes as well as…
Chemical sources of haze formation in Titan's atmosphere
Atreya, S. K.; Wilson, E. H.
A prominent feature of Titan's atmosphere is a thick haze region that acts as the end product of hydrocarbon and nitrile chemistry. Using a one-dimensional photochemical model, an investigation into the chemical mechanisms responsible for the formation of this haze region is conducted. The model derives profiles for Titan's atmospheric constituent…
X-Ray Emission from the Hot Interstellar Medium and Southwest Radio Lobe of the Nearby Radio Galaxy Centaurus A
Churazov, E.; Hardcastle, M. J.; Worrall, D. M. +5 more
We present results from two Chandra/ACIS-I observations and one XMM-Newton observation of X-ray emission from the interstellar medium (ISM) and the inner radio lobes of the nearby radio galaxy Centaurus A. The ISM has an average radial surface brightness profile that is well described by a β-model profile with index β=0.40+/-0.04 and a temperature…
On the Central Structure of M15
Baumgardt, Holger; Makino, Junichiro; Hut, Piet +2 more
We present a detailed comparison between the latest observational data on the kinematical structure of the core of M15, obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph and Wide Field Planetary Camera 2 instruments, and the results of dynamical simulations carried out using the special purpose GRAPE-6 computer. The obs…
On the Lyalpha emission from gamma-ray burst host galaxies: Evidence for low metallicities
Fruchter, A. S.; Wijers, R. A. M. J.; Pedersen, H. +11 more
We report on the results of a search for Lyalpha emission from the host galaxy of the z=2.140 GRB 011211 and other galaxies in its surrounding field. We detect Lyalpha emission from the host as well as from six other galaxies in the field. The restframe equivalent width of the Lyalpha line from the GRB 011211 host is about 21 Å. This is the fifth …
Spectroscopic Binaries, Velocity Jitter, and Rotation in Field Metal-poor Red Giant and Red Horizontal-Branch Stars
Latham, David W.; Stefanik, Robert P.; Morse, Jon A. +2 more
We summarize 2007 radial velocity measurements of 91 metal-poor field red giants. Excluding binary systems with orbital solutions, our coverage averages 13.7 yr per star, with a maximum of 18.0 yr. We report four significant findings. (1) Sixteen stars are found to be spectroscopic binaries, and we present orbital solutions for 14 of them. The spe…
Changes in Solar Dynamics from 1995 to 2002
Basu, Sarbani; Antia, H. M.
Data obtained by the GONG and MDI instruments over the last 7 years are used to study how solar dynamics-both rotation and other large scale flows-has changed with time. In addition to the well-known phenomenon of bands of faster and slower rotation moving toward the equator and pole, we find that the zonal flow pattern rises upward with time. Lik…