Search Publications
Proper Motion and Kinematics of the Ansae in NGC 7009
Monteiro, Hektor; Schwarz, Hugo E.; Fernández, Rodrigo
We have measured the proper motion (PM) and kinematics of the ansae in NGC 7009 using high-dispersion echelle spectra and archive narrowband Hubble Space Telescope images. Assuming that the ansae are moving at equal and opposite velocities from the central star, we obtain a system radial velocity of -53+/-2 km s-1, the eastern ansa appr…
Abundances of Neutron-Capture Elements in the Hot Extreme Helium Stars V1920 Cygni and HD 124448
Rao, N. Kameswara; Lambert, David L.; Pandey, Gajendra +1 more
Analysis of Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectra of two hot extreme helium (EHe) stars, V1920 Cyg and HD 124448, provides the first measurements of abundances of neutron-capture elements for EHe stars. Although the two stars have similar abundances for elements up through the iron group, they differ strik…
Observations of Nonthermal and Thermal Hard X-Ray Spikes in an M-Class Flare
Qiu, Jiong; Wang, Haimin; Ji, Haisheng +2 more
We report a study of an M2.3 flare, which occurred on 2002 September 9 in NOAA Active Region 0105. The observation was made at Big Bear Solar Observatory (BBSO) at the wavelength of Hα-1.3 Å, with a cadence of 40 ms. The flare was also observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Three kernels appear in Hα-1.3 Å i…
Constraining the X-Ray Luminosities of Asymptotic Giant Branch Stars: TX Camelopardalis and T Cassiopeia
Soker, Noam; Kastner, Joel H.
To probe the magnetic activity levels of asymptotic giant branch (AGB) stars, we used XMM-Newton to search for X-ray emission from two well-studied objects, TX Cam and T Cas. The former star displays polarized maser emission, indicating magnetic field strengths of B~5 G, and the latter is one of the nearest known AGB stars. Neither star was detect…
An Extreme, Blueshifted Iron-Line Profile in the Narrow-Line Seyfert 1 PG 1402+261: An Edge-on Accretion Disk or Highly Ionized Absorption?
Turner, T. J.; Porquet, D.; Reeves, J. N.
We report on a short XMM-Newton observation of the radio-quiet narrow-line Seyfert 1 galaxy PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6 and 9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity of 110,000 km s-1…
High-Resolution Ultraviolet Spectra of the Dwarf Seyfert 1 Galaxy NGC 4395: Evidence for Intrinsic Absorption
Filippenko, A. V.; Turner, T. J.; Kraemer, S. B. +5 more
We present ultraviolet spectra of the dwarf Seyfert 1 nucleus of NGC 4395, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope Space Telescope Imaging Spectrograph at velocity resolutions of 7-15 km s-1. We confirm our earlier claim of C IV absorption in low-resolution UV spectra and detect a n…
Short-Duration Active Region Brightenings Observed in the Extreme Ultraviolet and Hα by the Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer and Hida Domeless Solar Telescope
Fludra, A.; Brooks, D. H.; Kurokawa, H. +6 more
We present the first detection of an Hα counterpart to the EUV blinker. The observations come from a coordinated campaign between the Hida Observatory Domeless Solar Telescope (DST) and the Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer (CDS) conducted in 2002 July and August. Utilizing studies designed for high-cadence observa…
The Galaxy Density Environment of Gamma-Ray Burst Host Galaxies
Minniti, Dante; Bornancini, Carlos G.; Martínez, Héctor J. +3 more
We analyze cross-correlation functions between gamma-ray burst (GRB) hosts and surrounding galaxies. We have used data obtained with the Very Large Telescope at Cerro Paranal (Chile), as well as public Hubble Space Telescope data. Our results indicate that GRB host galaxies do not reside in high galaxy density environments. Moreover, the host gala…
The Counterstreaming Instability in Dwarf Elliptical Galaxies with Off-Center Nuclei
Debattista, Victor P.; De Rijcke, Sven
In many nucleated dwarf elliptical galaxies (dE,N's), the nucleus is offset by a significant fraction of the scale radius with respect to the center of the outer isophotes. Using a high-resolution N-body simulation, we demonstrate that the nucleus can be driven off-center by the m=1 counterstreaming instability, which is strong in flattened stella…
Dual Flows with Supersonic Velocities in the Sunspot Transition Region
Wilhelm, K.; Kjeldseth-Moe, O.; Brynildsen, N. +1 more
Observations of sunspot transition region lines that deviate significantly from a Gaussian shape are presented. Attention is given to ``dual flows,'' a line profile phenomenon in which two distinct velocities are observed within the same spatial resolution element. In 5 out of 12 sunspots we observe dual flows. Several emission line profiles are w…