Search Publications
Study of the Solar Cycle Dependence of Low-Degree p-Modes with Michelson Doppler Imager and VIRGO
Kosovichev, A. G.; Toutain, T.
Studying variations of observational properties of low-degree solar acoustic p-modes (radial, dipole, and quadrupole) with the activity cycle is important for understanding potential effects of the cycle in the deep interior, obtaining more accurate inversions for the sound speed and rotation, and also for estimating prospective investigation of s…
Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-heated Corona
Iwasawa, K.; Mineshige, S.; Kawanaka, N.
We investigate the iron Kα fluorescent line produced by hard X-ray photons from the magnetic reconnection-heated corona. The hot corona with temperature of ~109 K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons a…
Intense Diffuse Far-Ultraviolet Emission from the Orion Nebula
Henry, R. C.; Murthy, Jayant; Sahnow, David J.
We present spectra of the diffuse far-UV (900-1200 Å) emission from a region near the Orion Nebula: the first high-resolution spectra of the diffuse background radiation. These observations were made using serendipitous Far Ultraviolet Spectroscopic Explorer (FUSE) observations and were only possible because of the strength of the diffuse emission…
HST Images Do Not Support the Presence of Three High-Velocity, Low-Mass Runaway Stars in the Core of the Orion Nebula Cluster
O'Dell, C. R.; Robberto, Massimo; Poveda, Arcadio +1 more
A recent article has employed the determination from ground-based images of high proper motions in the Orion Nebula cluster to argue that JW 349, JW 355, and JW 451 are high-velocity (38, 89, and 69 km s-1, respectively) low-mass runaway stars. We report on the measurement of the proper motions of these stars using images made by the Hu…
The XMM-Newton View of the Relativistic Spectral Features in AX J0447-0627
Ballo, L.; Braito, V.; Della Ceca, R. +1 more
The XMM-Newton observation of the optically type 1 active galactic nucleus (AGN) AX J0447-0627 (z=0.214) unambiguously reveals a complex, bright, and prominent set of lines in the 4-8 keV rest-frame energy range. Although from a phenomenological point of view, the observed properties can be described by a simple power-law model plus five narrow Ga…
The First Optical Validation of an X-Ray Line-emitting Object: A Detection in the XMM-Newton Observation of the Chandra Deep Field-South
Braito, V.; Caccianiga, A.; Severgnini, P. +2 more
We present the first optical validation of an X-ray line-emitting object (XLEO) discovered in the XMM-Newton observation of the Chandra Deep Field-South. The object is an active galactic nucleus at zX~0.66. An optical spectrum of the source indeed confirms and refines (zo=0.665) the redshift obtained from the X-ray line. The …
Evolution of Barb Angle and Filament Eruption
Liu, Y.; Li, C.; Zhang, H. Q. +6 more
Hα observations of a quiescent U-shaped filament were obtained at Big Bear Solar Observatory and at Hida Observatory with the Flare Monitoring Telescope. The filament was located in the southern hemisphere on 1998 November 4. We study the evolution of the angle of a barb with respect to the axis of the filament and find the evolution can be divide…
Separating C Stars from Dust in the Central Region of the Seyfert 2 Galaxy NGC 1241
Díaz, Rubén J.; Dottori, Horacio; Carranza, Gustavo +2 more
The Seyfert 2 galaxy NGC 1241 presents a 1.5 kpc large circumnuclear ring (CNR) of star formation embracing a small bar plus leading arms. Those structures are Paα emitters but barely seen in Hα. It also presents stellar trailing arms inside the CNR. Gemini and HST imagery allow the construction of high-resolution (V-H) and (J-Ks) color…
Properties of the Solar Acoustic Source Inferred from Nonadiabatic Oscillation Spectra
Kosovichev, A. G.; Wachter, R.
Severino et al. suggested in 2001 that observed power and cross spectra of medium-degree p-modes in velocity and intensity can be described by splitting the solar background noise into correlated, coherent, and uncoherent components. We account for the nonadiabatic nature of solar oscillations by including the perturbations of the radiative energy…
Dust Morphology of Hidden Broad-Line Region and Non-Hidden Broad-Line Region Seyfert 2 Galaxies
Hwang, Chorng-Yuan; Yu, Po-Chieh
We investigate the nuclear dust properties of hidden broad-line region (HBLR) and non-HBLR Seyfert 2 galaxies. Optical images obtained from the Hubble Space Telescope for a selected sample of HBLR and non-HBLR Seyfert 2 galaxies are fitted with the Galfit package to probe the inner structures of these galaxies within the central 1 kpc regions. Mos…