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Is Thermal Expansion Driving the Initial Gas Ejection in NGC 6251?
Melia, Fulvio; Liu, Siming; Fatuzzo, Marco
The relativistic jets in active galactic nuclei (AGNs) are probably driven by the action of supermassive, spinning black holes. There is very little direct evidence for this, however, since the nuclei of active galaxies are difficult to study. This is now changing with new, high-resolution multiwavelength observations of nearby sources such as Sgr…
Star formation in the warped outer pseudoring of the spiral galaxy NGC 3642
Bosma, A.; Athanassoula, E.; Verdes-Montenegro, L.
NGC 3642 was classified as a spiral galaxy with three rings and no bar. We have performed an HI and optical study of this nearly face-on galaxy. We find that the nuclear ring might in fact be part of an inner one-armed spiral, that could be driving nuclear accretion and feeding the central activity in the inner kpc. The inner ring is faint, and th…
Optical Identification of the X-Ray Burster X1746-370 in the Globular Cluster NGC 6441
Anderson, Scott F.; Margon, Bruce; Deutsch, Eric W. +2 more
We find convincing observational evidence to confirm the optical identification of the X-ray burster X1746-370, located in the globular cluster NGC 6441. Chandra HRC-I imaging yields a much improved X-ray position for the source, which we show to be fully consistent with our rederived position of a UV-excess star, U1, in the same astrometric refer…
Evidence of a Strong N V/C IV Correlation between Emission and Absorption Lines in Active Galactic Nuclei
Green, Paul J.; Kuraszkiewicz, Joanna K.
The narrow absorption lines (NALs) that are seen in the rest-frame ultraviolet near the systemic redshift of active galactic nuclei (AGNs) are not always intrinsic to the near-nuclear region but may originate in the host galaxy or in neighboring galaxies intervening along the line of sight. A variety of criteria have been sought-and several identi…
Ion Effective Temperatures in Polar Coronal Holes: Observations versus Ion-Cyclotron Resonance
Patsourakos, S.; Habbal, S. R.; Hu, Y. Q.
The resonant cyclotron interaction between ion-cyclotron waves and solar wind species is considered nowadays to be a strong candidate for heating and acceleration of protons, α-particles, and heavy ions. A crucial physical parameter for determining the amount and the location of significant heating and acceleration, which the different solar wind …
New radio instrumentation for the study of sunspots and starspots
White, S. M.
Much of the radio emission from the Sun and similar stars depends directly on magnetic fields for its origin. For this reason, radio emission contains important diagnostic information on solar and stellar magnetic fields. This paper reviews radio measurements of coronal magnetic fields and discusses new radio instrumentation that will exploit this…
Variability in the solar constant from irradiances shortward of Lyman-Alpha
Tobiska, W. Kent
The variation in the solar constant, S(t), is reproduced by the SOLAR2000 Research Grade v1.05 empirical solar irradiance model and is described for 5 solar cycles between cycles 18 and 23 (February 14, 1947 through May 31, 2000). This solar constant variation is dependent upon the derivation data sets and the formulation of SOLAR2000 which are de…
Atmospheric Dynamics and Magnetic Activity Associated With A Coronal Mass Ejection
Zhang, Jun; Wang, Jingxiu; Yang, Zhiliang +1 more
By using multi-wavelength observations, we explored the atmospheric dynamics and the surface magnetic activity in NOAA 9026, which were associated with the initiation of a halo coronal mass ejection (CME) on 6 June, 2000. In an interval of less than two hours, two X-class X-ray flares took place successively, each along with one eruption of a fila…
Astrometric Orbits from a Direct Combination of Ground-Based Catalogs with the Hipparcos Catalog
Kiyaeva, O. V.; Goncharov, G. A.
Detectability and characteristics of the 2.223 MeV line emission from nearby X-ray binaries
Guessoum, N.; Jean, P.
We present an application and an improvement of the model of Jean & Guessoum (\cite{JG01}) for the production of the 2.223 MeV line resulting from the capture of neutrons in the atmosphere of the secondary in an X-ray binary system. In this model, the neutrons are produced in the accretion disk around the compact primary star and radiated in a…