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Stellar structure of irregular galaxies: Edge-on galaxies
Tikhonov, N. A.
Stellar photometry obtained using the Hubble Space Telescope is used to study the distributions of the number densities of stars of various ages in 12 irregular and dwarf spiral galaxies viewed edge-on. Two subsystems can be distinguished in all the galaxies: a thin disk comprised of young stars and a thick disk containing a large fraction of old …
An Estimation of the Acoustic Cutoff Frequency of the Sun Based on the Properties of the Low-Degree Pseudomodes
Jiménez, A.
The acoustic cutoff frequency (νac) is an important atmospheric parameter whose estimation has in the past been based on the study of power spectra that have yielded a wide range of values between 5300 and 5700 µHz. The discovery of a solar signal well beyond the acoustic cutoff frequency (pseudomodes) might lead one to think that…
Variations in D/H and D/O from New Far Ultraviolet Spectroscopic Explorer Observations
Chayer, Pierre; Kruk, Jeffrey W.; Oliveira, Cristina M. +1 more
We use data obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) to determine the interstellar abundances of D I, N I, O I, Fe II, and H2 along the sight lines to WD 1034+001, BD +39 3226, and TD1 32709. Our main focus is on determining the D/H, N/H, O/H, and D/O ratios along these sight lines, with logN(H)>20.0, that prob…
Gamma Rays and the Evolving, Compact Structures of the 2003 October 28 X17 Flare
Schrijver, C. J.; Hudson, H. S.; Tarbell, T. D. +2 more
The X17 flare on 2003 October 28 was observed by high-resolution imaging or spectroscopic instruments on CORONAS, GOES, INTEGRAL, RHESSI, SOHO, and TRACE. These spacecraft observed the temporal evolution of the γ-ray positron-annihilation and nuclear de-excitation line spectra, imaged the hard X-ray bremsstrahlung and EUV and UV emission, and meas…
Evidence for Tether-Cutting Reconnection in a Quadrupole Magnetic Configuration in the April 9, 2001, M7.9 Flare
Yurchyshyn, V.; Wang, H.; Karlický, M. +1 more
We studied the M7.9 flare on April 9, 2001 that occurred within a δ-sunspot of active region NOAA 9415. We used a multi-wavelength data set, which includes Yohkoh, TRACE, SOHO, and ACE spacecraft observations, Potsdam and Ondřejov radio data and Big Bear Solar Observatory (BBSO) images in order to study the large-scale structure of this two-ribbon…
A deep search for Martian dust rings and inner moons using the Hubble Space Telescope
Nicholson, Philip D.; Hamilton, Douglas P.; Showalter, Mark R.
It has long been suspected that Mars might be encircled by two faint rings, one originating from each of its moons Phobos and Deimos. Meteoroid impacts into these moons should release clouds of dust that quickly spread out to become rings; similar dust rings have been associated with several small inner moons of the gas giants. On May 28, 2001 Mar…
INTEGRAL observations of active galactic nuclei obscured by the Galactic plane
de Rosa, A.; Hill, A. B.; Walter, R. +9 more
In this paper, we present INTEGRAL observations of seven active galactic nuclei (AGNs): two newly discovered type 1 Seyferts, IGR J18027-1455 and J21247+5058 and five well-known Seyferts, NGC 6814 (type 1.5), Cygnus A (type 2), MCG-05-23-16 (type 2), ESO 103-G035 (type 2) and GRS 1734-292. For IGR J18027-1455 and J21247+5058, only INTEGRAL/IBIS da…
The 17-22 October (1999) solar-interplanetary-geomagnetic event: Very intense geomagnetic storm associated with a pressure balance between interplanetary coronal mass ejection and a high-speed stream
Balmaceda, Laura A.; Dal Lago, Alisson; Gonzalez, Walter D. +9 more
Using observations from the Advanced Composition Explorer (ACE) magnetic field and plasma experiments, we investigate the magnetic, thermal, and dynamic pressure balance in the border of a high-speed stream (HSS) and an average-speed interplanetary coronal mass ejection (ICME) observed on 21-22 October (1999). We believe that the HSS compressed th…
[TiII] and [NiII] emission from the strontium filament of η Carinae
Gull, T. R.; Smith, N.; Bautista, M. A. +2 more
We study the nature of the [TiII] and [NiII] emission from the so-called strontium filament found in the ejecta of η Carinae. To this purpose, we employ multilevel models of the TiII and NiII systems, which are used to investigate the physical condition of the filament and the excitation mechanisms of the observed lines. For the TiII ion, for whic…
A short hard X-ray flare from the blazar NRAO 530 observed by INTEGRAL
Maraschi, L.; Ghisellini, G.; Pian, E. +6 more
We report about a short flare from the blazar NRAO 530 occurred on 17 February 2004 and detected serendipitously by the IBIS/ISGRI detector on board INTEGRAL. In the 20-40 keV energy range, the source, that is otherwise below the detection limit, is detected at a level of ≈2 × 10-10 erg cm-2 s-1 during a time inter…