Science Archives Publication System

Photoevaporating Flows from the Cometary Knots in the Helix Nebula (NGC 7293)

DOI: 10.1086/318654 Bibcode: 2001ApJ...548..288L

Henney, W. J.; Raga, A. C.; López-Martín, L. +2 more

We explain the Hα emission of the cometary knots in the Helix Nebula (NGC 7293) with an analytical model that describes the emission of the head of the globules as a photoevaporated flow produced by the incident ionizing radiation of the central star. We compare these models with the Hα emission obtained from the Hubble Space Telescope (HST) archi…

2001 • The Astrophysical Journal

eHST 40

Interpretation of coronal off-limb spectral line width measurements

DOI: 10.1051/0004-6361:20010643 Bibcode: 2001A&A...374L...9M

Moran, T. G.

Spectral line widths measured above the solar limb have been used to infer wave velocity amplitude height dependencies, supporting Alfven wave coronal heating and wave driven solar wind models. Comparison of the inferred amplitude/density dependence with a constant magnetic field strength, undamped wave propagation model have shown good agreement,…

2001 • Astronomy and Astrophysics

SOHO 40

Simultaneous XMM-Newton and BeppoSAX observation of the Seyfert I galaxy IC 4329A

DOI: 10.1051/0004-6361:20011258 Bibcode: 2001A&A...378..806G

Gondoin, P.; Parmar, A. N.; Oosterbroek, T. +3 more

We report on a simultaneous XMM-Newton and BeppoSAX observation of the Seyfert 1 galaxy IC 4329A performed in 2001 January. Above 1 keV, EPIC spectra show a narrow Fe K emission line at 6.42^+0.04_-0.03 keV with an equivalent width of 43+/-1 eV. An absorption edge is detected at 7.1+/-0.4 keV in the source rest frame that has n…

2001 • Astronomy and Astrophysics

XMM-Newton 40

EPIC Simulations of Bright Companions to Neptune's Great Dark Spots

DOI: 10.1006/icar.2001.6603 Bibcode: 2001Icar..151..275S

Sromovsky, L. A.; Showman, A. P.; Dowling, T. E. +1 more

We present a three-dimensional model of the bright companion clouds associated with Neptune's Great Dark Spots (GDSs). Our results support the hypothesis that the bright companions of the southern-hemisphere GDS discovered in 1989 and of the northern-hemisphere GDS discovered in 1994 are methane clouds that form at or just below the tropopause and…

2001 • Icarus

eHST 40

When Did the Hubble Sequence Appear?: Morphology, Color, and Number-Density Evolution of the Galaxies in the Hubble Deep Field North

DOI: 10.1093/pasj/53.5.833 Bibcode: 2001PASJ...53..833K

Yamada, Toru; Kajisawa, Masaru

Using the HST WFPC2/NICMOS archival data of the Hubble Deep Field North, we constructed a nearly complete sample of the M_V < -20 (~ L^* + 1) galaxies to z = 2, and investigate when the Hubble sequence appeared, namely, the evolution of the morphology, colors, and the comoving number density of the sample. Even if taking int…

2001 • Publications of the Astronomical Society of Japan

eHST 40

Infrared Space Observatory Spectra of R Coronae Borealis Stars. I. Emission Features in the Interval 3-25 Microns

DOI: 10.1086/321504 Bibcode: 2001ApJ...555..925L

Rao, N. Kameswara; Lambert, David L.; Pandey, Gajendra +1 more

Infrared Space Observatory 3-25 µm spectra of the R Coronae Borealis stars V854 Cen, R CrB, and RY Sgr are presented and discussed. Sharp emission features coincident in wavelength with the well-known unidentified emission features are present in the spectrum of V854 Cen but not in the spectra of R CrB and RY Sgr. Since V854 Cen is not parti…

2001 • The Astrophysical Journal

ISO 40

Coronal Inflows and Sector Magnetism

DOI: 10.1086/338104 Bibcode: 2001ApJ...562L.107S

Sheeley, N. R., Jr.; Wang, Y. -M.

We have remeasured the rate of coronal inflows during 1996-2001, taking into account multiple occurrences per day, and have displayed the results in Carrington stack plots to study their long-term behavior. The stack plots show long-lived recurrence patterns related to the sectorial component of the Sun's large-scale field. In particular, most inf…

2001 • The Astrophysical Journal

SOHO 40

A 2000 Kilometer per Second ``Pristine'' Post-asymptotic Giant Branch Wind in the Proto-planetary Nebula He 3-1475

DOI: 10.1086/320687 Bibcode: 2001ApJ...553L.173S

Sahai, R.; Sánchez Contreras, C.

We analyze (archival) Space Telescope Imaging Spectrograph long-slit Hα spectra of the proto-planetary nebula He 3-1475. We find two remarkable blueshifted absorption features arising from the inner ~5×10¹⁶ cm of the nebula, revealing the presence of two different winds outflowing at high velocity from the central star. The kinematic ag…

2001 • The Astrophysical Journal

eHST 40

Numerical Magnetohydrodynamic (MHD) Modeling of Coronal Mass Ejections (CMEs)

DOI: 10.1023/A:1005284600631 Bibcode: 2001SSRv...95..191W

Plunkett, S. P.; Wu, S. T.; Andrews, M. D.

The Coronal Mass Ejection (CME) is arguably the most important discovery of solar eruptive phenomena in the 20th century. It is now also recognized that CMEs have great impact on the Earth's environment by inducing geomagnetic storms. Thus, development of simulation models to understand the physical mechanisms of CME initiation and propagation has…

2001 • Space Science Reviews

SOHO 40

On the nature of the hard X-ray source 4U 2206+54

DOI: 10.1051/0004-6361:20010476 Bibcode: 2001A&A...371.1056N

Reig, P.; Negueruela, I.

The recent discovery of a ~ 9.5\:d period in the X-ray lightcurve of the massive X-ray binary 4U 2206+54 has opened the possibility that it is a Be/X-ray binary with an unusually close orbit, which, together with its low intrinsic luminosity, suggests that the system is actually a Be + WD binary, in which a white dwarf accretes …

2001 • Astronomy and Astrophysics

IUE 40