Search Publications
Hubble Space Telescope Snapshot Survey of Post-AGB Objects
Szczerba, R.; Meixner, M.; Ueta, T. +3 more
The results of a Hubble Space Telescope (HST) snapshot survey of post-AGB objects are shown. The aim of the survey is to complement existing HST images of protoplanetary nebulae and to connect various types of nebulosities with the physical and chemical properties of their central stars. Nebulosities are detected in 15 of 33 sources. Images and ph…
Thermal X-Rays from Millisecond Pulsars: Constraining the Fundamental Properties of Neutron Stars
Bogdanov, Slavko; Grindlay, Jonathan E.; Rybicki, George B.
We model the X-ray properties of millisecond pulsars (MSPs) by considering hot-spot emission from a weakly magnetized neutron star (NS) covered by a hydrogen atmosphere. We investigate the limitations of using the thermal X-ray pulse profiles of MSPs to constrain the mass-to-radius (M/R) ratio of the NS. The accuracy is strongly dependent on the v…
Relationship between Rotating Sunspots and Flares
Zhang, Hongqi; Liu, Jihong; Zhang, Yin
Active Region (AR) NOAA 10486 was a super AR in the declining phase of solar cycle 23. Dominated by the rapidly rotating positive polarity of an extensive δ sunspot, it produced several powerful flare-CMEs. We study the evolution and properties of the rotational motion of the major poles of positive polarities and estimate the accumulated helicity…
Magnetogram Measures of Total Nonpotentiality for Prediction of Solar Coronal Mass Ejections from Active Regions of Any Degree of Magnetic Complexity
Falconer, D. A.; Moore, R. L.; Gary, G. A.
For investigating the magnetic causes of coronal mass ejections (CMEs) and for forecasting the CME productivity of active regions, in previous work we have gauged the total nonpotentiality of a whole active region by either of two measures, LSSM and LSGM, two measures of the magnetic field along the main neutral line in a vec…
Solving the Discrepancy between the Seismic and Photospheric Solar Radius
Schmutz, W.; Haberreiter, M.; Kosovichev, A. G.
Two methods are used to observationally determine the solar radius: One is the observation of the intensity profile at the limb; the other one uses f-mode frequencies to derive a "seismic" solar radius which is then corrected to optical depth unity. The two methods are inconsistent and lead to a difference in the solar radius of ~0.3 Mm. Because o…
Recent star formation in nearby 3CR radio-galaxies from UV HST observations
Capetti, A.; Baldi, R. D.
We analyzed HST images of 31 nearby (z ≲ 0.1) 3CR radio-galaxies. We compared their UV and optical images to detect evidence of recent star formation. Six objects were excluded because they are highly nucleated or had very low UV count rates. After subtracting the emission from their nuclei and/or jets, 12 of the remaining 25 objects, presenting a…
The Extended Star Formation History of the Andromeda Spheroid at 35 kpc on the Minor Axis
Ferguson, Henry C.; Brown, Thomas M.; Gilbert, Karoline M. +14 more
Using the HST ACS, we have obtained deep optical images reaching well below the oldest main-sequence turnoff in fields on the southeast minor axis of the Andromeda galaxy, 35 kpc from the nucleus. These data probe the star formation history in the extended halo of Andromeda—that region beyond 30 kpc that appears both chemically and morphologically…
Detailed high-energy characteristics of AXP 1RXS J170849-400910. Probing the magnetosphere using INTEGRAL, RXTE, and XMM-Newton
Kuiper, L.; Hermsen, W.; den Hartog, P. R.
1RXS J170849-400910 is one of four anomalous X-ray pulsars which emit persistent luminous radiation in soft X-rays (<10 keV) as well as in hard X-rays (>10 keV). In this paper we present detailed spectral and temporal characteristics over the whole X-ray band. For this purpose data have been used from INTEGRAL, RXTE and XMM-Newton. The hard …
Formation and evolution of the chaotic terrains by subsidence and magmatism: Hydraotes Chaos, Mars
Mangold, Nicolas; Neukum, Gerhard; Costard, François +3 more
The origin of the martian chaotic terrains is still uncertain; and a variety of geologic scenarios have been proposed. We provide topographic profiles of different chaos landscapes, notably Aureum and Hydraotes Chaos, showing that an initial shallow ground subsidence occurred at the first step of the chaos formation. We infer that the subsidence w…
Venus surface thermal emission at 1 µm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions
Erard, S.; Drossart, P.; Piccioni, G. +4 more
The Venus Express spacecraft images the nightside thermal emissions using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). At 1.02, 1.10, and 1.18 µm, thermal emission from the surface is observed. The signal is attenuated by scattering and absorption in the dense atmosphere. The measured flux at the top of the atmosphere is p…