Search Publications
Three-dimensional Structure of Coronal Mass Ejections from LASCO Polarization Measurements
Wang, Dennis; Dere, Kenneth P.; Howard, Russell
The three-dimensional structure of a coronal mass ejection (CME) is essential information for understanding the process by which they are ejected from the Sun. Coronagraphic measurements readily provide information on the structure of CMEs in the plane of the sky. It has been known for some time that polarization measurements can provide informati…
Hubble Space Telescope ACS Images of the GG Tauri Circumbinary Disk
Stapelfeldt, K. R.; Ford, H. C.; Illingworth, G. D. +6 more
Hubble Space Telescope Advanced Camera for Surveys images of the young binary GG Tauri and its circumbinary disk in V and I bandpasses were obtained in 2002 and are the most detailed of this system to date. They confirm features previously seen in the disk including a ``gap'' apparently caused by shadowing from circumstellar material, an asymmetri…
The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda I and Andromeda III
Da Costa, G. S.; Pritzl, Barton J.; Armandroff, Taft E. +1 more
We present the results of variable star searches of the M31 dwarf spheroidal (dSph) companions Andromeda I and Andromeda III using the Hubble Space Telescope. A total of 100 variable stars were found in And I, while 56 were found in And III. One variable found in And I and another in And III may be type II Cepheids. In addition to this variable in…
What a local sample of spectroscopic binaries can tell us about the field binary population
Schröder, Klaus-Peter; Fisher, James; Smith, Robert Connon
We study a sample of spectroscopic binaries (SBs) in the local solar neighbourhood (d<= 100 pc and MV<= 4) in an attempt to find the distributions of the period, P, the primary mass, m1, and the mass ratio q(=m2/m1), as well as the initial mass function (IMF) of the local population of field binari…
Irradiance models
Solanki, S. K.; Krivova, N. A.; Wenzler, T.
Measurements of solar irradiance have revealed variations at all the sampled time scales (ranging from minutes to the length of the solar cycle). One important task of models is to identify the causes of the observed (total and spectral) irradiance variations. Another major aim is to reconstruct irradiance over time scales longer than sampled by d…
INTEGRAL observations of five sources in the Galactic Center region
Sunyaev, R.; Revnivtsev, M.; Lutovinov, A. +1 more
A number of new X-ray sources (IGR J17091-3624, IGR/XTE J17391-3021, IGR J17464-3213 (=XTE J17464-3213 = H 1743-322), IGR J17597-2201, SAX/IGR J18027-2017) have been observed with the INTEGRAL observatory during ultra deep exposure of the Galactic Center region in August-September 2003. Most of them were permanently visible by INTEGRAL at energies…
Time series study of EUV spicules observed by SUMER/SoHO
Doyle, J. G.; Xia, L. D.; Popescu, M. D. +1 more
Here we study the dynamic properties of EUV spicules seen at the solar limb. The selected data were obtained as time series in polar coronal holes by SUMER/SoHO. The short exposure time and the almost fixed position of the spectrometer's slit allow the analysis of spicule properties such as occurrence, lifetime and Doppler velocity. Our data revea…
Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
Peterson, Bradley M.; Vestergaard, Marianne
We study the low-contrast Fe II emission blends in the ultraviolet (1250-2200 Å) and optical (4000-6000 Å) spectra of the Seyfert 1 galaxy NGC 5548 and show that these features vary in flux and that these variations are correlated with those of the optical continuum. The amplitude of variability of the optical Fe II emission is 50%-75% that of Hβ,…
Reevaluation of the Magnetic Structure and Evolution Associated with the Bastille Day Flare on 2000 July 14
Zhang, Hongqi; Liu, Chang; Wang, Haimin +1 more
The Bastille Day flare on 2000 July 14 was well observed by several space- and ground-based observatories and studied extensively by many researchers. Recently, we discovered that a large fraction of X-class flares are associated with a very interesting evolutionary pattern in δ sunspots: part of the outer δ spot structure decays rapidly after maj…
The early stage of a cosmic collision? XMM-Newton unveils two obscured AGN in the galaxy pair ESO509-IG066
Guainazzi, M.; Jiménez-Bailón, E.; Piconcelli, E. +1 more
We report the XMM-Newton discovery of a X-ray bright AGN pair in the interacting galaxy system ESO509-IG066. Both galaxies host an X-ray luminous (LX ∼ 1043 erg s-1) obscured nucleus with column densities NH ≃ 7 × 1022 cm-2 and NH ≃ 5 × 1021 cm-2. Th…