Search Publications
A string-inspired model for the low-ℓ CMB
Sagnotti, A.; Kitazawa, N.
We present a semi-analytic exploration of some low-ℓ angular power spectra inspired by “brane supersymmetry breaking (BSB)”. This mechanism splits Bose and Fermi excitations in string theory, leaving behind an exponential potential that is just too steep for the inflaton to emerge from the initial singularity while descending it. As a result, the …
Coronal energy input and dissipation in a solar active region 3D MHD model
Peter, H.; Bingert, S.; Bourdin, Ph. -A.
Context. We have conducted a 3D MHD simulation of the solar corona above an active region (AR) in full scale and high resolution, which shows coronal loops, and plasma flows within them, similar to observations.
Aims: We want to find the connection between the photospheric energy input by field-line braiding with the coronal energy conversion…
The Distance Measurement of NGC 1313 with Cepheids
Wang, Wei; Yoachim, Peter; Liu, Ji-Feng +1 more
We present the detection of Cepheids in the barred spiral galaxy NGC 1313, using the Wide Field and Planetary Camera 2 on the Hubble Space Telescope. Twenty B(F450W) and V(F555W) epochs of observations spanning over three weeks were obtained, on which the profile-fitting photometry of all stars in the monitored field was performed using the packag…
H2 Lyman and Werner band lines and their sensitivity for a variation of the proton-electron mass ratio in the gravitational potential of white dwarfs
Roueff, E.; Abgrall, H.; Bagdonaite, J. +2 more
Recently we published an accurate analysis of molecular hydrogen absorption in the photospheres of the white dwarf stars GD133 and GD29-38, previously observed with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. Constraints were derived on a possible dependence of the proton-electron mass ratio on gravitational fields that are …
Solar-cycle variations of the internetwork magnetic field
Faurobert, M.; Ricort, G.
Context. The quiet Sun exhibits a rich and complex magnetic structuring that is still not fully resolved or understood.
Aims: We intend to contribute to the debate about the origin of the internetwork magnetic fields and whether or not they are related to the global solar dynamo.
Methods: We analyzed center-to-limb polarization measureme…
Further evidence for the role of magnetotail current shape in substorm initiation
Kubyshkina, D.; Gordeev, E.; Tsyganenko, N. +3 more
Substorm initiation still remains an unsolved problem, even though there is a consensus among most researchers that its main stages include dayside reconnection and substorm expansion. Dayside reconnection results in magnetotail flux buildup to a certain critical level, after which [or after the interplanetary magnetic field (IMF) Bz turns northwa…
Dissecting the Power Sources of Low-Luminosity Emission-Line Galaxy Nuclei via Comparison of HST-STIS and Ground-Based Spectra
Filippenko, Alexei V.; Ho, Luis C.; Shields, Joseph C. +3 more
Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order…
Near-Sun speed of CMEs and the magnetic nonpotentiality of their source active regions
Tiwari, Sanjiv K.; Winebarger, Amy R.; Venkatakrishnan, P. +3 more
We show that the speed of the fastest coronal mass ejections (CMEs) that an active region (AR) can produce can be predicted from a vector magnetogram of the AR. This is shown by logarithmic plots of CME speed (from the SOHO Large Angle and Spectrometric Coronagraph CME catalog) versus each of ten AR-integrated magnetic parameters (AR magnetic flux…
Visible light and ultraviolet observations of coronal structures: physical properties of an equatorial streamer and modelling of the F corona
Spadaro, D.; Dolei, S.; Ventura, R.
The present work studies the characteristics of an equatorial streamer visible above the east limb of the Sun on March 2008, during the most recent minimum of solar activity. We analysed the visible light coronagraphic images of SOHO/LASCO and the ultraviolet observations in the H I Lyα spectral line obtained by SOHO/UVCS, and exploited the Dopple…
Role of higher-dimensional evolving wormholes in the formation of a big rip singularity
Setare, M. R.; Sepehri, A.
We study the four-dimensional Universe on the M2-M5 BIon in the thermal background. The BIon is a configuration in a flat space of a D-brane and a parallel anti-D-brane connected by a wormhole. When the branes and antibranes are well separated and the brane's spike is far from the antibrane's spike, the wormhole cannot be formed. However, when two…