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The young nuclear stellar disc in the SB0 galaxy NGC 1023
Morelli, L.; Dalla Bontà, E.; Corsini, E. M. +3 more
Small kinematically decoupled stellar discs with scalelengths of a few tens of parsec are known to reside in the centre of galaxies. Different mechanisms have been proposed to explain how they form, including gas dissipation and merging of globular clusters. Using archival Hubble Space Telescope imaging and ground-based integral-field spectroscopy…
Partitioning of integrated energy fluxes in four tail reconnection events observed by Cluster
Goldstein, Melvyn; Gurgiolo, Chris; Thaller, Scott +4 more
We present the partitioning of integrated energy flux from four tail reconnection events observed by Cluster, focusing on the relative contributions of Poynting flux, electron, H+ and O+ enthalpy, and kinetic energy flux in the tailward and earthward directions in order to study temporal and spatial features of each event. We further subdivide the…
Studying the Interstellar Medium and the Inner Region of NPS/LOOP 1 with Shadow Observations toward MBM36
Liu, W.; Galeazzi, M.; Ursino, E.
We analyzed data from a shadow observation of the high density molecular cloud MBM36 (l ∼ 4°, b ∼ 35°) with Suzaku. MBM36 is located in a region that emits relatively weakly in the 3/4 keV band compared to the surrounding North Polar Spur (NPS)/Loop 1 structure and the Galactic Bulge (GB). The contrast between high and low density targets in the M…
A Multi-instrument Analysis of a C4.1 Flare Occurring in a δ Sunspot
Guglielmino, S. L.; Romano, P.; Zuccarello, F. P. +5 more
We present an analysis of multi-instrument space- and ground-based observations relevant to a C4.1 solar flare that occurred in the active region (AR) NOAA 11267 on 2011 August 6. Solar Dynamics Observatory observations indicate that at the flare’s beginning, it was localized in the preceding sunspot of the AR, which exhibits a δ configuration. Al…
The fundamental parameters of the roAp star HD 24712. A rapidly oscillator at the red edge of the instability strip
Shulyak, D.; ten Brummelaar, T. A.; Perraut, K. +4 more
Context. There is still a debate about the nature of the mechanism that causes the pulsation excitation of the rapidly oscillating Ap stars that oscillate above the highest theoretically acoustic frequency. HD 24712 is a good test case for such a study because it is bright, its parallax accurately determined, and its frequency spectrum is well kno…
Stellar twins determine the distance of the Pleiades
Casey, Andrew R.; Hawkins, Keith; Jofré, Paula +5 more
Since the release of the Hipparcos catalogue in 1997, the distance to the Pleiades open cluster has been heavily debated. The distance obtained from Hipparcos and those by alternative methods differ by 10 to 15%. As accurate stellar distances are key to understanding stellar structure and evolution, this dilemma puts the validity of some stellar e…
On improving the accuracy of electron density profiles obtained at high altitudes by the ionospheric sounder on the Mars Express spacecraft
Gurnett, D. A.; Němec, F.; Morgan, D. D.
We attempt to improve the standard inversion routine used to obtain electron density profiles from the data measured by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) topside radar sounder on board the Mars Express spacecraft. Artificial ionospheric traces corresponding to how the MARSIS instrument would see model electro…
Solar Energetic Particle Event Associated with the 2012 July 23 Extreme Solar Storm
Wang, Rui; Yang, Zhongwei; Liu, Ying D. +3 more
We study the solar energetic particle (SEP) event associated with the 2012 July 23 extreme solar storm, for which Solar Terrestrial Relations Observatory (STEREO) and the spacecraft at L1 provide multi-point remote sensing and in situ observations. The extreme solar storm, with a superfast shock and extremely enhanced ejecta magnetic fields observ…
Hemispheric asymmetry in the near-Venusian magnetotail during solar maximum
Zhang, T. L.; Baumjohann, W.; Xiao, S. D.
During solar minimum the near-Venusian magnetotail exhibits a hemispheric asymmetry in the cross-tail field distribution. It implies that the magnetic field lines in the -E hemisphere are wrapped more tightly around Venus than in the +E hemisphere. Therefore, a strong field reversal region occurs in the magnetotail, which is prone to the magnetic …
Multi-wavelength Study of a Delta-spot. I. A Region of Very Strong, Horizontal Magnetic Field
Jaeggli, S. A.
Active region NOAA 11035 appeared in 2009 December, early in the new solar activity cycle. This region achieved a delta sunspot (δ spot) configuration when parasitic flux emerged near the rotationally leading magnetic polarity and traveled through the penumbra of the largest sunspot in the group. Both visible and infrared imaging spectropolarimetr…