Search Publications
Velocity Measurements for a Solar Active Region Fan Loop from Hinode/EIS Observations
Young, P. R.; Mason, H. E.; O'Dwyer, B.
The velocity pattern of a fan loop structure within a solar active region over the temperature range 0.15-1.5 MK is derived using data from the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. The loop is aligned toward the observer's line of sight and shows downflows (redshifts) of around 15 km s-1 up to a temperature of 0…
The VLT-FLAMES Tarantula Survey. IV. Candidates for isolated high-mass star formation in 30 Doradus
Crowther, P. A.; Bastian, N.; de Koter, A. +15 more
Whether massive stars (≳30 M⊙) can occasionally form in relative isolation (e.g. in clusters with M < 100 M⊙) or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star-formation theories as well as how the initial mass function of stars is sampled. Previous attempts to …
The Nature and Nurture of Bars and Disks
Corsini, E. M.; Aguerri, J. A. L.; Sánchez-Janssen, R. +2 more
The effects that interactions produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To this aim we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly …
Long-term Measurements of Sunspot Magnetic Tilt Angles
Li, Jing; Ulrich, Roger K.
Tilt angles of close to 30,600 sunspots are determined using Mount Wilson daily averaged magnetograms taken from 1974 to 2012, and SOHO/MDI magnetograms taken from 1996 to 2010. Within a cycle, more than 90% of sunspots have a normal polarity alignment along the east-west direction following Hale's law. The median tilts increase with increasing la…
The CHESS Survey of the L1157-B1 Shock Region: CO Spectral Signatures of Jet-driven Bow Shocks
Codella, C.; Ceccarelli, C.; Benedettini, M. +7 more
The unprecedented sensitivity of Herschel coupled with the high resolution of the HIFI spectrometer permits studies of the intensity-velocity relationship I(v) in molecular outflows, over a higher excitation range than possible up to now. Over the course of the CHESS Key Program, we have observed toward the bright bow shock region L1157-B1, the CO…
Nitrogen line spectroscopy in O-stars. III. The earliest O-stars
Puls, J.; Najarro, F.; Massey, P. +1 more
Context. The classification scheme proposed by Walborn et al. (2002, AJ, 123, 2754), based primarily on the relative strengths of the N ivλ4058 and N iiiλ4640 emission lines, has been used in a variety of studies to spectroscopically classify early O-type stars. Owing to the lack of a solid theoretical basis, this scheme has not yet been universal…
Magnetic Topology of Active Regions and Coronal Holes: Implications for Coronal Outflows and the Solar Wind
Mandrini, C. H.; van Driel-Gesztelyi, L.; Culhane, J. L. +8 more
During 2 - 18 January 2008 a pair of low-latitude opposite-polarity coronal holes (CHs) were observed on the Sun with two active regions (ARs) and the heliospheric plasma sheet located between them. We use the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows and measure their velocities. Solar-Terrestrial Relations Observatory (…
On Dark Peaks and Missing Mass: A Weak-lensing Mass Reconstruction of the Merging Cluster System A520
Bradač, Maruša; Massey, Richard; Gonzalez, Anthony H. +4 more
Merging clusters of galaxies are unique in their power to directly probe and place limits on the self-interaction cross-section of dark matter. Detailed observations of several merging clusters have shown the intracluster gas to be displaced from the centroids of dark matter and galaxy density by ram pressure, while the latter components are spati…
Hydrogen peroxide on Mars: Observations, interpretation and future plans
Encrenaz, T.; Atreya, S. K.; Greathouse, T. K. +1 more
Ever since the Viking mass spectrometer failed to detect organics on the surface of Mars in 1976 (Biemann et al., 1976), hydrogen peroxide (H2O2) has been suggested as a possible oxidizer of the Martian surface (Oyama and Berdahl, 1977). However, the search for H2O2 on Mars was unsuccessful for three dec…
Are the strengths of solar cycles determined by converging flows towards the activity belts?
Schüssler, M.; Cameron, R. H.
It is proposed that the observed near-surface inflows towards the active regions and sunspot zones provide a nonlinear feedback mechanism that limits the amplitude of a Babcock-Leighton-type solar dynamo and determines the variation of the cycle strength. This hypothesis is tested with surface flux transport simulations including converging latitu…