Search Publications
The basal chromospheric Mg II h+k flux of evolved stars: probing the energy dissipation of giant chromospheres
Pérez Martínez, M. Isabel; Schröder, K. -P.; Cuntz, M.
Of a total of 177 cool G, K and M giants and supergiants, we measured the Mg II h+k line emission of extended chromospheres in high-resolution (LWR) International Ultraviolet Explorer (IUE) spectra by using the IUE final data archive at the Space Telescope Science Institute (STScI) and derived the respective stellar surface fluxes. They represent …
On the degeneracy of the tidal Love number k2 in multi-layer planetary models: application to Saturn and GJ 436b
Stevenson, D. J.; Nettelmann, N.; Kramm, U. +1 more
Context. In order to accurately model giant planets, a whole set of observational constraints is needed. As the conventional constraints for extrasolar planets like mass, radius, and temperature allow for a large number of acceptable models, a new planetary parameter is desirable in order to further constrain planetary models. Such a parameter may…
Determining Interstellar Carbon Abundances from Strong-line Transitions
Murthy, J.; Babu, B. R. S.; Parvathi, V. S. +1 more
Carbon is arguably the most important element in the interstellar medium, yet its abundance in gas and dust is poorly understood due to a paucity of data. We explore the possibility of substantially increasing our knowledge of interstellar carbon by applying and assessing a new method for determining the column density of the dominant ion of inter…
Statistical properties of superactive regions during solar cycles 19-23
Zhang, J.; Wang, J. X.; Chen, A. Q. +2 more
Context. Each solar activity cycle is characterized by a small number of superactive regions (SARs) that produce the most violent of space weather events with the greatest disastrous influence on our living environment.
Aims: We aim to re-parameterize the SARs and study the latitudinal and longitudinal distributions of SARs.
Methods: We …
Saturn's very axisymmetric magnetic field: No detectable secular variation or tilt
Cao, Hao; Dougherty, Michele K.; Russell, Christopher T. +2 more
Saturn is the only planet in the solar system whose observed magnetic field is highly axisymmetric. At least a small deviation from perfect symmetry is required for a dynamo-generated magnetic field. Analyzing more than six years of magnetometer data obtained by Cassini close to the planet, we show that Saturn's observed field is much more axisymm…
The Formation of Kiloparsec-scale H I Holes in Dwarf Galaxies
Van Dyk, Schuyler D.; Cannon, John M.; Dolphin, Andrew E. +10 more
The origin of kpc-scale holes in the atomic hydrogen (H I) distributions of some nearby dwarf irregular galaxies presents an intriguing problem. Star formation histories (SFHs) derived from resolved stars give us the unique opportunity to study past star-forming events that may have helped shape the currently visible H I distribution. Our sample o…
Herschel observations of EXtra-Ordinary Sources (HEXOS): Methanol as a probe of physical conditions in Orion KL
Menten, K. M.; Martin, P. G.; Murphy, J. A. +45 more
We have examined methanol emission from Orion KL withthe Herschel/HIFI instrument, and detected two methanol bands centered at 524 GHz and 1061 GHz. The 524 GHz methanol band (observed in HIFI band 1a) is dominated by the isolated ΔJ = 0, K = -4 → -3, vt = 0 Q branch, and includes 25 E-type and 2 A-type transitions. The 1061 GHz methano…
Multitemporal observations of identical active dust devils on Mars with the High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC)
Neukum, G.; Reiss, D.; Zanetti, M.
Active dust devils were observed in Syria Planum in Mars Observer Camera - Wide Angle (MOC-WA) and High Resolution Stereo Camera (HRSC) imagery acquired on the same day with a time delay of ∼26 min. The unique operating technique of the HRSC allowed the measurement of the traverse velocities and directions of motion. Large dust devils observed in …
A Microlensing Measurement of Dark Matter Fractions in Three Lensing Galaxies
Wyithe, J. S. B.; Bate, N. F.; Floyd, D. J. E. +1 more
Direct measurements of dark matter distributions in galaxies are currently only possible through the use of gravitational lensing observations. Combinations of lens modeling and stellar velocity dispersion measurements provide the best constraints on dark matter distributions in individual galaxies, however they can be quite complex. In this paper…
The evolution of Titan's detached haze layer near equinox in 2009
West, Robert A.; Turtle, Elizabeth P.; Lavvas, Panayotis +5 more
Saturn's moon Titan has a massive atmosphere laden with layers of photochemical haze. We report a recent dramatic change in the vertical structure of this haze, with a persistent ‘detached’ layer dropping in altitude from over 500 km to only 380 km between 2007 and 2010. The detached haze layer appears to be a well-defined tracer for Titan's merid…