Search Publications
A 205 µm [N II] Map of the Carina Nebula
Stark, A. A.; Stacey, G. J.; Kamenetzky, J. +5 more
We present the results of a ~250 arcmin2 mapping of the 205 µm [N II] fine-structure emission over the northern Carina Nebula, including the Car I and Car II H II regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) a…
A Correlation Between Host Star Activity and Planet Mass for Close-in Extrasolar Planets?
Schmitt, J. H. M. M.; Poppenhaeger, K.
The activity levels of stars are influenced by several stellar properties, such as stellar rotation, spectral type, and the presence of stellar companions. Analogous to binaries, planetary companions are also thought to be able to cause higher activity levels in their host stars, although at lower levels. Especially in X-rays, such influences are …
Ensemble X-ray variability of active galactic nuclei from serendipitous source catalogues
Trevese, D.; Vagnetti, F.; Turriziani, S.
Context. The X-ray variability of the active galactic nuclei (AGN) has been most often investigated with studies of individual, nearby sources, and only a few ensemble analyses have been applied to large samples in wide ranges of luminosity and redshift.
Aims: We aim to determine the ensemble variability properties of two serendipitously sele…
The star formation history in the far outer disc of M33
Cole, A. A.; Tanvir, N. R.; Ferguson, A. M. N. +5 more
The outer regions of disc galaxies are becoming increasingly recognized as key testing sites for models of disc assembly and evolution. Important issues are the epoch at which the bulk of the stars in these regions formed and how discs grow radially over time. To address these issues, we use Hubble Space Telescope Advanced Camera for Surveys imagi…
Bipolar electric field signatures of reconnection separatrices for a hydrogen plasma at realistic guide fields
Divin, A.; Goldman, M. V.; Newman, D. L. +2 more
In preparation for the MMS mission we ask the question: how common are bipolar signatures linked to the presence of electron holes along separatrices emanating from reconnection regions? To answer this question, we conduct massively parallel simulations for realistic conditions and for the hydrogen mass ratio in boxes larger than considered in sim…
Influence of negatively charged plume grains and hemisphere coupling currents on the structure of Enceladus' Alfvén wings: Analytical modeling of Cassini magnetometer observations
Dougherty, Michele K.; Saur, Joachim; Kriegel, Hendrik +3 more
We present an analytical model of the Alfvén wing system that is generated by the interaction between the plume of Enceladus and the corotating plasma in Saturn's inner magnetosphere. Our primary purpose is to explain the orientation of the magnetic field perturbations detected in Enceladus' Alfvén wings by the Cassini magnetometer (MAG) instrumen…
New insight into the formation of hexamethylenetetramine (HMT) in interstellar and cometary ice analogs
Vinogradoff, V.; Duvernay, F.; Danger, G. +2 more
Aims: We investigate the purely thermal formation of hexamethylenetetramine (HMT, C6H12N4) in interstellar ice analogs from non-photolysed ice and compare our results with those for the formation from photolysed ice.
Methods: We use Fourier transform-infrared spectroscopy to follow residue formation from …
The Circumstellar Environment of R Coronae Borealis: White Dwarf Merger or Final-helium-shell Flash?
Ivison, R. J.; Olofsson, G.; Bond, Howard E. +21 more
In 2007, R Coronae Borealis (R CrB) went into a historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been obtained from 0.5 to 500 µm with Gemini/GMOS, Hubble Space Telescope/WFPC2, Spitzer/MIPS, and Herschel/SPIRE…
The Gradients in the 47 Tuc Red Giant Branch Bump and Horizontal Branch are Consistent with a Centrally Concentrated, Helium-enriched Second Stellar Generation
Nataf, D. M.; Gould, A.; Pinsonneault, M. H. +1 more
We combine ground- and space-based photometry of the Galactic globular cluster 47 Tuc to measure four independent lines of evidence for a helium gradient in the cluster, whereby stars in the cluster outskirts would have a lower initial helium abundance than stars in and near the cluster core. For our first and second lines of evidence, we show tha…
X-ray reverberation close to the black hole in RE J1034+396
Fabian, A. C.; Zoghbi, A.
In previous work, we discussed the detection of reverberation delays in the narrow-line Seyfert 1 (NLS1) 1H0707-495. The delays originate close to the black hole. Here, we show that RE J1034+396 shows very similar lag properties. At low frequencies (<1 × 10-4 Hz), the time lag between energy bands increases with energy separation, si…