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From CoRoT 102899501 to the Sun. A time evolution model of chromospheric activity on the main sequence
Deleuil, M.; Fridlund, M.; Gondoin, P. +7 more
Aims: The present study reports measurements of the rotation period of a young solar analogue, estimates of its surface coverage by photospheric starspots and of its chromospheric activity level, and derivations of its evolutionary status. Detailed observations of many young solar-type stars, such as the one reported in the present paper, pro…
A Rare Early-type Star Revealed in the Wing of the Small Magellanic Cloud
Gruendl, R. A.; Hamann, W. -R.; Gallagher, J. S., III +6 more
Sk 183 is the visually brightest star in the N90 nebula, a young star-forming region in the Wing of the Small Magellanic Cloud (SMC). We present new optical spectroscopy from the Very Large Telescope which reveals Sk 183 to be one of the most massive O-type stars in the SMC. Classified as an O3-type dwarf on the basis of its nitrogen spectrum, the…
CO Structure of the 21 µm Source IRAS 22272+5435: A Sign of a Jet Launch?
Zhang, Yong; Kwok, Sun; Yung, Bosco H. K. +3 more
We report the results of radio interferometric observations of the 21 µm source IRAS 22272+5435 in the CO J = 2-1 line. 21 µm sources are carbon-rich objects in the post-asymptotic-giant-branch phase of evolution, which show an unidentified emission feature at 21 µm. Since 21 µm sources usually also have circumstellar molec…
X-Ray and Near-infrared Observations of the Obscured Accreting Pulsar IGR J18179-1621
Nowak, M. A.; Chaty, S.; Rodriguez, J. +6 more
IGR J18179-1621 is an obscured accreting X-ray pulsar discovered by INTEGRAL on 2012 February 29. We report on our 20 ks Chandra-High Energy Transmission Gratings Spectrometer observation of the source performed on 2012 March 17, on two short contemporaneous Swift observations, and on our two near-infrared (Ks , Hn , and J
Determining the North-South Displacement of the Heliospheric Current Sheet from Coronal Streamer Observations
Wang, Y. -M.; Robbrecht, E.
Inferences based on interplanetary field measurements have suggested a statistical tendency for the heliospheric current sheet (HCS) to be displaced southward of the heliographic equator during the past four solar cycles. Here, we use synoptic maps of white-light streamer structures to determine more directly the longitudinally averaged latitude o…
Extreme-ultraviolet Spectroscopic Observation of Direct Coronal Heating during a C-class Solar Flare
Brosius, Jeffrey W.
With the Coronal Diagnostic Spectrometer operating in rapid cadence (9.8 s) stare mode during a C6.6 flare on the solar disk, we observed a sudden brightening of Fe XIX line emission (formed at temperature T ≈ 8 MK) above the pre-flare noise without a corresponding brightening of emission from ions formed at lower temperatures, including He I (0.0…
Empirical near-infrared colors for low-mass stars and brown dwarfs in the Orion Nebula Cluster. An empirical near-infrared isochrone at ~1 Myr
Robberto, M.; Scandariato, G.; Da Rio, N. +2 more
Context. Current atmospheric and evolutionary models for low-mass stars and brown dwarfs rely on approximate assumptions on the physics of the stellar structure and the atmospheric radiative transfer. This leads to biased theoretical predictions on the photospheric spectral energy distributions of these system, especially when applied to low surfa…
Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters
Hsia, Chih-Hao; Yung, Bosco H. K.; Nakashima, Jun-ichi +2 more
We report the results of Australia Telescope Compact Array observations of the Westerlund 1 (Wd1) region in the SiO v = 1, J = 1-0, and H2O 616-523 maser lines, and we also report the analysis of maser properties of red supergiants (RSGs) associated with six massive clusters including Wd1. The primary purpose of th…
Abrupt Changes of the Photospheric Magnetic Field in Active Regions and the Impulsive Phase of Solar Flares
Petrie, G. J. D.; Ling, A. G.; Cliver, E. W.
We compared time profiles of changes of the unsigned photospheric magnetic flux in active regions with those of their associated soft X-ray (SXR) bursts for a sample of 75 >= M5 flares well observed by Global Oscillation Network Group longitudinal magnetographs. Sixty-six of these events had stepwise changes in the spatially integrated unsigned…
The electromagnetic pickup of submicron-sized dust above Enceladus's northern hemisphere
Gurnett, Donald A.; Farrell, William M.; Kurth, William S. +3 more
As the saturnian magnetoplasma sweeps past Enceladus, it experiences both a decrease in electron content and sharp slowdown in the northern hemisphere region within ∼5 Enceladus Radii (Re). This slowdown is observed by Cassini in regions not obviously associated with the southern directed plume-originating ions. We suggest herein that t…