Search Publications

Development of a new calibration method for ground-based Paschen-alpha imaging data

Tamura, Yoichi; Kohno, Kotaro; Takahashi, Hidenori +24 more

ANIR (Atacama Near InfraRed camera) is a near infrared camera for the University of Tokyo Atacama 1.0m telescope installed at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The high altitude and the extremely low water vapor (precipitable water vapor:PWV=0.5mm) of the site enables us to perform observation of hydrogen Paschen alp…

Rosetta enters hibernation

Ferri, Paolo; Accomazzo, Andrea; Hubault, Armelle +3 more

The International Rosetta Mission was launched on 2nd March 2004 on its 10 years journey to comet 67P/Churyumov-Gerasimenko. Rosetta will reach the comet in 2014, orbit it for about 1.5 years down to distances of a few kilometres and deliver the Lander Philae onto its surface. Following the fly-by of Asteroid (21-)Lutetia in 2010, Rosetta continue…

Simultaneous observations of the exterior cusp region

Chen, J.; Fritz, T. A.; Walsh, B. M.

A case study is presented analyzing the properties and spatial extent of the exterior cusp region. The dynamic nature of the exterior cusp makes the large scale properties difficult to measure using a single spacecraft. We use simultaneous cusp observations of the four Cluster spacecraft as well as the Polar spacecraft to monitor the region. On 10…

Editorial: Interstellar Boundary Explorer (IBEX): Direct Sampling of the Interstellar Medium

McComas, D. J.

This special supplement issue of the Astrophysical Journal comprises six coordinated papers that provide the first detailed analyses of the direct sampling of interstellar neutral atoms by the Interstellar Boundary Explorer (IBEX). Interstellar atoms are the detritus of older stars—their stellar winds, novae, and supernovae—spread across the galax…

Multi-spacecraft observations of earthward flow bursts

Dandouras, I.; Lucek, E. A.; Dunlop, M. W. +3 more

Production of High-Temperature Plasmas During the Early Phases of a C9.7 Flare. II. Bi-directional Flows Suggestive of Reconnection in a Pre-flare Brightening Region

Hara, H.; Watanabe, T.; Harra, L. K. +1 more

The 6 June 2007 16:55 UT flare was well observed with high time-cadence sparse raster scans by the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft. The observation covers an active region area of 240 arcsec × 240 arcsec with the 1 arcsec slit in about 160 seconds.

Cold positrons from decaying dark matter

Boubekeur, Lotfi; Dodelson, Scott; Vives, Oscar

Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often, heavier particles decay into the lightest dark matter particle as the Universe evolves. Here, we explore the possibilities which arise if one of the products in a (heavyparticle)→(darkmatter) decay is a positron, and the lifetime is shorter tha…

On the small-scale fluctuations in the peak electron density of Martian ionosphere observed by MEX/MARSIS

Wang, X. -D.; Zou, H.; Wang, J. -S.

We reported the small-scale fluctuations in the peak electron density of dayside Martian ionosphere observed by MEX/MARSIS. MARSIS is an ionospheric sounder that can measure the vertical electron density profile of the topside ionosphere. In the experiment the ionospheric critical frequency can be determined within the accuracy of 5 kHz, correspon…

Frequency of Maunder Minimum Events in Solar-type Stars Inferred from Activity and Metallicity Observations

Tytler, David; Lubin, Dan; Kirkman, David

We consider the common proposition that the fraction of chromospherically very inactive stars in a solar-type sample is analogous to the fraction of the Sun's main-sequence lifetime spent in a grand minimum state. In a new approach to this proposition, we examine chromospheric activity log R'_HK in a stellar sample having Hipparcos paral…

Angular fluctuations in the CXB: is Fe 6.4 keV line tomography of the large-scale structure feasible?

Sunyaev, R.; Gilfanov, M.; Hütsi, G.

Context. Active galactic nuclei (AGN) are known to account for a major portion, if not all, of the cosmic X-ray background (CXB) radiation. The dominant sharp spectral feature in their spectra is the 6.4 keV fluorescent line of iron, which may contribute to as much as ~5-10% of the CXB spectral intensity at ~2-6 keV. Owing to cosmological redshift…