Search Publications
A New Method for the Assessment of Age and Age Spread of Pre-main-sequence Stars in Young Stellar Associations of the Magellanic Clouds
Da Rio, Nicola; Gouliermis, Dimitrios A.; Gennaro, Mario
We present a new method for the evaluation of the age and age spread among pre-main-sequence (PMS) stars in star-forming regions in the Magellanic Clouds, accounting simultaneously for photometric errors, unresolved binarity, differential extinction, stellar variability, accretion, and crowding. The application of the method is performed with the …
A Panchromatic View of PKS 0558-504: An Ideal Laboratory to Study the Disk-Jet Link
Papadakis, I. E.; Grupe, D.; Gliozzi, M. +3 more
PKS 0558-504 is the brightest radio-loud Narrow-line Seyfert 1 galaxy (NLS1) at X-ray energies. Here we present results from the radio, optical, UV, and X-ray bands obtained with Swift, XMM-Newton, and the Australia Telescope Compact Array (ATCA) during a ten-day monitoring campaign in 2008 September. The simultaneous coverage at several wavelengt…
The Velocity Distribution of Nearby Stars from Hipparcos Data. II. The Nature of the Low-velocity Moving Groups
Bovy, Jo; Hogg, David W.
The velocity distribution of nearby stars (lsim100 pc) contains many overdensities or "moving groups," clumps of comoving stars, that are inconsistent with the standard assumption of an axisymmetric, time-independent, and steady-state Galaxy. We study the age and metallicity properties of the low-velocity moving groups based on the reconstruction …
The Quiet Solar Atmosphere Observed and Simulated in Na I D1
Leenaarts, J.; Carlsson, M.; Hansteen, V. +2 more
The Na I D1 line in the solar spectrum is sometimes attributed to the solar chromosphere. We study its formation in quiet-Sun network and internetwork. We first present high-resolution profile-resolved images taken in this line with the imaging spectrometer Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope and compa…
Mapping the Distribution of Electron Temperature and Fe Charge States in the Corona with Total Solar Eclipse Observations
Rušin, V.; Druckmüller, M.; Esser, R. +7 more
The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the helioce…
Spatial Seismology of a Large Coronal Loop Arcade from TRACE and EIT Observations of its Transverse Oscillations
Foullon, C.; Verwichte, E.; Van Doorsselaere, T.
We present a study of transverse loop oscillations in a large coronal loop arcade, using observations from the Transition Region And Coronal Explorer (TRACE) and Extreme-ultraviolet Imaging Telescope (EIT). For the first time we reveal the presence of long-period transverse oscillations with periods between 24 minutes and 3 hr. One loop bundle, 69…
X-QUEST: A Comprehensive X-ray Study of Local ULIRGS and QSOs
Veilleux, Sylvain; Teng, Stacy H.
We present results from the X-ray portion of a multi-wavelength study of local ULIRGs and QSOs called QUEST (Quasar-ULIRG Evolution STudy). The data consist of new and archival X-ray data on 40 ULIRGs and 26 Palomar Green (PG) QSOs taken with Chandra and XMM-Newton. A combination of traditional and hardness ratio spectral fitting methods is used t…
Continued Cooling of the Crust in the Neutron Star Low-mass X-ray Binary KS 1731-260
Miller, Jon M.; Cackett, Edward M.; Wijnands, Rudy +3 more
Some neutron star low-mass X-ray binaries have very long outbursts (lasting several years) which can generate a significant amount of heat in the neutron star crust. After the system has returned to quiescence, the crust then thermally relaxes. This provides a rare opportunity to study the thermal properties of neutron star crusts, putting constra…
The 2009 December Gamma-ray Flare of 3C 454.3: The Multifrequency Campaign
Sakamoto, T.; Pian, E.; Fugazza, D. +81 more
During the month of 2009 December, the blazar 3C 454.3 became the brightest gamma-ray source in the sky, reaching a peak flux F ~ 2000 × 10-8 photons cm-2 s-1 for E > 100 MeV. Starting in 2009 November intensive multifrequency campaigns monitored the 3C 454 gamma-ray outburst. Here, we report on the results of a…
Dynamics of Vertical Threads and Descending Knots in a Hedgerow Prominence
Chae, Jongchul
The existence and behavior of vertical fine structures of plasma—threads and knots—are a significant observational clue to understanding the magnetic structure and dynamics of quiescent prominences on the quiet Sun. Based on the equation of motion in ideal MHD, we reason that the non-hydrostatic support of plasma against gravity in general require…