Search Publications
Tilt of Emerging Bipolar Magnetic Regions on the Sun
Kosovichev, A. G.; Stenflo, J. O.
Magnetic fields emerging from the Sun's interior carry information about the physical processes of magnetic field generation and transport in the convection zone. A statistical analysis of variations of the tilt angle of bipolar magnetic regions during the emergence, observed from SOHO MDI, shows that the systematic tilt with respect to the equato…
Supernova 1996cr: SN 1987A's Wild Cousin?
Bauer, F. E.; Brandt, W. N.; Dwarkadas, V. V. +4 more
We report on new VLT optical spectroscopic and multiwavelength archival observations of SN 1996cr, a previously identified ultraluminous X-ray source known as Circinus galaxy X-2. Our optical spectrum confirms SN 1996cr as a bona fide Type IIn supernova, while archival imaging from the Anglo-Australian Telescope archive isolates the explosion date…
The Complex Structure of the Cl 1604 Supercluster at z ~ 0.9
Kocevski, D.; Lemaux, B. C.; Lubin, L. M. +2 more
The Cl 1604 supercluster at z = 0.9 is one of a small handful of such structures discovered in the high-redshift universe and is the first target observed as part of the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey. To date, Cl 1604 is the largest structure mapped at z ~ 1, with the most constituent clusters and t…
X-Ray Properties of Protostars in the Orion Nebula
Robberto, M.; Grosso, N.; Micela, G. +8 more
The origin and evolution of the X-ray emission in very young stellar objects (YSOs) are not yet well understood because it is very hard to observe YSOs in the protostellar phase. Using COUP data, we study the X-ray properties of stars in the ONC in different evolutionary classes: luminosities, hydrogen column densities NH, effective pla…
Transverse Oscillations of Flowing Prominence Threads Observed with Hinode
Oliver, R.; Ballester, J. L.; Terradas, J. +1 more
Recent observations with the Hinode Solar Optical Telescope display an active region prominence whose fine threads oscillate in the vertical direction as they move along a path parallel to the photosphere. A seismological analysis of this event is carried out by taking advantage of the small radius of these structures compared to the total length …
The Nascent Red Sequence at z ~ 2
Demarco, R.; Pentericci, L.; Rosati, P. +12 more
We present new constraints on the evolution of the early-type galaxy color-magnitude relation (CMR) based on deep near-infrared imaging of a galaxy protocluster at z = 2.16 obtained using NICMOS on board the Hubble Space Telescope. This field contains a spectroscopically confirmed space overdensity of Lyα- and Hα-emitting galaxies that surrounds t…
Realistic Numerical Simulations of Solar Convection and Oscillations in Magnetic Regions
Kosovichev, A. G.; Mansour, N. N.; Jacoutot, L. +1 more
We have used 3D, compressible, nonlinear radiative magnetohydrodynamics simulation to study the influence of magnetic fields of various strengths on convective cells and on the excitation mechanisms of acoustic oscillations by calculating the spectral properties of the convective motions and oscillations. The results reveal substantial changes of …
The Puzzling White Dwarf Cooling Sequence in NGC 6791: A Simple Solution
Salaris, M.; Anderson, J.; Milone, A. P. +4 more
In this Letter we demonstrate that the puzzling bright peak in the luminosity function of the white dwarf (WD) cooling sequence of NGC 6791 can be naturally accounted for if ~34% of the observed WDs are WD+WD binary systems.
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, whic…Timing the Nearby Isolated Neutron Star RX J1856.5-3754
van Kerkwijk, M. H.; Kaplan, D. L.
RX J1856.5-3754 is the X-ray brightest among the nearby isolated neutron stars. Its X-ray spectrum is thermal, and is reproduced remarkably well by a blackbody, but its interpretation has remained puzzling. One reason is that the source did not exhibit pulsations, and hence a magnetic field strength—vital input to atmosphere models—could not be es…
Galaxy Mergers at z gtrsim 1 in the HUDF: Evidence for a Peak in the Major Merger Rate of Massive Galaxies
Ryan, R. E., Jr.; Windhorst, R. A.; Silk, J. +1 more
We present a measurement of the galaxy merger fraction and number density from observations in the Hubble Ultra Deep Field (HUDF) for 0.5 <= z <= 2.5. We fit the combination of broadband data and slitless spectroscopy of 1308 galaxies with stellar population synthesis models to select merging systems based on a stellar mass of >=1010…