Search Publications
Direct observation of cosmic strings via their strong gravitational lensing effect - II. Results from the HST/ACS image archive
Treu, Tommaso; Schrabback, Tim; Blandford, Roger D. +2 more
We have searched 4.5deg2 of archival Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) images for cosmic strings, identifying close pairs of similar, faint galaxies and selecting groups whose alignment is consistent with gravitational lensing by a long, straight string. We find no evidence for cosmic strings in five large-are…
Temporary liquid water in upper snow/ice sub-surfaces on Mars?
Möhlmann, Diedrich T. F.
It is investigated whether conditions for melting can be temporarily created in the upper sub-surface parts of snow/ice-packs on Mars at subzero surface temperatures by means of the solid-state greenhouse effect, as occurs in snow- and ice-covered regions on Earth. The conditions for this possible temporary melting are quantitatively described for…
γ Cassiopeiae: an X-ray Be star with personality
Motch, C.; Smith, M. A.; Lopes de Oliveira, R.
An exciting unsolved problem in the study of high energy processes of early type stars concerns the physical mechanism for producing X-rays near the Be star γ Cassiopeiae. By now we know that this source and several “
First Earth-based Detection of a Superbolide on Jupiter
Djorgovski, S. G.; Hueso, R.; Sánchez-Lavega, A. +14 more
Cosmic collisions on planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On 2010 June 3 a bolide in Jupiter's atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths. The bolide appeared as a flash of 2 s duration in video re…
A deep survey of the AKARI north ecliptic pole field . I. WSRT 20 cm radio survey description, observations and data reduction
Im, M.; Lee, H. M.; White, G. J. +17 more
Aims: The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ~1.7 degree2 field coinciding with the AKARI north ecliptic pole deep field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives.
Methods: The…
RR Lyrae Variables in M33. II. Oosterhoff Properties and Radial Trends
Yang, S. -C.; Sarajedini, Ata; Holtzman, Jon A. +1 more
We present the results of an extensive survey of RR Lyrae (RRL) stars in three fields along the major axis of the Triangulum Galaxy (M33). From images taken with the Advanced Camera for Surveys (ACS) Wide Field Channel on board the Hubble Space Telescope through two passbands (F606W and F814W), we have identified and characterized a total of 119 R…
Observational constraints on supermassive dark stars
Östlin, Göran; Rydberg, Claes-Erik; Zackrisson, Erik +6 more
Some of the first stars could be cooler and more massive than standard stellar models would suggest, due to the effects of dark matter annihilation in their cores. It has recently been argued that such objects may attain masses in the 104-107Msolar range and that such supermassive dark stars should be within reach …
On the Nature of the Compact Object in SS 433: Observational Evidence of X-ray Photon Index Saturation
Titarchuk, Lev; Seifina, Elena
We present an analysis of the X-ray spectral properties observed from the black hole candidate (BHC) binary SS 433. We have analyzed Rossi X-ray Timing Explorer data from this source, coordinated with Green Bank Interferometer/RATAN-600. We show that SS 433 undergoes an X-ray spectral transition from the low hard state to the intermediate state (I…
The β Pictoris disk imaged by Herschel PACS and SPIRE
Heras, A. M.; Walker, H. J.; Ivison, R. J. +40 more
We obtained Herschel PACS and SPIRE images of the thermal emission of the debris disk around the A5V star β Pic. The disk is well resolved in the PACS filters at 70, 100, and 160 µm. The surface brightness profiles between 70 and 160 µm show no significant asymmetries along the disk, and are compatible with 90% of the emission between …
Three-Dimensional Electron Density from Tomographic Analysis of LASCO-C2 Images of the K-Corona Total Brightness
Lamy, Philippe; Frazin, Richard A.; Vásquez, Alberto M. +1 more
We present the first quantitative three-dimensional (3D) tomographic reconstructions of electron density from coronagraph measurements of the K-corona's total brightness (B) made by LASCO-C2 on SOHO. This is possible because new calibrations of the LASCO-C2 images in both polarized brightness (pB) and B have now been made for the entire mission. T…