Search Publications
Tidal disruption of a super-Jupiter by a massive black hole
Walter, R.; Nikołajuk, M.
Aims: A strong, hard X-ray flare was discovered (IGR J12580+0134) by INTEGRAL in 2011, and is associated to NGC 4845, a Seyfert 2 galaxy never detected at high-energy previously. To understand what happened we observed this event in the X-ray band on several occasions.
Methods: Follow-up observations with XMM-Newton, Swift, and MAXI are …
Chandra, Keck, and VLA Observations of the Crab Nebula during the 2011-April Gamma-Ray Flare
Weisskopf, Martin C.; Tennant, Allyn F.; Fu, Hai +22 more
We present results from our analysis of Chandra X-Ray Observatory, W. M. Keck Observatory, and Karl G. Jansky Very Large Array (VLA) images of the Crab Nebula that were contemporaneous with the γ-ray flare of 2011 April. Despite hints in the X-ray data, we find no evidence for statistically significant variations that pinpoint the specific locatio…
The X-ray spectral properties of very-faint persistent neutron star X-ray binaries
Degenaar, N.; Wijnands, R.; Armas Padilla, M.
AX J1754.2-2754, 1RXS J171824.2-402934 and 1RXH J173523.7-354013 are three persistent neutron star low-mass X-ray binaries that display a 2-10 keV accretion luminosity LX of only (1-10) × 1034 erg s-1 (i.e. only ≃0.005-0.05 per cent of the Eddington limit). The phenomenology of accreting neutron stars which accrete…
AGN host galaxies at redshift z ≈ 0.7: peculiar or not?
Heymans, C.; Taylor, A. N.; Gray, M. E. +21 more
Aims: We perform a quantitative morphological comparison between the hosts of active galactic nuclei (AGN) and quiescent galaxies at intermediate redshifts (z ≈ 0.7). The imaging data are taken from the large HST/ACS mosaics of the GEMS and STAGES surveys. Our main aim is to test whether nuclear activity at this cosmic epoch is triggered by m…
Indication for an intermediate-mass black hole in the globular cluster NGC 5286 from kinematics
Kissler-Patig, M.; de Zeeuw, P. T.; Neumayer, N. +6 more
Context. Intermediate-mass black holes (IMBHs) fill the gap between stellar-mass black holes and supermassive black holes (SMBHs). The existence of the latter is widely accepted, but there are only few detections of intermediate-mass black holes (102 - 105M⊙) so far. Simulations have shown that intermediate-mass bl…
A Survey of H2O, CO2, and CO Ice Features toward Background Stars and low-mass Young Stellar Objects Using AKARI
Pontoppidan, K. M.; Sakon, I.; Noble, J. A. +2 more
We present near-infrared spectroscopic observations of 19 molecular clouds made using the AKARI satellite, and the data reduction pipeline written to analyze those observations. The 2.5-5 µm spectra of 30 objects—22 field stars behind quiescent molecular clouds and 8 low-mass young stellar objects in cores—were successfully extracted using t…
Supernova 2012ec: identification of the progenitor and early monitoring with PESSTO.
Sollerman, J.; Gal-Yam, A.; Inserra, C. +13 more
We present the identification of the progenitor of the Type IIP SN 2012ec in archival pre-explosion Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) and Advanced Camera for Surveys Wide Field Channel F814W images. The properties of the progenitor are further constrained by non-detections in pre-explosion WFPC2 F450W and F606W images. W…
Study on the Triggering Process of Solar Flares Based on Hinode/SOT Observations
Kusano, K.; Yamamoto, T. T.; Okamoto, T. J. +1 more
We investigated four major solar flare events that occurred in active regions NOAA 10930 (2006 December 13 and 14) and NOAA 11158 (2011 February 13 and 15) by using data observed by the Solar Optical Telescope on board the Hinode satellite. To reveal the trigger mechanism of solar flares, we analyzed the spatio-temporal correlation between the det…
Fragmentation and dynamical collapse of the starless high-mass star-forming region IRDC 18310-4
Smith, R.; Henning, Th.; Krause, O. +9 more
Context. Because of their short evolutionary time-scales, the earliest stages of high-mass star formation prior to the existence of any embedded heating source have barely been characterized until today.
Aims: We study the fragmentation and dynamical properties of a massive starless gas clump at the onset of high-mass star formation.
Met…
A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
Tlatov, A.; Illarionov, E.; Sokoloff, D. +1 more
We obtain the latitude-time distribution of the averaged tilt angle of solar bipoles. For large bipoles, which are mainly bipolar sunspot groups, the spatially averaged tilt angle is positive in the Northern solar hemisphere and negative in the Southern, with modest variations during the course of the solar cycle. We consider the averaged tilt ang…