Search results for "FOS"
showing 10 items of 15075 documents
Core-Collapse Supernovae: Reflections and Directions
2012
Core-collapse supernovae are among the most fascinating phenomena in astrophysics and provide a formidable challenge for theoretical investigation. They mark the spectacular end of the lives of massive stars and, in an explosive eruption, release as much energy as the sun produces during its whole life. A better understanding of the astrophysical role of supernovae as birth sites of neutron stars, black holes, and heavy chemical elements, and more reliable predictions of the observable signals from stellar death events are tightly linked to the solution of the long-standing puzzle how collapsing stars achieve to explode. In this article our current knowledge of the processes that contribute…
Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217
2014
As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\dot{M}_{out}$/$\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\sim$ 20$^{\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics o…
Science Objectives for an X-Ray Microcalorimeter Observing the Sun
2010
We present the science case for a broadband X-ray imager with high-resolution spectroscopy, including simulations of X-ray spectral diagnostics of both active regions and solar flares. This is part of a trilogy of white papers discussing science, instrument (Bandler et al. 2010), and missions (Bookbinder et al. 2010) to exploit major advances recently made in transition-edge sensor (TES) detector technology that enable resolution better than 2 eV in an array that can handle high count rates. Combined with a modest X-ray mirror, this instrument would combine arcsecondscale imaging with high-resolution spectra over a field of view sufficiently large for the study of active regions and flares,…
The atmospheric structure and fundamental parameters of the red supergiants AH Sco, UY Sct and KW Sgr
2013
We present the atmospheric structure and the fundamental properties of the red supergiants (RSGs) AH Sco, UY Sct, and KW Sgr based on VLTI/AMBER observations. We carried out spectro-interferometric observations of AH Sco, UY Sct, and KW Sgr in the near-infrared K band with the VLTI/AMBER instrument, and compared the data to a new grid of hydrostatic PHOENIX model atmospheres. In our visibility data, we observe molecular layers of water and CO in extended atmospheres. For a uniform disk modeling, we observe size increases at the water band of 10% to 25% and at the CO bandheads of 20%-35% with respect to the near continuum bandpass. The PHOENIX atmosphere models predict the spectra and the co…
Surface imaging of cool evolved stars in the era of the ELT
2019
Cool evolved stars are the main source of chemical enrichment of the interstellar medium. Understanding their mass loss offers a unique opportunity to study the cycle of matter. We discuss interferometric studies and their comparison to latest state-of-the-art dynamic model atmospheres. They show broad agreement for asymptotic giant branch stars. For red supergiants, however, current models cannot explain observed extensions by far, pointing to missing physical processes in their models, and uncertainties in our general understanding of mass loss. We present ongoing imaging and time-series observations that may provide the strongest constraint and may help to identify missing dynamic proces…
Performance Analysis of the SO/PHI Software Framework for On-board Data Reduction
2019
The Polarimetric and Helioseismic Imager (PHI) is the first deep-space solar spectropolarimeter, on-board the Solar Orbiter (SO) space mission. It faces: stringent requirements on science data accuracy, a dynamic environment, and severe limitations on telemetry volume. SO/PHI overcomes these restrictions through on-board instrument calibration and science data reduction, using dedicated firmware in FPGAs. This contribution analyses the accuracy of a data processing pipeline by comparing the results obtained with SO/PHI hardware to a reference from a ground computer. The results show that for the analyzed pipeline the error introduced by the firmware implementation is well below the requirem…
Structure of Small Magnetic Elements in the Solar Atmosphere
2012
High resolution images at different wavelengths, spectrograms and magnetograms, representing different levels of the solar atmosphere obtained with Hinode have been combined to study the 3-dimensional structure of the small magnetic elements in relation to their radiance. A small magnetic element is described as example of the study.
Observations of vortex motion in the solar photosphere using HINODE-SP data
2012
In this work, we focus in the magnetic evolution of a small region as seen by Hinode-SP during the time interval of about one hour. High-cadence LOS magnetograms and velocity maps were derived, allowing the study of different small-scale processes such as the formation/disappearance of bright points accompanying the evolution of an observed convective vortical motion.
Instabilities in Interacting Binary Stars
2017
The types of instability in the interacting binary stars are reviewed. The project "Inter-Longitude Astronomy" is a series of smaller projects on concrete stars or groups of stars. It has no special funds, and is supported from resources and grants of participating organizations, when informal working groups are created. Totally we studied 1900+ variable stars of different types. The characteristic timescale is from seconds to decades and (extrapolating) even more. The monitoring of the first star of our sample AM Her was initiated by Prof. V.P. Tsesevich (1907-1983). Since more than 358 ADS papers were published. Some highlights of our photometric and photo-polarimetric monitoring and math…
Supersonic Magnetic Flows in the Quiet Sun
2012
In this contribution we describe some recent observations of high-speed magnetized flows in the quiet Sun granulation. These observations were carried out with the Imaging Magnetograph eXperiment (IMaX) onboard the stratospheric balloon {\sc Sunrise}, and possess an unprecedented spatial resolution and temporal cadence. These flows were identified as highly shifted circular polarization (Stokes $V$) signals. We estimate the LOS velocity responsible for these shifts to be larger than 6 km s$^{-1}$, and therefore we refer to them as {\it supersonic magnetic flows}. The average lifetime of the detected events is 81.3 s and they occupy an average area of about 23\,000 km$^2$. Most of the events…