Search results for "STARS"
showing 10 items of 798 documents
Multimessenger Binary Mergers Containing Neutron Stars: Gravitational Waves, Jets, and γ-Ray Bursts
2021
Neutron stars (NSs) are extraordinary not only because they are the densest form of matter in the visible Universe but also because they can generate magnetic fields ten orders of magnitude larger than those currently constructed on earth. The combination of extreme gravity with the enormous electromagnetic (EM) fields gives rise to spectacular phenomena like those observed on August 2017 with the merger of a binary neutron star system, an event that generated a gravitational wave (GW) signal, a short γ-ray burst (sGRB), and a kilonova. This event serves as the highlight so far of the era of multimessenger astronomy. In this review, we present the current state of our theoretical understand…
7Be(n,α) and 7Be(n,p) cross-section measurement for the cosmological lithium problem at the n-TOF facility at CERN
2017
One of the most puzzling problems in Nuclear Astrophysics is the “Cosmological Lithium Problem”, i.e the discrepancy between the primordial abundance of \(^{7}\)Li observed in metal poor halo stars (Asplund et al. in Astrophys J 644:229–259, 2006, [1]), and the one predicted by Big Bang Nucleosynthesis (BBN). One of the reactions that could have an impact on the problem is \(^{7}\)Be(n,p)\(^{7}\)Li. Despite of the importance of this reaction in BBN, the cross-section has never been directly measured at the energies of interest for BBN. Taking advantage of the innovative features of the second experimental area at the n\(\_\)TOF facility at CERN (Sabate-Gilarte et al. in Eur Phys J A 53:210,…
The Gaia-ESO Survey: Chromospheric emission, accretion properties, and rotation in gamma Velorum and Chamaeleon
2015
Aims: One of the goals of the Gaia-ESO Survey (GES), which is conducted with FLAMES at the VLT, is the census and the characterization of the low-mass members of very young clusters and associations. We conduct a comparative study of the main properties of the sources belonging to γ Velorum (γ Vel) and Chamaeleon I (Cha I) young associations, focusing on their rotation, chromospheric radiative losses, and accretion. Methods: We used the fundamental parameters (effective temperature, surface gravity, lithium abundance, and radial velocity) delivered by the GES consortium in the first internal data release to select the members of γ Vel and Cha I among the UVES and GIRAFFE spectroscopic obser…
Zvaigžņotā Debess: 2016/17, Ziema (234)
2016
Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Balklavs. New Possibilities in Search of Cosmic Gravitational Waves (abridged) ; E.Mūkins. «Venus-9» and «Venus-10» Scientific Accomplishment (abridged) ; DEVELOPMENTS in SCIENCE: K.Schwartz. The Unknown Solar Corona ; DISCOVERIES: I.Pundure. Gaia Has Obtained Billion-Star 3D Map ; SPACE RESEARCH and EXPLORATION: J.Jaunbergs. Tar Lakes of Titan ; R.Misa. A Step Closer to Stars ; CONFERENCES and MEETINGS: J.Balodis. Copernicus Is Becoming an Impressive Business ; K.Bērziņš. Conference of Young European Radioastronomers at the Latvian Centre in Germany ; FLASHBACK: A.Alksnis. Short Trips and Faraway Journeys (concluded) ; For SCHOOL YOUTH: D.Bo…
All-sky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO O2 data
2019
We present results of an all-sky search for continuous gravitational waves (CWs), which can be produced by fast-spinning neutron stars with an asymmetry around their rotation axis, using data from the second observing run of the Advanced LIGO detectors. We employ three different semi-coherent methods ($\textit{FrequencyHough}$, $\textit{SkyHough}$, and $\textit{Time-Domain $\mathcal{F}$-statistic}$) to search in a gravitational-wave frequency band from 20 to 1922 Hz and a first frequency derivative from $-1\times10^{-8}$ to $2\times10^{-9}$ Hz/s. None of these searches has found clear evidence for a CW signal, so we present upper limits on the gravitational-wave strain amplitude $h_0$ (the …
GW190521: A Binary Black Hole Merger with a Total Mass of 150 M⊙
2020
LIGO Scientific Collaboration and Virgo Collaboration: et al.
All-sky search for short gravitational-wave bursts in the second Advanced LIGO and Advanced Virgo run
2019
We present the results of a search for short-duration gravitational-wave transients in the data from the second observing run of Advanced LIGO and Advanced Virgo. We search for gravitational-wave transients with a duration of milliseconds to approximately one second in the 32-4096 Hz frequency band with minimal assumptions about the signal properties, thus targeting a wide variety of sources. We also perform a matched-filter search for gravitational-wave transients from cosmic string cusps for which the waveform is well-modeled. The unmodeled search detected gravitational waves from several binary black hole mergers which have been identified by previous analyses. No other significant event…
XMM observations of NGC 2516 stars
2007
We present the characteristics of the X-ray variability of stars in the cluster NGC 2516 as derived from XMM-Newton/EPIC/pn data. The X-ray variations on short (hours), medium (months), and long (years) time scales have been explored. We detected 303 distinct X-ray sources by analysing six EPIC/pn observations; 194 of them are members of the cluster. Stars of all spectral types, from the early-types to the late-M dwarfs, were detected. Cone search capability for table J/A+A/456/977/table2 (X-ray and optical properties of NGC 2516 members in the XMM-Newton/EPIC/pn observations having more than 25 counts.)
XMM spectroscopy of TWA 5
2006
We present results of X-ray spectroscopy for TWA 5, a member of the young TW Hydrae association, observed with XMM-Newton. TWA 5 is a multiple system which shows H{alpha} emission, a signature typical of classical T Tauri stars, but no infrared excess. From this analysis of the RGS and EPIC spectra, we have derived the emission measure distribution vs. temperature of the X-ray emitting plasma, its abundances, and the electron density.
XMM-Newton survey of two Upper Scorpius regions
2007
We studied X-ray emission from young stars by analyzing the deep XMM-Newton observations of two regions of the Upper Scorpius association with an age of 5Myr. Based on near infrared and optical photometry we identified 22 Upper Scorpius photometric members among the 224 detected X-ray sources. We derived coronal properties of Upper Scorpius stars by performing X-ray spectral and timing analyses. The study of four strong and isolated stellar flares allowed us to derive the length of the flaring loops. Cone search capability for table J/A+A/459/199/tableb1 (Sources detected in the CTIO observations) Cone search capability for table J/A+A/459/199/tablec1 (Sources detected in the Danish 1.54m o…