Search results for "Astronomy & astrophysics"
showing 10 items of 1148 documents
MICROLENSING OF QUASAR ULTRAVIOLET IRON EMISSION
2013
We measure the differential microlensing of the UV Fe II and Fe III emission line blends between 14 quasar image pairs in 13 gravitational lenses. We find that the UV iron emission is strongly microlensed in four cases with amplitudes comparable to that of the continuum. Statistically modeling the magnifications, we infer a typical size of r{sub s}∼4√(M/M{sub ⊙}) light-days for the Fe line-emitting regions, which is comparable to the size of the region generating the UV continuum (∼3-7 light-days). This may indicate that a significant part of the UV Fe II and Fe III emission originates in the quasar accretion disk.
Long-term optical and X-ray variability of the Be/X-ray binary H 1145-619: Discovery of an ongoing retrograde density wave
2017
Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. We investigate the correlation between the optical emission and the X-ray activity to predict the occurrence of new X-ray outbursts from the inferred state of the circumstellar disc. We have performed a multiwavelength study of H 1145-619 from 1973 to 2017 and present here a global analysis of its variability over the last 40 years. We have used optical spectra from the SAAO, SMARTS and SALT telescopes and optical photometry from INTEGRAL/OMC and ASAS. We also used X-ray observations from INTEGRAL/…
The Gaia-ESO Survey: The origin and evolution of s-process elements
2018
Context. Several works have found an increase of the abundances of the s-process neutron-capture elements in the youngest Galactic stellar populations. These trends provide important constraints on stellar and Galactic evolution and they need to be confirmed with large and statistically significant samples of stars spanning wide age and distance intervals. Aims. We aim to trace the abundance patterns and the time evolution of five s-process elements - two belonging to the first peak, Y and Zr, and three belonging to the second peak, Ba, La, and Ce - using the Gaia-ESO IDR5 results for open clusters and disc stars. Methods. From the UVES spectra of cluster member stars, we determined the ave…
Three beta-decaying states in 128In and 130In resolved for the first time using Penning-trap techniques
2020
Isomeric states in 128In and 130In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing state-of-the-art ion manipulation techniques, three different beta-decaying states in 128In and 130In have been separated and their masses measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the isomer in 128Sn has been discovered in 128In at 1797.6(20) keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a 16⁺ spin-trap isomer. In 130In, the lowest-lying (10⁻) isom…
Unveiling the environment and faint features of the isolated galaxy CIG 96 with deep optical and HI observations
2018
Context. Asymmetries in atomic hydrogen (HI) in galaxies are often caused by the interaction with close companions, making isolated galaxies an ideal framework to study secular evolution. The AMIGA project has demonstrated that isolated galaxies show the lowest level of asymmetry in their HI integrated profiles compared to even field galaxies, yet some present significant asymmetries. CIG 96 (NGC 864) is a representative case reaching a 16% level. Aims. Our aim is to investigate the HI asymmetries of the spiral galaxy CIG 96 and what processes have triggered the star-forming regions observed in the XUV pseudo-ring. Methods. We performed deep optical observations at CAHA1.23m, CAHA2.2m and V…
Are pulsars born with a hidden magnetic field?
2015
The observation of several neutron stars in the center of supernova remnants and with significantly lower values of the dipolar magnetic field than the average radio-pulsar population has motivated a lively debate about their formation and origin, with controversial interpretations. A possible explanation requires the slow rotation of the proto-neutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels. An alternative possibility, the hidden magnetic field scenario, considers the accretion of the fallback of the supernova debris onto the neutron star as responsible for the submergence (or screening) of the field and its apparently low value. In this paper …
Inflight Radiometric Calibration of New Horizons' Multispectral Visible Imaging Camera (MVIC)
2017
© 2016 Elsevier Inc. We discuss two semi-independent calibration techniques used to determine the inflight radiometric calibration for the New Horizons’ Multi-spectral Visible Imaging Camera (MVIC). The first calibration technique compares the measured number of counts (DN) observed from a number of well calibrated stars to those predicted using the component-level calibration. The ratio of these values provides a multiplicative factor that allows a conversation between the preflight calibration to the more accurate inflight one, for each detector. The second calibration technique is a channel-wise relative radiometric calibration for MVIC's blue, near-infrared and methane color channels us…
Follow-up on non-leptonic Kaon decays at large $N_c$
2018
We report on the status of our dynamical simulations of a $SU (N_c )$ gauge theory with $N_c=3-6$ and $N_f =4$ fundamental fermions. These ensembles can be used to study the Large $N_c$ scaling of weak matrix elements in the GIM limit $m_c=m_u$, that might shed some light on the origin of the $\Delta I=1/2$ rule. We present preliminary results for the $K \to \pi$ matrix elements in the $N_c=3$ dynamical simulations, where we observe a significant effect of the quark loops that goes in the direction of enhancing the ratio of $A_0/A_2$ amplitudes. Finally, we present the relevant NLO Chiral Perturbation Theory predictions for the relation between $K \to \pi $ and $K \to \pi \pi$ amplitudes in…
The HADES RV Programme with HARPS-N@TNG. III. Flux-flux and activity-rotation relationships of early-M dwarfs
2016
(Abridged) Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres as well as for ongoing radial velocity exoplanet programmes. Despite the increasing interest in M dwarfs, our knowledge of the chromospheres of these stars is far from being complete. We aim to test whether the relations between activity, rotation, and stellar parameters and flux-flux relationships also hold for early-M dwarfs on the main-sequence. We analyse in an homogeneous and coherent way a well defined sample of 71 late-K/early-M dwarfs that are currently being observed in the framework of the HArps-n red Dwarf Exoplanet Survey (HADES). Rotational velocities are derived using the cr…
XMM-Newton observation of the supernova remnant Kes 78 (G32.8-0.1): Evidence for shock-cloud interaction
2017
The Galactic supernova remnant Kes 78 is surrounded by dense molecular clouds, whose projected position overlaps with the extended HESS gamma-ray source HESS J1852-000. The X-ray emission from the remnant has been recently revealed by Suzaku observations, which have shown indications for a hard X-ray component in the spectra, possibly associated with synchrotron radiation. We aim at describing the spatial distribution of the physical properties of the X-ray emitting plasma and at revealing the effects of the interaction of the remnant with the inhomogeneous ambient medium. We also aim at investigating the origin of the gamma-ray emission, which may be Inverse Compton radiation associated wi…