Search

Start Over Subject spectroscopy
771. FeI oscillator strengths for Gaia-ESO
ID:
ivo://CDS.VizieR/J/MNRAS/441/3127
Title:
FeI oscillator strengths for Gaia-ESO
Short Name:
J/MNRAS/441/3127
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Gaia-ESO Public Spectroscopic Survey (GES) is conducting a large-scale study of multi-element chemical abundances of some 100000 stars in the Milky Way with the ultimate aim of quantifying the formation history and evolution of young, mature and ancient Galactic populations. However, in preparing for the analysis of GES spectra, it has been noted that atomic oscillator strengths of important FeI lines required to correctly model stellar line intensities are missing from the atomic data base. Here, we present new experimental oscillator strengths derived from branching fractions and level lifetimes, for 142 transitions of FeI between 3526 and 10864{AA}, of which at least 38 are urgently needed by GES. We also assess the impact of these new data on solar spectral synthesis and demonstrate that for 36 lines that appear unblended in the Sun, Fe abundance measurements yield a small line-by-line scatter (0.08dex) with a mean abundance of 7.44dex in good agreement with recent publications.
772. FeI radiative lifetime and branching fractions
ID:
ivo://CDS.VizieR/J/ApJS/215/23
Title:
FeI radiative lifetime and branching fractions
Short Name:
J/ApJS/215/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
New radiative lifetimes, measured to +/-5% accuracy, are reported for 31 even-parity levels of Fe I ranging from 45061cm^-1^ to 56842cm^-1^. These lifetimes have been measured using single-step and two-step time-resolved laser-induced fluorescence on a slow atomic beam of iron atoms. Branching fractions have been attempted for all of these levels, and completed for 20 levels. This set of levels represents an extension of the collaborative work reported in Ruffoni et al. (2013ApJ...779...17R; 2014, J/MNRAS/441/3127). The radiative lifetimes combined with the branching fractions yields new oscillator strengths for 203 lines of Fe I. Utilizing a 1D-LTE model of the solar photosphere, spectral syntheses for a subset of these lines which are unblended in the solar spectrum yields a mean iron abundance of <log[{epsilon}(Fe)]>=7.45+/-0.06.
773. FeK lines in Seyfert 1 galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/426/2522
Title:
FeK lines in Seyfert 1 galaxies
Short Name:
J/MNRAS/426/2522
Date:
21 Oct 2021
Publisher:
CDS
Description:
We construct full broad-band models in an analysis of Suzaku observations of nearby Seyfert 1 active galactic nuclei (AGN) (z<=0.2) with exposures >50ks and with greater than 30000 counts in order to study their iron line profiles. This results in a sample of 46 objects and 84 observations. After a full modelling of the broad-band Suzaku and Swift-Burst Alert Telescope data (0.6-100keV), we find complex warm absorption is present in 59 per cent of the objects in this sample which has a significant bearing upon the derived FeK region parameters. Meanwhile 35 per cent of the 46 objects require some degree of high column density partial coverer in order to fully model the hard X-ray spectrum. We also find that a large number of the objects in the sample (22 per cent) require high velocity, high ionization outflows in the FeK region resulting from FeXXV and FeXXVI. A further four AGN feature highly ionized FeK absorbers consistent with zero outflow velocity, making a total of 14/46 (30%) AGN in this sample showing evidence for statistically significant absorption in the FeK region.
774. Fe-rich silicate analogues mass absorption coeff.
ID:
ivo://CDS.VizieR/J/A+A/606/A50
Title:
Fe-rich silicate analogues mass absorption coeff.
Short Name:
J/A+A/606/A50
Date:
21 Oct 2021
Publisher:
CDS
Description:
To model the cold dust emission observed in the diffuse interstellar medium, in dense molecular clouds or in cold clumps that could eventually form new stars, it is mandatory to know the physical and spectroscopic properties of this dust and to understand its emission. This work is a continuation of previous studies aiming at providing astronomers with spectroscopic data of realistic cosmic dust analogues for the interpretation of observations. The aim of the present work is to extend the range of studied analogues to iron-rich silicate dust analogues. Ferromagnesium amorphous silicate dust analogues were produced by a sol-gel method with a mean composition close to Mg_1-x_Fe_x_SiO_3_ with x=0.1, 0.2, 0.3, 0.4. Part of each sample was annealed at 500{deg}C for two hours in a reducing atmosphere to modify the oxidation state of iron. We have measured the mass absorption coefficient (MAC) of these eight ferromagnesium amorphous silicate dust analogues in the spectral domain 30-1000um for grain temperature in the range 10-300K and at room temperature in the 5-40um range. The MAC of ferromagnesium samples behaves in the same way as the MAC of pure Mg-rich amorphous silicate samples. In the 30-300K range, the MAC increases with increasing grain temperature whereas in the range 10-30K, we do not see any change of the MAC. The MAC cannot be described by a single power law in {lambda}^-{beta}^. The MAC of the samples does not show any clear trend with the iron content. However the annealing process has, on average, an effect on the MAC that we explain by the evolution of the structure of the samples induced by the processing. The MAC of all the samples is much higher than the MAC calculated by dust models. The complex behavior of the MAC of amorphous silicates with wavelength and temperature is observed whatever the exact silicate composition (Mg vs. Fe amount). It is a universal characteristic of amorphous materials, and therefore of amorphous cosmic silicates, that should be taken into account in astronomical modeling. The enhanced MAC of the measured samples compared to the MAC calculated for cosmic dust model implies that dust masses are overestimated by the models.
775. Fermi and Swift GRBs E_peak_-E_iso_ relation
ID:
ivo://CDS.VizieR/J/A+A/557/A100
Title:
Fermi and Swift GRBs E_peak_-E_iso_ relation
Short Name:
J/A+A/557/A100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used a sample of gamma-ray bursts (GRBs) detected by Fermi and Swift to reanalyze the correlation discovered by Amati et al. (2002A&A...390...81A) between E_pi_, the peak energy of the prompt GRB emission, and E_iso_, the energy released by the GRB assuming isotropic emission. This correlation has been disputed by various authors, and our aim is to assess whether it is an intrinsic GRB property or the consequence of selection effects. We constructed a sample of Fermi GRBs with homogeneous selection criteria, and we studied their distribution in the E_pi_-E_iso_ plane. Our sample is made of 43 GRBs with a redshift and 243 GRBs without a redshift. We show that GRBs with a redshift follow a broad E_pi_-E_iso_ relation, while GRBs without a redshift show several outliers. We use these samples to discuss the impact of selection effects associated with GRB detection and with redshift measurement.
776. FEROS Public Spectra
ID:
ivo://org.gavo.dc/feros/q/ssa
Title:
FEROS Public Spectra
Short Name:
FEROS SSAP
Date:
27 Dec 2024 08:31:01
Publisher:
The GAVO DC team
Description:
Spectra from FEROS spectrograph at La Silla's 1.5m telescope as obtained during commissioning and guaranteed time.
777. Fe XII UV line intensity ratios
ID:
ivo://CDS.VizieR/J/A+A/370/1071
Title:
Fe XII UV line intensity ratios
Short Name:
J/A+A/370/1071
Date:
21 Oct 2021
Publisher:
CDS
Description:
A new set of radiative and electron collisional data for Fe XII was presented in two earlier papers. In the present work, we derive level populations and theoretical line intensities for a range of plasma densities and temperatures. Observations of Fe XII lines obtained with the Solar EUV Rocket Telescope and Spectrograph are analysed both as a check on the quality of the new atomic data and to determine the electron density in active regions and the quiet Sun. The discrepancy between the electron density values determined from Fe XII line intensity ratios and those obtained from other ions is investigated.
778. F-G-K stars activity indicators
ID:
ivo://CDS.VizieR/J/A+A/658/A57
Title:
F-G-K stars activity indicators
Short Name:
J/A+A/658/A57
Date:
22 Feb 2022
Publisher:
CDS
Description:
Different relationships between the H{alpha} and CaII chromospheric emissions have been reported in solar-type stars. In particular, the time-series of emissions in these two lines are clearly anti-correlated for a few percent of the stars, contrary to what is observed on the Sun. Our objective is to characterise these relationships in more detail using complementary criteria, and to constrain the properties of filaments and plages that are necessary to explain the observations. We analysed the average level and variability of the H{alpha} and CaII emission for 441 F-G-K stars, paying particular attention to their (anti-)correlations on both short and long timescales. We also computed synthetic H{alpha} and CaII time-series for different assumptions of plage and filament properties and compared them with the observations. We were not able to find plage properties that, alone, are sufficient to reproduce the observations at all timescales simultaneously, even when allowing different H{alpha} and CaII emission relationships for different stars. We also specified the complex and surprising relationship between the average activity levels of both indexes, in particular for low-activity stars. We conclude that plages alone are unlikely to explain the observed variety of relationships between CaII and H{alpha} emission, and that the presence of other phenomena like filaments may help to reconcile the models with observations.
779. FGK stars magnetic activity in LAMOST-Kepler field
ID:
ivo://CDS.VizieR/J/ApJS/247/9
Title:
FGK stars magnetic activity in LAMOST-Kepler field
Short Name:
J/ApJS/247/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_HK_^+^, for 59816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with logR_HK_^+^. We estimate the power-law indexes between Reff and R_HK_^+^ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca ii H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
780. 2FGL J0846.0+2820 opt. counterpart follow-up
ID:
ivo://CDS.VizieR/J/ApJ/851/31
Title:
2FGL J0846.0+2820 opt. counterpart follow-up
Short Name:
J/ApJ/851/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical photometric and spectroscopic observations of the likely stellar counterpart to the unassociated Fermi Large Area Telescope (LAT) {gamma}-ray source 2FGL J0846.0+2820, selected for study based on positional coincidences of optical variables with unassociated LAT sources. Using optical spectroscopy from the SOAR telescope, we have identified a late-G giant in an eccentric (e=0.06) 8.133-day orbit with an invisible primary. Modeling the spectroscopy and photometry together led us to infer a heavy neutron star primary of ~2M_{sun}_ and a partially stripped giant secondary of ~0.8M_{sun}_. H{alpha} emission is observed in some of the spectra, perhaps consistent with the presence of a faint accretion disk. We find that the {gamma}-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009, accompanied by an increased variation in the optical brightness, and since then, it has not been detected by Fermi. The long period and giant secondary are reminiscent of the {gamma}-ray bright binary 1FGL J1417.7-4407, which hosts a millisecond pulsar (MSP) apparently in the final stages of the pulsar recycling process. The discovery of 2FGL J0846.0+2820 suggests the identification of a new subclass of MSP binaries that are the likely progenitors of typical field MSPs.

Limit your search

more »

more »

more »

more »

more »