Search

Start Over Subject spectroscopy
2811. SVOM-ECLAIRs known X-ray sources catalogue
ID:
ivo://CDS.VizieR/J/A+A/645/A18
Title:
SVOM-ECLAIRs known X-ray sources catalogue
Short Name:
J/A+A/645/A18
Date:
21 Oct 2021
Publisher:
CDS
Description:
The SVOM mission currently under development will carry various instruments, and in particular the coded-mask telescope ECLAIRs, with a large field of view of about 2sr, operating in the 4-150keV energy band. The main goal of ECLAIRs is to detect high-energy transients such as gamma-ray bursts. Its onboard trigger software will search for new hard X-ray sources appearing in the sky, as well as peculiar behaviour (e.g. strong outbursts) from known sources, in order to repoint the satellite to perform follow-up observations with its onboard narrow-field-of-view instruments. The presence of known X-ray sources must be disentangled from the appearance of new sources. This is done with the help of an onboard source catalogue, which we present in this paper. As an input we use catalogues of X-ray sources detected by Swift/BAT and MAXI/GSC and we study the influence of the sources on ECLAIRs' background level and on the quality of the sky-image reconstruction process. We show that the influence of the sources depends on the pointing direction on the sky, on the energy band, and on the exposure time. In the Galactic centre, the contribution from known sources largely dominates the cosmic X-ray background, which is, on the contrary, the main background in sky regions lacking strong sources. We also demonstrate the need to clean the contributions of these sources in order to maintain a low noise level in the sky images and to maintain a low threshold for the detection of new sources without introducing false triggers. We briefly describe one of our cleaning methods and its challenges. Finally, we present the overall structure of the onboard catalogue and the way it will be used to perform the source cleaning and disentangle detections of new sources from outbursts of known sources.
2812. Swan system of C2
ID:
ivo://CDS.VizieR/J/ApJS/169/472
Title:
Swan system of C2
Short Name:
J/ApJS/169/472
Date:
21 Oct 2021
Publisher:
CDS
Description:
The C2 Swan system (d ^3^{Pi}_g_-a ^3^{Pi}_u_) was observed in emission for the {Delta}v=-3 to {Delta}v=+2 sequences in the 14000-24000cm^-1^ spectral range using a Fourier transform spectrometer. We carried out a global simultaneous fit by including a wide range of vibrational states. A total of 34 bands with v'=0-10 and v"=0-9 were rotationally assigned. Numerous discrepancies were found in the assignments and in the measured transition wavenumbers between the new measurements and previous results. Most of the measured transition wavenumbers and their assignments for relatively low-v bands agreed with published data. On the contrary, for high-v bands our line positions and assignments disagreed with the tabulated literature values. In particular, the lines of six bands involving the levels with v'=4, 5, and 6 are almost completely different from the previous work. Major sources of the disagreement are thought to be line congestion and perturbations found in these bands. From the analysis, perturbations for v'=0, 1, 2, 4, 6, 8, 9, and 10 in the d ^3^{Pi}_g_ state were identified. A study of these rotational perturbations suggest that some of them are likely caused by interactions with high-v levels of the b ^3^{Sigma}^-^_g_ state.
2813. Swift/BAT AGN Spectroscopic Survey. I.
ID:
ivo://CDS.VizieR/J/ApJ/850/74
Title:
Swift/BAT AGN Spectroscopic Survey. I.
Short Name:
J/ApJ/850/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first catalog and data release of the Swift-BAT AGN Spectroscopic Survey. We analyze optical spectra of the majority of the detected AGNs (77%, 642/836) based on their 14-195keV emission in the 70-month Swift-BAT all-sky catalog. This includes redshift determination, absorption and emission-line measurements, and black hole mass and accretion rate estimates for the majority of obscured and unobscured AGNs (74%, 473/642), with 340 measured for the first time. With ~90% of sources at z<0.2, the survey represents a significant advance in the census of hard X-ray-selected AGNs in the local universe. In this first catalog paper, we describe the spectroscopic observations and data sets, and our initial spectral analysis. The FWHMs of the emission lines show broad agreement with the X-ray obscuration (~94%), such that Sy 1-1.8 have N_H_<10^21.9^cm^-2^, and Seyfert 2 have N_H_>10^21.9^cm^-2^. Seyfert 1.9, however, show a range of column densities. Compared to narrow-line AGNs in the SDSS, the X-ray-selected AGNs have a larger fraction of dusty host galaxies (H{alpha}/H{beta}>5), suggesting that these types of AGN are missed in optical surveys. Using the [OIII]{lambda}5007/H{beta} and [NII]{lambda}6583/H{alpha} emission-line diagnostic, about half of the sources are classified as Seyferts; ~15% reside in dusty galaxies that lack an H{beta} detection, but for which the upper limits on line emission imply either a Seyfert or LINER, ~15% are in galaxies with weak or no emission lines despite high-quality spectra, and a few percent each are LINERS, composite galaxies, H II regions, or in known beamed AGNs.
2814. Swift GRBs individual power density spectra
ID:
ivo://CDS.VizieR/J/A+A/589/A98
Title:
Swift GRBs individual power density spectra
Short Name:
J/A+A/589/A98
Date:
21 Oct 2021
Publisher:
CDS
Description:
Timing analysis can be a powerful tool for shading light on the still obscure emission physics and geometry of the prompt emission of gamma-ray bursts (GRBs). Fourier power density spectra (PDS) characterise time series as stochastic processes and can be used to search for coherent pulsations and, more in general, to investigate the dominant variability timescales in astrophysical sources. Because of the limited duration and of the statistical properties involved, modelling the PDS of individual GRBs is challenging, and only average PDS of large samples have been discussed in the literature thus far. We aim at characterising the individual PDS of GRBs to describe their variability in terms of a stochastic process, to explore their variety, and to carry out for the first time a systematic search for periodic signals and for a link between PDS properties and other GRB observables. We present a Bayesian procedure which uses a Markov chain Monte Carlo technique and apply it to study the individual power density spectra of 215 bright long GRBs detected with the Swift Burst Alert Telescope in the 15-150keV band from January 2005 to May 2015. The PDS are modelled with a power-law either with or without a break. Two classes of GRBs emerge: with or without a unique dominant time scale. A comparison with active galactic nuclei (AGNs) reveals similar distributions of PDS slopes. Unexpectedly, GRBs with subsecond dominant timescales and duration longer than a few ten seconds in the source frame appear to be either very rare or altogether absent. Three GRBs are found with possible evidence for periodic signal at 3.0-3.2{sigma} (Gaussian) significance, corresponding to a multi-trial chance probability of ~1%. Thus, we found no compelling evidence for periodic signal in GRBs. The analogy between the PDS of GRBs and of AGNs could tentatively hint at similar stochastic processes that rule BH accretion across different BH mass scales and objects. In addition, we find evidence that short dominant timescales and duration are not completely independent of each other, in contrast with commonly accepted paradigms.
2815. Synthetic galaxy spectra
ID:
ivo://CDS.VizieR/J/A+A/538/A38
Title:
Synthetic galaxy spectra
Short Name:
J/A+A/538/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an optimized library of synthetic galaxy spectra that are to be used for the Gaia satellite observations of unresolved galaxies. These galaxy spectral templates are useful for the optimal performance of the unresolved galaxy classifier (UGC) software. The UGC will assign spectral classes to the observed unresolved galaxies by Gaia (classification) and estimate some of their intrinsic astrophysical parameters, which were used to create the synthetic library (parametrization). We present the new optimized synthetic library of galaxy spectra and the classification and parametrization results using the Gaia-simulated version of this library. To optimize our synthetic library, we applied the principal component analysis (PCA) method to our synthetic spectra and studied the influence of the star-formation rate parameters on the spectra, and how these agree with some typical characteristics of the galaxy spectral types. We used support vector machines (SVM) to classify and parametrize the optimal simulated spectra. The library of synthetic galaxy spectra was optimized. In this new set of synthetic spectra, overlaps in spectral energy distributions and colors are highly suppressed, while the results of UGC classification are improved.
2816. Synthetic lines in the Sun
ID:
ivo://CDS.VizieR/J/A+A/528/A113
Title:
Synthetic lines in the Sun
Short Name:
J/A+A/528/A113
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have computed synthetic spectra from a realistic 3D numerical simulation of the solar photosphere. We provide the spatially averaged spectra for selected lines that are commonly used on solar applications. These data can be used to calibrate Doppler velocity measurements in the solar photosphere. The calculations are carried out along the solar disk from heliocentric angle mu=1.0 to mu=0.3.
2817. Synthetic Spectra Convolution Service
ID:
ivo://ov-gso/tsap/speconvol
Title:
Synthetic Spectra Convolution Service
Short Name:
speconvol
Date:
03 Apr 2024 08:16:45
Publisher:
OV-GSO Virtual Observatory services
Description:
Convolution of normalized synthetic stellar spectra. Up to 3 successive convolutions are allowed on a adjustable portion of a synthetic spectrum, in order to mimic an observable. These convolutions acount for macroturbulence velocity, rotational velocity and instrumental profile. Finally, the output can be Doppler-shifted in order to take into account a stellar radial velocity.
2818. Synthetic spectra in the near-IR
ID:
ivo://CDS.VizieR/III/238
Title:
Synthetic spectra in the near-IR
Short Name:
III/238
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a library of 952 synthetic spectra characterized by -2.5<=[Z/Z_sun_]<=+0.5, 4.5<=logg<=1.0, 3500<=T(eff)<=50000K, at a resolving power (lambda/Delta_lambda) of 20000 over the wavelength range 7650-8750{AA}. The wavelength range covers the near-IR Ca II triplet and the head of the hydrogen's Paschen series, the K I doublet (7664, 7699{AA}), the Na I doublet (8183, 8194{AA}) and the lines of Fe I multiplet N.60 at 8327 and 8388{AA}. The synthetic spectra are based on Kurucz's codes and line data.
2819. Synthetic spectra of galactic globular clusters
ID:
ivo://CDS.VizieR/J/A+A/534/A9
Title:
Synthetic spectra of galactic globular clusters
Short Name:
J/A+A/534/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
We calculated synthetic spectra for typical chemical element mixtures (i.e., a standard alpha-enhanced distribution, and distributions displaying CN and ONa anticorrelations) found in the various subpopulations harboured by individual Galactic globular clusters. From the spectra we determined bolometric corrections to the standard Johnson-Cousins and Stroemgren filters and finally predicted colours. These bolometric corrections and colour-transformations, coupled to our theoretical isochrones with the appropriate chemical composition, provided us with a complete and self-consistent set of theoretical predictions for the effect of abundance variations on the observed cluster colour-magnitude diagrams.
2820. Synthetic spectrophotometry for C-rich giants
ID:
ivo://CDS.VizieR/J/A+A/503/913
Title:
Synthetic spectrophotometry for C-rich giants
Short Name:
J/A+A/503/913
Date:
21 Oct 2021
Publisher:
CDS
Description:
Carbon rich objects represent an important phase during the late stages of evolution of low and intermediate mass stars. They contribute significantly to the chemical enrichment and to the infrared light of galaxies. A proper description of their atmospheres is crucial for the determination of fundamental parameters such as effective temperature or mass loss rate. We study the spectroscopic and photometric properties of carbon stars. In the first paper of this series we focus on objects that can be described by hydrostatic models neglecting dynamical phenomena like pulsation and mass loss. As a consequence, the reddening due to circumstellar dust is not included. Our results are collected in a database, which can be used in conjunction with stellar evolution and population synthesis calculations involving the AGB. We have computed a grid of 746 spherically symmetric COMARCS atmospheres covering effective temperatures between 2400 and 4000K, surface gravities from log(g[cm/s^2^])=0.0 to -1.0, metallicities ranging from the solar value down to one tenth of it and C/O ratios in the interval between 1.05 and 5.0. Subsequently, we used these models to create synthetic low resolution spectra and photometric data for a large number of filter systems. The tables including the results are electronically available. First tests of the application on stellar evolution calculations are shown. We have selected some of the most commonly used colours in order to discuss their behaviour as a function of the stellar parameters. A comparison with measured data shows that down to 2800K the agreement between predictions and observations of carbon stars is good and our results may be used to determine quantities like the effective temperature. Below this limit the synthetic colours are much too blue. The obvious reason for these problems is the neglect of circumstellar reddening and structural changes due to pulsation and mass loss.

Limit your search

more »

more »

more »

more »

more »