- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1503
- Title:
- Synthetic photometry of RR Lyr
- Short Name:
- J/MNRAS/371/1503
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The luminosities and effective temperatures, as well as the whole bolometric light curves of non-linear convective RR Lyrae models with 0.0001<=Z<=0.006, are transformed into the Sloan Digital Sky Survey (SDSS) photometric system. The obtained ugriz light curves, mean magnitudes and colours, pulsation amplitudes and colour-colour loops are shown and analytical relations connecting pulsational to intrinsic stellar parameters, similar to the ones currently used in the JohnsonCousins filters, are derived. Finally, the behaviour in the colour-colour planes is compared with available observations in the literature and possible systematic uncertainties affecting this comparison are discussed.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/504/3730
- Title:
- Synthetic RGB photometry of bright stars
- Short Name:
- J/MNRAS/504/3730
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the use of RGB photometry has exploded in the last decades due to the advent of high-quality and inexpensive digital cameras equipped with Bayer-like colour filter systems, there is surprisingly no catalogue of bright stars that can be used for calibration purposes. Since due to their excessive brightness, accurate enough spectrophotometric measurements of bright stars typically cannot be performed with modern large telescopes, we have employed historical 13-colour medium-narrow-band photometric data, gathered with quite reliable photomultipliers, to fit the spectrum of 1346 bright stars using stellar atmosphere models. This not only constitutes a useful compilation of bright spectrophotometric standards well spread in the celestial sphere, the UCM library of spectrophotometric spectra, but allows the generation of a catalogue of reference RGB magnitudes, with typical random uncertainties ~0.01 mag. For that purpose, we have defined a new set of spectral sensitivity curves, computed as the median of 28 sets of empirical sensitivity curves from the literature, that can be used to establish a standard RGB photometric system. Conversions between RGB magnitudes computed with any of these sets of empirical RGB curves and those determined with the new standard photometric system are provided. Even though particular RGB measurements from single cameras are not expected to provide extremely accurate photometric data, the repeatability and multiplicity of observations will allow access to a large amount of exploitable data in many astronomical fields, such as the detailed monitoring of light pollution and its impact on the night sky brightness, or the study of meteors, Solar system bodies, variable stars, and transient objects. In addition, the RGB magnitudes presented here make the sky an accessible and free laboratory for the calibration of the cameras themselves.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/717/257
- Title:
- Synthetic spectra of dark stars
- Short Name:
- J/ApJ/717/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first stars in the history of the Universe are likely to form in the dense central regions of {sim.to}10^5^-10^6^ M_{sun}_ cold dark matter halos at z{approx}10--50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 10^3^ M_{sun}_ are intrinsically too faint to be detected by JWST at z above 6. However, by exploiting foreground galaxy clusters as gravitational telescopes, certain varieties of cool (T_eff_<=30000K) dark stars should be within reach at redshifts up to z{approx}10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least {sim.to}1% of the total stellar mass in such objects.
- 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.
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/127/1227
- Title:
- Synthetic Stroemgren photometry
- Short Name:
- J/AJ/127/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new grid of theoretical color indices for the Stroemgren uvby photometric system has been derived from MARCS model atmospheres and SSG synthetic spectra for cool dwarf and giant stars having -3.0<=[Fe/H]<=+0.5 and 3000<=T_eff_<=8000K. In the present investigation, we have also analyzed the observed Stroemgren photometry for the classic Population II subdwarfs, compared our "final" (b-y)-Teff relationship with those derived empirically in a number of recent studies and examined in some detail the dependence of the m1 index on [Fe/H].
- ID:
- ivo://CDS.VizieR/J/MNRAS/412/1070
- Title:
- Synthetic supernova extinction curves
- Short Name:
- J/MNRAS/412/1070
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the supernova (SN) extinction curves to reproduce the observed properties of SST J1604+4304 which is a young infrared (IR) galaxy at z~1. The SN extinction curves used in this work were obtained from models of unmixed ejecta of Type II supernovae for the Salpeter initial mass function with a mass range from 8 to 30M_{sun}_ or 8 to 40M_{sun}_. The effect of dust distributions on the attenuation of starlight is investigated by performing the {chi}^2^ fitting method against various dust distributions. These are the commonly used uniform dust screen, the clumpy dust screen and the internal dust geometry. We add to these geometries three scattering properties, namely, no scattering, isotropic scattering and forward-only scattering. Judging from the {chi}^2^ values, we find that the uniform screen models with any scattering property provide good approximations to the real dust geometry.
- ID:
- ivo://CDS.VizieR/J/ApJS/99/173
- Title:
- Synthetic UV spectra of massive stars
- Short Name:
- J/ApJS/99/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An atlas of synthetic ultraviolet spectra of a population of massive stars is presented. The spectra are based on a stellar library of IUE high-dispersion spectra of O and Wolf-Rayet stars, coupled to an evolutionary synthesis code. Later spectral types are included via low-dispersion spectra. Line profiles of N V lambda 1240, Si IV lambda 1400, C IV lambda 1550, He II lambda 1640, and N IV lambda 1720 have been computed for star-formation histories and initial mass functions typically found in starburst regions. It is found that the lines are sensitive indicators for the presence or absence of massive stars. C IV lambda 1550 is the strongest stellar line in the ultraviolet spectrum of a typical starburst. If O stars with zero-age main-sequence masses above 50M_{sun}_ are present, C IV always shows a P Cygni profile. In the absence of such stars, only a blue-shifted absorption is present. During later epochs of the starburst, when late-O/early-B stars dominate, an unshifted photospheric absorption appears. Si IV lambda 1400 shows a conspicuous wind profile when luminous O supergiants are present. A strong P Cygni profile is found only for an instantaneous burst observed at 3 to 5Myr, which has a top-heavy IMF. The velocity of the blueshifted absorption is strongly correlated with the age and the upper cutoff mass (or slope) of the IMF. N V lambda 1240 traces the most massive stars and behaves rather similar to Si IV lambda 1400. Its usefulness as an indicator of very massive stars is limited due to the strong blending effect of the nearby Ly-alpha line. Nevertheless, strong N V lambda 1240 emission in a starburst suggests the presence of stars with masses in excess of 60M_{sun}_. He II lambda 1640 and N IV lambda 1720 are produced by very hot and luminous O and Wolf-Rayet stars. Both lines can have weak absorption or emission in a typical starburst but are predicted to be observable only under rare circumstances, such as in an instantaneous burst at t{approx.}3Myr. The profiles presented in the atlas can be compared to high-quality ultraviolet observations of galaxies with active star formation in order to constrain the massive star population. The atlas is published in its entirety in computer-readable form in the AAS CD-ROM series, Vol. 5.
