- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1098
- Title:
- UV-upturn of elliptical galaxies model
- Short Name:
- J/MNRAS/380/1098
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A long-standing problem in the study of elliptical galaxies is the far-ultraviolet (FUV) excess in their spectra (also known as UV-upturn, UV rising-branch, UV rising flux, or UVX). While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes. We have developed an evolutionary population synthesis (EPS) model for the FUV excess of elliptical galaxies based on the binary model of Han et al. (2002MNRAS.336..449H and 2003MNRAS.341..669H) for the formation of hot subdwarfs in our Galaxy. We give the colour evolution of a simple stellar population (SSP) (including binaries) of 10^10^M_{sun}_ for our standard simulation set. We have also compiled a file for the SED evolution, in which the SEDs without binary interactions are also supplied.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/581/A66
- Title:
- UV variability and accretion in NGC 2264
- Short Name:
- J/A+A/581/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric variability is a distinctive feature of young stellar objects; exploring variability signatures at different wavelengths provides insight into the physical processes at work in these sources. We explore the variability signatures at ultraviolet (UV) and optical wavelengths for several hundred accreting and non-accreting members of the star-forming region NGC 2264 (~3Myr).
- ID:
- ivo://CDS.VizieR/J/A+AS/121/461
- Title:
- UV variability of Fairall-9
- Short Name:
- J/A+AS/121/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is a study of the UV variability of the galaxy Fairall-9 between 1978 and 1991. Table 1 shows the UV continuum fluxes measured in three "line-free" windows centered at 1171, 1400 and 1910 A (observed wavelengths), and corrected for E(B-V)=0.035 extinction. The IUE Fine Error Sensor (FES) counts (optical photometry) are also given in this table, corrected for the same extinction. Tables 10, 11, 12 and 13 show the variability of the components for the main UV lines (Ly{alpha}+NV, SiIV, CIV and MgII). Line profile variability has been used to isolate four gaussian line components, which are sufficient to describe all lines at all levels of brightness in a consistent way: one narrow (i.e. unresolved at the IUE resolution) and three broad components: a central (velocity same as the narrow line), a redshifted (v=3300 km/s) and a blue shifted one (v=-3600 km/s). The Ly{alpha}-NV blend is fitted together in the Ly{alpha} region (Table 10), to account the NV presence (one narrow and one red component). The results for SiIV are shown in Table 11. In CIV (Table 12) have been included a very weak component bluer than the blue component, most likely associated with NIV] 1486. Table 13 shows MgII results.
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/2063
- Title:
- UV/X-ray activity of M dwarfs within 10pc
- Short Name:
- J/MNRAS/431/2063
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M dwarfs are the most numerous stars in the Galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual presence of life on them. We systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10pc to obtain a nearly volume-limited sample (~90 percent completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of H{alpha} emission and rotation to obtain a broad picture of stellar activity on M dwarfs. We make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. We also analyse the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (~10Myr). We find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the H{alpha}, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. We present here for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as flux ratio between the activity diagnostic and the bolometric flux of the star in analogy to the CaII R'HK index. For given spectral type, these indices display a spread of 2-3dex which is largest for M4 stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and H{alpha}, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TWHya members shows a drop of nearly three orders of magnitude for the luminosity in these bands between ~10Myr and few Gyr age. A few young field dwarfs (<1Gyr) in the 10-pc sample bridge the gap indicating that the drop in magnetic activity with age is a continuous process. The slope of the age decay is steeper for the X-ray than for the UV luminosity.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/361
- Title:
- Vacuum ultraviolet emission band systems of N2
- Short Name:
- J/A+AS/128/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observed wavenumbers of the emission lines belonging to 10 vacuum ultraviolet band systems of molecular nitrogen are classified into 283 bands, 220 of them reported for the first time
- ID:
- ivo://CDS.VizieR/J/A+AS/116/257
- Title:
- Variability in O-stars wind
- Short Name:
- J/A+AS/116/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables below list the Log of IUE observations incorporated in the paper. The table number corresponds to the figure number in the paper. The involved O star and the observing period are mentioned in the table header.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/9
- Title:
- Variability in UV line emission of F-M stars
- Short Name:
- J/ApJS/211/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Variations in stellar flux can potentially overwhelm the photometric signal of a transiting planet. Such variability has not previously been well-characterized in the ultraviolet lines used to probe the inflated atmospheres surrounding hot Jupiters. Therefore, we surveyed 38 F-M stars for intensity variations in four narrow spectroscopic bands: two enclosing strong lines from species known to inhabit hot Jupiter atmospheres, C.II {lambda}{lambda}1334, 1335 and SiIII{lambda}1206; one enclosing SiIV {lambda}{lambda}1393, 1402; and 36.5{AA} of interspersed continuum. For each star/band combination, we generated 60s cadence lightcurves from archival Hubble Space Telescope Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph time-tagged photon data. Within these lightcurves, we characterized flares and stochastic fluctuations as separate forms of variability. Flares: we used a cross-correlation approach to detect 116 flares. These events occur in the time-series an average of once per 2.5hr, over 50% last 4 minutes or less, and most produce the strongest response in SiIV. If the flare occurred during a transit measurement integrated for 60 minutes, 90/116 would destroy the signal of an Earth, 27/116 Neptune, and 7/116 Jupiter, with the upward bias in flux ranging from 1% to 109% of quiescent levels. Fluctuations: photon noise and underlying stellar fluctuations produce scatter in the quiescent data. We model the stellar fluctuations as Gaussian white noise with standard deviation {sigma}_x_. Maximum likelihood values of {sigma}_x_ range from 1% to 41% for 60s measurements. These values suggest that many cool stars will only permit a transit detection to high confidence in ultraviolet resonance lines if the radius of the occulting disk is >~1R_J_. However, for some M dwarfs this limit can be as low as several R_{oplus}_.
- ID:
- ivo://CDS.VizieR/J/A+A/420/571
- Title:
- V1974 Cyg IUE spectroscopy
- Short Name:
- J/A+A/420/571
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a detailed analysis of the IUE archival high resolution spectra of the classical nova V1974 Cyg 1992. The main UV resonance lines show P Cygni profiles in the first days, which change into symmetric pure emission lines, and then slowly become fainter and narrower. Lines of higher ionization species reach their peak luminosity later than those of low ionization.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/26
- Title:
- Very low-z SDSS galaxies with H{alpha} emission
- Short Name:
- J/ApJ/765/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Strong H{alpha} emitters (HAEs) dominate the z~4 Lyman-break galaxy (LBG) population. We have identified local analogs of these HAEs using the Sloan Digital Sky Survey. At z<0.4, only 0.04% of the galaxies are classified as HAEs with H{alpha} equivalent widths (>~500{AA}) comparable to that of z~4 HAEs. Local HAEs have lower stellar mass and lower ultraviolet (UV) luminosity than z~4 HAEs, yet the H{alpha}-to-UV luminosity ratio, as well as their specific star formation rate, is consistent with that of z~4 HAEs, indicating that they are scaled-down versions of high-z star-forming galaxies. Compared to the previously studied local analogs of LBGs selected using rest-frame UV properties, local HAEs show similar UV luminosity surface density, weaker D_n_(4000) break, lower metallicity, and lower stellar mass. This implies that the local HAEs are less evolved galaxies than the traditional Lyman break analogs. In the stacked spectrum, local HAEs show a significant He II{lambda}4686 emission line suggesting a population of hot, massive stars similar to that seen in some Wolf-Rayet galaxies. Low [N II]/[O III] line flux ratios imply that local HAEs are inconsistent with being systems that host bright active galactic nuclei. Instead, it is highly likely that local HAEs are galaxies with an elevated ionization parameter, either due to a high electron density or large escape fraction of hydrogen ionizing photons as in the case of Wolf-Rayet galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A25
- Title:
- VLT/X-shooter observations of PHL293B
- Short Name:
- J/A+A/533/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLT/X-shooter spectroscopic observations in the wavelength range {lambda}{lambda}3000-23000{AA} of the extremely metal-deficient blue compact dwarf (BCD) galaxy PHL 293B containing a luminous blue variable (LBV) star and compare them with previous data. This BCD is one of the two lowest-metallicity galaxies where LBV stars were detected, allowing us to study the LBV phenomenon in the extremely low metallicity regime. We determine abundances of nitrogen, oxygen, neon, sulfur, argon, and iron by analyzing the fluxes of narrow components of the emission lines using empirical methods and study the properties of the LBV from the fluxes and widths of broad emission lines.
