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6101. Spectral and UBV analysis of {epsilon} Aur
ID:
ivo://CDS.VizieR/J/A+A/530/A146
Title:
Spectral and UBV analysis of {epsilon} Aur
Short Name:
J/A+A/530/A146
Date:
21 Oct 2021
Publisher:
CDS
Description:
A series of 353 red electronic spectra (from three observatories, mostly from 6300 to 6700{AA}) obtained between 1994 and 2010, and of 171 UBV photometric observations (from two observatories) of the 2010 eclipse, were analyzed in an effort to better understand epsilon Aur, the well-known, but still enigmatic eclipsing binary with the longest known orbital period (~27yrs).
6102. Spectral classification of close binaries
ID:
ivo://CDS.VizieR/J/ApJS/143/513
Title:
Spectral classification of close binaries
Short Name:
J/ApJS/143/513
Date:
21 Oct 2021
Publisher:
CDS
Description:
A sample of 135 stars with composite spectra has been observed in the near-UV spectral region with the Aurelie spectrograph at the Observatoire de Haute-Provence. Using the spectral classifications of the cool components previously determined with near infrared spectra, we obtained reliable spectral types of the hot components of the sample systems. The hot components were isolated by the subtraction method using MK standards as surrogates of the cool components. We also derived the visual magnitude differences between the components using Willstrop's normalized stellar flux ratios. We propose a photometric model for each of these systems on the basis of our spectroscopic data and the Hipparcos data.
6103. Spectral classification of stars in NGC 6530
ID:
ivo://CDS.VizieR/J/A+A/546/A9
Title:
Spectral classification of stars in NGC 6530
Short Name:
J/A+A/546/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mechanisms involved in the star formation process and in particular the duration of the different phases of the cloud contraction are not yet fully understood. Photometric data alone suggest that objects coexist in the young cluster NGC 6530 with ages from ~1Myr up to 10Myrs. We want to derive accurate stellar parameters and, in particular, stellar ages to be able to constrain a possible age spread in the star-forming region NGC6530.
6104. Spectral distances to DA white dwarfs
ID:
ivo://CDS.VizieR/J/AJ/135/1239
Title:
Spectral distances to DA white dwarfs
Short Name:
J/AJ/135/1239
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using recent photometric calibrations, we develop greatly improved distance estimates for DA white dwarfs using multi-band synthetic photometry based on spectroscopic temperatures and gravities. Very good correlations are shown to exist between our spectroscopically based photometric distance estimates and those derived from trigonometric parallaxes. We investigate the uncertainties involved in our distance estimates, as well as discuss the circumstances where such techniques are most likely to fail. We apply our techniques to the large sample of Sloan Digital Sky Survey DA white dwarfs where automated fitting of HI Balmer profiles yields spectrometric temperatures and gravities. We determine simple empirical corrections to these temperatures and gravities with respect to published slit spectroscopy. After applying these T_eff_-logg corrections as well as appropriate interstellar extinction corrections, where necessary, we derive spectroscopically based photometric distances for 7062 DA stars from this sample.
6106. Spectral energy distributions of Roma BZCAT blazars
ID:
ivo://CDS.VizieR/J/ApJS/224/26
Title:
Spectral energy distributions of Roma BZCAT blazars
Short Name:
J/ApJS/224/26
Date:
21 Oct 2021
Publisher:
CDS
Description:
We combined multi-wavelength data for blazars from the Roma-BZCAT catalog and analyzed hundreds of X-ray spectra. We present the fluxes and spectral energy distributions (SEDs), in 12 frequency bands from radio to {gamma}-rays, for a final sample of 2214 blazars. Using a model-independent statistical approach, we looked for systematic trends in the SEDs; the most significant trends involved the radio luminosities and X-ray spectral indices of the blazars. We used a principal component analysis (PCA) to determine the basis vectors of the blazar SEDs and, in order to maximize the size of the sample, imputed missing fluxes using the K-nearest neighbors method. Using more than an order of magnitude more data than was available when Fossati et al. first reported trends of SED shape with blazar luminosity, we confirmed the anti-correlation between radio luminosity and synchrotron peak frequency, although with greater scatter than was seen in the smaller sample. The same trend can be seen between bolometric luminosity and synchrotron peak frequency. Finally, we used all of the available blazar data to determine an empirical SED description that depends only on the radio luminosity at 1.4GHz and the redshift. We verified that this statistically significant relation was not a result of the luminosity-luminosity correlations that are natural in flux-limited samples (i.e., where the correlation is actually caused by the redshift rather than the luminosity).
6107. Spectral & environment properties of z~2 QSO pairs
ID:
ivo://CDS.VizieR/J/ApJ/860/41
Title:
Spectral & environment properties of z~2 QSO pairs
Short Name:
J/ApJ/860/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at z~2.0-2.5 using the Wide Field Camera 3 on board the Hubble Space Telescope. The quasars in our sample are projected pairs with proper transverse separations R_{perp}_<=150kpc and line-of- sight velocity separations <~11000km/s. We construct a stacked ultraviolet (rest-frame wavelengths 700-2000{AA}) spectrum of pairs corrected for the intervening Lyman forest and Lyman continuum absorption. The observed spectral composite presents a moderate flux excess for the most prominent broad emission lines, a ~30% decrease in flux at {lambda}=800-900{AA} compared to a stack of brighter quasars not in pairs at similar redshifts, and lower values of the mean free path of the HI ionizing radiation for pairs ({lambda}_mfp_^912^=140.7+/-20.2h_70_^-1^Mpc) compared to single quasars ({lambda}_mfp_^912^=213.8+/-28h_70_^-1^Mpc) at the average redshift z~2.44. From the modeling of LLS absorption in these pairs, we find a higher (~20%) incidence of proximate LLSs with logN_HI_>=17.2 at {delta}v<5000km/s compared to single quasars (~6%). These two rates are different at the 5{sigma} level. Moreover, we find that optically thick absorbers are equally shared between foreground and background quasars. Based on these pieces of evidence, we conclude that there is a moderate excess of gas-absorbing Lyman continuum photons in our closely projected quasar pairs compared to single quasars. We argue that this gas arises mostly within large-scale structures or partially neutral regions inside the dark matter halos where these close pairs reside.
6108. Spectral lines of BK Peg and BW Aqr
ID:
ivo://CDS.VizieR/J/A+A/516/A42
Title:
Spectral lines of BK Peg and BW Aqr
Short Name:
J/A+A/516/A42
Date:
21 Oct 2021
Publisher:
CDS
Description:
Double-lined, detached eclipsing binaries are our main source for accurate stellar masses and radii. In this paper we focus on the 1.15-1.70M_{sun}_ interval where convective core overshoot is gradually ramped up in theoretical evolutionary models. We aim to determine absolute dimensions and abundances for the F-type detached eclipsing binary BK Peg, and to perform a detailed comparison with results from recent stellar evolutionary models, including a sample of previously studied systems with accurate parameters.
6109. Spectral observations of symbiotic LL Cas
ID:
ivo://CDS.VizieR/J/A+A/479/529
Title:
Spectral observations of symbiotic LL Cas
Short Name:
J/A+A/479/529
Date:
21 Oct 2021
Publisher:
CDS
Description:
All tables contain the results of the spectral and photometric observations of the symbiotic star LL Cas. Observations were carried out within 1986-2006 with a slit spectrograph attached to the 0.7-m telescope of the Fessenkov Astrophysical Institute (Almaty, Kazakhstan). Some photoelectric observations of LL Cas with broad-band filters were carried out on a photoelectric polarimeter mounted on the 1-m Zeiss telescope (Assy-Turgen, Kazakhstan).
6110. Spectra of T dwarfs. I.
ID:
ivo://CDS.VizieR/J/ApJ/564/421
Title:
Spectra of T dwarfs. I.
Short Name:
J/ApJ/564/421
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present near-infrared spectra for a sample of T dwarfs, including 11 new discoveries made using the 2 Micron All Sky Survey. These objects are distinguished from warmer (L-type) brown dwarfs by the presence of methane absorption bands in the 1-2.5{mu}m spectral region. A first attempt at a near-infrared classification scheme for T dwarfs is made, based on the strengths of CH_4_ and H_2_O bands and the shapes of the 1.25, 1.6, and 2.1{mu}m flux peaks. Subtypes T1 VT8 V are defined, and spectral indices useful for classification are presented.