- ID:
- ivo://CDS.VizieR/J/ApJS/233/16
- Title:
- Spectral data for neutral carbon (C I)
- Short Name:
- J/ApJS/233/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this critical compilation, all experimental data on the spectrum of neutral carbon known to us were methodically evaluated and supplemented by parametric calculations with Cowan's codes. The sources of experimental data vary from laboratory to astrophysical objects, and employ different instrumentations, from classical grating and Fourier transform spectrometers to precise laser spectroscopy setups and various other modern techniques. This comprehensive evaluation provides accurate atomic data on energy levels and wavelengths (observed and Ritz) with their estimated uncertainties, as well as a uniform description of the observed line intensities. In total, 412 previously known energy levels were optimized with the help of 1221 selected best-observed lines participating in 1365 transitions in the wavelength region 750{AA}-609.14{mu}m. The list of recommended energy levels is extended by including 21 additional levels found through quantum-defect extrapolations or parametric calculations with Cowan's codes. In addition, 737 possibly observable transitions are predicted. Critically evaluated transition probabilities for 1616 lines are provided, of which 241 are new. With accurate energy levels obtained, combined with additional observed data on high Rydberg states, the ionization limit was determined to be 90820.348(9)cm-1 or 11.2602880(11)eV, in fair agreement with the previously recommended value, but more accurate.
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- 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.
- ID:
- ivo://CDS.VizieR/Model.SED
- Title:
- Spectral Energy Distribution from VizieR (Ochsenbein+ 2012)
- Short Name:
- Model.SED
- Date:
- 05 Apr 2018 10:00:00
- Publisher:
- CDS
- 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).
- 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.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/4735
- Title:
- Spectral evolution of 4U 1543-47 in 2002
- Short Name:
- J/MNRAS/468/4735
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the viscous evolution of the accretion disc in 4U 1543-47, a black hole binary system, during the first 30 d after the peak of the 2002 burst by comparing the observed and theoretical accretion rate evolution dM(t)/dt. The observed dM(t)/dt is obtained from spectral modelling of the archival Proportional Counter Array aboard the RXTE observatory (RXTE/PCA) data. Different scenarios of disc decay evolution are possible depending on a degree of self-irradiation of the disc by the emission from its centre. If the self-irradiation, which is parametrized by factor C_irr_, had been as high as ~5x10^-3^, then the disc would have been completely ionized up to the tidal radius and the short time of the decay would have required the turbulent parameter {alpha}~3. We find that the shape of the \dot M(t) curve is much better explained in a model with a shrinking high-viscosity zone. If C_irr_~(2-3)x10^-4^, the resulting {alpha} lie in the interval 0.5-1.5 for the black hole masses in the range 6-10M_{sun}_, while the radius of the ionized disc is variable and controlled by irradiation. For very weak irradiation, C_irr_<1.5x10^-4^, the burst decline develops as in normal outbursts of dwarf novae with {alpha}~0.08-0.32. The optical data indicate that C_irr_ in 4U 1543-47 (2002) was not greater than approximately (3-6)x10^-4^. Generally, modelling of an X-ray nova burst allows one to estimate {alpha} that depends on the black hole parameters. We present the public 1D code FREDDI to model the viscous evolution of an accretion disc. Analytic approximations are derived to estimate {alpha} in X-ray novae using dM(t)/dt.
17087. Spectral fit of ULX sources
- ID:
- ivo://CDS.VizieR/J/ApJ/664/458
- Title:
- Spectral fit of ULX sources
- Short Name:
- J/ApJ/664/458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data from Chandra observations of 30 nearby galaxies were analyzed and 365 X-ray point sources were chosen whose spectra were not contaminated by excessive diffuse emission and not affected by photon pileup. The spectra of these sources were fitted using two spectral models (an absorbed power-law and a disk blackbody) to ascertain the dependence of estimated parameters on the spectral model used. It was found that the cumulative luminosity function depends on the choice of the spectral model, especially for luminosities >10^40^ergs/s. A large number (~80) of the sources have luminosities >10^39^ergs/s (ultraluminous X-ray sources) with indistinguishable average spectral parameters (inner disk temperature ~1keV and/or photon index GAMMA~2) with those of the lower luminosity ones.
- ID:
- ivo://CDS.VizieR/J/ApJ/682/821
- Title:
- Spectral fits of galaxy clusters in X-ray
- Short Name:
- J/ApJ/682/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM) for 192 well-observed galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broadband (0.7-7.0keV) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0-7.0keV) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broadband spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broadband temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise ratio (S/N) to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7-7.0keV (broad) and when the energy range is 2.0/(1+z)-7.0keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broadband temperature. On further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broadband temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components (T_X_=0.5-3.0keV) with emission measures >=10-30% of the primary hot component.
- ID:
- ivo://CDS.VizieR/J/ApJS/230/7
- Title:
- Spectral flux densities from 50MHz to 50GHz
- Short Name:
- J/ApJS/230/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The flux-density scale of Perley & Butler (2013ApJS..204...19P) is extended downward to ~50MHz by utilizing recent observations with the Karl G. Jansky Very Large Array (VLA) of 20 sources between 220MHz and 48.1GHz, and legacy VLA observations at 73.8MHz. The derived spectral flux densities are placed on an absolute scale by utilizing the Baars+ (1977A&A....61...99B) values for Cygnus A (3C405) for frequencies below 2GHz, and the Mars-based polynomials for 3C286, 3C295, and 3C196 from Perley & Butler above 2GHz. Polynomial expressions are presented for all 20 sources, with accuracy limited by the primary standards to 3%-5% over the entire frequency range. Corrections to the scales proposed by Perley & Butler, and by Scaife & Heald (2012MNRAS.423L..30S) are given.
17090. Spectral flux ratio of SN Ia
- ID:
- ivo://CDS.VizieR/J/A+A/500/L17
- Title:
- Spectral flux ratio of SN Ia
- Short Name:
- J/A+A/500/L17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new method to standardize Type Ia supernova (SN Ia) luminosities to ~<0.13mag using flux ratios from a single flux-calibrated spectrum per SN. Using Nearby Supernova Factory spectrophotometry of 58 SNe Ia, we performed an unbiased search for flux ratios that correlate with SN Ia luminosity. After developing the method and selecting the best ratios from a training sample, we verified the results on a separate validation sample and with data from the literature. We identified multiple flux ratios whose correlations with luminosity are stronger than those of light curve shape and color, previously identified spectral feature ratios, or equivalent width measurements. In particular, the flux ratio R(642/443)=Flux(642nm)/Flux(443nm) has a correlation of 0.95 with SN Ia absolute magnitudes. Using this single ratio as a correction factor produces a Hubble diagram with a residual scatter standard deviation of 0.125+/-0.011mag, compared with 0.161+/-0.015mag when fit with the SALT2 light curve shape and color parameters x1 and c. The ratio R(642/443) is an effective correction factor for both extrinsic dust reddening and intrinsic variations such as those of SN 1991T-like and SN 1999aa-like SNe. When combined with broad-band color measurements, spectral flux ratios can standardize SN Ia magnitudes to ~0.12mag. These are the first spectral metrics that give robust improvements over the standard normalization methods based upon light curve shape and color, and they provide among the lowest scatter Hubble diagrams ever published.