- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3904
- Title:
- Quasars narrow absorption lines from SDSS
- Short Name:
- J/MNRAS/450/3904
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We assemble 3524 quasars from the Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of the narrow C IV {lambda}{lambda}1548, 1551 and Mg II {lambda}{lambda}2796, 2803 absorption doublets in spectral regions shortward of 7000{AA} in the observed frame, which corresponds to time-scales of about 150-2643d in the quasar rest frame. In these quasar spectra, we detect 3580 CIV absorption systems with z_abs_=1.5188-3.5212 and 1809 MgII absorption systems with z_abs_=0.3948-1.7167. In term of the absorber velocity ({beta}) distribution in the quasar rest frame, we find a substantial number of CIV absorbers with {beta}<0.06, which might be connected to absorption of quasar outflows. The outflow absorption peaks at {upsilon}~2000km/s and drops rapidly below this peak value. Among 3580 CIV absorption systems, 52 systems (~1.5 percent) show obvious variations in equivalent widths in the absorber rest frame (W_r_): 16 enhanced, 16 emerged, 12 weakened and 8 disappeared systems, respectively. We find that changes in W_r_{lambda}1548 are related neither to the time-scales of the two SDSS observations nor to absorber velocities in the quasar rest frame. Variable absorption in low-ionization species is important to constrain the physical conditions of the absorbing gas. There are two variable MgII absorption systems measured from SDSS spectra detected by Hacker et al. (2013, J/MNRAS/434/163). However, in our MgII absorption sample, we find that neither shows variable absorption with confident levels of >4{sigma} for {lambda}2796 lines and >3{sigma} for {lambda}2803 lines.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/L6
- Title:
- Quasars narrow absorption lines from SDSS
- Short Name:
- J/MNRAS/468/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we report the discovery of a strong correlation between the variability of narrow absorption lines (NALs) and the ionizing continuum from a two-epoch spectral sample of 40 quasars containing 52 variable CIV {lambda}{lambda}1548, 1551 absorption doublets. According to the concordance index, this sample is classified into two subsamples. Subsample I shows an anti-correlation between the variations of absorption lines and the continuum, while Subsample II exhibits a positive correlation. These results imply that these variable CIV {lambda}{lambda}1548, 1551 absorption doublets are intrinsic to the corresponding quasars and that their variations are caused primarily by the fluctuations of the ionizing continuum. Based on our analysis, we propose that there might be two kinds of absorption gas: one that is very sensitive to the continuum variations, and another that is not. In addition, we suggest that in many cases the emergence or disappearance of NALs is caused by fluctuations of the ionizing continuum.
- ID:
- ivo://CDS.VizieR/J/ApJ/801/45
- Title:
- Quasars properties and reverberation mapping
- Short Name:
- J/ApJ/801/45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the practical feasibility of active galactic nucleus (AGN) broadband reverberation mapping and present first results. We lay out and apply a rigorous approach for the stochastic reverberation mapping of unevenly sampled multi-broadband flux measurements, assuming that the broad-line region (BLR) line flux is contributing up to 15% in some bands, and is directly constrained by one spectroscopical epoch. The approach describes variations of the observed flux as the continuum, modeled as a stochastic Gaussian process, and emission line contribution, modeled as a scaled, smoothed, and delayed version of the continuum. This approach can be used not only to interpolate in time between measurements, but also to determine confidence limits on continuum-line emission delays. This approach is applied to Sloan Digital Sky Survey observations in Stripe 82 (S82), providing flux measurements that are precise to 2% at ~60 epochs over ~10 yr. The strong annual variations in the epoch sampling prove a serious limitation in practice. In addition, suitable redshift ranges must be identified where strong, broad emission lines contribute to one filter, but not to another. By generating and evaluating problem-specific mock data, we verify that S82-like data can constrain {tau}_delay_ for a simple transfer function model. In application to real data, we estimate {tau}_delay_ for 323 AGNs with 0.225<z<0.846, combining information for different objects through the ensemble-scaling relationships for BLR size and black hole mass. Our analysis tentatively indicates a 1.7 times larger BLR size of H{alpha} and Mg II compared to Kaspi et al. (2000ApJ...533..631K; 2007ApJ...659..997K) and Vestergaard (2002ApJ...571..733V; 2006ApJ...641..689V), but the seasonal data sampling casts doubt on the robustness of the inference.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/83
- Title:
- Radial velocities, abundances & membership in TriII
- Short Name:
- J/ApJ/838/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby+ (2015ApJ...814L...7K) identified it as the most dark-matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of 3600_-2100_^+3500^M_{sun}_/L_{sun}_. On the other hand, Martin+ (2016ApJ...818...40M) measured an outer velocity dispersion that is 3.5+/-2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be {sigma}_v_<3.4km/s (90%C.L.). Our previous measurement of {sigma}_v_, based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses, or once possessed, a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/6
- Title:
- Radial velocities in {omega} Cen
- Short Name:
- J/ApJ/751/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The multi-object fiber-fed spectrograph AAOmega at the Anglo-Australian Telescope has been used to establish and measure accurate (<=1km/s) radial velocities for a new sample of members in the outer parts of the stellar system {omega} Centauri. The new sample more than doubles the number of known members with precise velocities that lie between 25' and 45' from the cluster center. Combining this sample with earlier work confirms that the line-of-sight velocity dispersion of {omega} Cen remains approximately constant at ~6.5km/s in the outer parts of the cluster, which contain only a small fraction of the total cluster stellar mass. It is argued that the approximately constant velocity dispersion in the outer regions is most likely a consequence of external influences, such as the tidal shock heating that occurs each time {omega} Cen crosses the Galactic plane. There is therefore no requirement to invoke dark matter or non-standard gravitational theories.
- ID:
- ivo://CDS.VizieR/J/AJ/145/111
- Title:
- Radial velocities of five spectroscopic binaries
- Short Name:
- J/AJ/145/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined spectroscopic orbits for five single-lined spectroscopic binaries, HD100167, HD135991, HD140667, HD158222, HD217924. Their periods range from 60.6 to 2403days and the eccentricities from 0.20 to 0.84. Our spectral classes for the stars confirm that they are of solar type, F9-G5, and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are close to the solar value and on average are 0.12 greater than abundances from a photometric calibration. Four of the five stars are rotating faster than their predicted pseudosynchronous rotational velocities.
- ID:
- ivo://CDS.VizieR/J/AJ/152/167
- Title:
- Radial velocities of HD 133131A and HD 133131B
- Short Name:
- J/AJ/152/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new precision radial velocity (RV) data set that reveals multiple planets orbiting the stars in the ~360 au, G2+G2 "twin" binary HD133131AB. Our six years of high-resolution echelle observations from MIKE and five years from the Planet Finder Spectrograph (PFS) on the Magellan telescopes indicate the presence of two eccentric planets around HD133131A with minimum masses of 1.43+/-0.03 and 0.63+/-0.15M_J_ at 1.44+/-0.005 and 4.79+/-0.92au, respectively. Additional PFS observations of HD133131B spanning five years indicate the presence of one eccentric planet of minimum mass 2.50+/-0.05M_J_ at 6.40+/-0.59au, making it one of the longest-period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with the PFS on Magellan, demonstrating the instrument's precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar parameters and measure a suite of 21 abundances across a wide range of condensation temperatures. The host stars are old (likely ~9.5Gyr) and metal-poor ([Fe/H]~-0.30), and we detect a ~0.03dex depletion in refractory elements in HD133131A versus B (with standard errors ~0.017). This detection and analysis adds to a small but growing sample of binary "twin" exoplanet host stars with precise abundances measured, and represents the most metal-poor and likely oldest in that sample. Overall, the planets around HD133131A and B fall in an unexpected regime in planet mass-host star metallicity space and will serve as an important benchmark for the study of long-period giant planets.
- ID:
- ivo://CDS.VizieR/J/ApJ/681/1254
- Title:
- Radial velocities of stars in the Galactic Center
- Short Name:
- J/ApJ/681/1254
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from K-band slit scan observations of a ~20"x20" region of the Galactic center (GC) in two separate epochs more than 5 years apart. The high-resolution (R={lamda}/{Delta}{lambda}>=14000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at ~2.2935um and the HeII lines at ~2.0581 and ~2.112, 2.113um: cool, narrow-line hot, and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at ~-7.8+/-10.3km/s and a standard deviation ~113.7+/-10.3km/s. Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of (3.9+/-1.1)x10^6^M_{sun}_, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late-type stars support the existence of a low-density region at the Galactic center suggested by earlier observations.
- ID:
- ivo://CDS.VizieR/J/A+A/529/L4
- Title:
- Reddening law of type Ia supernovae
- Short Name:
- J/A+A/529/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ 76 type Ia supernovae (SNe Ia) with optical spectrophotometry within 2.5 days of B-band maximum light obtained by the Nearby Supernova Factory to derive the impact of Si and Ca features on the supernovae intrinsic luminosity and determine a dust reddening law. We use the equivalent width of SiII {lambda}4131 in place of the light curve stretch to account for first-order intrinsic luminosity variability. The resulting empirical spectral reddening law exhibits strong features that are associated with CaII and SiII {lambda}6355. After applying a correction based on the CaII H&K equivalent width we find a reddening law consistent with a Cardelli extinction law. Using the same input data, we compare this result to synthetic rest-frame UBVRI-like photometry to mimic literature observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/419/1350
- Title:
- Red giants abundances in 4 open clusters
- Short Name:
- J/MNRAS/419/1350
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed high-dispersion echelle spectra (R>~50000) of red giant members for four open clusters to derive abundances for many elements. The spread in temperatures and gravities being very small among the red giants nearly the same stellar lines were employed thereby reducing the random errors. The errors of average abundance for the cluster were generally in the range 0.02-0.07dex. Our present sample covers Galactocentric distances of 8.3-10.5kpc. The [Fe/H] values are -0.02+/-0.05 for NGC 752, -0.07+/-0.06 for NGC 2360, -0.11+/-0.05 for NGC 1817 and -0.19+/-0.06 for NGC 2506. Abundances relative to Fe for elements from Na to Eu are equal within measurement uncertainties to published abundances for thin-disc giants in the field. This supports the view that field stars come from disrupted open clusters.
