- ID:
- ivo://CDS.VizieR/J/A+A/606/A67
- Title:
- Circumstellar envelopes CO photodissociation
- Short Name:
- J/A+A/606/A67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon monoxide is the most abundant molecule after H_2_ and is important for chemistry in circumstellar envelopes around late-type stars. The size of the envelope is important when modelling low-J transition lines and deriving mass-loss rates from such lines. Now that ALMA is coming to full power the extent of the CO emitting region can be measured directly for nearby asymptotic giant branch (AGB) stars. In parallel, it has become obvious in the past few years that the strength of the interstellar radiation field (ISRF) can have a significant impact on the interpretation of the emission lines. In this paper an update and extension of the classical Mamon et al. (1988ApJ...328..797M) paper is presented; these authors provided the CO abundance profile, described by two parameters, as a function of mass-loss rate and expansion velocity. Following recent work an improved numerical method and updated H_2_ and CO shielding functions are used and a larger grid is calculated that covers more parameter space, including the strength of the ISRF. The effect of changing the photodissociation radius on the low-J CO line intensities is illustrated in two cases.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/580/A131
- Title:
- Circumstellar-interacting supernovae
- Short Name:
- J/A+A/580/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Some circumstellar-interacting (CSI) supernovae (SNe) are produced by the explosions of massive stars that have lost mass shortly before the SN explosion. There is evidence that the precursors of some SNe IIn were luminous blue variable (LBV) stars. For a small number of CSI SNe, outbursts have been observed before the SN explosion. Eruptive events of massive stars are named SN impostors (SN IMs) and whether they herald a forthcoming SN or not is still unclear. The large variety of observational properties of CSI SNe suggests the existence of other progenitors, such as red supergiant (RSG) stars with superwinds. Furthermore, the role of metallicity in the mass loss of CSI SN progenitors is still largely unexplored. Our goal is to gain insight into the nature of the progenitor stars of CSI SNe by studying their environments, in particular the metallicity at their locations. We obtain metallicity measurements at the location of 60 transients (including SNe IIn, SNe Ibn, and SN IMs) via emission-line diagnostic on optical spectra obtained at the Nordic Optical Telescope and through public archives. Metallicity values from the literature complement our sample. We compare the metallicity distributions among the different CSI SN subtypes, and to those of other core-collapse SN types. We also search for possible correlations between metallicity and CSI SN observational properties. We find that SN IMs tend to occur in environments with lower metallicity than those of SNe IIn. Among SNe IIn, SN IIn-L(1998S-like) SNe show higher metallicities, similar to those of SNe IIL/P, whereas long-lasting SNe IIn (1988Z-like) show lower metallicities, similar to those of SN IMs. The metallicity distribution of SNe IIn can be reproduced by combining the metallicity distributions of SN IMs (which may be produced by major outbursts of massive stars like LBVs) and SNe IIP (produced by RSGs). The same applies to the distributions of the normalized cumulative rank (NCR) values, which quantifies the SN association to HII regions. For SNe IIn, we find larger mass-loss rates and higher CSM velocities at higher metallicities. The luminosity increment in the optical bands during SN IM outbursts tend to be larger at higher metallicity, whereas the SN IM quiescent optical luminosities tend to be lower. The difference in metallicity between SNe IIn and SN IMs indicates that LBVs are only one of the progenitor channels for SNe IIn, with 1988Z-like and 1998S-like SNe possibly arising from LBVs and RSGs, respectively. Finally, even though line-driven winds likely do not primarily drive the late mass-loss of CSI SN progenitors, metallicity has some impact on the observational properties of these transients.
- ID:
- ivo://CDS.VizieR/J/A+A/293/833
- Title:
- Circumstellar silicate grains
- Short Name:
- J/A+A/293/833
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the radiative transfer modelling studies relative to a large sample of circumstellar envelopes (~300 sources) undertaken by David & Papoular (1990A&A...237..425D) the complex dielectric function for circumstellar silicate grains is derived in the wavelength region from 0.35 to ~1355m.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1275
- Title:
- CIRS (Cluster Infall Regions in the SDSS). I.
- Short Name:
- J/AJ/132/1275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) to test the ubiquity of infall patterns around galaxy clusters and measure cluster mass profiles to large radii. The Cluster and Infall Region Nearby Survey (CAIRNS) found infall patterns in nine clusters, but the cluster sample was incomplete. Here we match X-ray cluster catalogs with SDSS, search for infall patterns, and compute mass profiles for a complete sample of X-ray-selected clusters. Very clean infall patterns are apparent in most of the clusters, with the fraction decreasing with increasing redshift due to shallower sampling. All 72 clusters in a well-defined sample limited by redshift (ensuring good sampling) and X-ray flux (excluding superpositions) show infall patterns sufficient to apply the caustic technique. This sample is by far the largest sample of cluster mass profiles extending to large radii to date. Similar to CAIRNS, cluster infall patterns are better defined in observations than in simulations. Further work is needed to determine the source of this difference. We use the infall patterns to compute mass profiles for 72 clusters and compare them to model profiles. Cluster scaling relations using caustic masses agree well with those using X-ray or virial mass estimates, confirming the reliability of the caustic technique. We confirm the conclusion of CAIRNS that cluster infall regions are well fitted by Navarro-Frenk-White (NFW) and Hernquist profiles and poorly fitted by singular isothermal spheres. This much larger sample enables new comparisons of cluster properties with those in simulations. The shapes (specifically NFW concentrations) of the mass profiles agree well with the predictions of simulations. The mass in the infall region is typically comparable to or larger than that in the virial region. Specifically, the mass inside the turnaround radius is on average 2.19+/-0.18 times that within the virial radius. This ratio agrees well with recent predictions from simulations of the final masses of dark matter halos.
- ID:
- ivo://CDS.VizieR/J/A+A/310/933
- Title:
- C isotopic ratio in N- and SC-type stars
- Short Name:
- J/A+A/310/933
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a result of quantitative analysis of ^12^C/^13^C ratios in 62 N-type and 15 SC-type carbon stars. By the use of CCD as a detector we can obtain spectra of resolution ~20,000 with enough signal-to-noise ratios for a large number of carbon stars, for which ^12^C/^13^C ratios have not yet been derived. Carbon isotopic ratios are determined from lines of the CN red system around 8000A, based on the iso-intensity method and line-blanketed model atmospheres. The average of ^12^C/^13^C ratios in 62 N-type carbon stars is found to be 27+/-11 (standard deviation). The majority of the N-type carbon stars studied (about 85%) are found to have ^12^C/^13^C ratios less than 40, and the number of stars which have ^12^C/^13^C ratios larger than 40 is found to be relatively small. This result shows a marked contrast to some of the previous results that have shown the opposite distribution, namely, ^12^C/^13^C ratios mostly larger than 40 in N-type carbon stars. The average of ^12^C/^13^C ratios in 15 SC-type carbon stars is found to be 22+/-14 (standard deviation). Most of the SC-type carbon stars studied are found to have ^12^C/^13^C ratios larger than 10, while only three of them turn out to be ^13^C-rich. This is in contrast with the earlier classification based on low resolution spectra which classified them as J-type, that is, ^13^C-rich. The earlier temperature scale which classified SC-type carbon stars as the latest (C8-9) based on their strong NaI D lines can not be necessarily justified. The strong NaI D lines of SC stars should be attributed to the peculiar atmospheric structure due to C/O ratios very near to unity. The resulting ^12^C/^13^C ratios are partly consistent with the scenario in which M giants evolve through SC-type to N-type carbon stars, as ^12^C produced during the helium shell flash is added to the envelope.
3786. Citizen GBOT Images SIAP
- ID:
- ivo://org.gavo.dc/citigbot/q/i
- Title:
- Citizen GBOT Images SIAP
- Short Name:
- citigbot sia
- Date:
- 30 Jan 2025 13:31:35
- Publisher:
- The GAVO DC team
- Description:
- This archive collects and re-publishes third-party, mostly amateur, images of the Gaia astrometry satellite to complemement the Ground Based Optical Tracking (GBOT) effort. Until Gaia passivation, there is a temporary upload facility at https://dc.g-vo.org/citigbot/q/upload/form.
- ID:
- ivo://CDS.VizieR/J/ApJ/666/757
- Title:
- CIV 1549{AA} emission line in AGNs
- Short Name:
- J/ApJ/666/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are exploring a spectroscopic unification for all types of broad-line emitting AGNs. The four-dimensional Eigenvector 1 (4DE1) parameter space organizes quasar diversity in a sequence primarily governed by Eddington ratio. This paper considers the role of CIV {lambda}1549 measures as 4DE1 diagnostics. We use HST archival spectra for 130 sources with S/N high enough to permit reliable CIV {lambda}1549 broad-component measures.
- ID:
- ivo://CDS.VizieR/J/MNRAS/449/1593
- Title:
- CIV absorption in BAL QSOs
- Short Name:
- J/MNRAS/449/1593
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is a large diversity in the CIV broad absorption line (BAL) profile among BAL quasars (BALQs). We quantify this diversity by exploring the distribution of the CIV BAL properties, full width at half-maximum (FWHM), maximum depth of absorption and its velocity shift (v_md_), using the Sloan Digital Sky Survey DR7 quasar catalogue. We find the following: (i) Although the median CIV BAL profile in the quasar rest-frame becomes broader and shallower as the UV continuum slope ({alpha}UV at 1700-3000{AA}) gets bluer, the median individual profile in the absorber rest-frame remains identical, and is narrow (FWHM=3500km/s) and deep. Only 4 percent of BALs have FWHM>10000km/s. (ii) As the HeII emission equivalent width (EW) decreases, the distributions of FWHM and v_md_ extend to larger values, and the median maximum depth increases. These trends are consistent with theoretical models in which softer ionizing continua reduce overionization, and allow radiative acceleration of faster BAL outflows. (iii) As {alpha}_UV_ becomes bluer, the distribution of v_md_ extends to larger values. This trend may imply faster outflows at higher latitudes above the accretion disc plane. (iv) For non-BALQs, the CIV emission line decreases with decreasing HeII EW, and becomes more asymmetric and blueshifted. This suggests an increasing relative contribution of emission from the BAL outflow to the Civ emission line as the ionizing spectral energy distribution (SED) gets softer, which is consistent with the increasing fraction of BALQs as the ionizing SED gets softer.
- ID:
- ivo://CDS.VizieR/J/A+A/473/791
- Title:
- CIV absorption in DLAs and sub-DLAs systems
- Short Name:
- J/A+A/473/791
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of CIV absorption in a sample of 63 damped Lyman-{alpha} (DLA) systems and 11 sub-DLAs in the redshift range 1.75<z_abs_<3.61, using a dataset of high-resolution (6.6km/s FWHM), high signal-to-noise VLT/UVES spectra. The complex absorption line profiles show both narrow and broad CIV components, indicating the presence of both warm, photoionized and hot, collisionally ionized gas. We report new correlations between the metallicity (measured in the neutral-phase) and each of the CIV column density, the CIV total line width, and the maximum CIV velocity.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/767
- Title:
- CIV and FeK{alpha} Baldwin effects in AGNs
- Short Name:
- J/ApJ/702/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use UV/optical and X-ray observations of 272 radio-quiet Type 1 active galactic nuclei and quasars to investigate the CIV Baldwin Effect (BEff). The UV/optical spectra are drawn from the Hubble Space Telescope, International Ultraviolet Explorer and Sloan Digital Sky Survey archives. The X-ray spectra are from the Chandra and XMM-Newton archives. We apply correlation and partial-correlation analyses to the equivalent widths (EWs), continuum monochromatic luminosities, and {alpha}_ox_, which characterizes the relative X-ray to UV brightness. The EW of the CIV{lambda}1549 emission line is correlated with both {alpha}_ox_ and luminosity. In our sample, narrow Fe K{alpha} 6.4keV emission lines are detected in 50 objects.
