Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/237/18
- Title:
- Cr, Co, and Ni abundances for metal-poor red giants
- Short Name:
- J/ApJS/237/18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the abundances of chromium, cobalt, and nickel in 4113 red giants, including 2277 stars in globular clusters (GCs), 1820 stars in the Milky Way's dwarf satellite galaxies, and 16 field stars. We measured the abundances from mostly archival Keck/DEIMOS medium-resolution spectroscopy with a resolving power of R~6500 and a wavelength range of approximately 6500-9000{AA}. The abundances were determined by fitting spectral regions that contain absorption lines of the elements under consideration. We used estimates of temperature, surface gravity, and metallicity that we previously determined from the same spectra. We estimated systematic error by examining the dispersion of abundances within mono- metallic GCs. The median uncertainties for [Cr/Fe], [Co/Fe], and [Ni/Fe] are 0.20, 0.20, and 0.13, respectively. Finally, we validated our estimations of uncertainty through duplicate measurements, and we evaluated the accuracy and precision of our measurements through comparison to high-resolution spectroscopic measurements of the same stars.
- ID:
- ivo://CDS.VizieR/J/A+A/324/1059
- Title:
- C-rich stars IR and UBVRI photometry
- Short Name:
- J/A+A/324/1059
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A study of circumstellar dust shells (CDS) around carbon stars is presented. This study is based on the analysis of the 1-100{mu}m broad-band spectra of 23 objects which have been monitored in the 1-20{mu}m region over several years at ESO. The sources in the sample range from Irr/SR variables and optical Miras to Extreme Carbon Stars which have only been discovered recently in infrared surveys. A modelling accounting for the photometric variations with phase (with up to 9 spectra per object) has been developed. All the CDSs in the sample can be modelled successfully in spherical geometry with a dust opacity law {prop.to}{lambda}^-1.3^ and a dust formation temperature ~950K. The modelling favors the case of an acceleration of dust, from the site of formation and on a distance of ~10^15^cm, over the case of a uniform expansion. Mass loss rates in the range 0.1-50x10^-6^M_{sun}_/yr are derived. The estimates based on this modelling are consistent with those derived from the CO emission line measurements. In view of the incoming near-infrared surveys (DENIS and 2MASS), an analysis of the location of carbon-rich sources in color diagrams is presented. It is shown that the near-infrared colors are well correlated with the mass loss rate. This property can be used to get an estimate, within a factor 3, of this rate for carbon stars without a priori on the distance.
- ID:
- ivo://CDS.VizieR/J/ApJ/778/98
- Title:
- Cross-correlation of SDSS QSOs and BOSS galaxies
- Short Name:
- J/ApJ/778/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 quasars and 349608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey (BOSS) at 0.3<z<0.9. The CCF can be reasonably well fit by a power-law model {xi}_QG_(r)=(r/r_0_)^-{gamma}^ on projected scales of r_p_=2-25h^-1^Mpc with r_0_=6.61+/-0.25h^-1^Mpc and {gamma}=1.69+/-0.07. We estimate a quasar linear bias of b_Q_=1.38+/-0.10 at <z>{=}0.53 from the CCF measurements, which corresponds to a characteristic host halo mass of ~4x10^12^h^-1^M_{sun}_, compared with a ~10^13^h^-1^M_{sun}_ characteristic host halo mass for CMASS galaxies. Based on the clustering measurements, most quasars at {overline}{z}~0.5 are not the descendants of their higher luminosity counterparts at higher redshift, which would have evolved into more massive and more biased systems at low redshift. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db_Q_/dlogL=0.20+/-0.34 or 0.11+/-0.32 (depending on different luminosity divisions) for quasar luminosities -23.5>M_i_(z=2)>-25.5, implying a weak luminosity dependence of clustering for luminous quasars at {overline}{z}~0.5. We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations and ambiguities in modeling the distribution of quasars with the standard HOD approach.
885. CS Cha B spectrum
- ID:
- ivo://CDS.VizieR/J/A+A/640/L12
- Title:
- CS Cha B spectrum
- Short Name:
- J/A+A/640/L12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct imaging provides a steady flow of newly discovered giant planets and brown dwarf companions. These multi-object systems can provide information about the formation of low-mass companions in wide orbits and/or speculate about possible migration scenarios. The accurate classification of the companions is crucial for testing formation pathways. In this work we characterize further the recently discovered candidate for a planetary-mass companion CS Cha b and determine if it is still accreting. MUSE is a 4-laser-adaptive-optics-assisted medium-resolution integral-field spectrograph in the optical part of the spectrum. We observed the CS Cha system to obtain the first spectrum of CS Cha b. The companion is characterized by modelling both the spectrum from 6300{AA}, to 9300{AA}, and the photometry using archival data from the visible to the near-infrared. We find evidence of accretion and outflow signatures in H{alpha} and OI emission. The atmospheric models with the highest likelihood indicate an effective temperature of 3450+/-50K with a logg of 3.6+/-0.5dex. Based on evolutionary models, we find that the majority of the object is obscured. We determine the mass of the faint companion with several methods to be between 0.07 Msun and 0.71M_{sun}_ with an accretion rate of dM/dt=4x10^-11^+/-0.4x10^-11^M_{sun}_/yr. Our results show that CS Cha B is most likely a mid M-type star that is obscured by a highly inclined disk, which has led to its previous classification by broadband NIR photometry as a planetary-mass companion. This shows that it is important and necessary to observe over a broad spectral range to constrain the nature of faint companions.
- ID:
- ivo://CDS.VizieR/J/ApJ/776/L20
- Title:
- C/2012 S1 (comet ISON) R photometry
- Short Name:
- J/ApJ/776/L20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report photometric observations for comet C/2012 S1 (ISON) obtained during the time period immediately after discovery (r=6.28AU) until it moved into solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8m telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from the CARA network. Additional pre-discovery data from the Pan STARRS1 survey extends the light curve back to 2011 September 30 (r=9.4AU). The images showed a similar tail morphology due to small micron sized particles throughout 2013. Observations at submillimeter wavelengths using the James Clerk Maxwell Telescope on 15 nights between 2013 March 9 (r=4.52AU) and June 16 (r=3.35AU) were used to search for CO and HCN rotation lines. No gas was detected, with upper limits for CO ranging between 3.5-4.5x10^27^molecules/s. Combined with published water production rate estimates we have generated ice sublimation models consistent with the photometric light curve. The inbound light curve is likely controlled by sublimation of CO_2_. At these distances water is not a strong contributor to the outgassing. We also infer that there was a long slow outburst of activity beginning in late 2011 peaking in mid-2013 January (r~5AU) at which point the activity decreased again through 2013 June. We suggest that this outburst was driven by CO injecting large water ice grains into the coma. Observations as the comet came out of solar conjunction seem to confirm our models.
- ID:
- ivo://CDS.VizieR/J/ApJ/900/140
- Title:
- CSP-II: sp. obs. of the 03fg-like SN Ia LSQ14fmg
- Short Name:
- J/ApJ/900/140
- Date:
- 02 Feb 2022 11:26:50
- Publisher:
- CDS
- Description:
- The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar" (or 03fg-like) group. The optical spectrum is typical of a 03fg-like SNIa, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than M_V_=-19mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than -20.5mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized 56Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.
- ID:
- ivo://CDS.VizieR/J/A+A/436/91
- Title:
- C star population in outer disk of M31
- Short Name:
- J/A+A/436/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFHT Megacam camera to survey ~1{deg}^2^ of the southern outer disc of M31, a region which includes the area where Battinelli et al. (2003, Cat. <J/AJ/125/1298>) have identified nearly one thousand C stars. In the outer M31 region not previously surveyed, we identify 361 new C star candidates, having similar photometric properties to the known ones, and confirm the slight decrease in the luminosity of C stars with galactocentric distances. We show that the Sloan g', r', i' filters are a viable approach, comparable to (CN-TiO), to identify C stars. We find that the (g'-r') colours of cool C stars can be so red that prohibitively long g' exposures are needed to acquire faint extragalactic C stars. This makes the Sloan filters a less promising approach to extend a C star survey to several Mpc. Our uniform large field survey detects the edge of M31 disk at ~35kpc. The intermediate-age population, represented by C stars, extends further to ~40kpc.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1298
- Title:
- C star population in outer disk of M31
- Short Name:
- J/AJ/125/1298
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We employ the CFH12K mosaic to identify carbon stars, using the R, I, CN, and TiO photometric technique, in a 2240 arcmin2 area, ranging from 17 to 30kpc of the southwest disk of M31, barely reaching the edge of the observed H I disk. We found 945 C stars with <I_0_>=19.94mag and {sigma}=0.47. The surface density of C stars along the major axis of M31 follows an exponential profile with a scale length of 4.85+/-0.35kpc, in agreement with adopted values for the scale length of the disk population. Our survey partially overlaps with the recently discovered G1 density enhancement by Ferguson et al. We confirm that no AGB star excess is detectable in the surveyed part of the clump. The C/M ratio, along the major axis, is derived over a distance range of 7kpc. The strong C/M gradient seen contrasts with results of previous studies of the C stars in M31.
890. C stars in IC 1613
- ID:
- ivo://CDS.VizieR/J/AJ/119/2780
- Title:
- C stars in IC 1613
- Short Name:
- J/AJ/119/2780
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a multifilter survey of the whole Magellanic-type galaxy IC 1613. Narrowband CN and TiO filters are used to identify carbon stars among red giants. We have identified 195 carbon stars, extending up to 15' from the center of the galaxy. We present well-calibrated R and I magnitudes for all stars. The large field surveyed allows a reliable foreground estimate of M stars, leading to a C/M ratio of 0.64, when giants as early as M0 are counted. Analysis of the photometric properties of the C star population reveals a narrow M_I_ distribution with a mean M_I_ of -4.69mag, with a dispersion of +/-0.28. IC 1613 has, for its absolute magnitude, a normal number of C stars.