- ID:
- ivo://CDS.VizieR/J/ApJ/836/186
- Title:
- Continuum-band lags in SDSS QSOs from PS1 obs.
- Short Name:
- J/ApJ/836/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band (g, r, i, z) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z~1 or z~0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN, we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ~2-3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g-r to g-i and then to g-z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe II lines and Mg II, which may point to changes in the accretion disk structure at higher metallicity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/562/A24
- Title:
- Cool carbon stars in the halo and Fornax dSph
- Short Name:
- J/A+A/562/A24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The population of cool carbon (C) stars located far from the galactic plane is probably made of debris of small galaxies such as the Sagittarius dwarf spheroidal galaxy (Sgr), which are disrupted by the gravitational field of the Galaxy. We aim to know this population better through spectroscopy, 2MASS photometric colours, and variability data. When possible, we compared the halo results to C star populations in the Fornax dwarf spheroidal galaxy, Sgr, and the solar neighbourhood. We first present a few new discoveries of C stars in the halo and in Fornax. The number of spectra of halo C stars is now 125. Forty percent show H{alpha} in emission. The narrow location in the JHK diagram of the halo C stars is found to differ from that of similar C stars in the above galaxies. The light curves of the Catalina and LINEAR variability databases were exploited to derive the pulsation periods of 66 halo C stars. A few supplementary periods were obtained with the TAROT telescopes. We confirm that the period distribution of the halo strongly resembles that of Fornax, and we found that it is very different from the C stars in the solar neighbourhood. There is a larger proportion of short-period Mira/SRa variables in the halo than in Sgr, but the survey for C stars in this dwarf galaxy is not complete, and the study of their variability needs to be continued to investigate the link between Sgr and the cool halo C stars.
- ID:
- ivo://CDS.VizieR/J/AJ/142/103
- Title:
- Cool evolved stars in SAGE-SMC and SAGE-LMC
- Short Name:
- J/AJ/142/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the infrared (IR) properties of cool, evolved stars in the Small Magellanic Cloud (SMC), including the red giant branch (RGB) stars and the dust-producing red supergiant (RSG) and asymptotic giant branch (AGB) stars using observations from the Spitzer Space Telescope Legacy program entitled "Surveying the Agents of Galaxy Evolution in the Tidally Stripped, Low Metallicity SMC", or SAGE-SMC. The survey includes, for the first time, full spatial coverage of the SMC bar, wing, and tail regions at IR wavelengths (3.6-160um). We identify evolved stars using a combination of near-IR and mid-IR photometry and point out a new feature in the mid-IR color-magnitude diagram that may be due to particularly dusty O-rich AGB stars. We find that the RSG and AGB stars each contribute ~20% of the global SMC flux (extended + point-source) at 3.6um, which emphasizes the importance of both stellar types to the integrated flux of distant metal-poor galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/500/1045
- Title:
- Cool stars and brown dwarfs in Lupus clouds
- Short Name:
- J/A+A/500/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most studies of the stellar and substellar populations of star-forming regions rely on using the signatures of accretion, outflows, disks, or activity characterizing the early stages of stellar evolution. However, these signatures rapidly decay with time. We present the results of a wide-area study of the stellar population of clouds in the Lupus star-forming region. When combined with 2MASS photometry, our data allow us to fit the spectral energy distributions of over 150000 sources and identify possible new members based on their photospheric fluxes, independent of any display of the signposts of youth.
- ID:
- ivo://CDS.VizieR/J/ApJ/597/323
- Title:
- Cool stars at the Galactic Center
- Short Name:
- J/ApJ/597/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present {lambda}/{Delta}{lambda}=550-1200 near-infrared H and K spectra for a magnitude-limited sample of 79 asymptotic giant branch and cool supergiant stars in the central ~5pc (diameter) of the Galaxy. We use a set of similar spectra obtained for solar neighborhood stars with known Teff and Mbol that is in the same range as the Galactic center (GC) sample to derive Teff and Mbol for the GC sample. We then construct the H-R diagram for the GC sample. Using an automated maximum likelihood routine, we derive a coarse star formation history of the GC.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1592
- Title:
- Cool stars in galactic clusters
- Short Name:
- J/MNRAS/403/1592
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the relevant trend of the bolometric correction (BC) at the cool-temperature regime of red giant stars and its possible dependence on stellar metallicity. Our analysis relies on a wide sample of optical-infrared spectroscopic observations, along the 3500{AA}=>2.5um wavelength range, for a grid of 92 red giant stars in five (three globular + two open) Galactic clusters, along the full metallicity range covered by the bulk of the stars, -2.2<=[Fe/H]<=+0.4.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/63
- Title:
- Cool WD atmosphere models. IV. Spectral evolution
- Short Name:
- J/ApJ/878/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As a result of competing physical mechanisms, the atmospheric composition of white dwarfs changes throughout their evolution, a process known as spectral evolution. Because of the ambiguity of their atmospheric compositions and the difficulties inherent to the modeling of their dense atmospheres, no consensus exists regarding the spectral evolution of cool white dwarfs (Teff<6000K). In the previous papers of this series, we presented and observationally validated a new generation of cool white dwarf atmosphere models that include all the necessary constitutive physics to accurately model those objects. Using these new models and a homogeneous sample of 501 cool white dwarfs, we revisit the spectral evolution of cool white dwarfs. Our sample includes all spectroscopically identified white dwarfs cooler than 8300K for which a parallax is available in Gaia DR2 and photometric observations are available in Pan-STARRS1 and 2MASS. Except for a few cool carbon-polluted objects, our models allow an excellent fit to the spectroscopic and photometric observations of all objects included in our sample. We identify a decrease of the ratio of hydrogen- to helium-rich objects between 7500 and 6250K, which we interpret as the signature of convective mixing. After this decrease, hydrogen-rich objects become more abundant up to 5000K. This puzzling increase, reminiscent of the non-DA gap, has yet to be explained. At lower temperatures, below 5000K, hydrogen-rich white dwarfs become rarer, which rules out the scenario in which the accretion of hydrogen from the interstellar medium dominates the spectral evolution of cool white dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A104
- Title:
- Coordinates for Arp's Baade's Window stars
- Short Name:
- J/A+A/529/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Identifications and coordinates for all stars in Arp's (1965ApJ...141...43A) finding chart for Baade's Window. For each star Arp's ID is presented, as are 2MASS and OGLE IDs when matches were found. All OGLE sources are in the BUL SC45 field. Coordinates are from 2MASS when available; for the remaining stars coordinates are calculated as described in the paper. All coordinates are in J2000. We include photometry and photometric errors from 2MASS (JHKs) and OGLE-II (VI); certain flags regarding the quality of the 2MASS photometry are also listed.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A103
- Title:
- CORNISH project. III. UCHII region catalogue
- Short Name:
- J/A+A/615/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of 239 ultra-compact HII regions (UCHIIs) found in the CORNISH survey at 5GHz and 1.5-arcsec resolution in the region 10{deg}<l<65{deg}, |b|<1{deg} is presented. This is the largest complete and well-selected sample of UCHIIs to date and provides the opportunity to explore the global and individual properties of this key state in massive star formation at multiple wavelengths. The nature of the candidates was validated, based on observational properties and calculated spectral indices, and the analysis is presented in this work. The physical sizes, luminosities and other physical properties were computed by utilising literature distances or calculating the distances whenever a value was not available. The near- and mid-infrared extended source fluxes were measured and the extinctions towards the UCHIIs were computed. The new results were combined with available data at longer wavelengths and the spectral energy distributions (SEDs) were reconstructed for 177 UCHIIs. The bolometric luminosities obtained from SED fitting are presented. By comparing the radio flux densities to previous observational epochs, we find about 5% of the sources appear to be time variable. This first high-resolution area survey of the Galactic plane shows that the total number of UCHIIs in the Galaxy is ~750 - a factor of 3-4 fewer than found in previous large area radio surveys. It will form the basis for future tests of models of massive star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/480/2423
- Title:
- CORNISH project IV. Radio-selected galactic PN
- Short Name:
- J/MNRAS/480/2423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new radio-selected sample of PNe from the CORNISH survey. We find 90 new PNe, of which 12 are newly discovered and 78 are newly classified as PN. A further 47 previously suspected PNe are confirmed as such from the analysis presented here and 24 known PNe are detected. Eight sources are classified as possible PNe or other source types.
