- ID:
- ivo://CDS.VizieR/J/A+A/570/A96
- Title:
- GTC spectra of z~2.3 quasars
- Short Name:
- J/A+A/570/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The advent of 8-10m class telescopes for the first time makes it possible to compare in detail quasars with similar luminosity and very different redshifts. We conducted a search for z-dependent gradients in line-emission diagnostics and derived physical properties by comparing, in a narrow bolometric luminosity range (logL~46.1+/-0.4erg/s), some of the most luminous local z<0.6 quasars with some of the lowest luminosity sources yet found at redshift z=2.1-2.5. Moderate signal-to-noise ratio spectra for 22 high-redshift sources were obtained with the 10.4m Gran Telescopio Canarias (GTC), for which the HST (largely the Faint Object Spectrograph) archive provides a low-redshift control sample. We compared the spectra in the context of the 4D Eigenvector 1 formalism, meaning that we divided both source samples into highly accreting population A and population B sources accreting at a lower rate. CIV {lambda}1549, the strongest and most reliable diagnostic line, shows very similar properties at both redshifts, which confirms the CIV {lambda}1549 profile differences at high redshift between populations A and B, which are well established in local quasars. The CIV {lambda}1549 blueshift that appears quasi-ubiquitous in higher L sources is found in only half (population A) of the quasars observed in the two samples. A CIV {lambda}1549 evolutionary Baldwin effect is certainly disfavored. We find evidence for lower metallicity in the GTC sample that may point toward a gradient with z. No evidence for a gradient in black hole mass or Eddington ratio is found. Spectroscopic differences established at low z are also present in much higher redshift quasars. Our results on the CIV {lambda}1549 blueshift suggest that it depends both on source luminosity and Eddington ratio. Given that our samples involve sources with very similar luminosity, the evidence for a systematic metallicity decrease, if real, points toward an evolutionary effect. Our samples are not large enough to effectively constrain possible changes of black hole mass or Eddington ratio with redshift. The two samples appear representative of a slowly evolving quasar population that is most likely present at all redshifts.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/589/A62
- Title:
- GTC transit light curves of CoRoT-29b
- Short Name:
- J/A+A/589/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The launch of the exoplanet space missions obtaining exquisite photometry from space has resulted in the discovery of thousands of planetary systems with very different physical properties and architectures. Among them, the exoplanet CoRoT-29b was identified in the light curves the mission obtained in summer 2011, and presented an asymmetric transit light curve, which was tentatively explained via the effects of gravity darkening. Here we use the OSIRIS spectrograph at the 10-m GTC telescope to measure with high precision the transit light curve of CoRoT-29b to characterize the reported asymmetry in its transit shape. To this end, using the OSIRIS spectrograph at the 10-m GTC telescope, we perform spectro-photometric differential observations, which allow us to both calculate a high-accuracy photometric light curve, and a study of the color-dependence of the transit. After careful data analysis, we find that there is no asymmetry in the transit of CoRoT-29b, in either of the two observed transits, separated by one calendar year. Due to the relative faintness of the star, we do not reach the precision necessary to perform transmission spectroscopy of its atmosphere, but we see no signs of color-dependency of the transit depth or duration. We conclude that the previously reported asymmetry is a time-dependent phenomenon which did not occur in more recent epochs, or possible instrumental effects in the discovery data need to be reconsidered.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A172
- Title:
- GTC transit light curves of HAT-P-11b
- Short Name:
- J/A+A/622/A172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground- or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. We obtained Gran Telescopio Canarias (GTC) long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of delta=0.62^+0.20^_-0.17_ and a spot-to-photosphere temperature difference of {Delta}T=429^+184^_-299_K.
- ID:
- ivo://CDS.VizieR/J/A+A/594/A65
- Title:
- GTC transit light curves of HAT-P-32b
- Short Name:
- J/A+A/594/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the hot Jupiter HAT-P-32b (also known as HAT-P-32Ab) to determine its optical transmission spectrum by measuring the wavelength-dependent, planet-to-star radius ratios in the region between 518-918nm. We used the OSIRIS instrument at the Gran Telescopio CANARIAS (GTC) in long-slit spectroscopy mode, placing HAT-P-32 and a reference star in the same slit and obtaining a time series of spectra covering two transit events. Using the best quality data set, we were able to yield 20 narrowband transit light curves, with each passband spanning a 20nm wide interval. After removal of all systematic noise signals and light curve modeling, the uncertainties for the resulting radius ratios lie between 337 and 972ppm. The radius ratios show little variation with wavelength, suggesting a high altitude cloud layer masking any atmospheric features. Alternatively, a strong depletion in alkali metals or a much smaller than expected planetary atmospheric scale height could be responsible for the lack of atmospheric features. Our result of a flat transmission spectrum is consistent with a previous ground-based study of the optical spectrum of this planet. This agreement between independent results demonstrates that ground-based measurements of exoplanet atmospheres can give reliable and reproducible results despite the fact that the data often is heavily affected by systematic noise as long as the noise source is well understood and properly corrected.
- ID:
- ivo://CDS.VizieR/J/A+A/641/A158
- Title:
- GTC transit light curves of WASP-69b
- Short Name:
- J/A+A/641/A158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the major atmospheric features in exoplanet atmospheres, detectable both from ground- and space-based facilities, is Rayleigh scattering. In hydrogen-dominated planetary atmospheres Rayleigh scattering causes the measured planetary radius to increase towards blue wavelengths in the optical range. We obtained a spectrophotometic time series of one transit of the Saturn-mass planet WASP-69b using the OSIRIS instrument at the Gran Telescopio Canarias. From the data we construct 19 spectroscopic transit light curves representing 20nm wide wavelength bins spanning from 515nm-905nm. We derive the transit depth for each curve individually by fitting an analytical model together with a Gaussian Processes to account for systematic noise in the light curves. We find that the transit depth increases towards bluer wavelengths, indicative of a larger effective planet radius. Our results are consistent with space-based measurements obtained in the near infrared using the Hubble Space telescope, which show a compatible slope of the transmission spectrum. We discuss the origin of the detected slope and argue between two possible scenarios: a Rayleigh scattering detection originating in the planet's atmosphere or a stellar activity induced signal from the host star.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A145
- Title:
- GTC transit light curves of WASP-127b
- Short Name:
- J/A+A/616/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Exoplanets with relatively clear atmospheres are prime targets for detailed studies of chemical compositions and abundances in their atmospheres. Alkali metals have been long suggested to exhibit broad wings due to pressure broadening, but most of the alkali detections only show very narrow absorption cores, probably due to the presence of clouds. Here we report the strong detection of the pressure-broadened spectral profiles of Na, K, and Li absorption in the atmosphere of the super-Neptune WASP-127b, at 5.0{sigma}, 4.1{sigma}, and 3.4{sigma}, respectively. We performed a spectral retrieval modeling on the high-quality optical transmission spectrum newly acquired with the 10.4m Gran Telescopio Canarias (GTC), in combination with the re-analyzed optical transmission spectrum obtained with the 2.5m Nordic Optical Telescope (NOT). By assuming a patchy cloudy model, we retrieved the abundances of Na, K, and Li, which are super-solar at 3.7{sigma} for K and 5.1{sigma} for Li (and only 1.8{sigma} for Na). We constrained the presence of haze coverage to be around 52%. We also found a hint of water absorption, but cannot constrain it with the global retrieval due to larger uncertainties in the probed wavelengths. WASP-127b will be extremely valuable for atmospheric characterization in the era of James Webb space telescope.
- ID:
- ivo://CDS.VizieR/J/A+A/600/L11
- Title:
- GTC transit light curves of WASP-52b
- Short Name:
- J/A+A/600/L11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first detection of sodium absorption in the atmosphere of the hot Jupiter WASP-52b. We observed one transit of WASP-52b with the low-resolution Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) at the 10.4m Gran Telescopio Canarias (GTC). The resulting transmission spectrum, covering the wavelength range from 522nm to 903nm, is flat and featureless, except for the significant narrow absorption signature at the sodium doublet, which can be explained by an atmosphere in solar composition with clouds at 1 mbar. A cloud-free atmosphere is stringently ruled out. By assessing the absorption depths of sodium in various bin widths, we find that temperature increases towards lower atmospheric pressure levels, with a positive temperature gradient of 0.88+/-0.65K/km , possibly indicative of upper atmospheric heating and a temperature inversion.
- ID:
- ivo://CDS.VizieR/J/A+A/605/A114
- Title:
- GTC transit light curves of WASP-48b
- Short Name:
- J/A+A/605/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained long-slit optical spectroscopy of one transit of WASP-48b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) spectrograph. We report a relatively flat transmission spectrum (wavelength coverage from 530 nm to 905 nm) for WASP-48b with no statistical significant detection of atmospheric species, although the theoretical models that fit the data more closely include TiO and VO.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A84
- Title:
- GUAPOS. identified transitions of C2H4O2
- Short Name:
- J/A+A/644/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased spectral survey of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this first paper, we discuss the detection and relative abundances of the three isomers of C_2_H_4_O_2_: methyl formate, glycolaldehyde, and acetic acid. Observations were carried out with the ALMA interferometer, covering all of band 3 (~32GHz bandwidth) with an angular resolution of 1.2"x1.2" (~4400aux4400au) and a spectral resolution of ~0.488MHz. The transitions of the three molecules have been analyzed with the software XCLASS to determine the physical parameters of the emitted gas. The comparison with chemical models in literature suggests the necessity of grain-surface routes for the formation of methyl formate in G31, while for glycolaldehyde both grain-surface reactions and gas-phase chemistry could be able to explain the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A129
- Title:
- GUAPOS II. Identified transitions of molecules
- Short Name:
- J/A+A/653/A129
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present an unbiased spectral survey of one of the most chemically rich hot molecular cores located outside the Galactic Center, in the high-mass star-forming region G31.41+0.31. In this second paper, we discuss the detection and relative abundances of the peptide-like bond molecules: HNCO, HC(O)NH2, CH_3_NCO, CH_3_C(O)NH_2_, CH_3_NHCHO, CH_3_CH_2_NCO, NH_2_C(O)NH_2_, NH_2_C(O)CN, and HOCH_2_C(O)NH_2_. Observations were carried out with the ALMA interferometer, covering all of band 3 (about 32GHz bandwidth) with an angular resolution of 1.2"x1.2" (about 4400aux4400au) and a spectral resolution of about 0.488MHz. The transitions of the nine molecules have been analyzed with the software MADCUBA to determine the physical parameters of the emitted gas. The results suggest that all these species are formed on grain surfaces in early evolutionary stages of molecular clouds, and that they are subsequently released back to the gas-phase through thermal desorption or shock-triggered desorption.