- ID:
- ivo://CDS.VizieR/J/MNRAS/330/75
- Title:
- Chemical abundances in UV-selected galaxies
- Short Name:
- J/MNRAS/330/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the chemical properties of a sample of UV-selected intermediate-redshift (0<=z<=0.4) galaxies in the context of their physical nature and star-formation history. This work represents an extension of our previous studies of the rest-frame UV-luminosity function (Treyer et al., 1998, Cat. <J/MNRAS/300/303>) and the star-formation properties of the same sample (Sullivan et al., 2000, Cat. <J/MNRAS/312/442>). We revisit the optical spectra of these galaxies and perform further emission-line measurements restricting the analysis to those spectra with the full set of emission lines required to derive chemical abundances. Our final sample consists of 68 galaxies with heavy-element abundance ratios and both UV and CCD B-band photometry.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/326/751
- Title:
- Chemical composition of halo and disk stars
- Short Name:
- J/A+A/326/751
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table A1 lists the Stromgren photometry together with color excesses, E(b-y), photometric metallicities, [Fe/H] , calculated from the calibrations of Schuster & Nissen (1989A&A...221...65S), and absolute magnitudes, M(V), and distances derived with the equations of Nissen & Schuster (1991A&A...251..457N) using the photometric metallicities. Table A2 contains coordinates, proper motions and radial velocities for the program stars as well as distances calculated from the calibrations Nissen & Schuster (1991A&A...251..457N) using the spectroscopic metallicities scaled to our photometric [Fe/H] system. Table A3 gives a list of the 209 spectral lines, which were analyzed, arranged element by element. The table contains the wavelength, the excitation potential of the lower level corresponding to the line, the gf-value, the enhancement factor of the classical van der Waals damping constant, the statistical weight of the upper level, and the equivalent widths measured for the two "standard" stars, HD 22879 and HD 76932. Table A4 contains the measured equivalent widths for all program stars. Table A5 gives abundance ratios and kinematical as well as orbital parameters for the program stars. First are given the data for the 16 disk stars, then follows the 14 halo stars.
- ID:
- ivo://CDS.VizieR/J/A+A/459/871
- Title:
- Chemically peculiar stars in the LMC
- Short Name:
- J/A+A/459/871
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high precision photometric Delta a observations of 417 objects in NGC 2136/7 and its surrounding field, of which five turned out to be bona fide magnetic CP stars. In addition, we discovered two Be/Ae stars. This intermediate band photometric system samples the depth of the 520nm flux depression by comparing the flux at the center with the adjacent regions with bandwidths of 11nm to 23nm. The Delta a photometric system is most suitable for detecting CP2 stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. From our investigations of NGC 1711, NGC 1866, NGC 2136/7, their surroundings, and one independent field of the LMC population, we derive an occurrence of classical chemically peculiar stars of 2.2(6)% in the LMC, which is only half the value found in the Milky Way. The mass and age distribution of the photometrically detected CP stars is not different from that of similar objects in galactic open clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/33
- Title:
- Chemical properties of 89 stars in the LMC disk
- Short Name:
- J/ApJ/761/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used high-resolution spectra obtained with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to derive kinematic properties and chemical abundances of Fe, O, Mg, and Si for 89 stars in the disk of the Large Magellanic Cloud (LMC). The derived metallicity and [{alpha}/Fe], obtained as the average of O, Mg, and Si abundances, allow us to draw a preliminary scheme of the star formation history of this region of the LMC. The derived metallicity distribution shows two main components: one component (comprising ~84% of the sample) peaks at [Fe/H]=-0.48dex and it shows an [{alpha}/Fe] ratio slightly under solar ([{alpha}/Fe]~-0.1dex). This population probably originated in the main star formation event that occurred 3-4Gyr ago (possibly triggered by tidal capture of the Small Magellanic Cloud). The other component (comprising ~16% of the sample) peaks at [Fe/H]~-0dex and it shows an [{alpha}/Fe]~0.2dex. This population was probably generated during the long quiescent epoch of star formation between the first episode and the most recent bursts. Indeed, in our sample we do not find stars with chemical properties similar to the old LMC globular clusters nor to the iron-rich and {alpha}-poor stars recently found in the LMC globular cluster NGC 1718 and also predicted to be in the LMC field, thus suggesting that both of these components are small (<1%) in the LMC disk population.
- ID:
- ivo://CDS.VizieR/J/A+A/653/A173
- Title:
- CHEOPS 55 Cnc light curve
- Short Name:
- J/A+A/653/A173
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- 55 Cnc e is a transiting super-Earth (radius 1.88R_{Earth}_ and mass 8M_{Earth}_) orbiting a G8V host star on a 17-hour orbit. Spitzer observations of the planet's phase curve at 4.5um revealed a time-varying occultation depth, and MOST optical observations are consistent with a time-varying phase curve amplitude and phase offset of maximum light. Both broadband and high-resolution spectroscopic analyses are consistent with either a high mean molecular weight atmosphere or no atmosphere for planet e. A long term photometric monitoring campaign on an independent optical telescope is needed to probe the variability in this system. We seek to measure the phase variations of 55 Cnc e with a broadband optical filter with the 30 cm effective aperture space telescope CHEOPS and explore how the precision photometry narrows down the range of possible scenarios. We observed 55 Cnc for 1.6 orbital phases in March of 2020. We designed a phase curve detrending toolkit for CHEOPS photometry which allows us to study the underlying flux variations of the 55 Cnc system. We detected a phase variation with a full-amplitude of 72+/-7ppm but do not detect a significant secondary eclipse of the planet. The shape of the phase variation resembles that of a piecewise-Lambertian, however the non-detection of the planetary secondary eclipse, and the large amplitude of the variations exclude reflection from the planetary surface as a possible origin of the observed phase variations. They are also likely incompatible with magnetospheric interactions between the star and planet but may imply that circumplanetary or circumstellar material modulate the flux of the system. Further precision photometry of 55 Cnc from CHEOPS will measure variations in the phase curve amplitude and shape over time this year.
- ID:
- ivo://CDS.VizieR/J/other/RNAAS/5.13
- Title:
- CHEOPS limb and gravity-darkening coefficients
- Short Name:
- J/other/RNAAS/5.
- Date:
- 17 Jan 2022 00:43:02
- Publisher:
- CDS
- Description:
- The goal of this Research Note is to provide the theoretical calculations of the limb-darkening coefficients (LDC) and gravity-darkening coefficients (GDC) for the space mission CHEOPS. We use two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX with spherical symmetry covering a wide range of effective temperatures, local gravities, and hydrogen/metal. These grids cover 19 metallicities ranging from 10^-5^ up to 10^+1^ solar abundances, 0<=logg<=6.0 and 2300K<=Te<=50000K. The specific intensity distribution was fitted using six approaches: linear, quadratic, square root, logarithmic, power-2, and a series with four terms. The calculations of the gravity darkening coefficient were performed for both stellar atmosphere models adopting an improved formulation.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A74
- Title:
- CHEOPS phase curve of WASP-189 b
- Short Name:
- J/A+A/659/A74
- Date:
- 10 Mar 2022 06:44:26
- Publisher:
- CDS
- Description:
- Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These "ultra-hot Jupiters" have atmospheres made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet atmospheric properties. We analyse the photometric observations of WASP-189 acquired with the instrument CHEOPS to derive constraints on the system architecture and the planetary atmosphere. We implement a light curve model suited for asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also model the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity and CHEOPS systematics. From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189, R_p_=1.600_-0.016_^+0.017^R_J_, with a precision of 1%, and the true orbital obliquity of the planetary system {Psi}_p_=89.6+/-1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth {delta}_ecl_=96.5_-5.0_^+4.5^ppm, from which we derive an upper limit on the geometric albedo: A_g_<0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope. Based on the derived system architecture, we predict the eclipse depth in the upcoming TESS observations to be up to ~165ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle between reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment J_2_ (oblateness).
- ID:
- ivo://CDS.VizieR/J/A+A/657/A52
- Title:
- CHEOPS transit light curves of WASP-103 b
- Short Name:
- J/A+A/657/A52
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay. WASP-103b is the exoplanet with the highest expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the Hubble Space Telescope (HST) and Spitzer to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation. We estimate the radial Love number of WASP-103b to be h_f_=1.59+/-0.53 This is the first time that the tidal deformation is directly detected (at 3 sigma) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and Spitzer light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact. The estimated Love number of WASP-103b is similar to Jupiters. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with James Webb Space Telescope (JWST) can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A94
- Title:
- CHEOPS WASP-189 b transit light curve
- Short Name:
- J/A+A/643/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CHEOPS (CHaracterising ExOPlanets Satellite), launched in December 2019, is a space mission dedicated to exoplanet follow-up with the capacity to perform photometric measurements at the20 ppm level. As CHEOPS observes in a broad optical passband, it can be used provide insights on the reflected light from exoplanets, and constrain the short-wavelength thermal emission for the hottest of planets through the observation of occultations and phase curves. We here report the first observation of an occultation by CHEOPS: that of the hot Jupiter WASP-189b, a M~2M_J_ planet orbiting an A-type star. We detect the occultation of WASP-189b at high significance in individual measurements, and derive an occultation depth of dF=87.9+/-4.3 ppm based on four occultations. We compare this measurement to model predictions and find that, when assuming inefficient heat redistribution, they are consistent with an unreflective atmosphere, heated to a temperature of 3435+/-27K. We furthermore present two transits of WASP-189b observed by CHEOPS. These transits have an asymmetric shape that we attribute to gravity darkening of the host star due to its high rotation rate. We use these measurements to refine the planetary parameters, finding a ~25% deeper transit compared to the discovery paper and updating the radius of WASP-189b to 1.619+/-0.021R_J_. We further measure the projected orbital obliquity to be lambda=86.4(+2.9,-4.4)deg, a value in good agreement with a previous measurement from spectroscopic observations, and derive a true obliquity of Psi=85.4+/-4.3deg. Finally, we provide reference values for the photometric precision attained by the CHEOPS satellite: for the V=6.6 mag star, and using a 1-hour binning, we obtain a residual RMS between 10 and 17ppm on the individual light curves, and 5.7ppm when combining four visits.
- ID:
- ivo://CDS.VizieR/J/ApJ/806/268
- Title:
- Cheshire Cat galaxies: redshifts and magnitudes
- Short Name:
- J/ApJ/806/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cheshire Cat is a relatively poor group of galaxies dominated by two luminous elliptical galaxies surrounded by at least four arcs from gravitationally lensed background galaxies that give the system a humorous appearance. Our combined optical/X-ray study of this system reveals that it is experiencing a line of sight merger between two groups with a roughly equal mass ratio with a relative velocity of ~1350 km/s. One group was most likely a low-mass fossil group, while the other group would have almost fit the classical definition of a fossil group. The collision manifests itself in a bimodal galaxy velocity distribution, an elevated central X-ray temperature and luminosity indicative of a shock, and gravitational arc centers that do not coincide with either large elliptical galaxy. One of the luminous elliptical galaxies has a double nucleus embedded off-center in the stellar halo. The luminous ellipticals should merge in less than a Gyr, after which observers will see a massive 1.2-1.5x10^14^ M_{sun}_ fossil group with an M_r_=-24.0 brightest group galaxy at its center. Thus, the Cheshire Cat offers us the first opportunity to study a fossil group progenitor. We discuss the limitations of the classical definition of a fossil group in terms of magnitude gaps between the member galaxies. We also suggest that if the merging of fossil (or near-fossil) groups is a common avenue for creating present-day fossil groups, the time lag between the final galactic merging of the system and the onset of cooling in the shock-heated core could account for the observed lack of well-developed cool cores in some fossil groups.
