- ID:
- ivo://CDS.VizieR/J/A+A/584/A104
- Title:
- Luhman 16AB Lucky imaging photometry & astrometry
- Short Name:
- J/A+A/584/A104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres. The brown-dwarf binary system Luhman 16AB is an interesting target for such a study, as its components stand at the L/T transition and show high levels of variability. Luhman 16AB is also the third closest system to the Solar system, allowing precise astrometric investigations with ground-based facilities. The aim of the work is to estimate the rotation period and study the astrometric motion of both components. We have monitored Luhman 16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54 m telescope at La Silla, through a special i+z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20mag and 0.34mag for Luhman 16A and 16B, respectively. We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman 16B rotates with a period of 5.1-hr, in very good agreement with previous measurements. For Luhman 16A, we report that it rotates slower than its companion and, even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8-hr. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete dataset was used to study the astrometric motion of Luhman16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/581/A73
- Title:
- Luhman 16AB X-shooter spectra
- Short Name:
- J/A+A/581/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained high signal-to-noise intermediate-resolution (R~6000-11000) optical (600-1000nm) and near-infrared (1000-2480nm) spectra of each component of the the closest brown dwarf binary, Luhman 16AB, with X-Shooter on the Very Large Telescope (VLT). We classify the primary and secondary as L6-L7.5 and T0+/-1, respectively, in agreement with previous measurements. We present measurements of the lithium pseudo-equivalent widths, which appears of similar strength on both components. The presence of lithium (^7^Li) in both components imply masses below 0.06M_{sun} while comparison with models suggests lower limits of 0.04M_{sun}. The detection of lithium in the T component is the first of its kind. Similarly, we assess the strength of other alkali lines (e.g. 6-7{AA} for RbI and 4-7{AA} for CsI features) and compare them with estimates for L and T dwarfs. We also derive effective temperatures and luminosities of each component of the binary (-4.66dex, 1305K) and (-4.68dex, 1320K) for the L and T dwarf, respectively. Using our radial velocity determinations, the binary does not appear to belong to any of the well-known moving group. Our preliminary theoretical analysis of the optical and J-band spectra indicates that the L- and T-type spectra can be reproduced with a single temperature and gravity but different relative chemical abundances which impact strongly the spectral energy distribution of L/T transition objects.
653. Lunar occultations
- ID:
- ivo://CDS.VizieR/J/A+AS/110/107
- Title:
- Lunar occultations
- Short Name:
- J/A+AS/110/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of 114 photoelectric observations are analysed. They were obtained at the two Stations of O.C.A.: Calern and Nice Observatories. We first give a short description of the two photometers used and then we present the interactive reduction method. The astrometric and photometric parameters are derived from each light-curve. Finally we summarize the results and discuss about the non point-like occulted stars: we present 38 double star measurements, for 16 objects, and 11 determinations of angular diameters, for 4 objects.
- ID:
- ivo://CDS.VizieR/J/A+A/522/A65
- Title:
- Lunar occultations at the ESO VLT
- Short Name:
- J/A+A/522/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lunar occultations (LO) are a very efficient and powerful technique that achieves the best combination of high angular resolution and sensitivity possible today at near-infrared wavelengths. Given that the events are fixed in time, that the sources are occulted randomly, and that the telescope use is minimal, the technique is very well suited for service mode observations. We have established a program of routine LO observations at the VLT observatory, especially designed to take advantage of short breaks available in-between other programs. We have used the ISAAC instrument in burst mode, capable of producing continuous read-outs at millisecond rates on a suitable subwindow. Given the random nature of the source selection, our aim has been primarily the investigation of a large number of stellar sources at the highest angular resolution in order to detect new binaries. Serendipitous results such as resolved sources and detection of circumstellar components were also anticipated.
- ID:
- ivo://CDS.VizieR/J/other/JAVSO/48.201
- Title:
- Maintaining the Ephemeris of 20 CoRoT planets
- Short Name:
- J/other/JAVSO/48
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present 33 transit minimum times of 20 transiting planets discovered by the CoRoT space mission, which have been obtained from ground-based observations since the mission's end in 2012, with the objective to maintain the ephemeris of these planets and to identify potential transit time variations. Twelve of the observed planets are in the CoRoT fields near the galactic center and the remaining eight planets are in the fields near the anticenter. We detect indications for significant transit timing variations in the cases of CoRoT 3b, 11b, 13b, 27b. For two more planets (CoRoT 18b and 20b) we conclude that timing offsets in early follow-up observations led to ephemeris in discovery publications that are inconsistent with timings from follow-up observations in later epochs. In the case of CoRoT-20b, this might be due to the influence from a further non-transiting planet. We also note that a significant majority (23 of 33) of our reported minimum times have negative O-C values, albeit most of them are within the expected uncertainty of the ephemeris.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1015
- Title:
- MAP observations of the position of Procyon
- Short Name:
- J/AJ/131/1015
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the analysis of observations of Procyon obtained with the Multichannel Astrometric Photometer during the years 1986-2004. While the results significantly increase the precision of the estimated characteristics of the components of the system, they are generally in good agreement with the most recent studies.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A57
- Title:
- MASCARA-2 b (HD185603) light curves and spectra
- Short Name:
- J/A+A/612/A57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present MASCARA-2 b, a hot Jupiter transiting the m_V_=7.6 A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million flux measurements of the star, corresponding to a total of almost 3000 hours of observations, revealing a periodic dimming in the flux with a depth of 1.3%. Photometric follow-up observations were performed with the NITES and IAC80 telescopes and spectroscopic measurements were obtained with the Hertzsprung SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of 3.474119^+0.000005^_-0.000006_ days at a distance of 0.057+/-0.006AU, has a radius of 1.83+/-0.07R_J_ and place a 99 % upper limit on the mass of <17M_J_. HD 185603 is a rapidly rotating early-type star with an effective temperature of 8980^+90^_-130_K and a mass and radius of 1.89^+0.06^_-0.05_M_sun_, 1.60+/-0.06R_sun_, respectively. Contrary to most other hot Jupiters transiting early-type stars, the projected planet orbital axis and stellar spin axis are found to be aligned with {lambda}=0.6+/-4{deg}. The brightness of the host star and the high equilibrium temperature, 2260+/-50K, of MASCARA-2 b make it a suitable target for atmospheric studies from the ground and space. Of particular interest is the detection of TiO, which has recently been detected in the similarly hot planets WASP-33 b and WASP-19 b.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A73
- Title:
- MASCARA-1 b (HD201585) light curves and spectra
- Short Name:
- J/A+A/606/A73
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of MASCARA-1 b, the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). It is a hot Jupiter orbiting a bright m_V_=8.3, rapidly rotating (vsini>100km/s) A8 star with a period of 2.148780+/-0.000008 days. The planet has a mass and radius of 3.7+/-0.9M_J_ and 1.5+/-0.3R_J_, respectively. As with most hot Jupiters transiting early-type stars we find a misalignment between the planet orbital axis and the stellar spin axis, which may be signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of 1.5+/-0.9g/cm^3^ and an equilibrium temperature of 2570^+50^_-30_K, one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A151
- Title:
- MASCARA-2b NaI & Ha absorption lines
- Short Name:
- J/A+A/616/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the HARPS-North high resolution spectrograph (R=115000) at Telescopio Nazionale Galileo (TNG) to observe one transit of the highly irradiated planet MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly resolve the spectral features of the atomic sodium (NaI) doublet and the H{alpha} line in its atmosphere, which are corroborated with the transmission calculated from their respective transmission light curves (TLC). In particular, we resolve two spectral features centred on the NaI doublet position with an averaged absorption depth of 0.17+/-0.03% for a 0.75{AA} bandwidth with line contrasts of 0.44+/-0.11% (D2) and 0.37+/-0.08% (D1). The NaI TLC have also been computed, showing a large Rossiter-McLaughlin (RM) effect, which has a 0.20+/-0.05% NaI transit absorption for a 0.75{AA} passband that is consistent with the absorption depth value measured from the final transmission spectrum. We observe a second feature centred on the H{alpha} line with 0.6+/-0.1% contrast and an absorption depth of 0.59+/-0.08% for a 0.75{AA} passband that has consistent absorptions in its TLC, which corresponds to an effective radius of R'/Rp=1.20+/-0.04. While the signal-to-noise ratio (S/N) of the final transmission spectrum is not sufficient to adjust different temperature profiles to the lines, we find that higher temperatures than the equilibrium (Teq=2260+/-50K) are needed to explain the lines contrast. Particularly, we find that the NaI lines core require a temperature of T=4210+/-180K and that H{alpha} requires a temperature of T=4330+/-520K. MASCARA-2b, like other planets orbiting A-type stars, receives a large amount of UV energy from its host star. This energy excites the atomic hydrogen and produces H{alpha} absorption, leading to the expansion and abrasion of the atmosphere. The study of other Balmer lines in the transmission spectrum would allow the determination of the atmospheric temperature profile and the calculation of the lifetime of the atmosphere with escape rate measurements. In the case of MASCARA-2b, residual features are observed in the H{beta} and H{gamma} lines, but they are not statistically significant.More transit observations are needed to confirm our findings in NaI and H{alpha} and to build up enough S/N to explore the presence of H{beta} and H{gamma} planetary absorptions.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A75
- Title:
- MASCARA-1 b occultation and transit light curves
- Short Name:
- J/A+A/658/A75
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The light curves of tidally locked hot Jupiters transiting fast-rotating, early-type stars are a rich source of information about both the planet and star, with full-phase coverage enabling a detailed atmospheric characterisation of the planet. Although it is possible to determine the true spin-orbit angle Psi -- a notoriously difficult parameter to measure -- from any transit asymmetry resulting from gravity darkening induced by the stellar rotation, the correlations that exist between the transit parameters have led to large disagreements in published values of Psi for some systems. We aimed to study these phenomena in the light curves of the ultra-hot Jupiter MASCARA-1 b, which is characteristically similar to well-studied contemporaries such as KELT-9 b and WASP-33 b. We obtained optical CHaracterising ExOPlanet Satellite (CHEOPS) transit and occultation light curves of MASCARA-1 b, and analysed them jointly with a Spitzer/IRAC 4.5 micron full-phase curve to model the asymmetric transits, occultations, and phase-dependent flux modulation. For the latter, we employed a novel physics-driven approach to jointly fit the phase modulation by generating a single 2D temperature map and integrating it over the two bandpasses as a function of phase to account for the differing planet-star flux contrasts. The reflected light component was modelled using the general ab initio solution for a semi-infinite atmosphere. When fitting the CHEOPS and Spitzer transits together, the degeneracies are greatly diminished and return results consistent with previously published Doppler tomography. Placing priors informed by the tomography achieves even better precision, allowing a determination of Psi=72.1^+2.5^_-2.4_deg. From the occultations and phase variations, we derived dayside and nightside temperatures of 3062^+66^_-68_K and 1720+/-330K, respectively. Our retrieval suggests that the dayside emission spectrum closely follows that of a blackbody. As the CHEOPS occultation is too deep to be attributed to blackbody flux alone, we could separately derive geometric albedo A_g_=0.166^+0.066^_-0.068_ and spherical albedo A_s_=0.266^+0.097^_-0.100_ from the CHEOPS data, and Bond albedo A_B_=0.053^+0.083^_-0.101_ from the Spitzer phase curve. Although small, the Ag and As indicate that MASCARA-1 b is more reflective than most other ultra-hot Jupiters, where H^-^ absorption is expected to dominate. Where possible, priors informed by Doppler tomography should be used when fitting transits of fast-rotating stars, though multi-colour photometry may also unlock an accurate measurement of Psi. Our approach to modelling the phase variations at different wavelengths provides a template for how to separate thermal emission from reflected light in spectrally resolved James Webb Space Telescope phase curve data.
