- ID:
- ivo://CDS.VizieR/J/ApJ/879/100
- Title:
- K2 rotation periods for Hyades & Praesepe members
- Short Name:
- J/ApJ/879/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze K2 light curves for 132 low-mass (1M_{sun}_>~M*>~0.1M_{sun}_) members of the 600-800Myr old Hyades cluster and measure rotation periods (P_rot_) for 116 of these stars. These include 93 stars with no prior P_rot_ measurements; the total number of Hyads with a known P_rot_ is now 232. We then combine literature binary data with Gaia DR2 photometry and astrometry to select single-star sequences in the Hyades and its roughly coeval Praesepe open cluster and derive a new reddening value of A_V_=0.035+/-0.011 for Praesepe. Comparing the effective temperature-P_rot_ distributions for the Hyades and Praesepe, we find that solar-type Hyads rotate, on average, 0.4d slower than their Praesepe counterparts. This P_rot_ difference indicates that the Hyades is slightly older than Praesepe: we apply a new gyrochronology model tuned with Praesepe and the Sun and find an age difference between the two clusters of 57Myr. However, this P_rot_ difference decreases and eventually disappears for lower-mass stars. This provides further evidence for stalling in the rotational evolution of these stars and highlights the need for more detailed analysis of angular momentum evolution for stars of different masses and ages.
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- ID:
- ivo://CDS.VizieR/J/ApJ/707/1707
- Title:
- Ks-band light curve of CoRoT-1b
- Short Name:
- J/ApJ/707/1707
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b from time series photometry with the ARC 3.5m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336+/-0.042% and is centered at phase 0.5022^+0.0023^_-0.0027_, consistent with a zero eccentricity orbit (e*cos{omega}=0.0035^+0.0036^_-0.0042_). We perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere and constrain the reflected and thermal emissions by combining our result with the recent 0.6, 0.71, and 2.09um secondary eclipse detections by Snellen et al. (2009Natur.459..543S), Gillon et al. (2009, J/A+A/506/359), and Alonso et al. (2009A&A...501L..23A). Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical-equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The closest blackbody-based and physical models provide the following atmosphere parameters: a temperature T=2460^+80^_-160_K; a very low Bond albedo A_B_=0.000^+0.081^_-0.000_; and an energy redistribution parameter P_n_=0.1, indicating a small but nonzero amount of heat transfer from the day to nightside. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity {kappa}_e_=0.05cm^2^/g, placed near the 0.1 bar atmospheric pressure level. This inversion layer is located 10 times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A54
- Title:
- Ks-band observations of WASP-33b
- Short Name:
- J/A+A/550/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, day-side emission from about a dozen hot Jupiters has been detected through ground-based secondary eclipse observations in the near-infrared. These near-infrared observations are vital for determining the energy budgets of hot Jupiters, since they probe the planet-spectral energy distribution near its peak. The aim of this work is to measure the Ks -band secondary eclipse depth of WASP-33b, the first planet discovered to transit an A-type star. This planet receives the highest level of irradiation of all transiting planets discovered to date. Furthermore, its host-star shows pulsations and is classified as a low-amplitude delta-Scuti. As part of our GROUnd-based Secondary Eclipse (GROUSE) project we have obtained observations of two separate secondary eclipses of WASP-33b in the Ks-band using the LIRIS instrument on the William Herschel Telescope (WHT). The telescope was significantly defocused to avoid saturation of the detector for this bright star (K~7.5). To increase the stability and the cadence of the observations, they were performed in staring mode. We collected a total of 5100 and 6900 frames for the first and the second night respectively, both with an average cadence of 3.3 seconds. On the second night the eclipse is detected at the 12-sigma level, with a measured eclipse depth of 0.244_-020_^+0.027^%. This eclipse depth corresponds to a brightness temperature of 3270_-160^+115^K. The measured brightness temperature on the second night is consistent with the expected equilibrium temperature for a planet with a very low albedo and a rapid re-radiation of the absorbed stellar light. For the other night the short out-of-eclipse baseline prevents good corrections for the stellar pulsations and systematic effects, which makes this dataset unreliable for eclipse depth measurements. This demonstrates the need of getting a sufficient out-of-eclipse baseline.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A69
- Title:
- K2-3 system characterized with HARPS-N & HARPS
- Short Name:
- J/A+A/615/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45pc), early-type M dwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb=6.6+/-1.1M_{Earth}_) and planet c (Mc=3.1^+1.3^_-1.2_M_{Earth}_). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md=2.7^+1.2^_-0.8_M_{Earth}_. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1percent) or massive water layers, with a water content >50 percent of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.
- ID:
- ivo://CDS.VizieR/J/AJ/162/102
- Title:
- LASSO; Robo-AO observation of 444 young stars
- Short Name:
- J/AJ/162/102
- Date:
- 14 Mar 2022 06:43:15
- Publisher:
- CDS
- Description:
- We present results from the Large Adaptive optics Survey for Substellar Objects, where the goal is to directly image new substellar companions (<70M_Jup_) at wide orbital separations (>~50au) around young (<~300Myr), nearby (<100pc), low-mass (~0.1-0.8 M{odot}) stars. We report on 427 young stars imaged in the visible (i') and near-infrared (J or H ) simultaneously with Robo-AO on the Kitt Peak 2.1m telescope and later the Maunakea University of Hawaii 2.2m telescope. To undertake the observations, we commissioned a new infrared camera for Robo-AO that uses a low-noise high-speed SAPHIRA avalanche photodiode detector. We detected 121 companion candidates around 111 stars, of which 62 companions are physically associated based on Gaia DR2 parallaxes and proper motions, another 45 require follow-up observations to confirm physical association, and 14 are background objects. The companion separations range from 2 to 1101 au and reach contrast ratios of 7.7 mag in the near-infrared compared to the primary. The majority of confirmed and pending candidates are stellar companions, with ~5 being potentially substellar and requiring follow-up observations for confirmation. We also detected a 43{+/-}9 M_Jup_ and an 81{+/-}5M_Jup_ companion that were previously reported. We found 34 of our targets have acceleration measurements detected using Hipparcos-Gaia proper motions. Of those, 58_-14_^+12^% of the 12 stars with imaged companion candidates have significant accelerations ({chi}^2^>11.8), while only 23_-6_^+11^% of the remaining 22 stars with no detected companion have significant accelerations. The significance of the acceleration decreases with increasing companion separation. These young accelerating low-mass stars with companions will eventually yield dynamical masses with future orbit monitoring.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/40
- Title:
- Late-type targets in Taurus, Cha I, and Upper Sco
- Short Name:
- J/ApJ/788/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M~0.01-0.1 M_{sun}_). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 ({rho}=0.105"/15 AU), 2MASS J04221332+1934392 ({rho}=0.05"/7 AU), and ISO 217 ({rho}=0.03"/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco ({tau}~10 Myr), we measure binary fractions of 14/93=0.15_-0.03_^+0.05^ for M4-M6 (M~0.1-0.3 M_{sun}_) and 4/108=0.04_-0.01_^+0.03^ for >M6 (M<~0.1 M_{sun}_) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.
- ID:
- ivo://CDS.VizieR/I/130
- Title:
- LDS Catalogue: Doubles with Common Proper Motion
- Short Name:
- I/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains all double stars with common proper motion discovered by Luyten since 1940 up to 1987 (references below). When Luyten had noticed that an entry was duplicated (ref. 8 and 9), only the former LDS number was kept in the data file but with the data given for the latter. The unique exception is LDS 6166, which is a duplicate of LDS 5662, but with an additional component. The systems classified as optical by Luyten were also rejected from the main data files. All the rejected data were put together in a separate file. All coordinates are for the equinox 1950; when the original publication gave another equinox (this is the case for ref. 1), the 1950-coordinates were calculated. The catalogue contains all the systems, sorted by increasing LDS numbers. Duplicate entries and optical systems listed by Luyten were rejected. The catalogue contains 6121 systems, including 87 triple and 1 quadruple systems. The number of records is thus 6210, since each triple system occupies 2 records and the quadruple system 3.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A121
- Title:
- LHS1140 radial velocity data
- Short Name:
- J/A+A/642/A121
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- LHS 1140 is an M dwarf known to host two transiting planets at orbital periods of 3.77 and 24.7 days. They were detected with HARPS and Spitzer. The external planet (LHS 1140 b) is a rocky super-Earth that is located in the middle of the habitable zone of this low-mass star. All these properties place this system at the forefront of the habitable exoplanet exploration, and it therefore constitutes a relevant case for further astrobiological studies, including atmospheric observations. We further characterize this system by improving the physical and orbital properties of the known planets, search for additional planetary-mass components in the system, and explore the possibility of co-orbitals. We collected 113 new high-precision radial velocity observations with ESPRESSO over a 1.5-yr time span with an average photon-noise precision of 1.07m/s. We performed an extensive analysis of the HARPS and ESPRESSO datasets and also analyzed them together with the new TESS photometry. We analyzed the Bayesian evidence of several models with different numbers of planets and orbital configurations. We significantly improve our knowledge of the properties of the known planets LHS 1140 b (Pb~24.7-days) and LHS 1140 c (Pc~3.77-days). We determine new masses with a precision of 6% for LHS 1140 b (6.48+/-0.46M_Earth_) and 9% for LHS 1140 c (m_c_=1.78+/-0.17M_Earth_). This reduces the uncertainties relative to previously published values by half. Although both planets have Earth-like bulk compositions, the internal structure analysis suggests that LHS 1140 b might be iron-enriched and LHS 1140 c might be a true Earth twin. In both cases, the water content is compatible to a maximum fraction of 10-12% in mass, which is equivalent to a deep ocean layer of 779+/-650 km for the habitable-zone planet LHS 1140 b. Our results also provide evidence for a new planet candidate in the system (m_d_=4.8+/-1.1M_Earth_) on a 78.9-day orbital period, which is detected through three independent methods. The analysis also allows us to discard other planets above 0.5M_Earth_ for periods shorter than 10 days and above 2 M_Earth_ for periods up to one year. Finally, our co-orbital analysis discards co-orbital planets in the tadpole and horseshoe configurations of LHS 1140 b down to 1M_Earth_ with a 95% confidence level (twice better than with the previous HARPS dataset). Indications for a possible co-orbital signal in LHS 1140 c are detected in both radial velocity (alternatively explained by a high eccentricity) and photometric data (alternatively explained by systematics), however. The new precise measurements of the planet properties of the two transiting planets in LHS 1140 as well as the detection of the planet candidate LHS 1140 d make this system a key target for atmospheric studies of rocky worlds at different stellar irradiations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/1368
- Title:
- Li abundances & vsini for star-planet systems
- Short Name:
- J/MNRAS/403/1368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine Li abundances and vsini values from new spectra of 53 stars with Doppler-detected planets not included in our previous papers in this series. We also examine two sets of stars without detected planets, which together serve as our comparison sample. Using the method of comparison of Li abundances and vsini values between two sets of stars we introduced in Gonzalez, we confirm that these two quantities are smaller among stars with planets (SWPs) compared to stars without detected planets near the solar temperature. The transition from low to high Li abundance among SWPs occurs near 5850K, a revision of about 50K from our previous determination. The transition from low to high vsini occurs near 6000K, but this temperature is not as well constrained.
- ID:
- ivo://CDS.VizieR/J/AJ/158/163
- Title:
- Li abundance values for stars in NGC 6819
- Short Name:
- J/AJ/158/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopy of 333 NGC 6819 stars and Gaia astrometry are used to map Li evolution from the giant branch tip to 0.5 mag below the Li dip. Isochrone comparison with [Fe/H]=-0.04, based upon neural network spectroscopic analysis, produces an age of 2.25 (2.4) Gyr for E(B-V)=0.16 (0.14) and (m-M)=12.40 (12.29). Despite originating outside the Li dip, only 10% of single subgiants/giants have measurable Li. Above the Li dip, the limiting A(Li) for single stars is 3.2+/-0.1 but the lower range is comparable to that found within the dip. The F-dwarf Li dip profile agrees with the Hyades/Praesepe, evolved forward. The Li level among stars populating the plateau fainter than the Li dip is A(Li)=2.83+/-0.16; the dispersion is larger than expected from spectroscopic error alone. Comparison of Li and V_ROT_ distributions among turnoff stars in NGC 7789, NGC 2506, NGC 3680, and NGC 6819 indicates that rotational spindown from the main sequence is critical in defining the boundaries of the Li dip. For higher-mass dwarfs, spindown is likewise correlated with Li depletion, creating a second dip, but at higher mass and on a longer timescale. The Li distribution among evolved stars of NGC 6819 is more representative of the older M67, where subgiant and giant stars emerge from within the Li dip, than the younger NGC 7789, where a broad range in V_ROT_ among the turnoff stars likely produces a range in mass among the giants.
