- ID:
- ivo://CDS.VizieR/J/A+A/650/A138
- Title:
- TRAPPIST-1 analogue stars TESS light curves
- Short Name:
- J/A+A/650/A138
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- As more exoplanets are being discovered around ultracool dwarfs, understanding their magnetic activity - and the implications for habitability - is of prime importance. To find stellar flares and photometric signatures related to starspots, continuous monitoring is necessary, which can be achieved with spaceborn observatories like the Transiting Exoplanet Survey Satellite (TESS). We present an analysis of TRAPPIST-1 like ultracool dwarfs with TESS full- frame image photometry from the first two years of the primary mission. A volume-limited sample up to 50pc is constructed consisting of 339 stars closer than 0.5mag to TRAPPIST-1 on the Gaia colour-magnitude diagram. The 30-min cadence TESS light curves of 248 stars were analysed, searching for flares and rotational modulation caused by starspots. The composite flare frequency distribution of the 94 identified flares shows a power law index similar to TRAPPIST-1, and contains flares up to E_TESS_=3*10^33^erg. Rotational periods shorter than 5 days were determined for 42 stars, sampling the regime of fast rotators. The ages of 88 stars from the sample were estimated using kinematic information. A weak correlation between rotational period and age is observed, which is consistent with magnetic braking.
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- ID:
- ivo://CDS.VizieR/J/A+A/658/A170
- Title:
- TRAPPIST-1 best-fit parameters
- Short Name:
- J/A+A/658/A170
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We analyze solutions drawn from the recently published posterior distribution of the TRAPPIST-1 system, which consists of seven Earth-size planets appearing to be in a resonant chain around a red dwarf. We show that all the planets are simultaneously in 2-planet and 3-planet resonances, apart from the innermost pair for which the 2-planet resonant angles circulate. By means of a frequency analysis, we highlight that the transit-timing variation (TTV) signals possess a series of common periods varying from days to decades, which are also present in the variations of the dynamical variables of the system. Shorter periods (e.g., the TTVs characteristic timescale of 1.3yr) are associated with 2-planet mean-motion resonances, while longer periods arise from 3-planet resonances. By use of N-body simulations with migration forces, we explore the origin of the resonant chain of TRAPPIST-1 and find that for particular disc conditions, a chain of resonances -- similar to the observed one -- can be formed which accurately reproduces the observed TTVs. Our analysis suggests that while the 4-yr collected data of observations hold key information on the 2-planet resonant dynamics, further monitoring of TRAPPIST-1 will soon provide signatures of three-body resonances, in particular the 3.3 and 5.1yr periodicities expected for the current best-fit solution. Additional observations would help to assess whether the innermost pair of planets is indeed resonant (its proximity to the 8:5 resonance being challenging to explain), and therefore give additional constraints on formation scenarios.
22463. TRAPPIST-1 h NIR spectrum
- ID:
- ivo://CDS.VizieR/J/A+A/658/A133
- Title:
- TRAPPIST-1 h NIR spectrum
- Short Name:
- J/A+A/658/A133
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The TRAPPIST-1 planetary system is favorable for transmission spectroscopy and offers the unique opportunity to study rocky-planets with possibly non-primary envelopes. We present here the transmission spectrum of the seventh planet of the TRAPPIST-1 system, TRAPPIST-1 h (R_P_=0.752R_{Earth}_, Teq=173K) using Hubble Space Telescope (HST), Wide Field Camera 3 Grism 141 (WFC3/G141) data. Our purpose is to reduce the HST observations of the seventh planet of TRAPPIST-1 system and by testing simple atmospheric hypothesis put new constraint on the composition and the nature of the planet. First we extracted and corrected the raw data to obtain a transmission spectrum in the Near-IR band (1.1-1.7um). TRAPPIST-1 is a cold M-dwarf and its activity could affect the transmission spectrum. We correct for stellar modulations using three different stellar contamination models, while some fit better the data, they are statistically not significant and the conclusion remains unchanged concerning the presence or not of an atmosphere. Finally, using a Bayesian atmospheric retrieval code we put new constraints on the atmosphere composition of TRAPPIST-1h. According to the retrieval analysis, there is no evidence of molecular absorption in the Near-InfraRed (NIR) spectrum. This suggests the presence of a high cloud deck or a layer of photochemical hazes in a primary atmosphere or a secondary atmosphere dominated by heavy species like nitrogen. This result could even be the consequence of the lack of an atmosphere as the spectrum is better fitted using a flat-line. Variations of transit depth around 1.3um are likely due to remaining scattering noise and results are not improved while changing the spectral resolution. TRAPPIST-1 h has probably lost its atmosphere or possesses a layer of clouds and hazes blocking the NIR signal. We can not distinguish yet between a primary cloudy or a secondary clear envelope using HST/WFC3 data but we can reject, in most cases with more than 3{sigma} confidence, the hypothesis of a clear atmosphere dominated by hydrogen and helium. By testing forced secondary atmospheric scenario, we find that a CO-rich atmosphere (i.e with a volume mixing ratio of 0.2) is one of the best fit to the spectrum with a Bayes Factor of 1.01 corresponding to a 2.1{sigma} detection.
- ID:
- ivo://CDS.VizieR/J/A+A/574/A38
- Title:
- TRAPPIST monitoring of comet C/2012 F6 (Lemmon)
- Short Name:
- J/A+A/574/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of the long-term narrowband photometry and imaging monitoring of comet C/2012 F6 (Lemmon) with the robotic TRAPPIST telescope (La Silla observatory). Observations covered 52 nights pre- and post-perihelion between December 11, 2012 and June 11, 2013. We followed the evolution of the OH, NH, CN, C_3_ and C_2_ production rates computed with the Haser model as well as the evolution of the A({theta})f_{rho}_ parameter as a proxy for the dust production. All five gas species display similar slopes for the heliocentric dependence. An asymmetry about perihelion is observed, the rate of brightening being steeper than the rate of fading. The chemical composition of the comet's coma is changing slightly along the orbit: the relative abundance of C_2_ to CN is decreasing for heliocentric distances larger than 1.4AU while the C_3_ to CN ratio is constant during our observations. The behavior of the dust is different from that of the gas, the slope of the heliocentric dependence becoming steeper in early February, correlated to a change of the visual lightcurve slope. However, the dust color does not vary during the observations. The application of several enhancement techniques on the images revealed structures in the CN, C3 and C2 images. These features imply the existence of one or several active zone(s) on the comet nucleus. The shape of the structures is similar in those three filters and changes from a roughly hourglass shape in December and January to a corkscrew shape in February and March. The structures in the continuum filters (sampling the dust) are not correlated to those observed for the gas. During several full nights in February, we observed changes in the CN and C2 structures repeating periodically due to the nucleus rotation, our derived rotational period being of 9.52+/-0.05 hours.
- ID:
- ivo://CDS.VizieR/J/MNRAS/497/3790
- Title:
- TRAPPIST-South UCD Transit Survey
- Short Name:
- J/MNRAS/497/3790
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We conducted a global analysis of the TRAPPIST Ultra-Cool Dwarf Transit Survey - a prototype of the SPECULOOS transit search conducted with the TRAPPIST-South robotic telescope in Chile from 2011 to 2017 - to estimate the occurrence rate of close-in planets such as TRAPPIST-1b orbiting ultra-cool dwarfs. For this purpose, the photometric data of 40 nearby ultra-cool dwarfs were reanalysed in a self-consistent and fully automated manner starting from the raw images. The pipeline developed specifically for this task generates differential light curves, removes non-planetary photometric features and stellar variability, and searches for transits. It identifies the transits of TRAPPIST-1b and TRAPPIST-1c without any human intervention. To test the pipeline and the potential output of similar surveys, we injected planetary transits into the light curves on a star-by-star basis and tested whether the pipeline is able to detect them. The achieved photometric precision enables us to identify Earth-sized planets orbiting ultra-cool dwarfs as validated by the injection tests. Our planet-injection simulation further suggests a lower limit of 10 per cent on the occurrence rate of planets similar to TRAPPIST-1b with a radius between 1 and 1.3 R_{Earth}_ and the orbital period between 1.4 and 1.8d.
22466. TRAPPIST-1 transit timings
- ID:
- ivo://CDS.VizieR/J/A+A/640/A112
- Title:
- TRAPPIST-1 transit timings
- Short Name:
- J/A+A/640/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf star, finding that it is orbited by seven transiting Earth-sized planets. At least three of these planets orbit within the classical habitable zone of the star, and all of them are well-suited for a detailed atmospheric characterization with the upcoming JWST. The main goals of the Spitzer Red Worlds program were (1) to explore the system for new transiting planets, (2) to intensively monitor the planets' transits to yield the strongest possible constraints on their masses, sizes, compositions, and dynamics, and (3) to assess the infrared variability of the host star. In this paper, we present the global results of the project. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5um. For a comprehensive study, we analyzed all light curves both individually and globally. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5um to constrain the brightness temperatures of their daysides. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We do not detect any significant variation of the transit depths of the planets throughout the different campaigns. Comparing our individual and global analyses of the transits, we estimate for TRAPPIST-1 transit depth measurements mean noise floors of ~35 and 25ppm in channels 1 and 2 of Spitzer/IRAC, respectively. We estimate that most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. Our analysis reveals a few outlier transits, but we cannot conclude whether or not they correspond to spot or faculae crossing events. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. Although we are limited by instrumental precision, the combined transmission spectrum of planet b to g tells us that their atmospheres seem unlikely to be CH_4_-dominated. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5um, and can only set 3{sigma} upper limits on their dayside brightness temperatures (611K for b 586K for c).
- ID:
- ivo://CDS.VizieR/J/AJ/154/115
- Title:
- Travel times of stars within about 300 lt-yr
- Short Name:
- J/AJ/154/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New means of interstellar travel are now being considered by various research teams, assuming lightweight spaceships to be accelerated via either laser or solar radiation to a significant fraction of the speed of light (c). We recently showed that gravitational assists can be combined with the stellar photon pressure to decelerate an incoming lightsail from Earth and fling it around a star or bring it to rest. Here, we demonstrate that photogravitational assists are more effective when the star is used as a bumper (i.e., the sail passes "in front of" the star) rather than as a catapult (i.e., the sail passes "behind" or "around" the star). This increases the maximum deceleration at {alpha} Cen A and B and reduces the travel time of a nominal graphene-class sail (mass-to-surface ratio 8.6*10^-4^g/m^2^) from 95 to 75 years. The maximum possible velocity reduction upon arrival depends on the required deflection angle from {alpha} Cen A to B and therefore on the binary's orbital phase. Here, we calculate the variation of the minimum travel times from Earth into a bound orbit around Proxima for the next 300 years and then extend our calculations to roughly 22000 stars within about 300lt-yr. Although {alpha} Cen is the most nearby star system, we find that Sirius A offers the shortest possible travel times into a bound orbit: 69 years assuming 12.5% c can be obtained at departure from the solar system. Sirius A thus offers the opportunity of flyby exploration plus deceleration into a bound orbit of the companion white dwarf after relatively short times of interstellar travel.
- ID:
- ivo://CDS.VizieR/J/ApJ/893/27
- Title:
- TRENDS high-contrast imaging survey. VIII.
- Short Name:
- J/ApJ/893/27
- Date:
- 19 Jan 2022 00:39:50
- Publisher:
- CDS
- Description:
- The physical properties of faint stellar and substellar objects often rely on indirect, model-dependent estimates. For example, the masses of brown dwarfs are usually inferred using evolutionary models, which are age dependent and have yet to be properly calibrated. With the goal of identifying new benchmark objects to test low-mass stellar and substellar models, we have carried out a comprehensive adaptive optics survey as part of the TaRgetting bENchmark-objects with the Doppler Spectroscopy (TRENDS) high-contrast imaging program. Using legacy radial velocity measurements from the High Resolution Echelle Spectrometer at Keck, we have identified several dozen stars that show long-term Doppler accelerations. We present follow-up high-contrast observations from the campaign and report the discovery of 31 comoving companions, as well as 11 strong candidate companions, to solar-type stars with well-determined parallax and metallicity values. Benchmark objects of this nature lend themselves to orbit determinations, dynamical mass estimates, and independent compositional assessment. This compendium of benchmark objects will serve as a convenient test group to substantiate theoretical evolutionary and atmospheric models near the hydrogen fusing limit.
- ID:
- ivo://CDS.VizieR/J/A+A/510/A107
- Title:
- TrES-2b multi-band transit observations
- Short Name:
- J/A+A/510/A107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new data set of transit observations of the TrES-2b exoplanet taken in spring 2009, using the 1.2m Oskar-Luehning telescope (OLT) of Hamburg Observatory and the 2.2m telescope at Calar Alto Observatory using BUSCA (Bonn University Simultaneous CAmera). Both the new OLT data, taken with the same instrumental setup as our data taken in 2008, as well as the simultaneously recorded multicolor BUSCA data confirm the low inclination values reported previously, and in fact suggest that the TrES-2b exoplanet has already passed the first inclination threshold (i_min,1_=83.417{deg}) and is not eclipsing the full stellar surface any longer.
22470. TrES-4b RV and Ic curves
- ID:
- ivo://CDS.VizieR/J/A+A/575/L15
- Title:
- TrES-4b RV and Ic curves
- Short Name:
- J/A+A/575/L15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We update the TrES-4 system parameters using high-precision HARPS-N radial-velocity measurements and new photometric light curves. A combined spectroscopic and photometric analysis allows us to determine a spectroscopic orbit with a semi-amplitude K=51+/-3m/s. The derived mass of TrES-4b is found to be M_p_=0.49+/-0.04M_Jup_, significantly lower than previously reported. Combined with the large radius (R_p_=1.84_-0.09_^+0.08^R_Jup_) inferred from our analysis, TrES-4b becomes the transiting hot Jupiter with the second-lowest density known. We discuss several scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the context of the exotic class of highly inflated transiting giant planets.
