- ID:
- ivo://CDS.VizieR/J/AJ/162/167
- Title:
- Transits time of M-dwarf TOI-1749
- Short Name:
- J/AJ/162/167
- Date:
- 16 Mar 2022 11:43:00
- Publisher:
- CDS
- Description:
- We report the discovery of one super-Earth- (TOI-1749b) and two sub-Neptune-sized planets (TOI-1749c and TOI-1749d) transiting an early M dwarf at a distance of 100pc, which were first identified as planetary candidates using data from the TESS photometric survey. We have followed up this system from the ground by means of multiband transit photometry, adaptive optics imaging, and low-resolution spectroscopy, from which we have validated the planetary nature of the candidates. We find that TOI-1749b, c, and d have orbital periods of 2.39, 4.49, and 9.05days, and radii of 1.4, 2.1, and 2.5R{Earth}, respectively. We also place 95% confidence upper limits on the masses of 57, 14, and 15M{Earth} for TOI-1749b, c, and d, respectively, from transit timing variations. The periods, sizes, and tentative masses of these planets are in line with a scenario in which all three planets initially had a hydrogen envelope on top of a rocky core, and only the envelope of the innermost planet has been stripped away by photoevaporation and/or core-powered mass-loss mechanisms. These planets are similar to other planetary trios found around M dwarfs, such as TOI-175b,c,d and TOI-270b,c,d, in the sense that the outer pair has a period ratio within 1% of 2. Such a characteristic orbital configuration, in which an additional planet is located interior to a near 2:1 period-ratio pair, is relatively rare around FGK dwarfs.
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- ID:
- ivo://CDS.VizieR/J/AJ/159/120
- Title:
- Transit time of K2-146b and K2-146c with K2 and HPF
- Short Name:
- J/AJ/159/120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-146 is a cool, 0.358M_{sun}_ dwarf that was found to host a mini-Neptune with a 2.67day period. The planet exhibited strong transit timing variations (TTVs) of greater than 30minutes, indicative of the presence of an additional object in the system. Here we report the discovery of the previously undetected outer planet in the system, K2-146c, using additional photometric data. K2-146c was found to have a grazing transit geometry and a 3.97day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146b and c were measured using observations spanning a baseline of almost 1200days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146b has a radius of 2.25{+/-}0.10R_{earth}_ and a mass of 5.6{+/-}0.7M_{earth}_, whereas K2-146c has a radius of 2.59_-0.39_^+1.81^R_{earth} and a mass of 7.1{+/-}0.9M_{earth}_. The inner and outer planets likely have moderate eccentricities of e=0.14{+/-}0.07 and 0.16{+/-}0.07, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2Myr. We show that the resonance angles of the planet pair are librating, which may be an indication that K2-146b and c are in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin.
- ID:
- ivo://CDS.VizieR/J/AJ/157/217
- Title:
- Transit times of five hot Jupiter WASP exoplanets
- Short Name:
- J/AJ/157/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6+/-11.7 s earlier than had been predicted, based on data stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with a constant period, ruling out an 81.6 s offset at the 6.4{sigma} level. The 1.3 day orbital period of WASP-4b appears to be decreasing at a rate of P=-12.6+/-1.2 ms per year. The apparent period change might be caused by tidal orbital decay or apsidal precession, although both interpretations have shortcomings. The gravitational influence of a third body is another possibility, though at present there is minimal evidence for such a body. Further observations are needed to confirm and understand the timing variation.
- ID:
- ivo://CDS.VizieR/J/AJ/159/150
- Title:
- Transit times of 11 hot Jupiters
- Short Name:
- J/AJ/159/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Many of the known hot Jupiters are formally unstable to tidal orbital decay. The only hot Jupiter for which orbital decay has been directly detected is WASP-12, for which transit-timing measurements spanning more than a decade have revealed that the orbital period is decreasing at a rate of dP/dt~10^-9^, corresponding to a reduced tidal quality factor of about 2x10^5^. Here, we present a compilation of transit-timing data for WASP-12 and 11 other systems that are especially favorable for detecting orbital decay: KELT-16; WASP-18, 19, 43, 72, 103, 114, and 122; HAT-P-23; HATS-18; and OGLE-TR-56. For most of these systems we present new data that extend the time baseline over which observations have been performed. None of the systems besides WASP-12 display convincing evidence for period changes, with typical upper limits on dP/dt on the order of 10^-9^ or 10^-10^, and lower limits on the reduced tidal quality factor on the order of 10^5^. One possible exception is WASP-19, which shows a statistically significant trend, although it may be a spurious effect of starspot activity.
- ID:
- ivo://CDS.VizieR/J/AJ/162/210
- Title:
- Transit Time Vartiations (TTVs) of WASP-43
- Short Name:
- J/AJ/162/210
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- WASP-43b is one of the most important candidates for detecting an orbital decay. We investigate pieces of evidence for this expectation as variations in its transit timings, based on the ground and space observations. The data set includes the transit observations at the TUBITAK National Observatory of Turkey and Transiting Exoplanet Survey Satellite (TESS). We present a global model of the system, based on the most precise photometry from space, ground, and archival radial velocity data. Using the homogenized data set and modeled light curves, we measure the mid-transit times for WASP-43b. Our analysis agrees with a linear ephemeris for which we refine the light elements for future observations of the system. However, there is a negative difference between the transit timings derived from TESS data in two sectors (9 and 35) and a hint of an orbital period decrease in the entire data set. Both findings are statistically insignificant due to the short baseline of observations, which prevents us from drawing firm conclusions about the orbital decay of this ultra-short-period planet. However, assuming the effect of this decrease of the period in the planet's orbit, we derive a lower limit for the reduced tidal quality factor as Q*'>(4.01{+/-}1.15)x10^5^ from the best-fitting quadratic function. Finally, we calculate a probable rotational period for this system as 7.52days from the out-of-transit flux variation in the TESS light curves due to spot modulation.
- ID:
- ivo://CDS.VizieR/J/AJ/158/133
- Title:
- Transit timing and light curves for K2-146
- Short Name:
- J/AJ/158/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- K2-146 is a mid-M dwarf (M_*_=0.331+/-0.009 M_{sun}_; R_*_=0.330+/-0.010 R_{sun}_), observed in Campaigns 5, 16, and 18 of the K2 mission. In Campaign 5 data, a single planet was discovered with an orbital period of 2.6 days and large transit timing variations due to an unknown perturber. Here, we analyze data from Campaigns 16 and 18, detecting the transits of a second planet, c, with an orbital period of 4.0 days, librating in a 3:2 resonance with planet b. Large, anticorrelated timing variations of both planets exist due to their resonant perturbations. The planets have a mutual inclination of 2.40{deg}+/-0.25{deg}, which torqued planet c more closely into our line of sight. Planet c was grazing in Campaign 5 and thus missed in previous searches; it is fully transiting in Campaigns 16 and 18, and its transit depth is three times larger. We improve the stellar properties using data from Gaia DR2 (Cat. I/345), and use dynamical fits to find that both planets are sub-Neptunes: their masses are 5.77+/-0.18 and 7.50+/-0.23 M_{Earth}_, and their radii are 2.04+/-0.06 and 2.19+/-0.07 R_{Earth}_, respectively. These mass constraints set the precision record for small exoplanets (a few gas giants have comparable relative precision). These planets lie in the photoevaporation valley when viewed in Radius-Period space, but due to the low-luminosity M-dwarf host star, they lie among the atmosphere-bearing planets when viewed in Radius-Irradiation space. This, along with their densities being 60-80% that of Earth, suggests that they may both have retained a substantial gaseous envelope.
- ID:
- ivo://CDS.VizieR/J/AJ/162/55
- Title:
- 65 Transit-timing variation planets properties
- Short Name:
- J/AJ/162/55
- Date:
- 16 Mar 2022 00:18:00
- Publisher:
- CDS
- Description:
- Transit surveys have revealed a significant population of compact multiplanet systems, containing several sub-Neptune-mass planets on close-in, tightly-packed orbits. These systems are thought to have formed through a final phase of giant impacts, which would tend to leave systems close to the edge of stability. Here, we assess this hypothesis, comparing observed eccentricities in systems exhibiting transit-timing variations versus the maximum eccentricities compatible with long-term stability. We use the machine-learning classifier SPOCK (Tamayo et al.) to rapidly classify the stability of numerous initial configurations and hence determine these stability limits. While previous studies have argued that multiplanet systems are often maximally packed, in the sense that they could not host any additional planets, we find that the existing planets in these systems have measured eccentricities below the limits allowed by stability by a factor of 2-10. We compare these results against predictions from the giant-impact theory of planet formation, derived from both N-body integrations and theoretical expectations that, in the absence of dissipation, the orbits of such planets should be distributed uniformly throughout the phase space volume allowed by stability. We find that the observed systems have systematically lower eccentricities than this scenario predicts, with a median eccentricity about four times lower than predicted. This suggests that, if these systems formed through giant impacts, then some dissipation must occur to damp their eccentricities. This may occur through interactions with the natal gas disk or a leftover population of planetesimals, or over longer timescales through the coupling of tidal and secular processes.
- ID:
- ivo://CDS.VizieR/J/A+A/655/A66
- Title:
- Transit Timing Variations bias in transit surveys
- Short Name:
- J/A+A/655/A66
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Transit Timing Variations (TTVs) can provide useful information for systems observed by transit, by putting constraints on the masses and eccentricities of the observed planets, or even constrain the existence of non-transiting companions. However, TTVs can also act as a detection bias that can prevent the detection of small planets in transit surveys, that would otherwise be detected by standard algorithm such as the Boxed Least Square algorithm (BLS) if their orbit was not perturbed. This bias is especially present for surveys with long baseline, such as Kepler, some of the TESS sectors, and the upcoming PLATO mission. Here we introduce a detection method that is robust to large TTVs, and illustrate it by recovering and confirming a pair of resonant super-Earths with 10 hour TTVs around Kepler-1705 (prev. KOI-4772). The method is based on a neural network trained to recover the tracks of low-SNR perturbed planets in river diagrams. We then recover the transit parameters of these candidates by fitting the lightcurve. The individual transit signal-to-noise of Kepler-1705b and c are about three time smaller than all the previously-known planets with TTVs of 3 hours or more, pushing the boundary in the recovering of these small, dynamically active planets. Recovering this type of object is essential to have a complete picture of the observed planetary systems, solving for a bias not often taken into account in statistical studies of exoplanet populations. In addition, TTVs are a means of obtaining mass estimates which can be essential to studying the internal structure of planets discovered by transit surveys. Finally, we show that due to the strong orbital perturbations, it is possible that the spin of the outer resonant planet of Kepler-1705 is trapped in a sub or super-synchronous spin-orbit resonance. This would have important consequences on the climate of the planet since a non-synchronous spin implies that the flux of the star is spread over the whole planetary surface.
- ID:
- ivo://CDS.VizieR/J/AJ/161/202
- Title:
- Transit timing variations of Kepler-90g and h
- Short Name:
- J/AJ/161/202
- Date:
- 10 Dec 2021
- Publisher:
- CDS
- Description:
- Exoplanet transit-timing variations (TTVs) caused by gravitational forces between planets can be used to determine planetary masses and orbital parameters. Most of the observed TTVs are small and sinusoidal in time, leading to degeneracies between the masses and orbital parameters. Here we report a TTV analysis of Kepler-90g and Kepler-90h, which exhibit large TTVs up to 25hr. With optimization, we find a unique solution that allows us to constrain all of the orbital parameters. The best-fit masses for Kepler-90g and 90h are 15.0_-0.8_^+0.9^M{Earth} (Earth mass) and 203_-5_^+5^M_{Earth}, respectively, with Kepler-90g having an unusually low apparent density of 0.15{+/-}0.05g/cm^3^. The uniqueness of orbital parameter solution enables a long-term dynamical integration, which reveals that although their periods are close to 2:3 orbital resonance, they are not locked in resonance, and the configuration is stable over billions of years. The dynamical history of the system suggests that planet interactions are able to raise the eccentricities and break the resonant lock after the initial formation.
- ID:
- ivo://CDS.VizieR/J/AJ/159/239
- Title:
- Transmission Spectroscopy Metric of exoplanets
- Short Name:
- J/AJ/159/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent years have seen increasing interest in the characterization of sub-Neptune-sized planets because of their prevalence in the Galaxy, contrasted with their absence in our solar system. HD97658 is one of the brightest stars hosting a planet of this kind, and we present the transmission spectrum of this planet by combining four Hubble Space Telescope transits, 12 Spitzer/IRAC transits, and eight Microvariability and Oscillations of Stars Telescope (MOST) transits of this system. Our transmission spectrum has a higher signal-to-noise ratio than those from previous works, and the result suggests that the slight increase in transit depth from wavelength 1.1-1.7{mu}m reported in previous works on the transmission spectrum of this planet is likely systematic. Nonetheless, our atmospheric modeling results are inconclusive, as no model provides an excellent match to our data. Nonetheless, we find that atmospheres with high C/O ratios (C/O~>0.8) and metallicities of ~>100 solar metallicity are favored. We combine the mid-transit times from all of the new Spitzer and MOST observations and obtain an updated orbital period of P=9.489295{+/-}0.000005, with a best-fit transit time center at T0=2456361.80690{+/-}0.00038(BJD). No transit timing variations are found in this system. We also present new measurements of the stellar rotation period (34{+/-}2days) and stellar activity cycle (9.6yr) of the host star HD97658. Finally, we calculate and rank the Transmission Spectroscopy Metric of all confirmed planets cooler than 1000K and with sizes between 1R_{Earth}_ and 4R_{Earth}_. We find that at least a third of small planets cooler than 1000K can be well characterized using James Webb Space Telescope, and of those, HD97658b is ranked fifth, meaning that it remains a high-priority target for atmospheric characterization.
