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2023 | |
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55. |
Search for Planets in Hot Jupiter Systems with Multi-Sector TESS Photometry. IV. Null Detections in 12 Systems Abstract: We present the results of our search for nearby planetary companions of transiting hot Jupiters in 12 planetary systems: HAT-P-24, HAT-P-39, HAT-P-42, HAT-P-50, KELT-2, KELT-15, KELT-17, WASP-23, WASP-63, WASP-76, WASP-79, and WASP-161. Our analysis was based on multi-sector time-series photometry from the Transiting Exoplanet Survey Satellite and precise transit timing data sets. We detected no additional transiting planets down to the 2-4 Earth radii regime. For ten hot Jupiters, no departure from linear transit ephemerides was observed. Whilst we refute long-term variations of the orbital period for WASP-161 b, which were claimed in the literature, we notice a tentative hint of the orbital period shortening for WASP-79 b. In addition, we spot a short-period transit timing variation for KELT-2A b with the characteristics typical of the so-called exomoon corridor. We conclude, however, that further observations are required to confirm these findings. |
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54. |
A hot super-Earth planet in the WASP-84 planetary system Abstract: Hot Jupiters have been perceived as loners devoid of planetary companions in close orbital proximity. However, recent discoveries based on space-borne precise photometry have revealed that at least some fraction of giant planets coexists with low-mass planets in compact orbital architectures. We report detecting a 1.446-day transit-like signal in the photometric time series acquired with the Transiting Exoplanet Survey Satellite (TESS) for the WASP-84 system, which is known to contain a hot Jupiter on a circular 8.5-day orbit. The planet was validated based on TESS photometry, and its signal was distilled in radial velocity measurements. The joint analysis of photometric and Doppler data resulted in a multi-planetary model of the system. With a mass of 15 Earth masses, radius of 2 Earth radii, and orbital distance of 0.024 au, the new planet WASP-84 c was classified as a hot super-Earth with the equilibrium temperature of 1300 K. A growing number of companions to hot Jupiters indicates that a non-negligible part of them must have formed under a quiescent scenario such as disc migration or in-situ formation. |
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53. |
Search for Planets in Hot Jupiter Systems with Multi-Sector TESS Photometry. III. A study of ten systems enhanced with new ground-based photometry Abstract: The loneliness of hot Jupiters supports the high-eccentricity migration as a primary path leading to the formation of systems with those planets stripped of any close-in planetary companions. Here we present the null results of searches for low-mass planets close to hot Jupiters in 10 planetary systems: HAT-P-4, HAT-P-10, HAT-P-12, HAT-P-17, HAT-P-19, HAT-P-32, HAT-P-44, Qatar-6, TrES-4, and WASP-48. We employed multi-sector time-series photometry from the Transiting Exoplanet Survey Satellite enhanced with new ground-based transit light curves to determine the sizes of hypothetical planets that might still avoid being detected. We redetermined transit parameters for the known hot Jupiters using a homogenous approach. We refuted transit timing variations for HAT-P-12 b, claimed recently in the literature. The transit timing data permitted us to place tighter constraints on third bodies in HAT-P-19 and HAT-P-32 systems detected in Doppler measurements. We also study four multi-periodic pulsating variable stars in the field around HAT-P-17. |
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2022 | |
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52. |
Planet-star interactions with precise transit timing. III. Entering the regime of dynamical tides Abstract: Hot Jupiters on extremely short-period orbits are expected to be unstable to tidal dissipation and spiral toward their host stars. That is because they transfer the angular momentum of the orbital motion through tidal dissipation into the stellar interior. Although the magnitude of this phenomenon is related to the physical properties of a specific star-planet system, statistical studies show that tidal dissipation might shape the architecture of hot Jupiter systems during the stellar lifetime on the main sequence. The efficiency of tidal dissipation remains poorly constrained in star-planet systems. Stellar interior models show that the dissipation of dynamical tides in radiation zones could be the dominant mechanism driving planetary orbital decay. These theoretical predictions can be verified with the transit timing method. We acquired new precise transit mid-times for five planets. They were previously identified as the best candidates for which orbital decay might be detected. Analysis of the timing data allowed us to place tighter constraints on the orbital decay rate. No statistically significant changes in their orbital periods were detected for all five hot Jupiters in systems HAT-P-23, KELT-1, KELT-16, WASP-18, and WASP-103. For planets HAT-P-23 b, WASP-18 b, and WASP-103 b, observations show that the mechanism of the dynamical tides dissipation probably does not operate in their host stars, preventing them from rapid orbital decay. This finding aligns with the models of stellar interiors of F-type stars, in which dynamical tides are not fully damped due to convective cores. For KELT-16 b, the span of transit timing data was not long enough to verify the theoretical predictions. KELT-1 b was identified as a potential laboratory for studying the dissipative tidal interactions of inertial waves in a convective layer. Continued observations of those two planets may provide further empirical verification of the tidal dissipation theory. |
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51. |
Search for Planets in Hot Jupiter Systems with Multi-Sector TESS Photometry. II. Constraints on Planetary Companions in 12 Systems Abstract: Uninterrupted observations from space-borne telescopes provide the photometric precision that is required to detect shallow transits of small planets missed by ground-based surveys. We used data from the Transiting Exoplanet Survey Satellite (TESS) to search for nearby planetary companions in 12 planetary systems with hot Jupiters: HD 2685, Qatar-10, WASP-4, WASP-48, WASP-58, WASP-91, WASP-120, WASP-121, WASP-122, WASP-140, XO-6, and XO-7. We also applied the transit timing method based on homogeneously determined mid-transit times in order to search for non-transiting companions that could gravitationally perturb the already known planets. We found no additional planets in those systems down to the regime of sub-Neptunian globes. This negative result is in line with statistical studies, supporting the high-eccentricity migration as a pathway of the investigated giant planets to the tight orbits observed today. |
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2021 | |
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50. |
Revisiting TrES-5 b: departure from a linear ephemeris instead of short-period transit timing variation Abstract: The orbital motion of the transiting hot Jupiter TrES-5 b was reported to be perturbed by a planetary companion on a nearby orbit. Such compact systems do not frequently occur in nature, and investigating their orbital architecture could shed some light on the formation processes of hot Jupiters. We acquired 15 new precise photometric time-series for 12 transits of TrES-5 b between June 2019 and October 2020 using 0.9-2.0 m telescopes. The method of precise transit timing was employed to verify the deviation of the planet from the Keplerian motion. Although our results show no detectable short-time variation in the orbital period of TrES-5 b and the existence of the additional nearby planet is not confirmed, the new transits were observed about two minutes earlier than expected. We conclude that the orbital period of the planet could vary on a long timescale. We found that the most likely explanation of the observations is the line-of-sight acceleration of the system's barycentre caused by the orbital motion induced by a massive, wide-orbiting companion. |
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2020 | |
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49. |
A Newtonian model for the WASP-148 exoplanetary system enhanced with
TESS and ground-based photometric observations Abstract: The WASP-148 planetary system has a rare architecture with a transiting Saturn-mass planet on a tight orbit which is accompanied by a slightly more massive planet on a nearby outer orbit. Using new space-born photometry and ground-based follow-up transit observations and data available in literature, we performed modeling that accounts for gravitational interactions between both planets. Thanks to the new transit timing data for planet b, uncertainties of orbital periods and eccentricities for both planets were reduced relative to previously published values by a factor of 3-4. Variation in transit timing has an amplitude of about 20 minutes and can be easily followed-up with a 1-m class telescopes from the ground. An approximated transit ephemeris, which accounts for gravitational interactions with an accuracy up to 5 minutes, is provided. No signature of transits was found for planet c down to the Neptune-size regime. No other transiting companions were found down to a size of about 2.4 Earth radii for interior orbits. We notice, however, that the regime of terrestrial-size planets still remains unexplored in that system. |
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48. |
Search for planets in hot Jupiter systems with multi-sector TESS
photometry. I. No companions in planetary systems KELT-18, KELT-23, KELT-24,
Qatar-8, WASP-62, WASP-100, WASP-119, and WASP-126 Abstract: Origins of giant planets on tight orbits, so called hot Jupiters, are a long-lasting question in the planetary formation and evolution theory. The answer seems to be hidden in architectures of those systems that remain only partially understood. Using multi-sector time-series photometry from the Transiting Exoplanet Survey Satellite, we searched for additional planets in the KELT-18, KELT-23, KELT-24, Qatar-8, WASP-62, WASP-100, WASP-119, and WASP-126 planetary systems using both the transit technique and transit timing method. Our homogenous analysis has eliminated the presence of transiting companions down to the terrestrial-size regime in the KELT-23 and WASP-62 systems, and down to mini-Neptunes or Neptunes in the remaining ones. Transit timing analysis has revealed no sign of either long-term trends or periodic perturbations for all the studied hot Jupiters, including the WASP-126 b for which deviations from a Keplerian model were claimed in the literature. The loneliness of the planets of the sample speaks in favour of the high-eccentricity migration mechanism that probably brought them to their tight orbits observed nowadays. As a byproduct of our study, the transit light curve parameters were redetermined with a substantial improvement of the precision for 6 systems. For KELT-24 b, a joint analysis allowed us to place a tighter constraint on its orbital eccentricity. |
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47. |
Star-planet tidal interactions in the WASP-12 system Abstract: To date, the exoplanet WASP-12 b is the only hot Jupiter for which the shortening of its orbital period was detected. A mechanism that drives this orbital decay remains a puzzle. Equilibrium stellar tides alone were found to be too weak to explain the observed rate of inspiral and dynamical stellar tides or planetary obliquity tides have been considered. Compared to other stars, WASP-12 is distinguished by its extremely high efficiency of the dissipation of the tidal energy, typical rather for sub-giants than for main sequence dwarfs. Therefore, it cannot be ruled out that the system is observed at a specific moment of the stellar evolution in which the star leaves the main sequence, heading towards the red giants branch. Using the new radial velocity (RV) measurements acquired with the HARPS-N instrument at the Telescopio Nazionale Galileo, we show that the observed orbital eccentricity of WASP-12 b is non-zero at a 5-sigma level, and the longitude of pericentre of this apparently eccentric orbit is close to 270 degrees. This orbital configuration is compatible with a solution containing a circular orbit and an RV signal induced by the tidal fluid flow in the star. The amplitude of the RV tides was found to be consistent with a value calculated using the equilibrium tide approximation. This finding opens new possibilities in probing the physical properties of stellar interiors. |
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46. |
Planet-star interactions with precise transit timing. II. The radial-velocity tides and a tighter constraint on the orbital decay rate in the WASP-18 system Abstract: From its discovery, the WASP-18 system with its massive transiting planet on a tight orbit was identified as a unique laboratory for studies on tidal planet-star interactions. In an analysis of Doppler data, which include five new measurements obtained with the HIRES/Keck-I instrument between 2012 and 2018, we show that the radial velocity signal of the photosphere following the planetary tidal potential can be distilled for the host star. Its amplitude is in agreement with both theoretical predictions of the equilibrium tide approximation and an ellipsoidal modulation observed in an orbital phase curve. Assuming a circular orbit, we refine system parameters using photometric time series from TESS. With a new ground-based photometric observation, we extend the span of transit timing observations to 28 years in order to probe the rate of the orbital period shortening. Since we found no departure from a constant-period model, we conclude that the modified tidal quality parameter of the host star must be greater than 3.9 x 106 with 95% confidence. This result is in line with conclusions drawn from studies of the population of hot Jupiters, predicting that the efficiency of tidal dissipation is 1 or 2 orders of magnitude weaker. As the WASP-18 system is one of the prime candidates for detection of orbital decay, further timing observations are expected to push the boundaries of our knowledge on stellar interiors. |
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45. |
An apparently eccentric orbit of the exoplanet WASP-12 b as a radial velocity signature of planetary-induced tides in the host star Abstract: Massive exoplanets on extremely tight orbits, such as WASP-12 b, induce equilibrium tides in their host stars. Following the orbital motion of the planet, the tidal fluid flow in the star can be detected with the radial velocity method. Its signature manifests as the second harmonics of the orbital frequency that mimics a non-zero orbital eccentricity. Using the new radial velocity measurements acquired with the HARPS-N spectrograph at the Telescopio Nazionale Galileo and combining them with the literature data, we show that the apparent eccentricity of WASP-12 b's orbit is non-zero at a 5.8 sigma level, and the longitude of periastron of this apparently eccentric orbit is close to 270 degrees. This orbital configuration is compatible with a model composed of a circular orbit and a signature of tides raised in the host star. The radial velocity amplitude of those tides was found to be consistent with the equilibrium tide approximation. The tidal deformation is predicted to produce a flux modulation with an amplitude of 80 ppm which could be detected using space-born facilities. |
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2019 | |
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44. |
Planet-star tidal interactions with precise transit timing Abstract: Theoretical calculation and some indirect observations show that massive exoplanets on the tightest orbits - so called hot Jupiters - must undergo orbital decay due to tidal dissipation within their host stars. This orbital evolution could be observationally accessible through precise transit timing over the course of decades. Meter-class telescopes are recognised as excellent instruments for such follow-up observations. They usually provide photometric time series of millimagnitude or even sub-millimagnitude precision for stars brighter than about 12 mag. Such observations allow one to determine individual mid-transit times with errors between 20 and 40 s, and when they are combined together, the averaged timing precision down to or even below 10 s can be achieved over time scales of months. The rate of planetary in-spiralling may not only help us to understand some aspects of evolution of planetary systems, but also can be used as a probe of the stellar internal structure. Since 2017 we have run a regular observing campaign aimed at transit timing for a sample of best candidates for in-falling planets. Among them there is WASP-12 b, transits of which exhibit pronounced departure from a linear ephemeris. New observations allow us to confirm the rapid decay rate for that planet, and to place constraints on the tidal dissipation efficiency in other systems. |
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2018 | |
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43. |
Planet-star interactions with precise transit timing. I. The refined orbital decay rate for WASP-12 b and initial constraints for HAT-P-23 b, KELT-1 b, KELT-16 b, WASP-33 b, and WASP-103 b Abstract: Theoretical calculations and some indirect observations show that massive exoplanets on tight orbits must decay due to tidal dissipation within their host stars. This orbital evolution could be observationally accessible through precise transit timing over a course of decades. The rate of planetary in-spiralling may not only help us to understand some aspects of evolution of planetary systems, but also can be used as a probe of the stellar internal structure. In this paper we present results of transit timing campaigns organised for a carefully selected sample of hot Jupiter-like planets which were found to be the best candidates for detecting planet-star tidal interactions on the Northern hemisphere. Among them, there is the WASP-12 system which is the best candidate for possessing an in-falling giant exoplanet. Our new observations support the scenario of orbital decay of WASP-12 b and allow us to refine its rate. The derived tidal quality parameter of the host star Q' = (1.82 +/- 0.32) x 105 is in agreement with theoretical predictions for subgiant stars. For the remaining systems - HAT-P-23, KELT-1, KELT-16, WASP-33, and WASP-103 - our transit timing data reveal no deviations from the constant-period models, hence constraints on the individual rates of orbital decay were placed. The tidal quality parameters of host stars in at least 4 systems - HAT-P-23, KELT-1, WASP-33, and WASP-103 - were found to be greater than the value reported for WASP-12. This is in line with the finding that those hosts are main sequence stars, for which efficiency of tidal dissipation is predicted to be relatively weak. |
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42. |
WASP-12 b - an exoplanet falling onto its host star? Abstract: With the orbital period as short as 26 hours, the transiting planet WASP-12 b belongs to a group of planets of the tightest orbits. We detected the apparent shortening of its orbital period that could be caused by orbital decay or apsidal precession due to tidal interactions. The reanalysis of available data allowed us to identify an alternative scenario that explains the departure of the transit timing from a linear ephemeris. We found a solution with an additional planet, whose mass is about 17 Earth masses and the orbital period is 3.2 d. We found that this planet can perturb the orbital motion of WASP-12 b that manifests as the apparent orbital decay. Our dynamical model shows that the planet is likely to transit the host star. We plan to acquire precise photometric time series for WASP-12 in the 2017/2018 observing season to confirm the existence of the postulated planet and to determine its parameters. |
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41. |
New transit timing observations for GJ 436 b, HAT-P-3 b, HAT-P-19 b, WASP-3 b, and XO-2 b Abstract: We present new transit observations acquired between 2014 and 2018 for the hot exoplanets GJ 436 b, HAT-P-3 b, HAT-P-19 b, WASP-3 b, and XO-2 b. New mid-transit times extend the timespan covered by observations of these exoplanets and allow us to refine their transit ephemerides. All new transits are consistent with linear ephemerides. |
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2016 | |
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40. |
On the orbital period of the exoplanet WASP-39 b Abstract: We present two new transit light curves acquired for the transiting planet WASP-39 b. Their mid-transit times allowed us to verify an orbital period and to refine a transit ephemeris. |
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39. |
Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b Abstract: Most hot Jupiters are expected to spiral in toward their host stars because the angular momentum of the orbital motion is transferred to the stellar spin. Their orbits can also precess as a result of planet-star interactions. Calculations show that both effects might be detected for the very-hot exoplanet WASP-12 b using the method of precise transit-timing over a time span of about 10 yr. We acquired new precise light curves for 29 transits of WASP-12 b, spannning four observing seasons from November 2012 to February 2016. New mid-transit times, together with those from the literature, were used to refine the transit ephemeris and analyze the timing residuals. We find that the transit times of WASP-12 b do not follow a linear ephemeris with a five-sigma confidence level. They may be approximated with a quadratic ephemeris that gives a change rate in the orbital period of (-2.56+/-0.40) x 10-2 s/yr. The tidal quality parameter of the host star was found to be equal to 2.5 x 105, which is similar to theoretical predictions for Sun-like stars. We also considered a model in which the observed timing residuals are interpreted as a result of the apsidal precession. We find, however, that this model is statistically less probable than the orbital decay. |
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38. |
New transit observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b, and WASP-39 b Abstract: We present new transit light curves for planets in six extrasolar planetary systems. They were acquired with 0.4-2.2 m telescopes located in west Asia, Europe, and South America. When combined with literature data, they allowed us to redetermine system parameters in a homogeneous way. Our results for individual systems are in agreement with values reported in previous studies. We refined transit ephemerides and reduced uncertainties of orbital periods by a factor between 2 and 7. No sign of any variations in transit times was detected for the planets studied. |
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2015 | |
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37. |
No variations in transit times for Qatar-1 b Abstract: The transiting hot Jupiter planet Qatar-1 b was presented to exhibit variations in transit times that could be of perturbative nature. A hot Jupiter with a planetary companion on a nearby orbit would constitute an unprecedented planetary configuration, important for theories of formation and evolution of planetary systems. We performed a photometric follow-up campaign to confirm or refute transit timing variations. We extend the baseline of transit observations by acquiring 18 new transit light curves acquired with 0.6-2.0 m telescopes. These photometric time series, together with data available in the literature, were analyzed in a homogenous way to derive reliable transit parameters and their uncertainties. We show that the dataset of transit times is consistent with a linear ephemeris leaving no hint for any periodic variations with a range of 1 min. We find no compelling evidence for the existence of a close-in planetary companion to Qatar-1 b. This finding is in line with a paradigm that hot Jupiters are not components of compact multi-planetary systems. Based on dynamical simulations, we place tighter constraints on a mass of any fictitious nearby planet in the system. Furthermore, new transit light curves allowed us to redetermine system parameters with the precision better than that reported in previous studies. Our values generally agree with previous determinations. |
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2014 | |
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36. |
On the GJ 436 planetary system Abstract: The GJ 436 system contains a transiting planet GJ 436 b which is a hot analogue of Neptune on an eccentric orbit. Recently, two additional transiting sub-Earth planets have been postulated in the literature. We observed three transits of GJ 436 b over the course of 3 years using two-meter class telescopes, each with a photometric precision better than one millimagnitude. We studied system dynamics based on the existence of the additional planets. We redetermined system parameters, which were in agreement with those found in the literature. We refined the orbital period of GJ 436 b and found no evidence of transit timing variations. The orbital motion of the GJ 436 c planet candidate was found to be significantly affected by the planet b with variations in transit times at a level of 20 minutes. As the orbital period of the GJ 436 d planet candidate remains unknown, our numerical experiments rule out orbits in low-order resonances with GJ 436 b. The GJ 436 system with the hot Neptune and additional two Earth-like planets, if confirmed, would be an important laboratory for studies of formation and evolution of planetary systems. |
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35. |
New transit observations of WASP-12 b Abstract: The transiting extrasolar planet WASP-12 b was announced to exhibit a sign of variations in transit timing. The postulated signal has a period of 550 days and a semi-amplitude of 2 min. Joint analysis of the radial velocities and transit timing resulted in a two-planet model which fits observations much better than a single-planet model. This finding allows us to advance the hypothesis that WASP-12 b is accompanied by additional, less massive planet on a tight orbit. Statistical studies of hot Jupiter candidates in the Kepler sample show that these planets are rare in multi-transiting planetary systems. Solitariness of hot Jupiters is postulated to be a result of the dynamical evolution of their planetary systems. The WASP-12 system would be an interesting outlier which would be challenging for theories of evolution of planetary systems. We present new observations gathered in the observing season 2012/2013 that confirm the transit timing signal and refine its characteristics. |
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34. |
Revisiting parameters for the WASP-1 planetary system Abstract: We present thirteen new transit light curves for the WASP-1 b exoplanet. Observations were acquired with 0.5 - 1.2-m telescopes between 2007 and 2013. Our homogeneous analysis, which also includes the literature data, results in determining precise system parameters. New values are in agreement with those reported in previous studies. Transit times follow a linear ephemeris with no sign of any transit time variations. This finding is in line with the paradigm that Jupiter-like planets on tight orbits are devoid of close planetary companions. |
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2013 | |
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33. |
New mid-transit times for HAT-P-36 b, TrES-3 b, and WASP-43 b Abstract: We present new mid-transit times for exoplanets HAT-P-36 b, TrES-3 b, and WASP-43 b, based on analysis of complete transit light curves obtained from 2009 to 2013. The mid-transit times for HAT-P-36 b allowed us to refine its transit ephemeris. Results for TrES-3 b are consistent with a linear ephemeris supporting no transit time variations. The orbital period of WASP-43 b was found to be shorter by 0.13 s than previously published. All new transit times were found to be consistent with linear ephemerides. |
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32. |
Constraints on a second planet in the WASP-3 system Abstract: There have been previous hints that the transiting planet WASP-3 b is accompanied by a second planet in a nearby orbit, based on small deviations from strict periodicity of the observed transits. Here we present 17 precise radial velocity measurements and 32 transit light curves that were acquired between 2009 and 2011. These data were used to refine the parameters of the host star and transiting planet. This has resulted in reduced uncertainties for the radii and masses of the star and planet. The radial-velocity data and the transit times show no evidence for an additional planet in the system. Therefore, we have determined the upper limit on the mass of any hypothetical second planet, as a function of its orbital period. |
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31. |
Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin Abstract: The transiting planet WASP-12 b was identified as a potential target for transit-timing studies because a departure from a linear ephemeris has been reported in the literature. Such deviations could be caused by an additional planet in the system. We attempt to confirm the claimed variations in transit timing and interpret their origin. We organised a multi-site campaign to observe transits by WASP-12 b in three observing seasons, using 0.5-2.6-metre telescopes. We obtained 61 transit light curves, many of them with sub-millimagnitude precision. The simultaneous analysis of the best-quality datasets allowed us to obtain refined system parameters, which agree with values reported in previous studies. The residuals versus a linear ephemeris reveal a possible periodic signal that may be approximated by a sinusoid with an amplitude of 0.00068+/-0.00013 d and period of 500+/-20 orbital periods of WASP-12 b. The joint analysis of timing data and published radial velocity measurements results in a two-planet model that explains observations better than do single-planet scenarios. We hypothesise that WASP-12 b might not be the only planet in the system, and there might be the additional 0.1 Jupiter mass body on a 3.6-d eccentric orbit. A dynamical analysis indicates that the proposed two-planet system is stable on long timescales. |
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2011 | |
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30. |
Analysis of new high-precision transit light curves of WASP-10 b: starspot occultations, small planetary radius, and high metallicity Abstract: The WASP-10 planetary system is intriguing because different values of radius have been reported for its transiting exoplanet. The host star exhibits activity in terms of photometric variability, which is caused by the rotational modulation of the spots. Moreover, a periodic modulation has been discovered in transit timing of WASP-10 b, which could be a sign of an additional body perturbing the orbital motion of the transiting planet. We attempt to refine the physical parameters of the system, in particular the planetary radius, which is crucial for studying the internal structure of the transiting planet. We also determine new mid-transit times to confirm or refute observed anomalies in transit timing. We acquired high-precision light curves for four transits of WASP-10 b in 2010. Assuming various limb-darkening laws, we generated best-fit models and redetermined parameters of the system. The prayer-bead method and Monte Carlo simulations were used to derive error estimates. Three transit light curves exhibit signatures of the occultations of dark spots by the planet during its passage across the stellar disk. The influence of stellar activity on transit depth is taken into account while determining system parameters. The radius of WASP-10 b is found to be no greater than 1.03 Jupiter radii, a value significantly smaller than most previous studies indicate. We calculate interior structure models of the planet, assuming a two-layer structure with one homogeneous envelope atop a rock core. The high value of the WASP-10 b's mean density allows one to consider the planet's internal structure including 270 to 450 Earth masses of heavy elements. Our new mid-transit times confirm that transit timing cannot be explained by a constant period if all literature data points are considered. They are consistent with the ephemeris assuming a periodic variation of transit timing. We show that possible starspot features affecting the transit's ingress or egress cannot reproduce variations in transit timing at the observed amplitude. |
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29. |
Refining Parameters of the XO-5 Planetary System with High-Precision Transit Photometry Abstract: Studies of transiting extrasolar planets offer an unique opportunity to get to know the internal structure of those worlds. The transiting exoplanet XO-5 b was found to have an anomalously high Safronov number and surface gravity. Our aim was to refine parameters of this intriguing system and search for signs of transit timing variations. We gathered high-precision light curves of two transits of XO-5 b. Assuming three different limb darkening laws, we found the best-fitting model and redetermined parameters of the system, including planet-to-star radius ratio, impact parameter and central time of transits. Error estimates were derived by the prayer bead method and Monte Carlo simulations. Although system's parameters obtained by us were found to agree with previous studies within one sigma, the planet was found to be notable smaller with the radius of 1.03+0.06-0.05 Jupiter radii. Our results confirm the high Safronov number and surface gravity of the planet. With two new mid-transit times, the ephemeris was refined to BJD(TDB)=(2454485.66842±0.00028) + (4.1877537±0.000017) E. No significant transit timing variation was detected. |
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28. |
High-precision photometry of WASP-12 b transits Abstract: The transiting extrasolar planet WASP-12~b was found to be one of the most intensely irradiated exoplanets. It is unexpectedly bloated and is losing mass that may accrete into the host star. Our aim was to refine the parameters of this intriguing system and search for signs of transit timing variations. We gathered high-precision light curves for two transits of WASP-12 b. Assuming various limb-darkening laws, we generated best-fitting models and redetermined parameters of the system. Error estimates were derived by the prayer bead method and Monte Carlo simulations. System parameters obtained by us are found to agree with previous studies within one sigma. Use of the non-linear limb-darkening laws results in the best-fitting models. With two new mid-transit times, the ephemeris was refined to BJD(TDB) = (2454508.97682±0.00020) + (1.09142245±0.00000033) E. Interestingly, indications of transit timing variation are detected at the level of 3.4 sigma. This signal can be induced by an additional planet in the system. Simplified numerical simulations shows that a perturber could be a terrestrial-type planet if both planets are in a low-order orbital resonance. However, we emphasise that further observations are needed to confirm variation and to constrain properties of the perturber. |
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27. |
A search for transit timing variation Abstract: Photometric follow-ups of transiting exoplanets (TEPs) may lead to discoveries of additional, less massive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. In 2009 we launched an international observing campaign, the aim of which is to detect and characterise signals of transit timing variation (TTV) in selected TEPs. The programme is realised by collecting data from 0.6-2.2-m telescopes spread worldwide at different longitudes. We present our observing strategy and summarise first results for WASP-3b with evidence for a 15 Earth-mass perturber in an outer 2:1 orbital resonance. |
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26. |
Towards the Rosetta Stone of planet formation Abstract: Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of their host systems may serve as the Rosetta Stone for planet formation theories. They would give strong constraints on several aspects of planet formation, e.g. time-scales (planet formation would then be possible within 10 Myrs), the radius of the planet could indicate whether planets form by gravitational collapse (being larger when young) or accretion growth (being smaller when young). We present a survey, the main goal of which is to find and then characterise TEPs in very young open clusters. |
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25. |
Transit timing variation and activity in the WASP-10 planetary system Abstract: Transit timing analysis may be an effective method of discovering additional bodies in extrasolar systems which harbour transiting exoplanets. The deviations from the Keplerian motion, caused by mutual gravitational interactions between planets, are expected to generate transit timing variations of transiting exoplanets. In 2009 we collected 9 light curves of 8 transits of the exoplanet WASP-10b. Combining these data with published ones, we found that transit timing cannot be explained by a constant period but by a periodic variation. Simplified three-body models which reproduce the observed variations of timing residuals were identified by numerical simulations. We found that the configuration with an additional planet of mass of about 0.1 Jupiter mass and orbital period of about 5.23 d, located close to the outer 5:3 mean motion resonance, is the most likely scenario. If the second planet is a transiter, the estimated flux drop will be about 0.3 per cent and can be observable with a ground-based telescope. Moreover, we present evidence that the spots on the stellar surface and rotation of the star affect the radial velocity curve giving rise to spurious eccentricity of the orbit of the first planet. We argue that the orbit of WASP-10b is essentially circular. Using the gyrochronology method, the host star was found to be 270±80 Myr old. This young age can explain the large radius reported for WASP-10b. |
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2010 | |
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24. |
Transit timing variation in exoplanet WASP-3b Abstract: Photometric follow-ups of transiting exoplanets may lead to discoveries of additional, less massive bodies in extrasolar systems. This is possible by detecting and then analysing variations in transit timing of transiting exoplanets. We present photometric observations gathered in 2009 and 2010 for exoplanet WASP-3b during the dedicated transit-timing-variation campaign. The observed transit timing cannot be explained by a constant period but by a periodic variation in the observations minus calculations diagram. Simplified models assuming the existence of a perturbing planet in the system and reproducing the observed variations of timing residuals were identified by three-body simulations. We found that the configuration with the hypothetical second planet of mass of about 15 Earth masses, located close to the outer 2:1 mean motion resonance is the most likely scenario reproducing observed transit timing. We emphasize, however, that more observations are required to constrain better the parameters of the hypothetical second planet in the WASP-3 system. For final interpretation not only transit timing but also photometric observations of the transit of the predicted second planet and the high precision radial-velocity data are needed. |
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23. |
The young open cluster Trumpler 3 Abstract: We present a photometric and spectroscopic study of the poorly investigated open cluster Trumpler 3. Basic parameters such as the age of 70±10 Myr, the color excess E(B-V)=0.30±0.02 mag, the distance of 0.69±0.03 kpc and the limiting radius of 12' were redetermined and compared with previous preliminary studies. The distance of 0.65±0.09 kpc was determined independently by spectral parallaxes. Simultaneously, our analysis allowed us to estimate a total number of members to be 570±90 and a total mass of the cluster to be 270±40 solar masses. We also determined a state of cluster's dynamical evolution. We conclude that Trumpler 3 is a young low-massive stellar ensemble with a typical mass function slope, located near to the outer edge of the Galaxy's Orion Spur. As a result of a wide-field search for short period variable stars, 24 variables were discovered in the cluster's area. Only one of them - a variable of the gamma-Dor type - was found to be a likely cluster member. |
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2009 | |
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22. |
The open cluster Berkeley 53 Abstract: We present a photometric study of the neglected open cluster Berkeley 53. We derived its fundamental parameters, such as the age, the interstellar reddening, and the distance from the Sun, based on BV photometry combined with near-infrared JHK data. The structure and the mass function of the cluster were also studied and the total number of members and the total mass were estimated. The cluster was found to be a rich and massive stellar system, located in the Perseus Arm of the Milky Way, 3.1+/-0.1 kpc from the Sun. Its age exceeds 1 Gy but it seems to be very young in the context of its dynamical evolution. The analysis of the two-color diagrams and color-magnitude diagrams indicates that the cluster is significantly reddened. However, both methods resulted in different values of E(B-V), i.e. 1.21+\-0.04 and 1.52+\-0.01, respectively. This discrepancy suggests the presence of an abnormal interstellar extinction law toward the cluster. |
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21. |
Space structure and dynamical evolution of the open star clusters Abstract: A characteristic of the structure and the dynamical evolution of open clusters is presented in this short review. Simple methods for analysing both issues are sketched and the literature references are given. |
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2008 | |
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20. |
Photometric Studies of Open Clusters: Abstract: Results of investigations of six poorly studied or unstudied open clusters are presented. The ages, interstellar reddenings, distances, and structural parameters were derived based on BV photometry combined with the near-infrared JHK data. The mass functions were analyzed for four objects and total masses, number of members, and dynamical-evolution parameters were estimated. Berkeley 95 was found to be an extremely young stellar cluster. King 17 and King 18 turned out to be an intermediate-age objects. Czernik 21, Czernik 38, and Juchert 11 were found to be old stellar ensembles of the age of about 1 Gyr old or older. Czernik 38 is located in the Sagittarius Arm while the remaining clusters belong to the Perseus Arm. |
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19. |
Variable stars in the field of the open cluster NGC 457 Abstract: We present results of the search for variable stars in the field of the young open cluster NGC 457. Twenty nine new and two known variables were detected and analysed. Six of them were found to be unquestionable or likely cluster members. |
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18. |
Photometric study of 9 doubtful open clusters Abstract: We present results of a photometric investigation of 9 poorly studied apparent open clusters. While the aim of our survey was to determine structural and astrophysical parameters for these objects, they were found not to be physical groups of stars. BV wide-field CCD photometry combined with the near-infrared JHK data from the 2MASS and proper motions were used to study their nature. Detailed analysis of radial density profiles, morphology of decontaminated colour-magnitude diagrams, and proper motion distributions indicate that these stellar ensembles are projective chance alignments of physically unrelated stars. |
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17. |
Photometric study of the open clusters NGC 2266 and NGC 7762 Abstract: Results of CCD photometric UBV monitoring of NGC 2266 and NGC 7762 are presented. Additional 2MASS JH photometry is used to determine basic parameters for both clusters. According to our analysis the limiting radius of NGC 2266 is 6'.2, log (age) = 9.08+/-0.04 with the subsolar metallicity of Z=0.004 ([Fe/H]=-0.68), E(B-V)=0.17 mag, and the distance of 2.80+/-0.15 kpc. No evidence of existence of an extended corona was found. As a result of 45 hours of monitoring, 12 out of 7200 observed stars were found to reveal light curve changes. However, no variable stars located within the cluster radius were detected. NGC 7762 was found to be very large stellar system with the limiting radius of 23'.5 including an extended corona well visible in the near-IR photometry. Cluster's astrophysical parameters such as log (age) = 9.38+/-0.04, E(B-V)=0.59 mag, and the distance of 0.8+/-0.2 kpc were determined as a result of fitting a solar-metallicity isochrone. The analysis of the near-IR data suggests existence of the abnormal interstellar extinction law towards NGC 7762 resulting with E(J-H)=0.11 mag. As a result of 55 hours of monitoring of 5500 stars in cluster's field, 2 out of 16 variable stars - a short period contact or semi-detached eclipsing system and a pulsating star of gamma Dor type - were found as likely members of NGC 7762. |
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16. |
Variable stars in the field of open cluster NGC 6939 Abstract: The results of CCD photometric survey performed with the 90/180 cm Schmidt-Cassegrain Telescope of the Nicolaus Copernicus University Astronomical Observatory in Piwnice (Poland) and the 70/172 cm Schmidt Telescope of the National Astronomical Observatory (NAO) at Rozhen (Bulgaria) of the field of 1 Gyr old open cluster NGC 6939 are presented. Twenty two variable stars were detected, four of them previously known. Four eclipsing systems (3 detached and 1 contact binary) were found to be members of the cluster. Analysis of the brightness of the contact binary V20 strongly supports the distance to the cluster of 1.74 +/- 0.20 kpc. The small population of contact binaries in NGC 6939 confirms also the relatively young age of the cluster. |
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2007 | |
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15. |
Wide-field stellar photometry in Piwnice Observatory Abstract: In this paper research projects based on the wide-field CCD photometry performed in Piwnice Observatory are discussed. The used telescopes, as well as dedicated software pipeline for data reduction are presented. The prospects for collaboration between Polish and Bulgarian institutes in the field of wide-field photometry are also discussed. |
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14. |
CCD BV survey of 42 open clusters Abstract: We present results of a photometric survey whose aim was to derive structural and astrophysical parameters for 42 open clusters. While our sample is definitively not representative of the total open cluster sample in the Galaxy, it does cover a wide range of cluster parameters and is uniform enough to allow for simple statistical considerations. BV wide-field CCD photometry was obtained for open clusters for which photometric, structural, and dynamical evolution parameters were determined. The limiting and core radii were determined by analyzing radial density profiles. The ages, reddenings, and distances were obtained from the solar metallicity isochrone fitting. The mass function was used to study the dynamical state of the systems, mass segregation effect and to estimate the total mass and number of cluster members. This study reports on the first determination of basic parameters for 11 out of 42 observed open clusters. The angular sizes for the majority of the observed clusters appear to be several times larger than the catalogue data indicate. The core and limiting cluster radii are correlated and the latter parameter is 3.2 times larger on average. The limiting radius increases with the cluster's mass, and both the limiting and core radii decrease in the course of dynamical evolution. For dynamically not advanced clusters, the mass function slope is similar to the universal IMF slope. For more evolved systems, the effect of evaporation of low-mass members is clearly visible. The initial mass segregation is present in all the observed young clusters, whereas the dynamical mass segregation appears in clusters older than about log(age)=8. Low-mass stars are deficient in the cores of clusters older than log(age)=8.5 and not younger than one relaxation time. |
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2005 | |
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13. |
Abstract: Od września 2002 roku w Obserwatorium Astronomicznym Uniwersytetu Mikołaja Kopernika realizowany jest projekt badawczy Semi-Automatic Variability Search (SAVS, Półautomatyczne Poszukiwanie Zmienności), którego celem jest odkrywanie gwiazd zmiennych w wybranych obszarach nieba północnego. Program ten kierowany jest przez dr. Andrzeja Niedzielskiego i został zainicjowany przez wybitnego polskiego uczonego - prof. Bohdana Paczyńskiego. |
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12. |
59 New Variable Stars from SAVS Sky Survey Abstract: Light curves of 59 new variable stars discovered by the Semi-Automatic Variability Search sky survey arepresented. For some of them the spectral types are determined as well. |
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11. |
The Semi-Automatic Variability Search. First Results of the BVR Survey Abstract: The first results of the Semi-Automatic Variability Search (SAVS) performed in the BVR passbands are presented. Periods, amplitudes and variability types for 25 new variable stars discovered in 13 selected test fields are given. An automated variability type assignment algorithm based on morphology of the phased monochromatic light curve is presented, tested and finally applied to our data. The precision of SAVS photometry and its transformation to the standard system is presented and discussed. |
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2004 | |
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10. |
28 New Variable Stars from SAVS Abstract: Light curves of 28 new variable stars discovered by the Semi-Automatic Variability Search sky survey are presented. For some of them the spectral types determined are presented as well. |
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9. |
Mass Ratio Determination of Binary Systems BD+14 5016, GSC 2757-769 and GSC 3472-641 Abstract: We present determination of spectroscopic mass ratios for three contact binary stars BD+14 5016, GSC 2757-769 and GSC 3472-641. The measurements of radial velocities allowed us to obtain spectroscopic orbital elements for these systems. |
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8. |
CCD Times of Minima of Some Eclipsing Binaries in 2003 Abstract: We present CCD observations of minima of 31 eclipsing binaries observed by SAVS sky survey in 2003. |
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7. |
First Results of the Semi-Automatic Variability Search Abstract: Technical features of the Semi-Automatic Variability Search (SAVS) operating at the Astronomical Observatory of the Nicolaus Copernicus University and the results of the first year of observations are presented. The user-friendly software developed for reduction of acquired CCD images and detection of new variable stars is also described. |
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2003 | |
|
6. |
Four New Short-Period Eclipsing Binary Stars Abstract: Four new eclipsing binary stars are identified: HD 65498, HD 67894, BD+20 2890 and GSC 03472-00641. For all of them new spectral types and luminosity classes are presented in addition to ephemerides and periods. |
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5. |
Spectroscopic and Photometric Solution of the Binary System BD+14 5016 Abstract: We present preliminary solution of the eclipsing binary star BD+14 5016. The obtained model indicates that the investigated star is an A-type W UMa system with a hot spot located on the surface of the more massive component. The system is in a large degree of overcontact of about 54 percent. |
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4. |
GSC 02757-00769 - A New EW Binary System Abstract: GSC 02757-00769 was found to be a new EW eclipsing binary with a period of 10 hours and amplitude of 0.24 magnitudes. |
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2002 | |
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3. |
BD+14 5016 - A New EW Eclipsing Binary Abstract: BD +14 5016 was found to be a new EW eclipsing binary with a period of 0.64 d and an amplitude of DeltaV=0.47 magnitudes. |
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2. |
Photometric Variability of FIRST J142643.2+315214 |
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2001 | |
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1. |
Abstract: W grudniu 1995 roku, po 6 latach podróży, do systemu jowiszowego dotarła sonda Galileo nazwana tak ma cześć odkrywcy czterech największych księżyców Jowisza - włoskiego uczonego Galileo Galilei. Misja ta trwa już od ponad pięciu lat i pomimo poważnych problemów technicznych z anteną główną czy pokładowym urządzeniem zapisującym zabrane dane, nieustannie dostarcza nowych, niezwykle cennych informacji, między innymi o lodowych księżycach: Europie, Ganimedesie oraz Kallisto. Zbierane w czasie bliskich przelotów w pobliżu tych satelitów dane odmieniły nasze wyobrażenia o ich budowie wewnętrznej i procesach zachodzących na ich powierzchniach. |
Last modified: 2023 Dec 09