arXiv subjects

G. Maciejewski

Publications and source records attributed to G. Maciejewski.

At least 37 records · Page 2Linked to original sources

arXiv2016

YETI observations of the young transiting planet candidate CVSO 30 b

CVSO 30 is a unique young low-mass system, because, for the first time, a close-in transiting and a wide directly imaged planet candidates are found around a common host star. The inner companion, CVSO 30 b, is the first possible young transiting planet orbiting a previously known weak-lined T-Tauri star. With five telescopes of the 'Young Exoplanet Transit Initiative' (YETI) located in Asia, Europe and South America we monitored CVSO 30 over three years in a total of 144 nights and detected 33 fading events. In two more seasons we carried out follow-up observations with three telescopes. We can confirm that there is a change in the shape of the fading event between different observations and that the fading event even disappears and reappears. A total of 38 fading event light curves were simultaneously modelled. We derived the planetary, stellar, and geometrical properties of the system and found them slightly smaller but in agreement with the values from the discovery paper. The period of the fading event was found to be 1.36 s shorter and 100 times more precise than the previous published value. If CVSO 30 b would be a giant planet on a precessing orbit, which we cannot confirm, yet, the precession period may be shorter than previously thought. But if confirmed as a planet it would be the youngest transiting planet ever detected and will provide important constraints on planet formation and migration time-scales.

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arXiv2016

TAPAS IV. TYC 3667-1280-1 b - the most massive red giant star hosting a warm Jupiter

We present the latest result of the TAPAS project that is devoted to intense monitoring of planetary candidates that are identified within the PennState-Toruń planet search. We aim to detect planetary systems around evolved stars to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidence of star-planet interaction processes. The paper is based on precise radial velocity measurements: 13 epochs collected over 1920 days with the Hobby-Eberly Telescope and its High-Resolution Spectrograph, and 22 epochs of ultra-precise HARPS-N data collected over 961 days. We present a warm-Jupiter ($T_{eq}=1350 K$, $m_{2} sin i=5.4\pm$0.4$M_{J}$) companion with an orbital period of 26.468 days in a circular ($e=0.036$) orbit around a giant evolved ($\log g=3.11\pm0.09$, $R=6.26\pm0.86R_{\odot}$) star with $M_{\star}=1.87\pm0.17M_{\odot}$. This is the most massive and oldest star found to be hosting a close-in giant planet. Its proximity to its host ($a=0.21au$) means that the planet has a $13.9\pm2.0\%$ probability of transits; this calls for photometric follow-up study. This massive warm Jupiter with a near circular orbit around an evolved massive star can help set constraints on general migration mechanisms for warm Jupiters and, given its high equilibrium temperature, can help test energy deposition models in hot Jupiters.

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arXiv2016

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

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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arXiv2016

Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b

Most hot Jupiters are expected to spiral in towards their host stars due to transfering of the angular momentum of the orbital motion to the stellar spin. Their orbits can also precess due to planet-star interactions. Calculations show that both effects could be detected for the very-hot exoplanet WASP-12 b using the method of precise transit timing over a timespan of the order of 10 yr. We acquired new precise light curves for 29 transits of WASP-12 b, spannning 4 observing seasons from November 2012 to February 2016. New mid-transit times, together with literature ones, were used to refine the transit ephemeris and analyse the timing residuals. We find that the transit times of WASP-12 b do not follow a linear ephemeris with a 5 sigma confidence level. They may be approximated with a quadratic ephemeris that gives a rate of change 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 10^5 that is comparable to theoretical predictions for Sun-like stars. We also consider 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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arXiv2016

Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. III. HD 5583 and BD+15 2375 - two cool giants with warm companions

Evolved stars are crucial pieces to understand the dependency of the planet formation mechanism on the stellar mass and to explore deeper the mechanism involved in star-planet interactions. Over the past ten years, we have monitored about 1000 evolved stars for radial velocity variations in search for low-mass companions under the Penn State - Torun Centre for Astronomy Planet Search program with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision measurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo under the TAPAS project. We aim to detect planetary systems around evolved stars to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidence of star-planet interaction processes. For HD 5583 we obtained 14 epochs of precise RV measurements collected over 2313 days with the Hobby-Eberly Telescope (HET), and 22 epochs of ultra-precise HARPS-N data collected over 976 days. For BD+15 2375 we collected 24 epochs of HET data over 3286 days and 25 epochs of HARPS-S data over 902 days. We report the discovery of two planetary mass objects orbiting two evolved Red Giant stars: HD~5583 has a m sin i = 5.78 M$_{J}$ companion at 0.529~AU in a nearly circular orbit (e=0.076), the closest companion to a giant star detected with the RV technique, and BD+15~2735 that with a m sin i= 1.06 M$_{J}$ holds the record of the lightest planet found so far orbiting an evolved star (in a circular e=0.001, 0.576~AU orbit). These are the third and fourth planets found within the TAPAS project, a HARPS-N monitoring of evolved planetary systems identified with the Hobby-Eberly Telescope.

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arXiv2015

The GAPS Programme with HARPS-N at TNG VIII: Observations of the Rossiter-McLaughlin effect and characterisation of the transiting planetary systems HAT-P-36 and WASP-11/HAT-P-10

We determine the true and the projected obliquity of HAT-P-36 and WASP-11/HAT-P-10 systems, respectively, which are both composed of a relatively cool star and a hot-Jupiter planet. Thanks to the high-resolution spectrograph HARPS-N, we observed the Rossiter-McLaughlin effect for both the systems by acquiring precise radial-velocity measurements during planetary transit events. We also present photometric observations comprising six light curves covering five transit events, obtained using three medium-class telescopes and the telescope-defocussing technique. One transit of WASP-11/HAT-P-10 was followed simultaneously from two observatories. The three transit light curves of HAT-P-36b show anomalies that are attributable to starspot complexes on the surface of the parent star, in agreement with the analysis of its spectra that indicate a moderate activity. By analysing the complete HATNet data set of HAT-P-36, we estimated the stellar rotation period by detecting a periodic photometric modulation in the light curve caused by star spots, obtaining Prot=15.3 days, which implies that the inclination of the stellar rotational axis with respect to the line of sight is 65 degree. We used the new spectroscopic and photometric data to revise the main physical parameters and measure the sky-projected misalignment angle of the two systems. We found λ=-14 degree for HAT-P-36 and λ=7 degree for WASP-11/HAT-P-10, indicating in both cases a good spin-orbit alignment. In the case of HAT-P-36, we also measured its real obliquity, which turned out to be 25 degrees.

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arXiv2015

WASP-14 b: Transit Timing analysis of 19 light curves

Although WASP-14 b is one of the most massive and densest exoplanets on a tight and eccentric orbit, it has never been a target of photometric follow-up monitoring or dedicated observing campaigns. We report on new photometric transit observations of WASP-14 b obtained within the framework of "Transit Timing Variations @ Young Exoplanet Transit Initiative" (TTV@YETI). We collected 19 light-curves of 13 individual transit events using six telescopes located in five observatories distributed in Europe and Asia. From light curve modelling, we determined the planetary, stellar, and geometrical properties of the system and found them in agreement with the values from the discovery paper. A test of the robustness of the transit times revealed that in case of a non-reproducible transit shape the uncertainties may be underestimated even with a wavelet-based error estimation methods. For the timing analysis we included two publicly available transit times from 2007 and 2009. The long observation period of seven years (2007-2013) allowed us to refine the transit ephemeris. We derived an orbital period 1.2 s longer and 10 times more precise than the one given in the discovery paper. We found no significant periodic signal in the timing-residuals and, hence, no evidence for TTV in the system.

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arXiv2015

No variations in transit times for Qatar-1 b

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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arXiv2015

Three red giants with substellar-mass companions

We present three giant stars from the ongoing Penn State-Toruń Planet Search with the Hobby-Eberly Telescope, which exhibit radial velocity variations that point to a presence of planetary --mass companions around them. BD+49 828 is a $M=1.52 \pm 0.22$ $M_{\odot}$ K0 giant with a $m sini$=$1.6^{+0.4}_{-0.2}$ $M_{J}$ minimum mass companion in $a=4.2^{+0.32}_{-0.2}$ AU ($2590^{+300}_{-180}$d), $e=0.35^{+0.24}_{-0.10}$ orbit. HD 95127, a log$L$/$L_{\odot}$=$2.28 \pm 0.38$, $R = 20\pm 9$ $R_{\odot}$, $M=1.20 \pm 0.22$ $M_{\odot}$ K0 giant has a $m sini$=$5.01^{+0.61}_{-0.44}$ $M_{J}$ minimum mass companion in $a=1.28^{+0.01}_{-0.01}$ AU ($482^{+5}_{-5}$d), $e=0.11^{+0.15}_{-0.06}$ orbit. Finally, HD 216536, is a $M=1.36 \pm 0.38$ $M_{\odot}$ K0 giant with a $m sin i=1.47^{+0.20}_{-0.12}$ $M_{J}$ minimum mass companion in $a=0.609^{+0.002}_{-0.002}$ AU ($148.6^{+0.7}_{-0.7}$d), $e=0.38^{+0.12}_{-0.10}$ orbit. Both, HD 95127 b and HD 216536 b in their compact orbits, are very close to the engulfment zone and hence prone to ingestion in the near future. BD+49 828 b is among the longest period planets detected with the radial velocity technique until now and it will remain unaffected by stellar evolution up to a very late stage of its host. We discuss general properties of planetary systems around evolved stars and planet survivability using existing data on exoplanets in more detail.

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arXiv2015

On the GJ 436 planetary system

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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arXiv2014

Tracking Advanced Planetary Systems with HARPS-N (TAPAS). I. A multiple planetary system around the red giant star TYC 1422-614-1

Context. Stars that have evolved-off the Main Sequence are crucial in expanding the frontiers of knowledge on exoplanets toward higher stellar masses, and to constrain star-planet interaction mechanisms. These stars, however suffer from intrinsic activity that complicates the interpretation of precise radial velocity measurement and are often avoided in planet searches. We have, over the last 10 years, monitored about 1000 evolved stars for radial velocity variations in search for low-mass companions under the Penn State - Toruń Centre for Astronomy Planet Search with the Hobby-Eberly Telescope. Selected prospective candidates that required higher RV precision meassurements have been followed with HARPS-N at the 3.6 m Telescopio Nazionale Galileo. Aims. To detect planetary systems around evolved stars, to be able to build sound statistics on the frequency and intrinsic nature of these systems, and to deliver in-depth studies of selected planetary systems with evidences of star-planet interaction processes. Methods. We have obtained for TYC 1422-614-1 69 epochs of precise radial velocity measurements collected over 3651 days with the Hobby-Eberly Telescope, and 17 epochs of ultra precise HARPS-N data collected over 408 days. We have complemented these RV data with photometric time-series from the All Sky Automatic Survey archive. Results. We report the discovery of a multiple planetary system around the evolved K2 giant star TYC 1422-614-1. The system orbiting the 1.15 M$_\odot$ star is composed of a planet with mass m$sin i$=2.5 M$_J$ in a 0.69 AU orbit, and a planet/brown dwarf with m$sin i$=10 M$_J$ in a 1.37 AU orbit. The multiple planetary system orbiting TYC 1422-614-1 is the first finding of the TAPAS project, a HARPS-N monitoring of evolved planetary systems identified with the Hobby-Eberly Telescope.

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arXiv2014

Transit timing of TrES-2: a combined analysis of ground- and space-based photometry

Homogeneous observations and careful analysis of transit light curves can lead to the identification of transit timing variations (TTVs). TrES-2 is one of few exoplanets, which offer the matchless possibility to combine long-term ground-based observations with continuous satellite data. Our research aimed at the search for TTVs that would be indicative of perturbations from additional bodies in the system. We also wanted to refine the system parameters and the orbital elements. We obtained 44 ground-based light curves of 31 individual transit events of TrES-2. Eight 0.2 - 2.2-m telescopes located at six observatories in Germany, Poland and Spain were used. In addition, we analysed 18 quarters (Q0-Q17) of observational data from NASA's space telescope Kepler including 435 individual transit events and 11 publicly available ground-based light curves. Assuming different limb darkening (LD) laws we performed an analysis for all light curves and redetermined the parameters of the system. We also carried out a joint analysis of the ground- and space-based data. The long observation period of seven years (2007-2013) allowed a very precise redetermination of the transit ephemeris. For a total of 490 transit light curves of TrES-2, the time of transit mid-point was determined. The transit times support neither variations on long time-scale nor on short time-scales. The nearly continuous observations of Kepler show no statistically significant increase or decrease in the orbital inclination i and the transit duration D. Only the transit depth shows a slight increase which could be an indication of an increasing stellar activity. In general, system parameters obtained by us were found to be in agreement with previous studies but are the most precise values to date.

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arXiv2014

Transit Timing Analysis in the HAT-P-32 system

We present the results of 45 transit observations obtained for the transiting exoplanet HAT-P-32b. The transits have been observed using several telescopes mainly throughout the YETI network. In 25 cases, complete transit light curves with a timing precision better than $1.4\:$min have been obtained. These light curves have been used to refine the system properties, namely inclination $i$, planet-to-star radius ratio $R_\textrm{p}/R_\textrm{s}$, and the ratio between the semimajor axis and the stellar radius $a/R_\textrm{s}$. First analyses by Hartman et al. (2011) suggest the existence of a second planet in the system, thus we tried to find an additional body using the transit timing variation (TTV) technique. Taking also literature data points into account, we can explain all mid-transit times by refining the linear ephemeris by 21ms. Thus we can exclude TTV amplitudes of more than $\sim1.5$min.

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arXiv2014

Investigation of a transiting planet candidate in Trumpler 37: an astrophysical false positive eclipsing spectroscopic binary star

We report our investigation of the first transiting planet candidate from the YETI project in the young (~4 Myr old) open cluster Trumpler 37. The transit-like signal detected in the lightcurve of the F8V star 2M21385603+5711345 repeats every 1.364894+/-0.000015 days, and has a depth of 54.5+/-0.8 mmag in R. Membership to the cluster is supported by its mean radial velocity and location in the color-magnitude diagram, while the Li diagnostic and proper motion are inconclusive in this regard. Follow-up photometric monitoring and adaptive optics imaging allow us to rule out many possible blend scenarios, but our radial-velocity measurements show it to be an eclipsing single-lined spectroscopic binary with a late-type (mid-M) stellar companion, rather than one of planetary nature. The estimated mass of the companion is 0.15-0.44 solar masses. The search for planets around very young stars such as those targeted by the YETI survey remains of critical importance to understand the early stages of planet formation and evolution.

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arXiv2014

Revisiting parameters for the WASP-1 planetary system

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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arXiv2013

Constraints on a second planet in the WASP-3 system

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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arXiv2013

Planetary-mass companions to the K-giants BD+15 2940 and HD 233604

We report the discovery of planetary-mass companions to two red giants by the ongoing Penn State - Torun Planet Search (PTPS) conducted with the 9.2-m Hobby-Eberly Telescope. The 1.1 Ms K0-giant, BD+15 2940, has a 1.1 Mj minimum mass companion orbiting the star at a 137.5-day period in a 0.54 AU orbit what makes it the closest - in planet around a giant and possible subject of engulfment as the consequence of stellar evolution. HD 233604, a 1.5 Ms K5-giant, is orbited by a 6.6 Mj minimum mass planet which has a period of 192 days and a semi-major axis of only 0.75 AU making it one of the least distant planets to a giant star. The chemical composition analysis of HD 233604 reveals a relatively high 7Li abundance which may be a sign of its early evolutionary stage or recent engulfment of another planet in the system. We also present independent detections of planetary-mass companions to HD 209458 and HD 88133, and stellar activity-induced RV variations in HD 166435, as part of the discussion of the observing and data analysis methods used in the PTPS project.

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arXiv2013

Follow-up photometry of TrES-3

We present new observations of the transiting system TrES-3 obtained from 2009 to 2011 at several observatories. The orbital parameters of the system were re- determined and a new linear ephemeris was calculated. The best quality light curve was used for light curve analysis, an other datasets were used to determine mid-transit times, Tc, and study transit time variation (TTV). For planet parameter determination we used two independent codes and finally, we concluded that our parameters are in agreement with previous studies. Based on our observations, we determined 14 mid-transit times. Together with published Tc we found that the timing residuals showed no significant deviation from the linear ephemeris. We concluded that a periodic TTV signal with an amplitude greater than 1 minute over a 4-year time span seems to be unlikely. Our analysis of an upper mass limit allows us to exclude an additional Earth-mass planet close to inner 3:1, 2:1, and 5:3 and outer 3:5, 1:2, and 1:3 mean-motion resonances. Using the long-term integration and applying the method of maximum eccentricity, the region from 0.015 au to 0.05 au was found unstable and the region beyond the 0.05 au was found to have a chaotic behaviour and its depletion increases with increasing values of the initial eccentricity as well as inclination.

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