arXiv subjects

St. Raetz

Publications and source records attributed to St. Raetz.

At least 19 recordsLinked to original sources

arXiv2024

Long-term stellar activity of M dwarfs: A combined K2 and TESS study of two early M-type stars

Studies of the rotation and activity of M type stars are essential to enhance our understanding of stellar dynamos and angular momentum evolution. Using the outstanding photometric capabilities of space telescopes rotation signals even with low amplitudes can be investigated in up to now unrivaled detail. By combining data of K2 and the TESS prime mission the star spot activity of M dwarfs can be monitored on half a decade timescale. In the framework of our study on the rotation-activity relation for bright and nearby M dwarfs we also aim at an investigation of the long-term activity. While K2 was observing fields distributed around the ecliptic plane, the TESS prime mission was oriented along a line of ecliptic longitude with one camera centered on an ecliptic pole. Due to these different observing strategies, the overlap between K2 and the TESS prime mission is marginal. However, 45 stars from our sample were observed with both missions of which two early M-type stars that fulfill our selection criteria, EPIC 202059229 and EPIC 245919787, were analyzed in more detail. We found that for both stars the rotation period did not change while the rotational phase did change for EPIC 245919787 by ~0.2. The amplitude of the spot induced variability changed for both stars but more significant for EPIC 245919787. By comparing the cumulative flare frequency distributions we found that the flare activity for EPIC 202059229 is unchanged while it slightly changes for EPIC 245919787 between the K2 and TESS epochs. Using a combination of light curves from K2 and TESS that span a baseline up to 4.5 years we could measure significant differential rotation for EPIC 245919787. Furthermore, we show that combining missions like K2 and TESS is a promising method for detecting stellar activity cycles.

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arXiv2024

Transitions in magnetic behavior at the substellar boundary

We aim at advancing our understanding of magnetic activity and the underlying dynamo mechanism at the end of the main-sequence. To this end, we collected simultaneous X-ray and radio observations for a sample of M7-L0 dwarfs using XMM-Newton jointly with the JVLA and the ATCA. We also included data from the all-sky surveys of eROSITA on board the Russian Spektrum-Roentgen-Gamma mission (SRG) and rotation periods from TESS together with an archival compilation of X-ray and radio data for UCDs from the literature. We limit the sample to objects with rotation period <1d, focusing on the study of a transition in magnetic behavior suggested by a drastic change in the radio detection rate at vsini \approx 38 km/s. We compiled the most up-to-date radio/X-ray luminosity relation for 26 UCDs with rotation periods lower than 1d, finding that rapid rotators lie the furthest away from the G\"udel-Benz relation previously studied for earlier-type stars. Radio bursts are mainly experienced by very fast UCDs, while X-ray flares are seen along the whole range of rotation. We examined the L_{\rm x}/L_{\rm bol} vs P_{\rm rot} relation, finding no evident relation between the X-ray emission and rotation, reinforcing previous speculations on a bimodal dynamo across late-type dwarfs. One radio-detected object has a rotation period consistent with the range of auroral bursting sources; while it displays moderately circularly polarized emission. A radio flare from this object is interpreted as gyrosynchrotron emission, and it displays X-ray and optical flares. We also found a slowly rotating apparent auroral emitter, that is also one of the X-ray brightest radio-detected UCDs. We speculate that this UCD is experiencing a transition of its magnetic behavior since it produces signatures expected from higher mass M dwarfs along with emerging evidence of auroral emission.

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arXiv2023

Complete X-ray census of Mdwarfs in the solar Neighborhood I. GJ 745 AB: Coronal-hole Stars in the 10 pc Sample

We have embarked in a systematic study of the X-ray emission in a volume-limited sample of M dwarf stars, in order to explore the full range of activity levels present in their coronae and, thus, to understand the conditions in their outer atmospheres and their possible impact on the circumstellar environment. We identify in a recent catalog of the Gaia objects within 10 pc from the Sun all the stars with spectral type between M0 and M4, and search systematically for X-ray measurements of this sample. To this end, we use both archival data (from ROSAT, XMM-Newton, and from the ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Russian Spektrum-Roentgen-Gamma mission) and our own dedicated XMM-Newton observations. To make inferences on the properties of the M dwarf corona we compare the range of their observed X-ray emission levels to the flux radiated by the Sun from different types of magnetic structures: coronal holes, background corona, active regions and cores of active regions. At the current state of our project, with more than 90\% of the 10pc M dwarf sample observed in X-rays, only GJ 745 A has no detection. With an upper limit luminosity of log Lx [erg/s] < 25.4 and an X-ray surface flux of log FX,SURF [erg/cm^2/s] < 3.6 GJ 745 A defines the lower boundary of the X-ray emission level of M dwarfs. Together with its companion GJ 745 B, GJ 745 A it is the only star in this volume-complete sample located in the range of FX,SURF that corresponds to the faintest solar coronal structures, the coronal holes. The ultra-low X-ray emission level of GJ 745 B (log Lx [erg/s] = 25.6 and log FX,SURF [erg/cm^2/s] = 3.8) is entirely attributed to flaring activity, indicating that, while its corona is dominated by coronal holes, at least one magnetically active structure is present and determines the total X-ray brightness and the coronal temperature of the star.

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arXiv2022

The Great Flare of 2021 November 19 on AD Leo. Simultaneous XMM-Newton and TESS observations

We present a detailed analysis of a superflare on the active M dwarf star AD Leonis. The event presents a rare case of a stellar flare observed simultaneously in X-rays (with XMM-Newton) and in optical (with the Transiting Exoplanet Survey Satellite, TESS). The radiated energy both in the 0.2-12 keV X-ray band ($1.26 \pm 0.01 \cdot 10^{33}$ erg) and the bolometric value ($E_{F,bol} = 5.57 \pm 0.03 \cdot 10^{33}$ erg) put this event at the lower end of the superflare class. The exceptional photon statistics deriving from the proximity of AD Leo has enabled measurements in the 1-8 AA GOES band for the peak flux (X1445 class) and integrated energy ($E_{F,GOES} = 4.30 \pm 0.05 \cdot 10^{32}$ erg), making possible a direct comparison with data on flares from our Sun. From extrapolations of empirical relations for solar flares we estimate that a proton flux of at least $10^5\,{cm^{-2} s^{-1} sr^{-1}}$ accompanied the radiative output. With a time lag of 300s between the peak of the TESS white-light flare and the GOES band flare peak as well as a clear Neupert effect this event follows very closely the standard (solar) flare scenario. Time-resolved spectroscopy during the X-ray flare reveals, in addition to the time evolution of plasma temperature and emission measure, a temporary increase of electron density and elemental abundances, and a loop that extends in the corona by 13% of the stellar radius ($4 \cdot 10^9$ cm). Independent estimates of the footprint area of the flare from TESS and XMM-Newton data suggest a high temperature of the optical flare (25000 K), but we consider more likely that the optical and X-ray flare areas represent physically distinct regions in the atmosphere of AD Leo.

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arXiv2022

Flares and rotation of M dwarfs with habitable zones accessible to TESS planet detections

We characterize the magnetic activity of M dwarfs to provide the planet community with information on the energy input from the star; in particular, in addition to the frequency of optical flares directly observed with TESS, we aim at estimating the corresponding X-ray flare frequencies, making use of the small pool of known events observed simultaneously in both wavebands. We identified 112 M dwarfs with a TESS magnitude <= 11.5 for which TESS can probe the full habitable zone for transits. These 112 stars have 1276 two-minute cadence TESS light curves from the primary mission, which we searched for rotational modulation and flares. We study the link between rotation and flares and between flare properties, for example the flare amplitude-duration relation and cumulative flare energy frequency distributions (FFDs). Assuming that each optical flare is associated with a flare in the X-ray band, and making use of published simultaneous Kepler/K2 and XMM-Newton flare studies, we estimate the X-ray energy released by our detected TESS flare events. Our calibration also involves the relation between flare energies in the TESS and K2 bands. We detected more than 2500 optical flare events on a fraction of about 32% of our targets and found reliable rotation periods only for 12 stars, which is a fraction of about 11%. For these 12 targets, we present cumulative FFDs and FFD power law fits. We construct FFDs in the X-ray band by calibrating optical flare energies to the X-rays. In the absence of directly observed X-ray FFDs for main-sequence stars, our predictions can serve for estimates of the high-energy input to the planet of a typical fast-rotating early- or mid-M dwarf.

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arXiv2022

YETI follow-up observations of the T Tauri star CVSO30 with transit-like dips

The T Tauri star CVSO30, also known as PTFO8-8695, was studied intensively with ground based telescopes as well as with satellites over the last decade. It showed a variable light curve with additional repeating planetary transit-like dips every ~0.8h. However, these dimming events changed in depth and duration since their discovery and from autumn 2018 on, they were not even present or near the predicted observing times. As reason for the detected dips and their changes within the complex light curve, e.g. a disintegrating planet, a circumstellar dust clump, stellar spots, possible multiplicity and orbiting clouds at a Keplerian co-rotating radius were discussed and are still under debate. In this paper, we present additional optical monitoring of CVSO30 with the meter class telescopes of the Young Exoplanet Transit Initiative in Asia and Europe over the last seven years and characterize CVSO30 with the new Early Data Release 3 of the ESA Gaia Mission. As a result, we describe the evolution of the dimming events in the optical wavelength range since 2014 and present explanatory approaches for the observed variabilities. We conclude that orbiting clouds of gas at a Keplerian co-rotating radius are the most promising scenario to explain most changes in CVSO30's light curve.

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arXiv2022

First eROSITA-TESS results for M dwarfs: Mass dependence of the X-ray activity rotation relation and an assessment of sensitivity limits

We present a study of the activity-rotation relation for M dwarf stars, using new X-ray data from the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG), combined with photometric rotation periods from the Transiting Exoplanet Survey Satellite (TESS). The stars used in this work are selected from the superblink proper motion catalog of nearby M dwarfs. We study the 135 stars with both a detection in the first eROSITA survey (eRASS1) and a rotation period measurement from TESS jointly with the sample of 197 superblink M dwarfs re-adapted from our previous work. We fit the activity-rotation relation for stars with rotation periods shorter than ~10 d (saturated regime) using three mass bins. The surprising positive slope for stars in our lowest mass bin ($M_{\star} \leq 0.4 {\rm M_\odot}$) is due to a paucity of stars with intermediate rotation periods (~ 1-10 d), probably caused by fast period evolution. The much higher fraction of eRASS1 detections compared to stars that have also rotation periods from TESS shows that eROSITA is also sensitive for slower rotating M dwarfs that are in the unsaturated regime with periods inaccessible to TESS.

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arXiv2021

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

We present the first study of nearby M dwarfs with the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG). To this end we extracted the Gaia DR2 data for the ~9000 nearby M dwarfs in the superblink proper motion catalog and calculated their stellar parameters from empirical relations with optical-IR colors. We cross-matched this catalog with the eROSITA Final Equatorial Depth Survey (eFEDS) and the first eROSITA all-sky survey (eRASS1). Our sample consists of 704 stars (SpT = K5-M7). This unprecedented data base for X-ray emitting M dwarfs allowed to quantitatively constrain the mass dependence of the X-ray luminosity, and to determine the change in the activity level with respect to pre-main-sequence stars. We also combined these data with the Transiting Exoplanet Survey Satellite (TESS) observations that are available for 501 of 704 X-ray detected M dwarfs and determined the rotation period for 180 of them. With the joint eROSITA-TESS sample, and combining it with our historical X-ray and rotation data for M dwarfs, we examined the mass dependence in the saturated regime of the rotation-activity relation. A first comparison of eROSITA hardness ratios and spectra shows that 65% of our X-ray detected M dwarfs have coronal temperatures of $\sim 0.5$ keV. We investigated their long-term X-ray variability by comparing the eRASS1 and ROSAT all-sky survey (RASS) measurements. Evidence for X-ray flares is found in various parts of our analysis: directly from inspection of the eFEDS light curves, in the relation between RASS and eRASS1 X-ray luminosities, and in stars displaying X-ray emission hotter than the bulk of the sample according to the hardness ratios. Finally, we point out the need of X-ray spectroscopy for more M dwarfs to study the coronal temperature-luminosity relation, not well constrained by our eFEDS results.

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arXiv2020

The rotation-activity relation of M dwarfs: From K2 to TESS and PLATO

Studies of the rotation-activity relation of late-type stars are essential to enhance our understanding of stellar dynamos and angular momentum evolution. We study the rotation-activity relation with K2 for M dwarfs where it is especially poorly understood. We analyzed the light curves of all bright and nearby M dwarfs form the Superblink proper motion catalog that were in the K2 field of view. For a sample of 430 M dwarfs observed in campaigns C0-C19 in long cadence mode we determined the rotation period and a wealth of activity diagnostics. Our study of the rotation-activity relation based on photometric activity indicators confirmed the previously published abrupt change of the activity level at a rotation period of ~10d. Our more than three times larger sample increases the statistical significance of this finding.

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arXiv2020

Relation of X-ray activity and rotation in M dwarfs and predicted time-evolution of the X-ray luminosity

We present a sample of 14 M dwarf stars observed with XMM-Newton and Chandra, for which we also computed rotational periods from Kepler Two-Wheel (K2) Mission light curves. We compiled X-ray and rotation data from the literature and homogenized all data sets to provide the largest uniform sample of M dwarfs (302 stars) for X-ray activity and rotation studies to date. We then fit the relation between $L_{\rm x} - P_{\rm rot}$ using three different mass bins to separate partially and fully convective stars. We found a steeper slope in the unsaturated regime for fully convective stars and a nonconstant $L_{\rm x}$ level in the saturated regime for all masses. In the $L_{\rm x}/L_{\rm bol}-R_{\rm O}$ space we discovered a remarkable double gap that might be related to a discontinuous period evolution. Then we combined the evolution of $P_{\rm rot}$ predicted by angular momentum evolution models with our new results on the empirical $L_{\rm x} - P_{\rm rot}$ relation to provide an estimate for the age decay of X-ray luminosity. We compare predictions of this relationship with the actual X-ray luminosities of M stars with known ages from 100 Myr to a few billion years. We find remarkably good agreement between the predicted $L_{\rm x}$ and the observed values for partially convective stars. However, for fully convective stars at ages of a few billion years, the constructed $L_{\rm x}-$age relation overpredicts the X-ray luminosity because the angular momentum evolution model underpredicts the rotation period of these stars. Finally, we examine the effect of different parameterizations for the Rossby number ($R_{\rm O}$) on the shape of the activity-rotation relation in $L_{\rm x}/L_{\rm bol}-R_{\rm O}$ space, and we find that the slope in the unsaturated regime and the location of the break point of the dual power-law depend sensitively on the choice of $R_{\rm O}$.

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arXiv2020

Rotation-activity relations and flares of M dwarfs with K2 long- and short-cadence data

Using light curves obtained by the K2 mission, we study the relation between stellar rotation and magnetic activity with special focus on stellar flares. Our sample comprises 56 bright and nearby M dwarfs observed by K2 during campaigns C0-C18 in long- and short-cadence mode. We derive rotation periods for 46 M dwarfs and measure photometric activity indicators such as amplitude of the rotational signal, standard deviation of the light curves, and the basic flare properties (flare rate, flare energy, flare duration, and flare amplitude). We found 1662 short-cadence flares, 363 of which have a long-cadence counterpart with flare energies of up to $5.6\cdotp10^{34}$erg. The flare amplitude, duration, and frequency derived from the short-cadence light curves differ significantly from those derived from the long-cadence data. The analysis of the short-cadence light curves results in a flare rate that is 4.6 times higher than the long-cadence data. We confirm the abrupt change in activity level in the rotation-activity relation at a critical period of ~10d when photometric activity diagnostics are used. This change is most drastic in the flare duration and frequency for short-cadence data. Our flare studies revealed that the highest flare rates are not found among the fastest rotators and that stars with the highest flare rates do not show the most energetic flares. We found that the superflare frequency ($E\geq5\cdotp10^{34}$erg) for the fast-rotating M stars is twice higher than for solar like stars in the same period range. By fitting the cumulative FFD, we derived a power-law index of $\alpha=1.84 \pm 0.14$, consistent with previous M dwarf studies and the value found for the Sun.

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arXiv2019

CoRoT-18 b: Analysis of high-precision transit light curves with starspot features

When a planet occults a spotty area on a stellar surface, the flux increases and a characteristic feature in a light curve - a bump - is observed. Among the planets detected by the CoRoT-mission CoRoT-18 is especially interesting as it exhibited spot crossings that we have analysed in detail. We used four ground-based observations obtained at a 1.5-m telescope in Spain and the 13 available CoRoT-transits to refine and constrain stellar, planetary and geometrical parameters of the system. We found that the derived physical properties slightly deviate from the previously published values, most likely due to the different treatment of the stellar activity. Following a spot over several transits enabled us to measure the stellar rotation period and the spin-orbit alignment. Our derived values of Prot=5.19 +/- 0.03 d and Lambda=6 +/- 13 deg are in agreement with the literature values that were obtained with other methods. Although we cannot exclude a very old age for CoRoT-18, our observations support the young star hypothesis and, hence, yield constraints on the time-scale of planet formation and migration.

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arXiv2019

Diagnosing the Clumpy Protoplanetary Disk of the UXor Type Young Star GM Cephei

UX Orionis stars (UXors) are Herbig Ae/Be or T Tauri stars exhibiting sporadic occultation of stellar light by circumstellar dust. GM\,Cephei is such a UXor in the young ($\sim4$~Myr) open cluster Trumpler\,37, showing prominent infrared excess, emission-line spectra, and flare activity. Our photometric monitoring (2008--2018) detects (1)~an $\sim$3.43~day period, likely arising from rotational modulation by surface starspots, (2)~sporadic brightening on time scales of days due to accretion, (3)~irregular minor flux drops due to circumstellar dust extinction, and (4)~major flux drops, each lasting for a couple of months with a recurrence time, though not exactly periodic, of about two years. The star experiences normal reddening by large grains, i.e., redder when dimmer, but exhibits an unusual "blueing" phenomenon in that the star turns blue near brightness minima. The maximum extinction during relatively short (lasting $\leq 50$~days) events, is proportional to the duration, a consequence of varying clump sizes. For longer events, the extinction is independent of duration, suggestive of a transverse string distribution of clumps. Polarization monitoring indicates an optical polarization varying $\sim3\%$--8$\%$, with the level anticorrelated with the slow brightness change. Temporal variation of the unpolarized and polarized light sets constraints on the size and orbital distance of the circumstellar clumps in the interplay with the young star and scattering envelope. These transiting clumps are edge-on manifestations of the ring- or spiral-like structures found recently in young stars with imaging in infrared of scattered light, or in submillimeter of thermalized dust emission.

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arXiv2018

Transit analysis of the CoRoT-5, CoRoT-8, CoRoT-12, CoRoT-18, CoRoT-20, and CoRoT-27 systems with combined ground- and space-based photometry

We have initiated a dedicated project to follow-up with ground-based photometry the transiting planets discovered by CoRoT in order to refine the orbital elements, constrain their physical parameters and search for additional bodies in the system. From 2012 September to 2016 December we carried out 16 transit observations of six CoRoT planets (CoRoT-5b, CoRoT-8b, CoRoT-12b, CoRoT-18b, CoRoT-20b, and CoRoT-27b) at three observatories located in Germany and Spain. These observations took place between 5 and 9 yr after the planet's discovery, which has allowed us to place stringent constraints on the planetary ephemeris. In five cases we obtained light curves with a deviation of the mid-transit time of up to ~115min from the predictions. We refined the ephemeris in all these cases and reduced the uncertainties of the orbital periods by factors between 1.2 and 33. In most cases our determined physical properties for individual systems are in agreement with values reported in previous studies. In one case, CoRoT-27b, we could not detect any transit event in the predicted transit window.

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arXiv2017

On the nature of the candidate T-Tauri star V501 Aurigae

We report new multi-colour photometry and high-resolution spectroscopic observations of the long-period variable V501 Aur, previously considered to be a weak-lined T-Tauri star belonging to the Taurus-Auriga star-forming region. The spectroscopic observations reveal that V501 Aur is a single-lined spectroscopic binary system with a 68.8-day orbital period, a slightly eccentric orbit (e ~ 0.03), and a systemic velocity discrepant from the mean of Taurus-Auriga. The photometry shows quasi-periodic variations on a different, ~55-day timescale that we attribute to rotational modulation by spots. No eclipses are seen. The visible object is a rapidly rotating (vsini ~ 25 km/s) early K star, which along with the rotation period implies it must be large (R > 26.3 Rsun), as suggested also by spectroscopic estimates indicating a low surface gravity. The parallax from the Gaia mission and other independent estimates imply a distance much greater than the Taurus-Auriga region, consistent with the giant interpretation. Taken together, this evidence together with a re-evaluation of the LiI~$\lambda$6707 and H$\alpha$ lines shows that V501 Aur is not a T-Tauri star, but is instead a field binary with a giant primary far behind the Taurus-Auriga star-forming region. The large mass function from the spectroscopic orbit and a comparison with stellar evolution models suggest the secondary may be an early-type main-sequence star.

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arXiv2016

Long-Term Photometry of IC 348 with the YETI Network

We present long-term photometric observations of the young open cluster IC 348 with a baseline time-scale of 2.4 yr. Our study was conducted with several telescopes from the Young Exoplanet Transit Initiative (YETI) network in the Bessel $R$ band to find periodic variability of young stars. We identified 87 stars in IC 348 to be periodically variable; 33 of them were unreported before. Additionally, we detected 61 periodic non-members of which 41 are new discoveries. Our wide field of view was the key to those numerous newly found variable stars. The distribution of rotation periods in IC 348 has always been of special interest. We investigate it further with our newly detected periods but we cannot find a statistically significant bimodality. We also report the detection of a close eclipsing binary in IC 348 composed of a low-mass stellar component ($M \gtrsim 0.09\,\mathrm{M}_{\odot}$) and a K0 pre-main sequence star ($M \approx 2.7\,\mathrm{M}_{\odot}$). Furthermore, we discovered three detached binaries among the background stars in our field of view and confirmed the period of a fourth one.

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arXiv2016

Direct Imaging discovery of a second planet candidate around the possibly transiting planet host CVSO 30

We surveyed the 25 Ori association for direct-imaging companions. This association has an age of only few million years. Among other targets, we observed CVSO 30, which has recently been identified as the first T Tauri star found to host a transiting planet candidate. We report on photometric and spectroscopic high-contrast observations with the Very Large Telescope, the Keck telescopes, and the Calar Alto observatory. They reveal a directly imaged planet candidate close to the young M3 star CVSO 30. The JHK-band photometry of the newly identified candidate is at better than 1 sigma consistent with late-type giants, early-T and early-M dwarfs, and free-floating planets. Other hypotheses such as galaxies can be excluded at more than 3.5 sigma. A lucky imaging z' photometric detection limit z'= 20.5 mag excludes early-M dwarfs and results in less than 10 MJup for CVSO 30 c if bound. We present spectroscopic observations of the wide companion that imply that the only remaining explanation for the object is that it is the first very young (< 10 Myr) L-T-type planet bound to a star, meaning that it appears bluer than expected as a result of a decreasing cloud opacity at low effective temperatures. Only a planetary spectral model is consistent with the spectroscopy, and we deduce a best-fit mass of 4-5 Jupiter masses (total range 0.6-10.2 Jupiter masses). This means that CVSO 30 is the first system in which both a close-in and a wide planet candidate are found to have a common host star. The orbits of the two possible planets could not be more different: they have orbital periods of 10.76 hours and about 27000 years. The two orbits may have formed during a mutual catastrophic event of planet-planet scattering.

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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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