Szilard Csizmadia’s research while affiliated with German Aerospace Center (DLR) and other places

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Publications (36)


Figure 4. TESS and RBO light curves fitted by exoplanet jointly with RVs, with a focus on the transit region. Time is subtracted from the transit mid-time for each light curve. In all plots, the detrended data are in grey, and the model and 16%-84% confidence levels are in blue (for TESS transits) and red (for ground-based transits). In each upper plot, the point at x=-0.05 represents the median uncertainty in the photometric data.
Searching for GEMS: TOI-6383Ab, a giant planet transiting an M3-dwarf star in a binary system
  • Preprint
  • File available

September 2024

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25 Reads

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Shubham Kanodia

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Caleb I. Canas

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[...]

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We report on the discovery of a transiting giant planet around the 3500 K M3-dwarf star TOI-6383A located 172 pc from Earth. It was detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by a combination of ground-based follow-up photometry and precise radial velocity measurements. This planet has an orbital period of \sim1.791 days, mass of 1.040±\pm0.094 MJM_J and a radius of 1d.0080.033+0.036 RJ^{+0.036}_{-0.033} ~R_J, resulting in a mean bulk density of 1.260.17+0.18^{+0.18}_{-0.17} g cm3^{-3}. TOI-6383A has an M-dwarf companion star, TOI-6383B, which has a stellar effective temperature TeffT_{eff} \sim 3100 K and a projected orbital separation of 3100 AU. TOI-6383A is a low-mass dwarf star hosting a giant planet and is an intriguing object for planetary evolution studies due to its high planet-to-star mass ratio. This discovery is part of the \textit{Searching for Giant Exoplanets around M-dwarf Stars (GEMS)} Survey, intending to provide robust and accurate estimates of the occurrence of GEMS and the statistics on their physical and orbital parameters. This paper presents an interesting addition to the small number of confirmed GEMS, particularly notable since its formation necessitates massive, ust-rich protoplanetary discs and high accretion efficiency (>> 10\%).

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The PLATO Mission

June 2024

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267 Reads

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2 Citations

PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.


Modelling the Light Curves of Transiting Exomoons: a Zero-order Photodynamic Agent Added to the Transit and Light Curve Modeller

November 2023

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24 Reads

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1 Citation

Monthly Notices of the Royal Astronomical Society Letters

Despite the ever-growing number of exoplanets discovered and the extensive analyses carried out to find their potential satellites, only two exomoon candidates, Kepler-1625b-i and Kepler-1708 b-i, have been discovered to date. A considerable amount of effort has been invested in the development of algorithms for modelling, searching, and detecting exomoons in exoplanetary light curves. In this work, we incorporate moon handling capabilities into the state-of-the-art and publicly available code, the Transit and Light Curve Modeller (TLCM). The code is designed for the analysis of transiting exoplanet systems with the inclusion of a wavelet-based noise handling algorithm. Here we present an updated version of TLCM that is capable of modelling a planet-moon system on an elliptical orbit around its host, while also accounting for mutual eclipses between the two bodies – a so-called photodynamic model.


Figure 1. Phase-folded transit for all available TESS sectors. The TESS data is shown as black dots, the rolling median is shown as blue dots, and the final TLCM model is shown in red.
Figure 2. Top: RVs and the best-fit model for all of our data sets of WASP-106, showing the Keplerian orbit. The orbital phase is shown on the x-axis, with the radial velocity being shown on the y-axis. The different instruments are marked according to the legend, with "HARPS1" and "HARPS2" describing the first and second observation made with the HARPS spectrograph. The best-fit model is shown as the red curve. Bottom: residuals of our best-fitting model.
Figure 3. Same as Figure 2, but zoomed in on the Rossiter-McLaughlin anomaly.
Observation Log for Rossiter-McLaughlin Observations for our Target WASP-106 b
Radial Velocity Data of WASP-106 b
The Orbit of Warm Jupiter WASP-106 b is Aligned with its Star

September 2023

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39 Reads

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9 Citations

The Astronomical Journal

Understanding orbital obliquities, or the misalignment angles between a star’s rotation axis and the orbital axis of its planets, is crucial for unraveling the mechanisms of planetary formation and migration. In this study, we present an analysis of Rossiter–McLaughlin (RM) observations of the warm Jupiter exoplanet WASP-106 b. The high-precision radial velocity measurements were made with HARPS and HARPS-N during the transit of this planet. We aim to constrain the orientation of the planet’s orbit relative to its host star’s rotation axis. The RM observations are analyzed using a code which models the RM anomaly together with the Keplerian orbit given several parameters in combination with a Markov chain Monte Carlo implementation. We measure the projected stellar obliquity in the WASP-106 system for the first time and find λ = (−1 ± 11)°, supporting the theory of quiescent migration through the disk.


Company for the Ultra-high Density, Ultra-short Period Sub-Earth GJ 367 b: Discovery of Two Additional Low-mass Planets at 11.5 and 34 Days*

September 2023

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49 Reads

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18 Citations

The Astrophysical Journal Letters

GJ 367 is a bright ( V ≈ 10.2) M1 V star that has been recently found to host a transiting ultra-short period sub-Earth on a 7.7 hr orbit. With the aim of improving the planetary mass and radius and unveiling the inner architecture of the system, we performed an intensive radial velocity follow-up campaign with the HARPS spectrograph—collecting 371 high-precision measurements over a baseline of nearly 3 yr—and combined our Doppler measurements with new TESS observations from sectors 35 and 36. We found that GJ 367 b has a mass of M b = 0.633 ± 0.050 M ⊕ and a radius of R b = 0.699 ± 0.024 R ⊕ , corresponding to precisions of 8% and 3.4%, respectively. This implies a planetary bulk density of ρ b = 10.2 ± 1.3 g cm ⁻³ , i.e., 85% higher than Earth’s density. We revealed the presence of two additional non-transiting low-mass companions with orbital periods of ∼11.5 and 34 days and minimum masses of M c sin i c = 4.13 ± 0.36 M ⊕ and M d sin i d = 6.03 ± 0.49 M ⊕ , respectively, which lie close to the 3:1 mean motion commensurability. GJ 367 b joins the small class of high-density planets, namely the class of super-Mercuries, being the densest ultra-short period small planet known to date. Thanks to our precise mass and radius estimates, we explored the potential internal composition and structure of GJ 367 b, and found that it is expected to have an iron core with a mass fraction of 0.91 − 0.23 + 0.07 . How this iron core is formed and how such a high density is reached is still not clear, and we discuss the possible pathways of formation of such a small ultra-dense planet.


Summary of stellar properties of WASP-106.
Observation log for Rossiter-McLaughlin observations for our target WASP-106 b.
The Orbit of Warm Jupiter WASP-106 b is aligned with its Star

August 2023

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14 Reads

Understanding orbital obliquities, or the misalignment angles between a star's rotation axis and the orbital axis of its planets, is crucial for unraveling the mechanisms of planetary formation and migration. In this study, we present an analysis of Rossiter-McLaughlin (RM) observations of the warm Jupiter exoplanet WASP-106 b. The high-precision radial velocity measurements were made with HARPS and HARPS-N during the transit of this planet. We aim to constrain the orientation of the planet's orbit relative to its host star's rotation axis. The RM observations are analyzed using a code which models the RM anomaly together with the Keplerian orbit given several parameters in combination with a Markov chain Monte Carlo implementation. We measure the projected stellar obliquity in the WASP-106 system for the first time and find λ=(1±11)\lambda = (-1 \pm 11)^\circ, supporting the theory of quiescent migration through the disk.


Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days

July 2023

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27 Reads

GJ 367 is a bright (V \approx 10.2) M1 V star that has been recently found to host a transiting ultra-short period sub-Earth on a 7.7 hr orbit. With the aim of improving the planetary mass and radius and unveiling the inner architecture of the system, we performed an intensive radial velocity follow-up campaign with the HARPS spectrograph -- collecting 371 high-precision measurements over a baseline of nearly 3 years -- and combined our Doppler measurements with new TESS observations from sectors 35 and 36. We found that GJ 367 b has a mass of MbM_\mathrm{b} = 0.633 ±\pm 0.050 M_{\oplus} and a radius of RbR_\mathrm{b} = 0.699 ±\pm 0.024 R_{\oplus}, corresponding to precisions of 8% and 3.4%, respectively. This implies a planetary bulk density of ρb\rho_\mathrm{b} = 10.2 ±\pm 1.3 g cm3^{-3}, i.e., 85% higher than Earth's density. We revealed the presence of two additional non transiting low-mass companions with orbital periods of \sim11.5 and 34 days and minimum masses of McsinicM_\mathrm{c}\sin{i_\mathrm{c}} = 4.13 ±\pm 0.36 M_{\oplus} and MdsinidM_\mathrm{d}\sin{i_\mathrm{d}} = 6.03 ±\pm 0.49 M_{\oplus}, respectively, which lie close to the 3:1 mean motion commensurability. GJ 367 b joins the small class of high-density planets, namely the class of super-Mercuries, being the densest ultra-short period small planet known to date. Thanks to our precise mass and radius estimates, we explored the potential internal composition and structure of GJ 367 b, and found that it is expected to have an iron core with a mass fraction of 0.910.23+0.07^{+0.07}_{-0.23}. How this iron core is formed and how such a high density is reached is still not clear, and we discuss the possible pathways of formation of such a small ultra-dense planet.


LHS 1903 provides evidence for gas-depleted formation of planets around M-dwarfs

July 2023

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140 Reads

Many important advances in planet formation theory have come from the discovery of unexpected planets. The thousands of discovered exoplanets have unveiled demographic trends, such as the bimodality of planetary radius distribution known as the radius valley. Modelling these trends can probe underlying processes, e.g. the formation environment and atmospheric evolution. Here, we report the discovery and characterisation of a four-planet system around the kinematically thick-disk M-dwarf LHS 1903 with orbital periods of 2.16, 6.23, 12.57, and 29.32 days that becomes the only known M-dwarf hosting four small, well-characterised planets spanning the radius valley. We utilise high-precision transit photometry from the Transiting Exoplanet Survey Satellite (TESS) and the CHaracterising ExOPlanets Satellite (CHEOPS) to measure the radii of LHS 1903 b, c, d, and e (1.382+/-0.046, 2.046^+0.078_-0.074, 2.500^+0.078_-0.077, and 1.732^+0.059_-0.058 R_oplus). Combined with HARPS-N radial velocity data, we determine the planetary bulk densities (1.24^+0.21_-0.19, 0.53^+0.11_-0.09, 0.38^+0.09_-0.08, and 1.11^+0.33_-0.31 rho_oplus). Our compositional analysis finds that planet b is rocky, planets c and d have extended atmospheres, and LHS 1903 e does not have a gaseous envelope. Our discovery that planet e, the longest-period well-characterised terrestrial M-dwarf planet, lacks an extended atmosphere causes tension with thermally-driven mass loss radius valley predictions, but supports a gas-depleted formation explanation. The observed broken atmospheric-mass fraction trend is at odds with current formation theory, but provides further evidence for a gas-depleted formation environment for terrestrial M-dwarf planets.


Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

June 2023

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55 Reads

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15 Citations

Monthly Notices of the Royal Astronomical Society

HIP 9618 (HD 12572, TOI-1471, TIC 306263608) is a bright (G = 9.0 mag) solar analogue. TESS photometry revealed the star to have two candidate planets with radii of 3.9 ± 0.044 R⊕ (HIP 9618 b) and 3.343 ± 0.039 R⊕ (HIP 9618 c). While the 20.77291 d period of HIP 9618 b was measured unambiguously, HIP 9618 c showed only two transits separated by a 680-d gap in the time series, leaving many possibilities for the period. To solve this issue, CHEOPS performed targeted photometry of period aliases to attempt to recover the true period of planet c, and successfully determined the true period to be 52.56349 d. High-resolution spectroscopy with HARPS-N, SOPHIE, and CAFE revealed a mass of 10.0 ± 3.1M⊕ for HIP 9618 b, which, according to our interior structure models, corresponds to a 6.8±1.4  per cent6.8\pm 1.4~{{\ \rm per\ cent}} gas fraction. HIP 9618 c appears to have a lower mass than HIP 9618 b, with a 3-sigma upper limit of <18M⊕. Follow-up and archival RV measurements also reveal a clear long-term trend which, when combined with imaging and astrometric information, reveal a low-mass companion (0.080.05+0.12M0.08^{+0.12}_{-0.05} M_\odot) orbiting at 26.011.0+19.026.0^{+19.0}_{-11.0} au. This detection makes HIP 9618 one of only five bright (K < 8 mag) transiting multiplanet systems known to host a planet with P > 50 d, opening the door for the atmospheric characterization of warm (Teq < 750 K) sub-Neptunes.


Citations (10)


... WASP-106 b is a warm Jupiter orbiting an F9 star on a circular and aligned orbit roughly every 9 days (Stassun et al. 2017;Harre et al. 2023;Wright et al. 2023). The circulation timescale of this planet, estimated to be of the order of the system's age (Stassun et al. 2017), suggests that WASP-106 b's orbit has not undergone circularization from a highly eccentric starting point, but instead, it has likely maintained a nearly circular orbit throughout the system's lifetime. ...

Reference:

High-resolution Transmission Spectroscopy of Warm Jupiters: An ESPRESSO Sample with Predictions for ANDES
The Orbit of Warm Jupiter WASP-106 b is Aligned with its Star

The Astronomical Journal

... The inferred mean molecular weight of the upper atmosphere was 5.5 ± 1.2 amu, lower than that of the volatile gases and higher than that of hydrogen and helium gas, leading the investigators to propose that all of those gases exist in a homogeneous mixture. • GJ 367 b, a planet with a radius of 0.70 R ⊕ and an exceptionally high density of 10.2 ± 1.3 g/cm 3 orbiting a 0.45 M ⊙ star with a period of only 7.7 hours (Lam et al. 2021;Goffo et al. 2023). JWST observations covering a complete orbit failed to detect any hint of an atmosphere, supporting the notion that GJ 367 b and similar planets are airless "lava worlds" (Zhang et al. 2024a). ...

Company for the Ultra-high Density, Ultra-short Period Sub-Earth GJ 367 b: Discovery of Two Additional Low-mass Planets at 11.5 and 34 Days*

The Astrophysical Journal Letters

... For shallower TESS monotransits ( < 1000 ppm) usually associated with smaller planets it is extremely difficult to detect additional transits from the ground. In these cases space facilities such as CHEOPS (Benz et al. 2021 ) can be used to detect further transits, for example (Osborn et al. 2023 ;Tuson et al. 2023 ;Ulmer-Moll et al. 2023 ). ...

Two warm Neptunes transiting HIP 9618 revealed by TESS and Cheops

Monthly Notices of the Royal Astronomical Society

... With a period of about 77 days, it is above the period threshold of 60 days, suggested by Alvarado-Montes et al. (2017), below which the exomoon would collide with the planet. As described in Ehrenreich et al. (2023), the observation aimed to search for exomoon should be centered on the transit of the planet, and should span the time equivalent of the Hill radius of the planet, because a stable exomoon is expected to lie within the planet Hill sphere (Domingos et al. 2006). For this reason, the improvement we obtained on the linear ephemerides of planet e has a crucial importance for the planning and scheduling of future observations. ...

A full transit of v 2 Lupi d and the search for an exomoon in its Hill sphere with CHEOPS

Astronomy and Astrophysics

... However, since both are metal-rich, they are also likely to have high-metallicity atmospheres. Such highmetallicity atmospheres experience much lower escape rates as heavier species require more energy to remove (Wilson et al. 2022;Owen & Jackson 2012). Since we only considered a pure H/He composition in our atmospheric evolution models, our results in Fig. 18 constitute an upper bound to the evaporation histories of the planets. ...

A pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 characterized with CHEOPS

Monthly Notices of the Royal Astronomical Society

... The inferred mean molecular weight of the upper atmosphere was 5.5 ± 1.2 amu, lower than that of the volatile gases and higher than that of hydrogen and helium gas, leading the investigators to propose that all of those gases exist in a homogeneous mixture. • GJ 367 b, a planet with a radius of 0.70 R ⊕ and an exceptionally high density of 10.2 ± 1.3 g/cm 3 orbiting a 0.45 M ⊙ star with a period of only 7.7 hours (Lam et al. 2021;Goffo et al. 2023). JWST observations covering a complete orbit failed to detect any hint of an atmosphere, supporting the notion that GJ 367 b and similar planets are airless "lava worlds" (Zhang et al. 2024a). ...

GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star
  • Citing Article
  • December 2021

... The importance of ephemeris maintenance and refinement is epitomized by the automatic ephemeris fitting in ETD, which is based on quality-weighted sets of the uploaded transit observations. Amateur data have been taken into account in several publications presenting improved transit ephemeris; e.g. for planets found by CoRoT (Klagyivik et al. 2021), TESS (Peluso et al. 2023) or WASP (Noguer et al. 2024). Transit re-observations may also give rise to the detection of transit timing variations (TTVs) -these are deviations from strict periodicity that indicate non-linear ephemeris. ...

Orbital Period Refinement of CoRoT Planets with TESS Observations

Frontiers in Astronomy and Space Sciences

... Iron-rich planetary objects have also been discovered around other type of stars. For example, the terrestrial exoplanet GJ 367 b is found to be orbiting around an M-type star (Lam et al. 2021;Goffo et al. 2023). It has a mass of 0.633M ⊕ , a radius of 0.699R ⊕ , and a mean density ofρ = 10.22 g cm −3 , implying that its iron composition is about 90%. ...

GJ 367b: A dense, ultrashort-period sub-Earth planet transiting a nearby red dwarf star
  • Citing Article
  • December 2021

Science

... Many recent studies have sought to distinguish between the variety of proposed radius valley emergence mechanisms. Examples include searches for population-level trends as functions of planet radius, instellation, stellar mass, and age (Berger et al. 2020(Berger et al. , 2023Loyd et al. 2020;Rogers et al. 2021;Van Eylen et al. 2021;Petigura et al. 2022;Bonfanti et al. 2024;Cherubim et al. 2023). Other examples include modeling different regimes in which XUV-driven escape dominates over CPML, or vice-versa (Owen & Schlichting 2024), searching for signatures of atmospheric escape , and comparative studies of multitransiting systems (Owen & Campos Estrada 2020, hereafter OC20). ...

Masses and compositions of three small planets orbiting the nearby M dwarf L231-32 (TOI-270) and the M dwarf radius valley

Monthly Notices of the Royal Astronomical Society

... We use our results from the global modelling to estimate the circularisation timescale for TOI-2490b for a range of ★ and values. We follow a similar method from Carmichael et al. (2020) and Acton et al. (2021). We vary the tidal quality factors as they are not well constrained in the literature, although there are values for the 3 Gyr old CWW 89Ab of ★ > 10 9 and > 10 4.15 (Beatty et al. 2018) and > 10 4.5 for 2MASS J05352184-0546085 (Heller et al. 2010). ...

NGTS-19b: A high mass transiting brown dwarf in a 17-day eccentric orbit

Monthly Notices of the Royal Astronomical Society