arXiv subjects

Zoltan Csubry

Publications and source records attributed to Zoltan Csubry.

15 recordsLinked to original sources

arXiv2026

Two warm sub-Saturn mass planets identified from the TESS Full Frame Images

Context. Characterization of warm giants is crucial to constrain giant planet formation and evolution. Measuring the mass and radius of these planets, combined with their moderated irradiation, allows us to estimate their planetary bulk composition, which is a key quantity to comprehend giant planet formation and structure. Aims. We present the discovery of two transiting warm giant planets orbiting solar-type stars from the Transiting Exoplanet Survey Satellite (TESS), which were characterized by further spectroscopic and photometric ground-based observations. Methods. We performed a joint analysis of photometric data with radial velocities to confirm and characterize TOI-883 b and TOI-899 b, two sub-Saturns orbiting solar-like stars. Results. TOI-883 b and TOI-899 b have masses of $0.123 \pm 0.012$ $M_J$ and $0.213 \pm 0.024$ $M_J$, radius of $0.604 \pm 0.028$ $R_J$ and $0.991 \pm 0.044$ $R_J$, periods of $10.06$ d and $12.85$ d and equilibrium temperature of $1086 \pm 19$ K and $1040 \pm 19$ K, respectively. Conclusions. While having similar masses, orbital periods and stellar host properties, these planets seem to have different internal compositions, which could point to distinct formation histories. Both planets are suitable targets for atmospheric studies to further constrain formation scenarios of planets in the Neptune-Saturn mass range

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arXiv2025

A Compact Multi-Planet System of Three Transiting Giant Planets Around TIC118798035

We report the discovery and characterization of three transiting giant planets in the TIC118798035 system. The three planets were identified as transiting candidates from data of the TESS mission, and confirmed with ground-based photometric transit observations along with radial velocity variations obtained with FEROS, HARPS and ESPRESSO. The three planets present transit timing variations (TTVs). We performed a N-body orbital fitting to the TTVs and radial velocities finding that TIC118798035 b is as warm low-density Neptune with a mass of 0.0250$\pm$0.0023 $M_J$, a radius of 0.655$\pm$0.018 $R_J$, and an orbital period of 11.507 d; TIC118798035 c is a warm Saturn with a mass of 0.403$\pm$0.024 $M_J$, a radius of 0.973$\pm$0.023 $R_J$, and an orbital period of 22.564 d; and TIC118798035 d is a warm Jupiter with a mass of 0.773$\pm$0.052 $M_J$, a radius of 0.923$\pm$0.044 $R_J$, and an orbital period of 48.925 d. The bulk metallicities of the three planets don't fully follow the mass-metallicity correlation found for the giant planets of the solar system, which hints at a somewhat different formation history for the planets of the TIC118798035 system. TIC118798035 is the only system having more than two transiting planets larger than 0.5 $R_J$ with a precise orbital and physical characterization, amenable for future atmospheric studies.

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arXiv2025

AutoWISP: Automated Processing of Wide-Field Color Images

We have developed a software pipeline, AutoWISP, for extracting high-precision photometry from citizen scientists' observations made with consumer-grade color digital cameras (digital single-lens reflex, or DSLR, cameras), based on our previously developed tool, AstroWISP. The new pipeline is designed to convert these observations, including color images, into high-precision light curves of stars. We outline the individual steps of the pipeline and present a case study using a Sony-alpha 7R II DSLR camera, demonstrating sub-percent photometric precision, and highlighting the benefits of three-color photometry of stars. Project PANOPTES will adopt this photometric pipeline and, we hope, be used by citizen scientists worldwide. Our aim is for AutoWISP to pave the way for potentially transformative contributions from citizen scientists with access to observing equipment.

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arXiv2025

The T16 Project: Image Subtraction Light Curves from TESS Cycle 1 Full-Frame Images for Stars with T < 16

We present 83,717,159 light curves for 56,401,549 stars with T < 16 mag observed in the Full-Frame Images (FFIs) of Cycle 1 of the NASA TESS mission. These light curves were extracted from subtracted images produced by the Cluster Difference Imaging Survey (CDIPS; Bouma et al. 2019). We make public the raw image subtraction light curves, together with light curves detrended against instrumental systematics. We compare the light curves to other publicly available light curves from the TESS FFIs, finding that for a substantial fraction of stars with T < 16, the T16 project provides the highest precision FFI light curves available. We demonstrate that the detrended T16 light curves are generally as good as, or better than, the light curves from other projects for the known TOIs. We also show that the un-detrended light curves can be used to study high amplitude variable stars. The light curves are being made available through the NASA Mikulski Archive for Space Telescopes (MAST). Light curve production is underway for additional TESS Cycles.

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arXiv2024

Three Warm Jupiters orbiting TOI-6628, TOI-3837, TOI-5027 and one sub-Saturn orbiting TOI-2328

We report the discovery and characterization of three new transiting giant planets orbiting TOI-6628, TOI-3837 and TOI-5027, and one new warm sub-Saturn orbiting TOI-2328, whose transits events were detected in the lightcurves of the Transiting Exoplanet Survey Satellite \textbf{(TESS)} space mission. By combining TESS lightcurves with ground-based photometric and spectroscopic follow-up observations we confirm the planetary nature of the observed transits and radial velocity variations. TOI-6628~$b$ has a mass of 0.75$\pm$0.06~$M_\mathrm{J}$, a radius of 0.98$\pm$0.05~$R_J$ and is orbiting a metal-rich star with a period of 18.18424$\pm{0.00001}$ days and an eccentricity of 0.667$\pm0.016$, making it one of the most eccentric orbits of all known warm giants. TOI-3837~$b$ has a mass of 0.59$\pm$0.06~$M_\mathrm{J}$, a radius of 0.96$\pm$0.05~$R_J$ and orbits its host star every 11.88865$\pm$0.00003~days, with a moderate eccentricity of 0.198$^{+0.046}_{-0.058}$. With a mass of 2.01$\pm$0.13~$M_\mathrm{J}$ and a radius of 0.99$^{+0.07}_{-0.12}$ $R_J$, TOI-5027~$b$ orbits its host star in an eccentric orbit with $e$~=~0.395$^{+0.032}_{-0.029}$ every 10.24368$\pm{0.00001}$~days. TOI-2328~$b$ is a Saturn-like planet with a mass of 0.16$\pm$0.02~$M_\mathrm{J}$ and a radius of 0.89$\pm$0.04~$R_J$, orbiting its host star in a nearly circular orbit with $e$~=~0.057$^{+0.046}_{-0.029}$ at an orbital period of 17.10197$\pm{0.00001}$ days. All four planets have orbital periods above 10 days, and our planet interior structure models are consistsent a rocky-icy core with a H/He envelope, providing evidence supporting the core accretion model of planet formation for this kind of planets.

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arXiv2020

HAT-P-68b: A Transiting Hot Jupiter Around a K5 Dwarf Star

We report the discovery by the ground-based HATNet survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 $\pm$ 0.043 $M_{Jup}$, and radius of 1.072 $\pm$ 0.012 $R_{Jup}$. The planet is in a circular P = 2.2984-day orbit around a moderately bright V = 13.937 $\pm$ 0.030 magnitude K dwarf star of mass 0.673 $+$ 0.020 $-$0.014 $M_{\odot}$, and radius 0.6726 $\pm$ 0.0069 $R_{\odot}$. The planetary nature of this system is confirmed through follow-up transit photometry obtained with the FLWO~1.2m telescope, high-precision RVs measured using Keck-I/HIRES, FLWO~1.5m/TRES, and OHP~1.9m/Sophie, and high-spatial-resolution speckle imaging from WIYN~3.5m/DSSI. HAT-P-68 is at an ecliptic latitude of $+3^{\circ}$ and outside the field of view of both the NASA TESS primary mission and the K2 mission. The large transit depth of 0.036 mag ($r$-band) makes HAT-P-68b a promising target for atmospheric characterization via transmission spectroscopy.

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arXiv2019

TOI-150b and TOI-163b: two transiting hot Jupiters, one eccentric and one inflated, revealed by TESS near and at the edge of the JWST CVZ

We present the discovery of TYC9191-519-1b (TOI-150b, TIC 271893367) and HD271181b (TOI-163b, TIC 179317684), two hot Jupiters initially detected using 30-minute cadence Transiting Exoplanet Survey Satellite TESS photometry from Sector 1 and thoroughly characterized through follow-up photometry (CHAT, Hazelwood, LCO/CTIO, El Sauce, TRAPPIST-S), high-resolution spectroscopy (FEROS, CORALIE) and speckle imaging (Gemini/DSSI), confirming the planetary nature of the two signals. A simultaneous joint fit of photometry and radial velocity using a new fitting package juliet reveals that TOI-150b is a $1.254\pm0.016\ R_J$, massive ($2.61^{+0.19}_{-0.12}\ M_J$) hot Jupiter in a $5.857$-day orbit, while TOI-163b is an inflated ($R_P$ = $1.478^{+0.022}_{-0.029} R_J$, $M_P$ = $1.219\pm0.11 M_J$) hot Jupiter on a $P$ = $4.231$-day orbit; both planets orbit F-type stars. A particularly interesting result is that TOI-150b shows an eccentric orbit ($e=0.262^{+0.045}_{-0.037}$), which is quite uncommon among hot Jupiters. We estimate that this is consistent, however, with the circularization timescale which is slightly larger than the age of the system. These two hot Jupiters are both prime candidates for further characterization --- in particular, both are excellent candidates for determining spin-orbit alignments via the Rossiter-McLaughlin (RM) effect and for characterizing atmospheric thermal structures using secondary eclipse observations considering they are both located closely to the James Webb Space Telescope (JWST) Continuous Viewing Zone (CVZ).

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arXiv2018

K2-287b: an Eccentric Warm Saturn transiting a G-dwarf

We report the discovery of K2-287b, a Saturn mass planet orbiting a G-dwarf with a period of $P \approx 15$ days. First uncovered as a candidate using K2 campaign 15 data, follow-up photometry and spectroscopy were used to determine a mass of $M_P = 0.317 \pm 0.026$ $M_J$, radius $R_P = 0.833 \pm 0.013$ $R_J$, period $P = 14.893291 \pm 0.000025$ days and eccentricity $e = 0.476 \pm 0.026$. The host star is a metal-rich $V=11.410 \pm 0.129$ mag G dwarf for which we estimate a mass $M_* = 1.056$ $M_\odot$, radius $R_* = 1.07 \pm 0.01$ $R_\odot$, metallicity [Fe/H] = $0.20 \pm 0.05$ and $T_{eff} = 5673 \pm 75$ K. This warm eccentric planet with a time-averaged equilibrium temperature of $T_{eq} \approx 800$ K adds to the small sample of giant planets orbiting nearby stars whose structure is not expected to be affected by stellar irradiation. Follow-up studies on the K2-287 system could help in constraining theories of migration of planets in close-in orbits.

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arXiv2018

HATS-54b-HATS-58Ab: five new transiting hot Jupiters including one with a possible temperate companion

We report the discovery by the HATSouth project of 5 new transiting hot Jupiters (HATS-54b through HATS-58Ab). HATS-54b, HATS-55b and HATS-58Ab are prototypical short period ($P = 2.5-4.2$ days, $R_p\sim1.1-1.2$ $R_J$) hot-Jupiters that span effective temperatures from 1350 K to 1750 K, putting them in the proposed region of maximum radius inflation efficiency. The HATS-58 system is composed of two stars, HATS-58A and HATS-58B, which are detected thanks to Gaia DR2 data and which we account for in the joint modelling of the available data --- with this, we are led to conclude that the hot jupiter orbits the brighter HATS-58A star. HATS-57b is a short-period (2.35-day) massive (3.15 $M_J$) 1.14 $R_J$, dense ($2.65\pm0.21$ g cm$^{-3}$) hot-Jupiter, orbiting a very active star ($2\%$ peak-to-peak flux variability). Finally, HATS-56b is a short period (4.32-day) highly inflated hot-Jupiter (1.7 $R_J$, 0.6 $M_J$), which is an excellent target for future atmospheric follow-up, especially considering the relatively bright nature ($V=11.6$) of its F dwarf host star. This latter exoplanet has another very interesting feature: the radial velocities show a significant quadratic trend. If we interpret this quadratic trend as arising from the pull of an additional planet in the system, we obtain a period of $P_c = 815^{+253}_{-143}$ days for the possible planet HATS-56c, and a minimum mass of $M_c\sin i_c = 5.11 \pm 0.94$ $M_J$. The candidate planet HATS-56c would have a zero-albedo equilibrium temperature of $T_\textrm{eq}=332\pm 50$ K, and thus would be orbiting close to the habitable zone of HATS-56. Further radial-velocity follow-up, especially over the next two years, is needed to confirm the nature of HATS-56c.

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arXiv2017

HATS-22b, HATS-23b and HATS-24b: Three new transiting Super-Jupiters from the HATSouth Project

We report the discovery of three moderately high-mass transiting hot Jupiters from the HATSouth survey: HATS-22b, HATS-23b and HATS-24b. These planets add to the numbers of known planets in the ~2MJ regime. HATS-22b is a 2.74+/-0.11 MJ mass and 0.953+0.048/-0.029 RJ radius planet orbiting a V = 13.455 +/- 0.040 sub-silar mass (M_star = 0.759+/-0.019 M_sun; R_star = 0.759+/-0.019 R_sun) K-dwarf host star on an eccentric (e = 0.079 +/- 0.026) orbit. This planet's high planet-to-stellar mass ratio is further evidence that migration mechanisms for hot Jupiters may rely on exciting orbital eccentricities that bring planets closer to their parent stars followed by tidal circularisation. HATS-23b is a 1.478 +/- 0.080 MJ mass and 1.69 +/- 0.24 RJ radius planet on a grazing orbit around a V = 13.901 +/- 0.010 G-dwarf with properties very similar to those of the Sun (M_star = 1.115 +/- 0.054 M_sun; R_star = 1.145 +/- 0.070 R_sun). HATS-24b orbits a moderately bright V = 12.830 +/- 0.010 F-dwarf star (M_star = 1.218 +/- 0.036 M_sun; R_star = 1.194+0.066/-0.041 R_sun). This planet has a mass of 2.39 +0.21/-0.12 MJ and an inflated radius of 1.516 +0.085/-0.065 RJ.

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arXiv2016

No Conclusive Evidence for Transits of Proxima b in MOST photometry

The analysis of Proxima Centauri's radial velocities recently led Anglada-Escudé et al. (2016) to claim the presence of a low mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a-priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the MOST space telescope. We report here that we cannot make a compelling case that Proxima b transits in our precise photometric time series. Imposing an informative prior on the period and phase, we do detect a candidate signal with the expected depth. However, perturbing the phase prior across 100 evenly spaced intervals reveals one strong false-positive and one weaker instance. We estimate a false-positive rate of at least a few percent and a much higher false-negative rate of 20-40%, likely caused by the very high flare rate of Proxima Centauri. Comparing our candidate signal to HATSouth ground-based photometry reveals that the signal is somewhat, but not conclusively, disfavored (1-2 sigmas) leading us to argue that the signal is most likely spurious. We expect that infrared photometric follow-up could more conclusively test the existence of this candidate signal, owing to the suppression of flare activity and the impressive infrared brightness of the parent star.

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arXiv2016

HAT-P-65b and HAT-P-66b: Two Transiting Inflated Hot Jupiters and Observational Evidence for the Re-Inflation of Close-In Giant Planets

We present the discovery of the transiting exoplanets HAT-P-65b and HAT-P-66b, with orbital periods of 2.6055 d and 2.9721 d, masses of $0.527 \pm 0.083$ M$_{J}$ and $0.783 \pm 0.057$ M$_{J}$ and inflated radii of $1.89 \pm 0.13$ R$_{J}$ and $1.59^{+0.16}_{-0.10}$ R$_{J}$, respectively. They orbit moderately bright ($V=13.145 \pm 0.029$, and $V=12.993 \pm 0.052$) stars of mass $1.212 \pm 0.050$ M$_{\odot}$ and $1.255^{+0.107}_{-0.054}$ M$_{\odot}$. The stars are at the main sequence turnoff. While it is well known that the radii of close-in giant planets are correlated with their equilibrium temperatures, whether or not the radii of planets increase in time as their hosts evolve and become more luminous is an open question. Looking at the broader sample of well-characterized close-in transiting giant planets, we find that there is a statistically significant correlation between planetary radii and the fractional ages of their host stars, with a false alarm probability of only 0.0041%. We find that the correlation between the radii of planets and the fractional ages of their hosts is fully explained by the known correlation between planetary radii and their present day equilibrium temperatures, however if the zero-age main sequence equilibrium temperature is used in place of the present day equilibrium temperature then a correlation with age must also be included to explain the planetary radii. This suggests that, after contracting during the pre-main-sequence, close-in giant planets are re-inflated over time due to the increasing level of irradiation received from their host stars. Prior theoretical work indicates that such a dynamic response to irradiation requires a significant fraction of the incident energy to be deposited deep within the planetary interiors.

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arXiv2016

HATS-18 b: An Extreme Short--Period Massive Transiting Planet Spinning Up Its Star

We report the discovery by the HATSouth network of HATS-18 b: a 1.980 +/- 0.077 Mj, 1.337 +0.102 -0.049 Rj planet in a 0.8378 day orbit, around a solar analog star (mass 1.037 +/- 0.047 Msun, and radius 1.020 +0.057 -0.031 Rsun) with V=14.067 +/- 0.040 mag. The high planet mass, combined with its short orbital period, implies strong tidal coupling between the planetary orbit and the star. In fact, given its inferred age, HATS-18 shows evidence of significant tidal spin up, which together with WASP-19 (a very similar system) allows us to constrain the tidal quality factor for Sun-like stars to be in the range 6.5 <= lg(Q*/k_2) <= 7 even after allowing for extremely pessimistic model uncertainties. In addition, the HATS-18 system is among the best systems (and often the best system) for testing a multitude of star--planet interactions, be they gravitational, magnetic or radiative, as well as planet formation and migration theories.

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arXiv2015

HAT-P-50b, HAT-P-51b, HAT-P-52b, and HAT-P-53b: Three Transiting Hot Jupiters and a Transiting Hot Saturn From the HATNet Survey

We report the discovery and characterization of four transiting exoplanets by the HATNet survey. The planet HAT-P-50b has a mass of 1.35 M_J and a radius of 1.29 R_J, and orbits a bright (V = 11.8 mag) M = 1.27 M_sun, R = 1.70 R_sun star every P = 3.1220 days. The planet HAT-P-51b has a mass of 0.31 M_J and a radius of 1.29 R_J, and orbits a V = 13.4 mag, M = 0.98 M_sun, R = 1.04 R_sun star with a period of P = 4.2180 days. The planet HAT-P-52b has a mass of 0.82 M_J and a radius of 1.01 R_J, and orbits a V = 14.1 mag, M = 0.89 M_sun, R = 0.89 R_sun star with a period of P = 2.7536 days. The planet HAT-P-53b has a mass of 1.48 M_J and a radius of 1.32 R_J, and orbits a V = 13.7 mag, M = 1.09 M_sun, R = 1.21 R_sun star with a period of P = 1.9616 days. All four planets are consistent with having circular orbits and have masses and radii measured to better than 10% precision. The low stellar jitter and favorable R_P/R_star ratio for HAT-P-51 make it a promising target for measuring the Rossiter-McLaughlin effect for a Saturn-mass planet.

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arXiv2014

Stellar rotational periods in the planet hosting open cluster Praesepe

By using the dense coverage of the extrasolar planet survey project HATNet, we Fourier analyze 381 high-probability members of the nearby open cluster Praesepe (Beehive/M44/NGC 2632). In addition to the detection of 10 variables (of δScuti and other types), we identify 180 rotational variables (including the two known planet hosts). This sample increases the number of known rotational variables in this cluster for spectral classes earlier than M by more than a factor of three. These stars closely follow a color/magnitude -- period relation from early F to late K stars. We approximate this relation by polynomials for an easier reference to the rotational characteristics in different colors. The total (peak-to-peak) amplitudes of the large majority (94%) of these variables span the range of 0.005 to 0.04 mag. The periods cover a range from 2.5 to 15 days. These data strongly confirm that Praesepe and the Hyades have the same gyrochronological ages. Regarding the two planet hosts, Pr0211 (the one with the shorter orbital period) has a rotational period that is ~2 days shorter than the one expected from the main rotational pattern in this cluster. This, together with other examples discussed in the paper, may hint that star-planet interaction via tidal dissipation can be significant in some cases in the rotational evolution of stars hosting Hot Jupiters.

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