arXiv subjects

Gabor Furesz

Publications and source records attributed to Gabor Furesz.

At least 19 recordsLinked to original sources

arXiv2026

The Lightspeed project: high-speed, ultra-low read noise imaging and polarimetry for the Magellan telescopes

Lightspeed will be an ultra-fast (> kHz), ultra-low read noise, multicolor (ugriz + IR) imager for the 6.5 meter Magellan Clay telescope. In a single-channel configuration, Lightspeed will also enable single-shot linear polarimetry, narrowband imaging, or white-light imaging. Lightspeed is designed around groundbreaking single-photon-resolving detector technologies: deep sub-electron read noise CMOS image sensors from Fairchild Imaging and a HgCdTe avalanche photodiode array from Leonardo. Here we present Lightspeed's basic optical design concept, predict its on-sky performance, and highlight science cases that Lightspeed has the potential to revolutionize. Lightspeed builds upon the success of proto-Lightspeed, a single-channel prototype employing commercial-off-the-shelf re-imaging optics. proto-Lightspeed is now available as a PI instrument on the Clay telescope. We also discuss the current status of proto-Lightspeed and lessons learned from its commissioning, applicable to the development of Lightspeed and any other instrument seeking to integrate scientific CMOS image sensors.

astro-ph.IM↗

arXiv2026

Optimal mitigation of random telegraph noise for improved photometry at high frame rates

Random telegraph noise (RTN) is a major contributor to read noise in many CMOS image sensors considered for astronomical use. While scientific CMOS image sensors deliver lower read noise than traditional charge-coupled devices, mitigating RTN would widen this gap and enable more precise photometry when using the fast readout rates achievable by CMOS image sensors. We report the levels of RTN in three CMOS image sensors used in astronomical instruments: the Sony IMX455, Gpixel GSENSE400, and Fairchild Imaging HWK4123. For the IMX455 in a high gain mode, RTN is the dominant source of pixels with high read noise and increases the overall read noise floor by >20%. RTN is present in the GSENSE400 and HWK4123 but to smaller effects. We compare two strategies for RTN mitigation: masking pixels exhibiting RTN or using a new algorithm for correcting RTN jumps. For faint (< 3 e-/pix/frame) observations of a stellar field with the IMX455, both masking and our algorithm improved the signal-to-noise ratio (SNR) of light curves by >5% on average. Larger improvements were achieved for sources falling on multiple RTN pixels. Our algorithm outperforms masking, especially when the point spread function is undersampled, masked pixels are near the source center, or read noise and shot noise are comparable. In such cases, masking may even deteriorate photometric precision. In other cases, masking remains an effective RTN mitigation technique. We have made available our software for identifying RTN pixels, parametrizing their bias level distributions, and applying our correction algorithm.

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arXiv2026

proto-Lightspeed: a high-speed, ultra-low read noise imager on the Magellan Clay Telescope

proto-Lightspeed is a new instrument that has been commissioned on the Nasmyth East port of the Magellan Clay Telescope at Las Campanas Observatory to deliver high-speed optical imaging with deep sub-electron read noise. Making use of commercial re-imaging lenses and the ORCA-Quest 2 camera from Hamamatsu, proto-Lightspeed images a field $1'$ in diameter at up to $200$ Hz or windowed fields at higher rates, up to 6600 Hz for a $1.6''\times 1'$ field of view. proto-Lightspeed delivers seeing-limited image quality in the $g'$, $r'$, and $i'$ bands and adjustable magnification for pixel scales between $0.017''-0.050''$. proto-Lightspeed is well suited to studying compact binary systems, exoplanet transits, rapid flaring associated with accretion, periodic optical emission from pulsars, occultations of background stars by small trans-Neptunian Objects, and any other rapidly variable source. proto-Lightspeed will be a P.I. instrument beginning in 2026B, available for use by members of the Magellan Consortium. In this paper, we discuss the design and performance of the instrument, results from its two commissioning runs, and plans for a facility instrument, Lightspeed, to support simultaneous multicolor imaging across a $7'\times4'$ field.

astro-ph.IM↗

arXiv2026

An eclipsing 8.56 minute orbital period mass-transferring binary

We report the discovery of ATLAS J101342.5-451656.8 (hereafter ATLAS J1013-4516), an 8.56 minute orbital period mass transferring AM Canum Venaticorum binary with mean Gaia magnitude G=19.51. The system was identified via periodic variability in Asteroid Terrestrial-impact Last Alert System light curves of Gaia white dwarf candidates. Follow-up spectroscopy with the Large Lenslet Array Magellan Spectrograph reveals a helium dominated accretion disk, while high speed ULTRACAM photometry shows pronounced primary and secondary eclipses. We construct a decade long orbital timing baseline using ATLAS and Gaia survey photometry together with high speed observations from ULTRACAM on the NTT and proto Lightspeed on the Magellan Clay telescope. From this baseline we measure an orbital period derivative Pdot = -1.60 +/- 0.07 x 10^-12 seconds per second. Interpreted in the context of stable mass transfer, the magnitude and sign of Pdot indicate orbital evolution governed by the interplay between gravitational wave driven angular momentum losses and mass transfer, directly probing the donor star structural response to mass loss. Assuming angular momentum loss dominated by gravitational radiation, we constrain the component masses and infer the characteristic gravitational wave strain. We predict a four year Laser Interferometer Space Antenna signal to noise ratio greater than 10, establishing ATLAS J1013-4516 as a strong prospective space based gravitational wave source that probes long term orbital evolution in the mass transferring regime.

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arXiv2026

The Lazuli Space Observatory: Architecture & Capabilities

The Lazuli Space Observatory is a 3-meter aperture astronomical facility designed for rapid-response observations and precision astrophysics across visible to near-infrared wavelengths (400-1700 nm bandpass). An off-axis, freeform telescope delivers diffraction-limited image quality (Strehl $>$0.8 at 633 nm) to three instruments across a wide, flat focal plane. The three instruments provide complementary capabilities: a Wide-field Context Camera (WCC) delivers multi-band imaging over a 35' $\times$ 12' footprint with high-cadence photometry; an Integral Field Spectrograph (IFS) provides continuous 400-1700 nm spectroscopy at R $\sim$ 100-500 for stable spectrophotometry; and an ExtraSolar Coronagraph (ESC) enables high-contrast imaging expected to reach raw contrasts of $10^{-8}$ and post-processed contrasts approaching $10^{-9}$. Operating from a 3:1 lunar-resonant orbit, Lazuli will respond to targets of opportunity in under four hours--a programmatic requirement designed to enable routine temporal responsiveness that is unprecedented for a space telescope of this size. Lazuli's technical capabilities are shaped around three broad science areas: (1) time-domain and multi-messenger astronomy, (2) stars and planets, and (3) cosmology. These capabilities enable a potent mix of science spanning gravitational wave counterpart characterization, fast-evolving transients, Type Ia supernova cosmology, high-contrast exoplanet imaging, and spectroscopy of exoplanet atmospheres. While these areas guide the observatory design, Lazuli is conceived as a general-purpose facility capable of supporting a wide range of astrophysical investigations, with open time for the global community. We describe the observatory architecture and capabilities in the preliminary design phase, with science operations anticipated following a rapid development cycle from concept to launch. [Abstract abridged]

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arXiv2025

The WINTER Observatory: A One-Degree InGaAs Survey Camera to study the Transient Infrared Sky

The Wide-field Infrared Transient Explorer (WINTER) is a near-infrared time-domain survey instrument operating on a dedicated 1-meter robotic telescope at Palomar Observatory. The project takes advantage of recent technology advances in time-domain astronomy, robotic telescopes, large-format sensors, and rapid data reduction and alert software for timely follow up of events. Since June of 2023, WINTER robotically surveys the sky each night to a median depth of J_AB = 18.5 mag, balancing a variety of science programs including searching for kilonovae from gravitational-wave alerts, blind surveys to study galactic and extragalactic transients and variables, and building up reference images of the near-infrared sky. The project also serves as a technology demonstration for new large-format Indium Gallium Arsenide (InGaAs) sensors for wide-field science in the near infrared without cryogenically cooled optics or detectors. WINTER's custom camera combines six InGaAs sensors with a novel tiled fly's-eye optical design to cover a >1 deg^2 field of view with 1 arcsecond pixels in the Y-, J-, and shortened-H-band filters (0.9 - 1.7 micron). This paper presents the design, performance, and early on-sky science of the WINTER observatory.

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arXiv2025

WINTER on S250206dm: A near-infrared search for an electromagnetic counterpart to a gravitational-wave event

We present near-infrared follow-up observations of the International Gravitational Wave Network (IGWN) event S250206dm with the Wide-Field Infrared Transient Explorer (WINTER). WINTER is a near-infrared time-domain survey designed for electromagnetic follow-up of gravitational-wave sources localized to $\leq$300 deg$^{2}$. The instrument's wide field of view (1.2 deg$^2$), dedicated 1-m robotic telescope, and near-infrared coverage (0.9-1.7 microns) are optimized for searching for kilonovae, which are expected to exhibit a relatively long-lived near-infrared component. S250206dm is the only neutron star merger in the fourth observing run (to date) localized to $\leq$300 deg$^{2}$ with a False Alarm Rate below one per year. It has a $55\%$ probability of being a neutron star-black hole (NSBH) merger and a $37\%$ probability of being a binary neutron star (BNS) merger, with a $50\%$ credible region spanning 38 deg$^2$, an estimated distance of 373 Mpc, and an overall false alarm rate of approximately one in 25 years. WINTER covered $43\%$ of the probability area at least once and $35\%$ at least three times. Through automated and human candidate vetting, all transient candidates found in WINTER coverage were rejected as kilonova candidates. Unsurprisingly, given the large estimated distance of 373 Mpc, the WINTER upper limits do not constrain kilonova models. This study highlights the promise of systematic infrared searches and the need for future wider and deeper infrared surveys.

astro-ph.HE↗

arXiv2025

Characterization of the Teledyne COSMOS Camera: A Large Format CMOS Image Sensor for Astronomy

The Teledyne COSMOS-66 is a next-generation CMOS camera designed for astronomical imaging, featuring a large-format sensor ($8120 \times 8120$ pixels, each $10 \mu m$), high quantum efficiency, high frame rates, and a correlated multi-sampling mode that achieves low read noise. We performed a suite of bench-top and on-sky tests to characterize this sensor and analyze its suitability for use in astronomical instruments. This paper presents measurements of linearity, conversion gain, read noise, dark current, quantum efficiency, image lag, and crosstalk. We found that the sensor exhibits nonlinear response below 5% of saturation. This nonlinearity is plausibly attributable to the trapping of electrons in each pixel. We developed and implemented a pixel-by-pixel nonlinearity correction, enabling accurate photometric measurements across the dynamic range. After implementing this correction, operating in the correlated multi-sampling mode, the sensor achieved an effective read noise of $2.9 e^-$ and dark current of $0.12 e^-/pix/s$ at $-25^\circ C$. The quantum efficiency exceeded 50% from 250 nm to 800 nm, peaking at 89% at 600 nm. We observed significant optical crosstalk between the pixels, likely caused by photoelectron diffusion. To demonstrate the sensor's astronomical performance, we mounted it on the WINTER 1m telescope at Palomar Observatory. These tests confirmed that the linearity calibration enables accurate stellar photometry and validated our measured noise levels. Overall, the COSMOS-66 delivers similar noise performance to large-format CCDs, with higher frame rates and relaxed cooling requirements. If pixel design improvements are made to mitigate the nonlinearity and crosstalk, then the camera may combine the advantages of low-noise CMOS image sensors with the integration simplicity of large-format CCDs, broadening its utility to a host of astronomical science cases.

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arXiv2024

A gravitational wave detectable candidate Type Ia supernova progenitor

Type Ia supernovae, critical for studying cosmic expansion, arise from thermonuclear explosions of white dwarfs, but their precise progenitor pathways remain unclear. Growing evidence supports the ``double-degenerate'' scenario, where two white dwarfs interact. The absence of other companion types capable of explaining the observed Ia rate, along with observations of hyper-velocity white dwarfs interpreted as surviving companions of such systems provide compelling evidence in favor of this scenario. Upcoming millihertz gravitational wave observatories like the Laser Interferometer Space Antenna (LISA) are expected to detect thousands of double-degenerate systems, though the most compact known candidate Ia progenitors produce only marginally detectable gravitational wave signals. Here, we report observations of ATLAS J1138-5139, a binary white dwarf system with an orbital period of 28 minutes. Our analysis reveals a 1 solar mass carbon-oxygen white dwarf accreting from a helium-core white dwarf. Given its mass, the accreting carbon-oxygen white dwarf is poised to trigger a typical-luminosity Type Ia supernova within a few million years, or to evolve into a stably mass-transferring AM CVn system. ATLAS J1138-5139 provides a rare opportunity to calibrate binary evolution models by directly comparing observed orbital parameters and mass transfer rates closer to merger than any previously identified candidate Type Ia progenitor. Its compact orbit ensures detectability by LISA, demonstrating the potential of millihertz gravitational wave observatories to reveal a population of Type Ia progenitors on a Galactic scale, paving the way for multi-messenger studies offering insights into the origins of these cosmologically significant explosions.

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arXiv2023

Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS

While the sample of confirmed exoplanets continues to increase, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated ($\sim$1277 $F_{\oplus}$) and bloated Saturn-mass planet (1.69$^{+0.05}_{-0.06}$$R_{Jup}$ and 0.43$^{+0.09}_{-0.08}$$M_{Jup}$) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82$^{+0.03}_{-0.03}$$R_{Jup}$ and a mass of 0.30$^{+0.07}_{-0.08}$~$M_{Jup}$ in a 6.40 day orbit. Despite its high insolation flux ($\sim$600 $F_{\oplus}$), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39$^{+0.02}_{-0.04}$$M_{Jup}$ planet in a 4.88 day orbit with a grazing transit (b = 1.04$^{+0.05}_{-0.06 }$) that results in a poorly constrained radius of 1.61$^{+0.46}_{-0.64}$$R_{Jup}$. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and $\textit{JWST}$. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation and migration of exoplanets across various stellar types.

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arXiv2021

TIC 172900988: A Transiting Circumbinary Planet Detected in One Sector of TESS Data

We report the first discovery of a transiting circumbinary planet detected from a single sector of TESS data. During Sector 21, the planet TIC 172900988b transited the primary star and then 5 days later it transited the secondary star. The binary is itself eclipsing, with a period of P = 19.7 days and an eccentricity of e = 0.45. Archival data from ASAS-SN, Evryscope, KELT, and SuperWASP reveal a prominent apsidal motion of the binary orbit, caused by the dynamical interactions between the binary and the planet. A comprehensive photodynamical analysis of the TESS, archival and follow-up data yields stellar masses and radii of M1 = 1.2384 +/- 0.0007 MSun and R1 = 1.3827 +/- 0.0016 RSun for the primary and M2 = 1.2019 +/- 0.0007 MSun and R2 = 1.3124 +/- 0.0012 RSun for the secondary. The radius of the planet is R3 = 11.25 +/- 0.44 REarth (1.004 +/- 0.039 RJup). The planet's mass and orbital properties are not uniquely determined - there are six solutions with nearly equal likelihood. Specifically, we find that the planet's mass is in the range of 824 < M3 < 981 MEarth (2.65 < M3 < 3.09 MJup), its orbital period could be 188.8, 190.4, 194.0, 199.0, 200.4, or 204.1 days, and the eccentricity is between 0.02 and 0.09. At a V = 10.141 mag, the system is accessible for high-resolution spectroscopic observations, e.g. Rossiter-McLaughlin effect and transit spectroscopy.

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arXiv2021

TESS Hunt for Young and Maturing Exoplanets (THYME) V: A Sub-Neptune Transiting a Young Star in a Newly Discovered 250 Myr Association

The detection and characterization of young planetary systems offers a direct path to study the processes that shape planet evolution. We report on the discovery of a sub-Neptune-size planet orbiting the young star HD 110082 (TOI-1098). Transit events we initially detected during TESS Cycle 1 are validated with time-series photometry from Spitzer. High-contrast imaging and high-resolution, optical spectra are also obtained to characterize the stellar host and confirm the planetary nature of the transits. The host star is a late F dwarf (M=1.2 Msun) with a low-mass, M dwarf binary companion (M=0.26 Msun) separated by nearly one arcminute (~6200 AU). Based on its rapid rotation and Lithium absorption, HD 110082 is young, but is not a member of any known group of young stars (despite proximity to the Octans association). To measure the age of the system, we search for coeval, phase-space neighbors and compile a sample of candidate siblings to compare with the empirical sequences of young clusters and to apply quantitative age-dating techniques. In doing so, we find that HD 110082 resides in a new young stellar association we designate MELANGE-1, with an age of 250(+50/-70) Myr. Jointly modeling the TESS and Spitzer light curves, we measure a planetary orbital period of 10.1827 days and radius of Rp = 3.2(+/-0.1) Earth radii. HD 110082 b's radius falls in the largest 12% of field-age systems with similar host star mass and orbital period. This finding supports previous studies indicating that young planets have larger radii than their field-age counterparts.

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arXiv2021

TESS discovery of a super-Earth and three sub-Neptunes hosted by the bright, Sun-like star HD 108236

We report the discovery and validation of four extrasolar planets hosted by the nearby, bright, Sun-like (G3V) star HD~108236 using data from the Transiting Exoplanet Survey Satellite (TESS). We present transit photometry, reconnaissance and precise Doppler spectroscopy as well as high-resolution imaging, to validate the planetary nature of the objects transiting HD~108236, also known as the TESS Object of Interest (TOI) 1233. The innermost planet is a possibly-rocky super-Earth with a period of $3.79523_{-0.00044}^{+0.00047}$ days and has a radius of $1.586\pm0.098$ $R_\oplus$. The outer planets are sub-Neptunes, with potential gaseous envelopes, having radii of $2.068_{-0.091}^{+0.10}$ $R_\oplus$, $2.72\pm0.11$ $R_\oplus$, and $3.12_{-0.12}^{+0.13}$ $R_\oplus$ and periods of $6.20370_{-0.00052}^{+0.00064}$ days, $14.17555_{-0.0011}^{+0.00099}$ days, and $19.5917_{-0.0020}^{+0.0022}$ days, respectively. With V and K$_{\rm s}$ magnitudes of 9.2 and 7.6, respectively, the bright host star makes the transiting planets favorable targets for mass measurements and, potentially, for atmospheric characterization via transmission spectroscopy. HD~108236 is the brightest Sun-like star in the visual (V) band known to host four or more transiting exoplanets. The discovered planets span a broad range of planetary radii and equilibrium temperatures, and share a common history of insolation from a Sun-like star ($R_\star = 0.888 \pm 0.017$ R$_\odot$, $T_{\rm eff} = 5730 \pm 50$ K), making HD 108236 an exciting, opportune cosmic laboratory for testing models of planet formation and evolution.

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arXiv2020

Interstellar and Circumgalactic Properties of an Unseen $z=6.84$ Galaxy: Abundances, Ionization, and Heating in the Earliest Known Quasar Absorber

We analyze relative abundances and ionization conditions in a strong absorption system at z=6.84, seen in the spectrum of the z=7.54 background quasar ULAS J134208.10+092838.61. Singly ionized C, Si, Fe, Mg, and Al measurements are consistent with a warm neutral medium that is metal-poor but not chemically pristine. Firm non-detections of C IV and Si IV imply that any warm ionized phase of the IGM or CGM has not yet been enriched past the ultra-metal-poor regime (<0.001Z_{solar}), unlike lower redshift DLAs where these lines are nearly ubiquitous. Relative abundances of the heavy elements 794 Myr after the Big Bang resemble those of metal-poor damped Lyman Alpha systems at intermediate redshift and Milky Way halo stars, and show no evidence of enhanced [alpha/Fe], [C/Fe] or other signatures of yields dominated by massive stars. A detection of the CII* fine structure line reveals local sources of excitation from heating, beyond the level of photo-excitation supplied by the CMB. We estimate the total and [CII] cooling rates, balancing against ISM heating sources to develop an heuristic two-phase model of the neutral medium. The implied heating requires a surface density of star formation slightly exceeding that of the Milky Way but not at the level of a strong starburst. For a typical (assumed) NHI=10^{20.6}, an abundance of [Fe/H]=-2.2 matches the columns of species in the neutral phase. To remain undetected in C IV, a warm ionized phase would either need much lower [C/H]<-4.2 over an absorption path of 1 kpc, or else a very small absorption path (a few pc). While still speculative, these results suggest a significant reduction in heavy element enrichment outside of neutral star forming regions of the ISM, as would be expected in early stages of galactic chemical evolution.

astro-ph.GA↗

arXiv2020

TOI 694 b and TIC 220568520 b: Two Low-Mass Companions Near the Hydrogen Burning Mass Limit Orbiting Sun-like Stars

We report the discovery of TOI 694 b and TIC 220568520 b, two low-mass stellar companions in eccentric orbits around metal-rich Sun-like stars, first detected by the Transiting Exoplanet Survey Satellite (TESS). TOI 694 b has an orbital period of 48.05131$\pm$0.00019 days and eccentricity of 0.51946$\pm$0.00081, and we derive a mass of 89.0$\pm$5.3 $M_J$ (0.0849$\pm$0.0051 $M_\odot$) and radius of 1.111$\pm$0.017 $R_J$ (0.1142$\pm$0.0017 $R_\odot$). TIC 220568520 b has an orbital period of 18.55769$\pm$0.00039 days and eccentricity of 0.0964$\pm$0.0032, and we derive a mass of 107.2$\pm$5.2 $M_J$ (0.1023$\pm$0.0050 $M_\odot$) and radius of 1.248$\pm$0.018 $R_J$ (0.1282$\pm$0.0019 $R_\odot$). Both binary companions lie close to and above the Hydrogen burning mass threshold that separates brown dwarfs and the lowest mass stars, with TOI 694 b being 2-$σ$ above the canonical mass threshold of 0.075 $M_\odot$. The relatively long periods of the systems mean that the magnetic fields of the low-mass companions are not expected to inhibit convection and inflate the radius, which according to one leading theory is common in similar objects residing in short-period tidally-synchronized binary systems. Indeed we do not find radius inflation for these two objects when compared to theoretical isochrones. These two new objects add to the short but growing list of low-mass stars with well-measured masses and radii, and highlight the potential of the TESS mission for detecting such rare objects orbiting bright stars.

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arXiv2020

A super-Earth and two sub-Neptunes transiting the nearby and quiet M dwarf TOI-270

We report the Transiting Exoplanet Survey Satellite discovery of three small planets transiting one of the nearest and brightest M dwarf hosts to date, TOI-270 (TIC 259377017; K-mag 8.3; 22.5 parsec). The M3V-type star is transited by the super-Earth-sized TOI-270 b (1.247+0.089-0.083 R_earth) and the sub-Neptune-sized exoplanets TOI-270 c (2.42+-0.13 R_earth) and TOI-270 d (2.13+-0.12 R_earth). The planets orbit close to a mean-motion resonant chain, with periods (3.36, 5.66, and 11.38 days) near ratios of small integers (5:3 and 2:1). TOI-270 is a prime target for future studies since: 1) its near-resonance allows detecting transit timing variations for precise mass measurements and dynamical studies; 2) its brightness enables independent radial velocity mass measurements; 3) the outer planets are ideal for atmospheric characterisation via transmission spectroscopy; and 4) the quiet star enables future searches for habitable zone planets. Altogether, very few systems with small, temperate exoplanets are as suitable for such complementary and detailed characterisation as TOI-270.

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arXiv2020

TOI-1338: TESS' First Transiting Circumbinary Planet

We report the detection of the first circumbinary planet found by TESS. The target, a known eclipsing binary, was observed in sectors 1 through 12 at 30-minute cadence and in sectors 4 through 12 at two-minute cadence. It consists of two stars with masses of 1.1 MSun and 0.3 MSun on a slightly eccentric (0.16), 14.6-day orbit, producing prominent primary eclipses and shallow secondary eclipses. The planet has a radius of ~6.9 REarth and was observed to make three transits across the primary star of roughly equal depths (~0.2%) but different durations -- a common signature of transiting circumbinary planets. Its orbit is nearly circular (e ~ 0.09) with an orbital period of 95.2 days. The orbital planes of the binary and the planet are aligned to within ~1 degree. To obtain a complete solution for the system, we combined the TESS photometry with existing ground-based radial-velocity observations in a numerical photometric-dynamical model. The system demonstrates the discovery potential of TESS for circumbinary planets, and provides further understanding of the formation and evolution of planets orbiting close binary stars.

astro-ph.EP↗

arXiv2020

Securing the legacy of TESS through the care and maintenance of TESS planet ephemerides

Much of the science from the exoplanets detected by the TESS mission relies on precisely predicted transit times that are needed for many follow-up characterization studies. We investigate ephemeris deterioration for simulated TESS planets and find that the ephemerides of 81% of those will have expired (i.e. 1$σ$ mid-transit time uncertainties greater than 30 minutes) one year after their TESS observations. We verify these results using a sample of TESS planet candidates as well. In particular, of the simulated planets that would be recommended as JWST targets by Kempton et al. (2018), $\sim$80% will have mid-transit time uncertainties $>$ 30 minutes by the earliest time JWST would observe them. This rapid deterioration is driven primarily by the relatively short time baseline of TESS observations. We describe strategies for maintaining TESS ephemerides fresh through follow-up transit observations. We find that the longer the baseline between the TESS and the follow-up observations, the longer the ephemerides stay fresh, and that 51% of simulated primary mission TESS planets will require space-based observations. The recently-approved extension to the TESS mission will rescue the ephemerides of most (though not all) primary mission planets, but the benefits of these new observations can only be reaped two years after the primary mission observations. Moreover, the ephemerides of most primary mission TESS planets (as well as those newly discovered during the extended mission) will again have expired by the time future facilities such as the ELTs, Ariel and the possible LUVOIR/OST missions come online, unless maintenance follow-up observations are obtained.

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