arXiv subjects

Daniel A. Yahalomi

Publications and source records attributed to Daniel A. Yahalomi.

33 records · Page 2Linked to original sources

arXiv2022

Validation of 13 Hot and Potentially Terrestrial TESS Planets

The James Webb Space Telescope (JWST) will be able to probe the atmospheres and surface properties of hot, terrestrial planets via emission spectroscopy. We identify 18 potentially terrestrial planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS) that would make ideal targets for these observations. These planet candidates cover a broad range of planet radii ($R_{\rm p} \sim 0.6 - 2.0 R_\oplus$) and orbit stars of various magnitudes ($K_s = 5.78 - 10.78$, $V = 8.4 - 15.69$) and effective temperatures ($T_{\rm eff }\sim 3000 - 6000$ K). We use ground-based observations collected through the TESS Follow-up Observing Program (TFOP) and two vetting tools -- DAVE and TRICERATOPS -- to assess the reliabilities of these candidates as planets. We validate 13 planets: TOI-206 b, TOI-500 b, TOI-544 b, TOI-833 b, TOI-1075 b, TOI-1411 b, TOI-1442 b, TOI-1693 b, TOI-1860 b, TOI-2260 b, TOI-2411 b, TOI-2427 b, and TOI-2445 b. Seven of these planets (TOI-206 b, TOI-500 b, TOI-1075 b, TOI-1442 b, TOI-2260 b, TOI-2411 b, and TOI-2445 b) are ultra-short-period planets. TOI-1860 is the youngest ($133 \pm 26$ Myr) solar twin with a known planet to date. TOI-2260 is a young ($321 \pm 96$ Myr) G dwarf that is among the most metal-rich ([Fe/H] = $0.22 \pm 0.06$ dex) stars to host an ultra-short-period planet. With an estimated equilibrium temperature of $\sim 2600$ K, TOI-2260 b is also the fourth hottest known planet with $R_{\rm p} < 2 \, R_\oplus$.

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arXiv2022

A Possible Alignment Between the Orbits of Planetary Systems and their Visual Binary Companions

Astronomers do not have a complete picture of the effects of wide-binary companions (semimajor axes greater than 100 AU) on the formation and evolution of exoplanets. We investigate these effects using new data from Gaia EDR3 and the TESS mission to characterize wide-binary systems with transiting exoplanets. We identify a sample of 67 systems of transiting exoplanet candidates (with well-determined, edge-on orbital inclinations) that reside in wide visual binary systems. We derive limits on orbital parameters for the wide-binary systems and measure the minimum difference in orbital inclination between the binary and planet orbits. We determine that there is statistically significant difference in the inclination distribution of wide-binary systems with transiting planets compared to a control sample, with the probability that the two distributions are the same being 0.0037. This implies that there is an overabundance of planets in binary systems whose orbits are aligned with those of the binary. The overabundance of aligned systems appears to primarily have semimajor axes less than 700 AU. We investigate some effects that could cause the alignment and conclude that a torque caused by a misaligned binary companion on the protoplanetary disk is the most promising explanation.

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arXiv2022

TKS V. Twin sub-Neptunes Transiting the Nearby G Star HD 63935

We present the discovery of two nearly identically-sized sub-Neptune transiting planets orbiting HD 63935, a bright ($V=8.6$ mag), sun-like ($T_{eff}=5560K$) star at 49 pc. TESS identified the first planet, HD 63935 b (TOI-509.01), in Sectors 7 and 34. We identified the second signal (HD 63935 c) in Keck HIRES and Lick APF radial velocity data as part of our followup campaign. It was subsequently confirmed with TESS photometry in Sector 34 as TOI-509.02. Our analysis of the photometric and radial velocity data yields a robust detection of both planets with periods of $9.0600 \pm 0.007$ and $21.40 \pm 0.0019$ days, radii of $2.99 \pm 0.14$ and $2.90 \pm 0.13$ $R_\oplus$, and masses of $10.8 \pm 1.8$ and $11.1 \pm 2.4$ $M_\oplus$. We calculate densities for planets b and c consistent with a few percent of the planet mass in hydrogen/helium envelopes. We also describe our survey's efforts to choose the best targets for JWST atmospheric followup. These efforts suggest that HD 63935 b will have the most clearly visible atmosphere of its class. It is the best target for transmission spectroscopy (ranked by Transmission Spectroscopy Metric, a proxy for atmospheric observability) in the so-far uncharacterized parameter space comprising sub-Neptune-sized (2.6 $R_\oplus$ $<$ $R_p$ $<$ 4 $R_\oplus$), moderately-irradiated (100 $F_\oplus$ $<$ $F_p$ $<$ 1000 $F_\oplus$) planets around G-stars. Planet c is also a viable target for transmission spectroscopy, and given the indistinguishable masses and radii of the two planets, the system serves as a natural laboratory for examining the processes that shape the evolution of sub-Neptune planets.

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arXiv2021

Two Massive Jupiters in Eccentric Orbits from the TESS Full Frame Images

We report the discovery of two short-period massive giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS). Both systems, TOI-558 (TIC 207110080) and TOI-559 (TIC 209459275), were identified from the 30-minute cadence Full Frame Images and confirmed using ground-based photometric and spectroscopic follow-up observations from TESS's Follow-up Observing Program Working Group. We find that TOI-558 b, which transits an F-dwarf ($M_{*}=1.349^{+0.064}_{-0.065}\ M_{\odot}$, $R_{*}=1.496^{+0.042}_{-0.040}\ R_{\odot}$, $T_{eff}=6466^{+95}_{-93}\ K$, age $1.79^{+0.91}_{-0.73}\ Gyr$) with an orbital period of 14.574 days, has a mass of $3.61\pm0.15\ M_{\rm J}$, a radius of $1.086^{+0.041}_{-0.038}\ R_{\rm J}$, and an eccentric (e=$0.300^{+0.022}_{-0.020}$) orbit. TOI-559 b transits a G-dwarf ($M_{*}=1.026\pm0.057\ M_{\odot}$, $R_{*}=1.233^{+0.028}_{-0.026}\ R_{\odot}$, $T_{eff}=5925^{+85}_{-76}\ K$, age $6.8^{+2.5}_{-2.0}\ Gyr$) in an eccentric (e=$0.151\pm0.011$) 6.984-day orbit with a mass of $6.01^{+0.24}_{-0.23}\ M_{\rm J}$ and a radius of $1.091^{+0.028}_{-0.025}\ R_{\rm J}$. Our spectroscopic follow-up also reveals a long-term radial velocity trend for TOI-559, indicating a long-period companion. The statistically significant orbital eccentricity measured for each system suggests that these planets migrated to their current location through dynamical interactions. Interestingly, both planets are also massive ($>3\ M_{\rm J}$), adding to the population of massive giant planets identified by TESS. Prompted by these new detections of high-mass planets, we analyzed the known mass distribution of hot and warm Jupiters but find no significant evidence for multiple populations. TESS should provide a near magnitude-limited sample of transiting hot Jupiters, allowing for future detailed population studies.

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arXiv2021

The Magellan-TESS Survey I: Survey Description and Mid-Survey Results

$Kepler$ revealed that roughly one-third of Sun-like stars host planets orbiting within 100 days and between the size of Earth and Neptune. How do these planets form, what are they made of, and do they represent a continuous population or multiple populations? To help address these questions, we began the Magellan-TESS Survey (MTS), which uses Magellan II/PFS to obtain radial velocity (RV) masses of 30 TESS-detected exoplanets and develops an analysis framework that connects observed planet distributions to underlying populations. In the past, small planet RV measurements have been challenging to obtain due to host star faintness and low RV semi-amplitudes, and challenging to interpret due to the potential biases in target selection and observation planning decisions. The MTS attempts to minimize these biases by focusing on bright TESS targets and employing a quantitative selection function and observing strategy. In this paper, we (1) describe our motivation and survey strategy, (2) present our first catalog of planet density constraints for 27 TESS Objects of Interest (TOIs; 22 in our population analysis sample, 12 that are members of the same systems), and (3) employ a hierarchical Bayesian model to produce preliminary constraints on the mass-radius (M-R) relation. We find that the biases causing previous M-R relations to predict fairly high masses at $1~R_\oplus$ have been reduced. This work can inform more detailed studies of individual systems and offer a framework that can be applied to future RV surveys with the goal of population inferences.

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arXiv2021

The TESS Objects of Interest Catalog from the TESS Prime Mission

We present 2,241 exoplanet candidates identified with data from the Transiting Exoplanet Survey Satellite (TESS) during its two-year prime mission. We list these candidates in the TESS Objects of Interest (TOI) Catalog, which includes both new planet candidates found by TESS and previously-known planets recovered by TESS observations. We describe the process used to identify TOIs and investigate the characteristics of the new planet candidates, and discuss some notable TESS planet discoveries. The TOI Catalog includes an unprecedented number of small planet candidates around nearby bright stars, which are well-suited for detailed follow-up observations. The TESS data products for the Prime Mission (Sectors 1-26), including the TOI Catalog, light curves, full-frame images, and target pixel files, are publicly available on the Mikulski Archive for Space Telescopes.

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arXiv2020

Two young planetary systems around field stars with ages between 20-320 Myr from TESS

Planets around young stars trace the early evolution of planetary systems. We report the discovery and validation of two planetary systems with ages $\lesssim 300$ Myr from observations by the Transiting Exoplanet Survey Satellite. TOI-251 is a 40-320 Myr old G star hosting a 2.74 +0.18/-0.18 REarth mini-Neptune with a 4.94 day period. TOI-942 is a 20-160 Myr old K star hosting a system of inflated Neptune-sized planets, with TOI-942b orbiting with a period of 4.32 days, with a radius of 4.81 +0.20/-0.20 REarth, and TOI-942c orbiting in a period of 10.16 days with a radius of 5.79 +0.19/-0.18 REarth. Though we cannot place either host star into a known stellar association or cluster, we can estimate their ages via their photometric and spectroscopic properties. Both stars exhibit significant photometric variability due to spot modulation, with measured rotation periods of $\sim 3.5$ days. These stars also exhibit significant chromospheric activity, with age estimates from the chromospheric calcium emission lines and X-ray fluxes matching that estimated from gyrochronology. Both stars also exhibit significant lithium absorption, similar in equivalent width to well-characterized young cluster members. TESS has the potential to deliver a population of young planet-bearing field stars, contributing significantly to tracing the properties of planets as a function of their age.

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arXiv2020

The K2 and TESS Synergy. I. Updated Ephemerides and Parameters for K2-114, K2-167, K2-237, and K2-261

Although the Transiting Exoplanet Survey Satellite (TESS) primary mission observed the northern and southern ecliptic hemispheres, generally avoiding the ecliptic, and the Kepler space telescope during the K2 mission could only observe near the ecliptic, many of the K2 fields extend far enough from the ecliptic plane that sections overlap with TESS fields. Using photometric observations from both K2 and TESS, combined with archival spectroscopic observations, we globally modeled four known planetary systems discovered by K2 that were observed in the first year of the primary TESS mission. Specifically, we provide updated ephemerides and system parameters for K2-114 b, K2-167 b, K2-237 b, and K2-261 b. These were some of the first K2 planets to be observed by TESS in the first year and include three Jovian sized planets and a sub-Neptune with orbital periods less than 12 days. In each case, the updated ephemeris significantly reduces the uncertainty in prediction of future times of transit, which is valuable for planning observations with the James Webb Space Telescope and other future facilities. The TESS extended mission is expected to observe about half of the K2 fields, providing the opportunity to perform this type of analysis on a larger number of systems.

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arXiv2020

The TESS Phase Curve of KELT-1b Suggests a High Dayside Albedo

We measured the optical phase curve of the transiting brown dwarf KELT-1b (TOI 1476, Siverd et al. 2012) using data from the TESS spacecraft. We found that KELT-1b shows significant phase variation in the TESS bandpass, with a relatively large phase amplitude of $234^{+43}_{-44}$ ppm and a secondary eclipse depth of $371^{+47}_{-49}$ ppm. We also measured a marginal eastward offset in the dayside hotspot of $18.3^\circ\pm7.4^\circ$ relative to the substellar point. We detected a strong phase curve signal attributed to ellipsoidal distortion of the host star, with an amplitude of $399\pm19$ ppm. Our results are roughly consistent with the Spitzer phase curves of KELT-1b (Beatty et al. 2019), but the TESS eclipse depth is deeper than expected. Our cloud-free 1D models of KELT-1b's dayside emission are unable to fit the full combined eclipse spectrum. Instead, the large TESS eclipse depth suggests that KELT-1b may have a significant dayside geometric albedo of $\mathrm{A}_\mathrm{g}\sim0.5$ in the TESS bandpass, which would agree with the tentative trend between equilibrium temperature and geometric albedo recently suggested by Wong et al. 2020. We posit that if KELT-1b has a high dayside albedo, it is likely due to silicate clouds (Gao et al. 2020) that form on KELT-1b's nightside (Beatty et al. 2019, Keating et al. 2019) and are subsequently transported onto the western side of KELT-1b's dayside hemisphere before breaking up.

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arXiv2020

TOI-481 b & TOI-892 b: Two long period hot Jupiters from the Transiting Exoplanet Survey Satellite

We present the discovery of two new 10-day period giant planets from the Transiting Exoplanet Survey Satellite ($TESS$) mission, whose masses were precisely determined using a wide diversity of ground-based facilities. TOI-481 b and TOI-892 b have similar radii ($0.99\pm0.01$ $\rm R_{J}$ and $1.07\pm0.02$ $\rm R_{J}$, respectively), and orbital periods (10.3311 days and 10.6266 days, respectively), but significantly different masses ($1.53\pm0.03$ $\rm M_{J}$ versus $0.95\pm0.07$ $\rm M_{J}$, respectively). Both planets orbit metal-rich stars ([Fe/H]= $+0.26\pm 0.05$ dex and [Fe/H] = $+0.24 \pm 0.05$ dex, for TOI-481 and TOI-892, respectively) but at different evolutionary stages. TOI-481 is a $\rm M_{\star}$ = $1.14\pm0.02$ $\rm M_{\odot}$, $\rm R_{\star}$ = $1.66\pm0.02$ $\rm R_{\odot}$ G-type star ($T_{\rm eff}$ = $5735 \pm 72$ K), that with an age of 6.7 Gyr, is in the turn-off point of the main sequence. TOI-892, on the other hand, is a F-type dwarf star ($T_{\rm eff}$ = $6261 \pm 80$ K), which has a mass of $\rm M_{\star}$ = $1.28\pm0.03$ $\rm M_{\odot}$, and a radius of $\rm R_{\star}$ = $1.39\pm0.02$ $\rm R_{\odot}$. TOI-481 b and TOI-892 b join the scarcely populated region of transiting gas giants with orbital periods longer than 10 days, which is important to constrain theories of the formation and structure of hot Jupiters.

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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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arXiv2019

TOI-132 b: A short-period planet in the Neptune desert transiting a $V=11.3$ G-type star

The Neptune desert is a feature seen in the radius-mass-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here we report the {\it TESS} discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC\,8003-1117-1 (TOI-132). {\it TESS} photometry shows transit-like dips at the level of $\sim$1400 ppm occurring every $\sim$2.11 days. High-precision radial velocity follow-up with HARPS confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of $\sim$11.5 m s$^{-1}$, which, when combined with the stellar mass of $0.97\pm0.06$ $M_{\odot}$, provides a planetary mass of 22.83$^{+1.81}_{-1.80}$ $M_{\oplus}$. Modeling the {\it TESS} high-quality light curve returns a planet radius of 3.43$^{+0.13}_{-0.14}$ $R_{\oplus}$, and therefore the planet bulk density is found to be 3.11$^{+0.44}_{-0.450}$ g cm$^{-3}$. Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3$^{+1.2}_{-2.3}$\%. TOI-132 b is a {\it TESS} Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding the Neptune desert.

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arXiv2019

An Eccentric Massive Jupiter Orbiting a Sub-Giant on a 9.5 Day Period Discovered in the Transiting Exoplanet Survey Satellite Full Frame Images

We report the discovery of TOI-172 b from the Transiting Exoplanet Survey Satellite (TESS) mission, a massive hot Jupiter transiting a slightly evolved G-star with a 9.48-day orbital period. This is the first planet to be confirmed from analysis of only the TESS full frame images, because the host star was not chosen as a two minute cadence target. From a global analysis of the TESS photometry and follow-up observations carried out by the TESS Follow-up Observing Program Working Group, TOI-172 (TIC 29857954) is a slightly evolved star with an effective temperature of $T_{\rm eff}$ =$5645\pm50$ K, a mass of $M_{\star}$ = $1.128^{+0.065}_{-0.061}$ $M_{\odot}$, radius of $R_{\star}$ = $1.777^{+0.047}_{-0.044}$ $R_{\odot}$, a surface gravity of $\log$ $g_{\star}$ = $3.993^{+0.027}_{-0.028}$, and an age of $7.4^{+1.6}_{-1.5}$ Gyr. Its planetary companion (TOI-172 b) has a radius of $R_{\rm P}$ = $0.965^{+0.032}_{-0.029}$ $R_{\rm J}$, a mass of $M_{\rm P}$ = $5.42^{+0.22}_{-0.20}$ $M_{\rm J}$, and is on an eccentric orbit ($e = 0.3806^{+0.0093}_{-0.0090}$). TOI-172 b is one of the few known massive giant planets on a highly eccentric short-period orbit. Future study of the atmosphere of this planet and its system architecture offer opportunities to understand the formation and evolution of similar systems.

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arXiv2019

The Mass of the White Dwarf Companion in the Self-Lensing Binary KOI-3278: Einstein vs. Newton

KOI-3278 is a self-lensing stellar binary consisting of a white-dwarf secondary orbiting a Sun-like primary star. Kruse and Agol (2014) noticed small periodic brightenings every 88.18 days in the Kepler photometry and interpreted these as the result of microlensing by a white dwarf with about 63$\%$ of the mass of the Sun. We obtained two sets of spectra for the primary that allowed us to derive three sets of spectroscopic estimates for its effective temperature, surface gravity, and metallicity for the first time. We used these values to update the Kruse and Agol (2014) Einsteinian microlensing model, resulting in a revised mass for the white dwarf of $0.539^{+0.022}_{-0.020} \, M_{\odot}$. The spectra also allowed us to determine radial velocities and derive orbital solutions, with good agreement between the two independent data sets. An independent Newtonian dynamical MCMC model of the combined velocities yielded a mass for the white dwarf of $0.5122^{+0.0057}_{-0.0058} \, M_{\odot}$. The nominal uncertainty for the Newtonian mass is about four times better than for the Einsteinian, $\pm 1.1\%$ vs. $\pm 4.1\%$ and the difference between the two mass determinations is $5.2 \%$. We then present a joint Einsteinian microlensing and Newtonian radial velocity model for KOI-3278, which yielded a mass for the white dwarf of $0.5250^{+0.0082}_{-0.0089} \, M_{\odot}$. This joint model does not rely on any white dwarf evolutionary models or assumptions on the white dwarf mass-radius relation. We discuss the benefits of a joint model of self-lensing binaries, and how future studies of these systems can provide insight into the mass-radius relation of white dwarfs.

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arXiv2017

A Quadruply Lensed SN Ia: Gaining a Time-Delay...Losing a Standard Candle

We investigate the flux ratio anomalies between macro-model predictions and the observed brightness of the supernova iPTF16geu, as published in a recent paper by More et al., 2017. This group suggested that these discrepancies are, qualitatively, likely due to microlensing. We analyze the plausibility of attributing this discrepancy to microlensing, and find that the discrepancy is too large to be due to microlensing alone. This is true whether one assumes knowledge of the luminosity of the supernova or allows the luminosity to be a free parameter. Varying the dark/stellar ratio likewise doesn't help. In addition, other macro-models with quadruplicity from external shear or ellipticity do not significantly improve to model. Finally, microlensing also makes it difficult to accurately determine the standard candle brightness of the supernova, as the likelihood plot for the intrinsic magnitude of the source (for a perfect macro-model) has a full width half maximum of 0.73 magnitudes. As such, the error for the standard candle brightness is quite large. This reduces the utility of the standard candle nature of type Ia supernovae.

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