- ID:
- ivo://CDS.VizieR/J/AJ/156/227
- Title:
- Photometric observations of the K2-22 system
- Short Name:
- J/AJ/156/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 45 ground-based photometric observations of the K2-22 system collected between 2016 December and 2017 May, which we use to investigate the evolution of the transit of the disintegrating planet K2-22b. Last observed in early 2015, in these new observations we recover the transit at multiple epochs and measure a typical depth of <1.5%. We find that the distribution of our measured transit depths is comparable to the range of depths measured in observations from 2014 and 2015. These new observations also support ongoing variability in the K2-22b transit shape and time, although the overall shallowness of the transit makes a detailed analysis of these transit parameters difficult. We find no strong evidence of wavelength-dependent transit depths for epochs where we have simultaneous coverage at multiple wavelengths, although our stacked Las Cumbres Observatory data collected over days-to-months timescales are suggestive of a deeper transit at blue wavelengths. We encourage continued high-precision photometric and spectroscopic monitoring of this system in order to further constrain the evolution timescale and to aid comparative studies with the other few known disintegrating planets.
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- ID:
- ivo://CDS.VizieR/J/AJ/154/30
- Title:
- Photometric study of fourteen low-mass binaries
- Short Name:
- J/AJ/154/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New CCD photometric observations of fourteen short-period low-mass eclipsing binaries (LMBs) in the photometric filters I, R, and V were used for a light curve analysis. A discrepancy remains between observed radii and those derived from the theoretical modeling for LMBs, in general. Mass calibration of all observed LMBs was performed using only the photometric indices. The light curve modeling of these selected systems was completed, yielding the new derived masses and radii for both components. We compared these systems with the compilation of other known double-lined LMB systems with uncertainties of masses and radii less then 5%, which includes 66 components of binaries where both spectroscopy and photometry were combined together. All of our systems are circular short-period binaries, and for some of them, the photospheric spots were also used. A purely photometric study of the light curves without spectroscopy seems unable to achieve high enough precision and accuracy in the masses and radii to act as meaningful test of the M-R relation for low-mass stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/786/97
- Title:
- Photospheric properties of T Tauri stars
- Short Name:
- J/ApJ/786/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Estimates of the mass and age of young stars from their location in the H-R diagram are limited by not only the typical observational uncertainties that apply to field stars, but also by large systematic uncertainties related to circumstellar phenomena. In this paper, we analyze flux-calibrated optical spectra to measure accurate spectral types and extinctions of 281 nearby T Tauri stars (TTSs). The primary advances in this paper are (1) the incorporation of a simplistic accretion continuum in optical spectral type and extinction measurements calculated over the full optical wavelength range and (2) the uniform analysis of a large sample of stars, many of which are well known and can serve as benchmarks. Comparisons between the non-accreting TTS photospheric templates and stellar photosphere models are used to derive conversions from spectral type to temperature. Differences between spectral types can be subtle and difficult to discern, especially when accounting for accretion and extinction. The spectral types measured here are mostly consistent with spectral types measured over the past decade. However, our new spectral types are one to two subclasses later than literature spectral types for the original members of the TW Hya Association (TWA) and are discrepant with literature values for some well-known members of the Taurus Molecular Cloud. Our extinction measurements are consistent with other optical extinction measurements but are typically 1 mag lower than near-IR measurements, likely the result of methodological differences and the presence of near-IR excesses in most CTTSs. As an illustration of the impact of accretion, spectral type, and extinction uncertainties on the H-R diagrams of young clusters, we find that the resulting luminosity spread of stars in the TWA is 15%-30%. The luminosity spread in the TWA and previously measured for binary stars in Taurus suggests that for a majority of stars, protostellar accretion rates are not large enough to significantly alter the subsequent evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/482/5379
- Title:
- Physical & orbital properties of detached EBs
- Short Name:
- J/MNRAS/482/5379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified and photometrically characterized a sample of 230 detached close-orbiting eclipsing binaries with low-mass main-sequence components (LMMS) from the Catalina Sky Survey. These low-mass stars have both components below 1.0M_{sun}_, orbital periods shorter than 2-days and effective temperatures below to 5720K. The adopted method provided a robust estimate of stellar parameters (as mass and fractional radius) by using only light curves and photometric colors, since no spectroscopic information was available for these objects. Each light curve was modeled with the JKTEBOP code together with an asexual genetic algorithm to obtain the most coherent values for the fitted parameters. This new sample of short-period detached eclipsing binaries, with low-mass main-sequence stars (LMMS) considerably increases the number of previously known systems. Which allows us to derive masses and radii in statistically significant samples for the investigation of the correlation between radius inflation and other basic stellar parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/L19
- Title:
- Physics of Kepler hot rocky planetary candidates
- Short Name:
- J/ApJ/742/L19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper outlines a simple approach to evaluate the atmospheric composition of hot rocky planets by assuming different types of planetary composition and using corresponding model calculations. To explore hot atmospheres above 1000K, we model the vaporization of silicate magma and estimate the range of atmospheric compositions according to the planet's radius and semi-major axis for the Kepler 2011 February data release. Our results show five atmospheric types for hot, rocky super-Earth atmospheres, strongly dependent on the initial composition and the planet's distance to the star. We provide a simple set of parameters that can be used to evaluate atmospheric compositions for current and future candidates provided by the Kepler mission and other searches.
- ID:
- ivo://CDS.VizieR/J/AJ/156/22
- Title:
- Planetary candidates from K2 Campaign 16
- Short Name:
- J/AJ/156/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Given that Campaign 16 of the K2 mission is one of just two K2 campaigns observed so far in "forward-facing" mode, which enables immediate follow-up observations from the ground, we present a catalog of interesting targets identified through photometry alone. Our catalog includes 30 high-quality planet candidates (showing no signs of being non-planetary in nature), 48 more ambiguous events that may be either planets or false positives, 164 eclipsing binaries, and 231 other regularly periodic variable sources. We have released light curves for all targets in C16 and have also released system parameters and transit vetting plots for all interesting candidates identified in this paper. Of particular interest is a candidate planet orbiting the bright F dwarf HD 73344 (V=6.9, K=5.6) with an orbital period of 15 days. If confirmed, this object would correspond to a 2.56+/-0.18 R_{Earth}_ planet and would likely be a favorable target for radial velocity characterization. This paper is intended as a rapid release of planet candidates, eclipsing binaries, and other interesting periodic variables to maximize the scientific yield of this campaign, and as a test run for the upcoming TESS mission, whose frequent data releases call for similarly rapid candidate identification and efficient follow up.
- ID:
- ivo://CDS.VizieR/J/ApJS/222/14
- Title:
- Planetary candidates from 1st yr K2 mission
- Short Name:
- J/ApJS/222/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Kepler Space Telescope is currently searching for planets transiting stars along the ecliptic plane as part of its extended K2 mission. We processed the publicly released data from the first year of K2 observations (Campaigns 0, 1, 2, and 3) and searched for periodic eclipse signals consistent with planetary transits. Out of the 59174 targets that we searched, we detect 234 planetary candidates around 208 stars. These candidates range in size from gas giants to smaller than the Earth, and range in orbital periods from hours to over a month. We conducted initial reconnaissance spectroscopy of 68 of the brighter candidate host stars, and present high-resolution optical spectra for these stars. We make all of our data products, including light curves, spectra, and vetting diagnostics available to users online.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/11
- Title:
- Planet candidates and EBs in K2 campaigns 0-8
- Short Name:
- J/ApJS/244/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We implement a search for exoplanets in campaigns zero through eight (C0-8) of the K2 extension of the Kepler spacecraft. We apply a modified version of the Quasi-periodic Automated Transit Search (QATS) planet search algorithm to K2 light curves produced by the EVEREST pipeline, carrying out the C0-8 search on 1.5x10^5^ target stars with magnitudes in the range of Kp=9-15. We detect 818 transiting planet candidates, of which 374 were undiscovered by prior searches, with {64, 15, 5, 2, 1} in {2, 3, 4, 5, 6}-planet multiplanet candidate systems, respectively. Of the new planets detected, 100 orbit M dwarfs, including one that is potentially rocky and in the habitable zone. A total of 154 of our candidates reciprocally transit with our solar system: they are geometrically aligned to see at least one solar system planet transit. We find candidates that display transit timing variations and dozens of candidates on both period extremes with single transits or ultrashort periods. We point to evidence that our candidates display similar patterns in frequency and size-period relation to confirmed planets, such as tentative evidence for the radius gap. Confirmation of these planet candidates with follow-up studies will increase the number of K2 planets by up to 50%, and characterization of their host stars will improve statistical studies of planet properties. Our sample includes many planets orbiting bright stars amenable for radial velocity follow-up and future characterization with JWST. We also list the 579 eclipsing binary systems detected as part of this search.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/7
- Title:
- Planet candidates discovered using K2's 1st yr
- Short Name:
- J/ApJS/226/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 197 planet candidates discovered using data from the first year of the NASA K2 mission (Campaigns 0-4), along with the results of an intensive program of photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. We distill these candidates into sets of 104 validated planets (57 in multi-planet systems), 30 false positives, and 63 remaining candidates. Our validated systems span a range of properties, with median values of R_P_=2.3R_{Earth}_, P=8.6 days, Teff=5300K, and Kp=12.7mag. Stellar spectroscopy provides precise stellar and planetary parameters for most of these systems. We show that K2 has increased by 30% the number of small planets known to orbit moderately bright stars (1-4R_{Earth}_, Kp=9-13mag). Of particular interest are 76 planets smaller than 2R_{Earth}_, 15 orbiting stars brighter than Kp=11.5mag, 5 receiving Earth-like irradiation levels, and several multi-planet systems-including 4 planets orbiting the M dwarf K2-72 near mean-motion resonances. By quantifying the likelihood that each candidate is a planet we demonstrate that our candidate sample has an overall false positive rate of 15%-30%, with rates substantially lower for small candidates (<2R_{Earth}_) and larger for candidates with radii >8R_{Earth}_ and/or with P<3days. Extrapolation of the current planetary yield suggests that K2 will discover between 500 and 1000 planets in its planned four-year mission, assuming sufficient follow-up resources are available. Efficient observing and analysis, together with an organized and coherent follow-up strategy, are essential for maximizing the efficacy of planet-validation efforts for K2, TESS, and future large-scale surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/155/21
- Title:
- Planet candidates from K2 campaigns 5-8
- Short Name:
- J/AJ/155/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 151 planet candidates orbiting 141 stars from K2 campaigns 5-8 (C5-C8), identified through a systematic search of K2 photometry. In addition, we identify 16 targets as likely eclipsing binaries, based on their light curve morphology. We obtained follow-up optical spectra of 105/141 candidate host stars and 8/16 eclipsing binaries to improve stellar properties and to identify spectroscopic binaries. Importantly, spectroscopy enables measurements of host star radii with ~10% precision, compared to ~40% precision when only broadband photometry is available. The improved stellar radii enable improved planet radii. Our curated catalog of planet candidates provides a starting point for future efforts to confirm and characterize K2 discoveries.
