Search

We present the discovery and characterization of six short-period, transiting giant planets from NASA's Transiting Exoplanet Survey Satellite (TESS) -- TOI-1811 (TIC 376524552), TOI-2025 (TIC 394050135), TOI-2145 (TIC 88992642), TOI-2152 (TIC 395393265), TOI-2154 (TIC 428787891), & TOI-2497 (TIC 97568467). All six planets orbit bright host stars (8.9, Comment: 20 Pages, 6 Figures, 8 Tables, Accepted by MNRAS

A near-Earth object (NEO) is any small Solar system body whose orbit brings it to proximity with Earth. Currently, more than 20000 NEOs are detected, most of which have diameters less than 1 km. The study of NEOs is significant to understand the solar system. NEOs formed in the very early stage of solar system according to isotope dating, and remain most original material in proto-planetary disk. Thus, the study of NEOs can reveal the components of early solar system. Besides, NEOs are also important to explain the formation of Earth-Moon systems in giant impact hypothesis, i.e., a mar-size asteroid hit Earth 4.5 billion years ago and the fragments around Earth formed Moon via gravitational accretion. Furthermore, survey of NEOs is also important for human beings, because of the potentially hazardous objects (PHOs), which lead to the Cretaceous-Paleogene (K-Pg) extinction event, as well as the Tunguska event. Fortunately, we have lots of NEO survey programs, e.g., Catalina Sky Survey, Near-Earth Asteroid Tracking, Pan-STARRS, Zwicky Transient Facility in ground, and Near-Earth Object WISE in space with near infrared telescope, etc. These projects provide a nearly completed catalog for NEOs with diameter>1 km. We can determine the orbits of these NEOs via the astrometric time series data. However, lots of smaller NEOs with diameter millions tons) of the asteroid. Besides, the big fragments of the asteroid after explosion may lead to more impacts on Earth and make conditions worse. Better forethought plans need experts in astronomy, geology, life science, climatology etc., to discuss together. The NEOs may be harmful if it impacts Earth. However, the resources on asteroid, e.g., water, metal can be utilized by human beings. Utilizing the resources in space is the only way to break through the limits of Earth’s resources, and extend the footprint of human being further in space. Currently, some companies are set up and aim to mine on asteroids, e.g., the Planetary Resources Company and the Deep Space Industries. Chinese people also set up a company named Origin Space to study the plan in this field. Although, there is a long way to go, including lots of crucial techniques need to be studied, the success of development of the resources on asteroid would bring our technique and civilization in a new era.

A type of compactly spaced and comparably sized multi-exoplanet system similar to TRAPPIST-1 has been discovered recently. The stability of these systems is an important issue, requiring further study. We examined how the initial inclinations influence the stability of multi-planet systems and derived an empirical formula describing the dependence of the instability time-scale on planetary mass, space separation and initial inclination. We find the following. (i) If space separations between planets are greater than 12RH (mutual Hill radius), coplanar multi-planet systems with 10−6 ≤ μ ≤ 10−3 (reduced planetary mass μ = m/M*) will remain stable within 1010Tin (the innermost orbital period). (ii) If initial inclinations of planets are smaller than 10° and space separations are greater than 10RH, multi-planet systems consisting of ≥5 planets with μ ≥ 10−5 will remain stable within 1010Tin. (iii) Initial inclinations in [0°, 10°] have inconsequential effects on the instability time-scales of massive multi-planet systems (μ ≥ 10−5), because eccentricities (excited during evolution) dominate the stability of these systems. (iv) If the initial inclinations are large enough (≥10°), sharp increases of instability time-scales in groups with 10−3 ≥ μ ≥ 10−5 will be moderated. This article presents a comprehensive study of the influence of inclination on the stability of multi-planet systems and discusses critical space separations for a multi-planet system becoming unstable.

The habitability of planets is closely connected with the stellar activity, mainly the frequency of flares and the distribution of flare energy. Kepler and TESS find many flaring stars are detected via precise time-domain photometric data, and the frequency and energy distribution of stellar flares on different types of stars are studied statistically. However, the completeness and observational bias of detected flare events from different missions (e.g. Kepler and TESS) vary a lot. We use a unified data processing and detection method for flares events based on the light curve from Kepler and TESS. Then we perform injection and recovery tests in the original light curve of each star for each flare event to correct the completeness and energy of flares. Three samples of flaring stars are selected from Kepler and TESS, with rotating periods from 1 to $\sim$ 5 days. Adopting a hot-blackbody assumption, our results show that the cumulative flare frequency distributions (FFDs) of the same stars in Kepler and TESS bands tend to be consistent after correction, revealing a more natural flaring frequency and energy distribution. Our results also extend the low-energy limit in cumulative FFD fitting to $10^{31.5-33}$ erg on different types of stars. For solar-type stars, the average power-law index of cumulative FFD ($\alpha_{\rm cum}$) is $-0.84$, which indicates that low-energy flares contribute less to the total flare energy. With a piecewise correlation between $\alpha_{\rm cum}$ and $T_{\rm eff}$, $\alpha_{\rm cum}$ first rises with $T_{\rm eff}$ from M2 to K1 stars, then slightly decreases for stars hotter than K1., Comment: 22 pages, 12 figures, 4 tables. Published in AJ

The dynamical history of stars influences the formation and evolution of planets significantly. To explore the influence of dynamical history on planet formation and evolution from observations, we assume that stars who experienced significantly different dynamical histories tend to have different relative velocities. Utilizing the accurate Gaia-Kepler Stellar Properties Catalog, we select single main-sequence stars and divide these stars into three groups according to their relative velocities, i.e. high-V, medium-V, and low-V stars. After considering the known biases from Kepler data and adopting prior and posterior correction to minimize the influence of stellar properties on planet occurrence rate, we find that high-V stars have a lower occurrence rate of super-Earths and sub-Neptunes (1--4 R$_{\rm \oplus}$, P, Comment: 30 pages, 17 figures, accepted for publication in AJ

The point spread function (PSF) plays a very important part in image post-processing and high-precion astrometry and photometry. It is necessary to analyse the properties of the PSF before we use it to process data. However, in real observations, the PSF is affected by many different factors and the shape of it has inevitable spatial and temporal variations that can be hard to describe. In this paper, we propose a clustering method to evaluate the shape variations of PSFs. We analyse the performance of this method with simulated PSFs under different observation conditions. Then, we process two observational data sets with this method. The PSF clustering results can provide a reference for checking observation conditions and can be used for astrometry based on PSF fitting. In general, our method can reveal the morphologic similarities of different PSFs and can provide a reference for observations. The cluster revealed by our method can provide a reference for the evaluation of observation conditions and for the post-processing of astronomical observation data.

Telescopes with a wide field of view (greater than 1°) and small apertures (less than 2 m) are workhorses for observations such as sky surveys and fast-moving object detection, and play an important role in time-domain astronomy. However, images captured by these telescopes are contaminated by optical system aberrations, atmospheric turbulence, tracking errors and wind shear. To increase the quality of images and maximize their scientific output, we propose a new blind deconvolution algorithm based on statistical properties of the point spread functions (PSFs) of these telescopes. In this new algorithm, we first construct the PSF feature space through principal component analysis, and then classify PSFs from a different position and time using a self-organizing map. According to the classification results, we divide images of the same PSF types and select these PSFs to construct a prior PSF. The prior PSF is then used to restore these images. To investigate the improvement that this algorithm provides for data reduction, we process images of space debris captured by our small-aperture wide-field telescopes. Comparing the reduced results of the original images and the images processed with the standard Richardson–Lucy method, our method shows a promising improvement in astrometry accuracy.

International audience; The CHinense Exoplanet Searching Program from Antarctica is a ground-based wide-field photometric survey using the AST3 and CSTAR telescopes located at Dome A, Antarctica. Blessed with the unparalleled observing conditions on the highest point of the Antarctic plateau, three remotely controlled, fully automatic telescopes (AST3-I, AST3-II, and CSTAR-II) carried out continuous high-precision photometric surveys through the polar nights of 2016 and 2017. During the observing seasons of 2016, a total of 26,578 light curves were obtained for stars within the area of the southern continuous viewing zone of TESS, covering an i-band magnitude range from 7.5 to 15. At m i = 10, photometric precision reaches ∼2 mmag, allowing possible discoveries of sub-Jupiter-size exoplanets. Here we report 20 stellar flares with i-band energies larger than 1034 erg detected in the 2016 data set of AST3-II, all from different sources. We model the stellar flares and calculate the durations, amplitudes, energies, and skewnesses. The flare properties and the stellar properties of their sources are presented in this work.

We analyze 1598 serendipitous Chandra X-ray observations of 462 radio-quiet quasars to constrain the frequency of extreme amplitude X-ray variability that is intrinsic to the quasar corona and innermost accretion flow. The quasars in this investigation are all spectroscopically confirmed, optically bright ($m_i \leq$ 20.2), and contain no identifiable broad absorption lines in their optical/ultraviolet spectra. This sample includes quasars spanning $z \approx$ 0.1 - 4 and probes X-ray variability on timescales of up to $\approx$ 12 rest-frame years. Variability amplitudes are computed between every epoch of observation for each quasar and are analyzed as a function of timescale and luminosity. The tail-heavy distributions of variability amplitudes at all timescales indicate that extreme X-ray variations are driven by an additional physical mechanism and not just typical random fluctuations of the coronal emission. Similarly, extreme X-ray variations of low-luminosity quasars seem to be driven by an additional physical mechanism, whereas high-luminosity quasars seem more consistent with random fluctuations. The amplitude at which an X-ray variability event can be considered extreme is quantified for different timescales and luminosities. Extreme X-ray variations occur more frequently at long timescales ( $\Delta t \gtrsim$ 300 days) than at shorter timescales, and in low-luminosity quasars compared to high-luminosity quasars over a similar timescale. A binomial analysis indicates that extreme intrinsic X-ray variations are rare, with a maximum occurrence rate of, Comment: 19 pages, 11 figures

We present 127 new transit light curves for 39 hot Jupiter systems, obtained over the span of five years by two ground-based telescopes. A homogeneous analysis of these newly collected light curves together with archived spectroscopic, photometric, and Doppler velocimetric data using EXOFASTv2 leads to a significant improvement in the physical and orbital parameters of each system. All of our stellar radii are constrained to accuracies of better than 3\%. The planetary radii for 37 of our 39 targets are determined to accuracies of better than $5\%$. Compared to our results, the literature eccentricities are preferentially overestimated due to the Lucy-Sweeney bias. Our new photometric observations therefore allow for significant improvement in the orbital ephemerides of each system. Our correction of the future transit window amounts to a change exceeding $10\,{\rm min}$ for ten targets at the time of JWST's launch, including a $72\,{\rm min}$ change for WASP-56. The measured transit mid-times for both literature light curves and our new photometry show no significant deviations from the updated linear ephemerides, ruling out in each system the presence of companion planets with masses greater than $0.39 - 5.0\, rm M_{\oplus}$, $1.23 - 14.36\, \rm M_{\oplus}$, $1.65 - 21.18\, \rm M_{\oplus}$, and $0.69 - 6.75\, \rm M_{\oplus}$ near the 1:2, 2:3, 3:2, and 2:1 resonances with the hot Jupiters , respectively, at a confidence level of $\pm 1\,\sigma$. The absence of resonant companion planets in the hot Jupiter systems is inconsistent with the conventional expectation from disk migration., Comment: 28 pages,9 figures, accepted for publication in ApJS

Located at Dome A, the highest point of the Antarctic plateau, the Chinese Kunlun station is considered to be one of the best ground-based photometric sites because of its extremely cold, dry, and stable atmosphere(Saunders et al. 2009). A target can be monitored from there for over 40 days without diurnal interruption during a polar winter. This makes Kunlun station a perfect site to search for short-period transiting exoplanets. Since 2008, an observatory has been built at Kunlun station and three telescopes are working there. Using these telescopes, the AST3 project has been carried out over the last six years with a search for transiting exoplanets as one of its key programs (CHESPA). In the austral winters of 2016 and 2017, a set of target fields in the Southern CVZ of TESS (Ricker et al. 2009) were monitored by the AST3-II telescope. In this paper, we introduce the CHESPA and present the first data release containing photometry of 26,578 bright stars (m_i < 15). The best photometric precision at the optimum magnitude for the survey is around 2 mmag. To demonstrate the data quality, we also present a catalog of 221 variables with a brightness variation greater than 5 mmag from the 2016 data. Among these variables, 179 are newly identified periodic variables not listed in the AAVSO databasea), and 67 are listed in the Candidate Target List(Stassun et al. 2017). These variables will require careful attention to avoid false-positive signals when searching for transiting exoplanets. Dozens of new transiting exoplanet candidates will be also released in a subsequent paper(Zhang et al. 2018b)., 42 pages, 23 figures and 4 tables, ApJS accepted

We report first results from the CHinese Exoplanet Searching Program from Antarctica (CHESPA)---a wide-field high-resolution photometric survey for transiting exoplanets carried out using telescopes of the AST3 (Antarctic Survey Telescopes times 3) project. There are now three telescopes (AST3-I, AST3-II, and CSTAR-II) operating at Dome A---the highest point on the Antarctic Plateau---in a fully automatic and remote mode to exploit the superb observing conditions of the site, and its long and uninterrupted polar nights. The search for transiting exoplanets is one of the key projects for AST3. During the Austral winters of 2016 and 2017 we used the AST3-II telescope to survey a set of target fields near the southern ecliptic pole, falling within the continuous viewing zone of the TESS mission \citep{Ricker10}. The first data release of the 2016 data, including images, catalogs and lightcurves of 26578 bright stars ($7.5\le i \le15$) was presented in \citet{Zhang18}. The best precision, as measured by the RMS of the lightcurves at the optimum magnitude of the survey ($i=10$), is around 2\,mmag. We detect 222 objects with plausible transit signals from these data, 116 of which are plausible transiting exoplanet candidates according to their stellar properties as given by the TESS Input Catalog \citep{Stassun17}, Gaia DR2 \citep{Gaia18} and TESS-HERMES spectroscopy \citep{Sharma18}. With the first data release from TESS expected in late 2018, this candidate list will be a timely for improving the rejection of potential false positives., 49 pages, 23 figures, 3 tables

International audience; From the experiences learned in three decades of exoplanet search, wide-field transit surveys have proven to be one of the most effective ways to detect exoplanets. Wide field of view, however, suffers from high false-positive rates caused by blended eclipsing binaries. The chromaticity in eclipse depth is an effective feature to distinguish low-depth eclipsing binaries from transiting exoplanets, making multiple-band photometry follow-up advantageous before a target is passed onto more expensive spectroscopic follow-up. Moreover, a multiple-band photometric survey is itself a powerful method to find and vet planetary candidates and narrow down the candidate list of high-priority targets. In this work, we report the first results of a dual-band (Sloan-g and -i) wide-field photometry survey—the Chinese Small Telescope ARray II (CSTAR-II), an updated version of the original CSTAR. As a key component of the Chinese Exoplanet Searching Program from Antarctica, CSTAR-II has been tested thoroughly at a remote arctic site near Mohe during the winter of 2014. In total, 13,531 light curves with the best overall photometric precision of ∼3 mmag were extracted from 7721 stars in the Sloan-g and -i bands. Using a robust method, we have detected 63 variables, of which 48 are newly discovered. The dual-band photometric results as well as the stellar properties of the detected sources are provided in this work.

During the evolution of proto-planetary disc, photo-evaporations of both central and external stars play important roles. Considering the complicated radiation surroundings in the clusters, where the star formed, the proto-planetary discs survive in different lifetimes due to flyby events. In this paper, we mainly focus on the disc around a T Tauri star, which encounters with another main-sequence star with different temperatures in hyperbolic orbits with different peri-center distances, eccentricities and inclinations. We find the criterion for gap-opening due to photo-evaporation of central star after the flyby event. A gap is opened in the late stage of gas disc, and induce that the gap only influence the planet formation and migration limitedly. If the flyby orbit has a moderate value of peri-center distance, which weakly depends on the eccentricity and inclination, the external photo-evaporation lead to a maximum mass loss during the flyby event. Flyby stars in orbits with smaller eccentricities or larger inclinations induce larger mass loss. Adopting a simple multiple flyby models, we conclude that in open clusters, gas discs usually survive in typical lifetimes between 1 and 10 Myr, except there are many massive stars in dense open clusters. In globular clusters, discs disperse very quickly and hardly produce the gas giant planets. The fast-depleted discs are probably responsible for the null detection of giant planets in globular clusters., Comment: accepted by MNRAS

The three Antarctic Survey Telescopes (AST3) aim to carry out time domain imaging survey at Dome A, Antarctica. The first of the three telescopes (AST3-1) was successfully deployed on January 2012. AST3-1 is a 500\,mm aperture modified Schmidt telescope with a 680\,mm diameter primary mirror. AST3-1 is equipped with a SDSS $i$ filter and a 10k $\times$ 10k frame transfer CCD camera, reduced to 5k $\times$ 10k by electronic shuttering, resulting in a 4.3 deg$^2$ field-of-view. To verify the capability of AST3-1 for a variety of science goals, extensive commissioning was carried out between March and May 2012. The commissioning included a survey covering 2000 deg$^2$ as well as the entire Large and Small Magellanic Clouds. Frequent repeated images were made of the center of the Large Magellanic Cloud, a selected exoplanet transit field, and fields including some Wolf-Rayet stars. Here we present the data reduction and photometric measurements of the point sources observed by AST3-1. We have achieved a survey depth of 19.3\,mag in 60 s exposures with 5\,mmag precision in the light curves of bright stars. The facility achieves sub-mmag photometric precision under stable survey conditions, approaching its photon noise limit. These results demonstrate that AST3-1 at Dome A is extraordinarily competitive in time-domain astronomy, including both quick searches for faint transients and the detection of tiny transit signals., 12 pages, 8 figures, accepted for publication in MNRAS, the dataset is public in http://explore.china-vo.org/

Planetary systems can survive the stellar evolution, as evidenced by the atmospheric metal pollution and dusty disks of single white dwarfs. Recent observations show that 1 to 4 percent of single white dwarfs are accompanied by dusty disks, while the occurrence rate of metal pollution is about 25 to 50 percent . The dusty disks and metal pollution have been associated with accretion of remnant planetary systems around white dwarfs, yet the relation between these two phenomena is still unclear. Here we suggest an evolutionary scenario to link the two observational phenomena. By analyzing a sample of metal polluted white dwarfs, we find that the mass accretion rate onto the white dwarf generally follows a broken power law decay, which matches well with the theoretical prediction, if assuming dust accretion is primarily driven by Poynting-Robertson drag and the dust source is primarily delivered via dynamically falling asteroids perturbed by a Jovian planet. The presence of disks is mainly at the early stage (about 0.1 to 0.7 billion years) of the whole process of metal pollution, which is detectable until about 8 billion years, naturally explaining the fraction (about 2-16 percent) of metal-polluted white dwarfs having dusty disks. The success of this scenario also implies that the configuration of an asteroid belt with an outer gas giant might be common around stars of several solar masses., Comment: 33 pages, 3 figures, 10 supplementary figures, 3 supplementary tables. Published in Nature Astronomy

We present ten $R$-band photometric observations of eight different transits of the hot Jupiter HAT-P-33b, which has been targeted by our Transiting Exoplanet Monitoring Project (TEMP). The data were obtained by two telescopes at the Xinglong Station of National Astronomical Observatories of China (NAOC) from 2013 December through 2016 January, and exhibit photometric scatter of $1.6-3.0\,\rm{mmag}$. After jointly analyzing the previously published photometric data, radial-velocity (RV) measurements, and our new light curves, we revisit the system parameters and orbital ephemeris for the HAT-P-33b system. Our results are consistent with the published values except for the planet-to-star radius ratio ($R_{P}/R_{*}$), the ingress/egress duration ($\tau$) and the total duration ($T_{14}$), which together indicate a slightly shallower and shorter transit shape. Our results are based on more complete light curves, whereas the previously published work had only one complete transit light curve. No significant anomalies in Transit Timing Variations (TTVs) are found, and we place upper mass limits on potential perturbers, largely supplanting the loose constraints provided by the extant RV data. The TTV limits are stronger near mean-motion resonances, especially for the low-order commensurabilities. We can exclude the existence of a perturber with mass larger than 0.6, 0.3, 0.5, 0.5, and $0.3\,{\rm M_\oplus}$ near the 1:3, 1:2, 2:3, 3:2, and 2:1 resonances, respectively., Comment: Accepted for AJ

Proxima Centauri is known as the closest star from the Sun. Recently, radial velocity observations revealed the existence of an Earth-mass planet around it. With an orbital period of ~11 days, the surface of Proxima Centauri b is temperate and might be habitable. We took a photometric monitoring campaign to search for its transit, using the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. A transit-like signal appearing on 2016 September 8th, is identified tentatively. Its midtime, $T_{C}=2,457,640.1990\pm0.0017$ HJD, is consistent with the predicted ephemeris based on RV orbit in a 1$\sigma$ confidence interval. Time-correlated noise is pronounced in the light curve of Proxima Centauri, affecting detection of transits. We develop a technique, in a Gaussian process framework, to gauge the statistical significance of potential transit detection. The tentative transit signal reported here, has a confidence level of $2.5\sigma$. Further detection of its periodic signals is necessary to confirm the planetary transit of Proxima Centauri b. We plan to monitor Proxima Centauri in next Polar night at Dome A in Antarctica, taking the advantage of continuous darkness. \citet{Kipping17} reported two tentative transit-like signals of Proxima Centauri b, observed by the Microvariability and Oscillation of Stars space Telescope in 2014 and 2015, respectively. The midtransit time of our detection is 138 minutes later than that predicted by their transit ephemeris. If all the signals are real transits, the misalignment of the epochs plausibly suggests transit timing variations of Proxima Centauri b induced by an outer planet in this system., Comment: 17 pages, 8 figures, 2 tables, accepted by The Astronomical Journal

Many exoplanets have been found in orbits close to their host stars and thus they are subject to the effects of photo-evaporation. Previous studies have shown that a large portion of exoplanets detected by the Kepler mission have been significantly eroded by photo-evaporation. In this paper, we numerically study the effects of photo-evaporation on the orbital evolution of a hypothesized moon system around a planet. We find that photo-evaporation is crucial to the stability of the moon system. Photo-evaporation can erode the atmosphere of the planet thus leading to significant mass loss. As the planet loses mass, its Hill radius shrinks and its moons increase their orbital semi-major axes and eccentricities. When some moons approach their critical semi-major axes, global instability of the moon system would be triggered, which usually ends up with two, one or even zero surviving moons. Some lost moons could escape from the moon system to become a new planet orbiting the star or run away further to become a free-floating object in the Galaxy. Given the destructive role of photo-evaporation, we speculate that exo-moons are less common for close-in planets ($, accepted by ApJ , 14 pages, 9 figures, 2 tables

Author(s): Wang, Yong-Hao; Wang, Songhu; Hinse, Tobias C; Wu, Zhen-Yu; Davis, Allen B; Hori, Yasunori; Yoon, Joh-Na; Han, Wonyong; Nie, Jun-Dan; Liu, Hui-Gen; Zhang, Hui; Zhou, Ji-Lin; Wittenmyer, RA; Peng, Xi-Yan; Laughlin, Gregory | Abstract: © 2019. The American Astronomical Society. All rights reserved. During the past five years, 6, 7, and 26 transit observations were carried out for the HAT-P-9b, HAT-P-32b, and HAT-P-36b systems, respectively, through the Transiting Exoplanet Monitoring Project network. Combined with the published photometric data and radial-velocity measurements, our new photometry allows us to revisit the system parameters and search for additional close-in planetary companions in these hot Jupiter systems. We measure an updated R P /R ∗ = 0.1260 ±0.0011 for HAT-P-36 system in the R band, which is 4.5σ larger than the published i-band radius ratio of 0.1186 ±0.0012. We also perform a transit timing variation (TTV) analysis for each system. Because no significant TTVs were found, we place an upper mass limit on an additional planet for each system.

We report the photometry of six transits of the hot Jupiter HAT-P-29b obtained from 2013 October to 2015 January. We analyze the new light curves, in combination with the published photometric, and Doppler velocimetric, and spectroscopic measurements, finding an updated orbital ephemeris for the HAT-P-29 system, $T_{\rm C}[0]= 2456170.5494(15)\,[\rm{BJD_{TDB}}]$ and $P=5.723390(13) \,{\rm days}$. It is $17.63\,{\rm s}$ ($4.0\,\sigma$) longer than the previously published value, amounting to errors exceeding $2.5\,\rm{hrs}$ at the time of writing (on UTC 2018 June 1). The measured transit mid-times for HAT-P-29b show no compelling evidence of timing anomalies from a linear model, which rules out the presence of a perturbers with masses greater than $0.6$, $0.7$, $0.5$, and $0.4\,{\rm M_\oplus}$ near the $1:2$, $2:3$, $3:2$, and $2:1$ resonances with HAT-P-29b, respectively., Comment: Accepted for publication in AJ

We present eight new light curves of the transiting extra-solar planet HAT-P-25b obtained from 2013 to 2016 with three telescopes at two observatories. We use the new light curves, along with recent literature material, to estimate the physical and orbital parameters of the transiting planet. Specifically, we determine the mid-transit times (T$_{C}$) and update the linear ephemeris, T$_{C[0]}$=2456418.80996$\pm$0.00025 [$\mathrm{BJD}_\mathrm{TDB}$] and P=3.65281572$\pm$0.00000095 days. We carry out a search for transit timing variations (TTVs), and find no significant TTV signal at the $\Delta T=$80 s-level, placing a limit on the possible strength of planet-planet interactions ($\mathrm{TTV_{G}}$). In the course of our analysis, we calculate the upper mass-limits of the potential nearby perturbers. Near the 1:2, 2:1, and 3:1 resonances with HAT-P-25b, perturbers with masses greater than 0.5, 0.3, and 0.5 $\mathrm{M_{\oplus}}$ respectively, can be excluded. Furthermore, based on the analysis of TTVs caused by light travel time effect (LTTE) we also eliminate the possibility that a long-period perturber exists with $M_{\rm p}> 3000 \,\mathrm{M_{J}}$ within $a=11.2\,{\rm AU}$ of the parent star., Comment: Published in PASP

The nearly circular (mean eccentricity ~0.06) and coplanar (mean mutual inclination ~3 deg) orbits of the Solar System planets motivated Kant and Laplace to put forth the hypothesis that planets are formed in disks, which has developed into the widely accepted theory of planet formation. Surprisingly, the first several hundred extrasolar planets (mostly Jovian) discovered using the Radial Velocity (RV) technique are commonly on eccentric orbits ( ~ 0.3). This raises a fundamental question: Are the Solar System and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the LAMOST observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), while the other half are multiple-transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with ~0.3, while the multiples are on nearly circular ( = 0.04^{+0.03}_{-0.04}) and coplanar ( = 1.4^{+0.8}_{-1.1} deg) orbits similar to the Solar System planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation ~(1-2)x between mean eccentricities and mutual inclinations. The prevalence of circular orbits and the common relation may imply that the solar system is not so atypical in the galaxy after all., Comment: 2016 PNAS published, see http://www.pnas.org/content/early/2016/09/21/1604692113.abstract

This is the first report of the antioxidant response of Daphnia magna following a short-term response to the water soluble fractions of no. 20 diesel oil. Daphnia magna was exposed for 24h to nominal concentrations of 0, 0.005, 0.01, 0.05, 0.1, 0.5 or 1.0 mg/L diesel oil. Following this exposure, the activities of catalase (CAT) and glutathione S-transferase (GST) were induced significantly on the whole compared to control group; the activity of selenium-dependent glutathione peroxidase (Se-GPx) were inhibited significantly on the whole; the activity of superoxide dismutase (SOD) only responded to diesel oil exposure at the two highest exposure concentrations; the activity of glutathione reductase (GR) and the content of reduced glutathione (GSH) were greatly activated in Group 4; and the content of oxidized glutathione (GSSG) were induced at two different concentrations. Total glutathione (tGSH) and GSH/GSSG ratio were also calculated to analyze the occurrence of oxidative stress. In conclusion, ...

Transit times around single stars can be described well by a linear ephemeris. However, transit times in circumbinary systems are influenced both by the gravitational perturbations and the orbital phase variations of the central binary star. Adopting a coplanar analog of Kepler-16 as an example, we find that circumbinary planets can transit the same star more than once during a single planetary orbit, a phenomenon we call "tight transits". In certain geometric, the projected orbital velocity of the planet and the secondary star can approach zero and change sign, resulting in very long transits and/or 2-3 transits during a single binary orbit. Whether tight transits are possible for a particular system depends primarily on the binary mass ratio and the orbital architecture of both the binary and the planet. We derive a time-dependent criterion to judge when tight transits are possible for any circumbinary system. These results are verified with full dynamical integrations that also reveal other tight transit characteristics, i.e., the transit durations and the intervals between tight transits. For the seven currently known circumbinary systems, we estimate these critical parameters both analytically and numerically. Due to the mutual inclination between the planet and the binary, tight transits can only occur across the less massive star B in Kepler-16, -34, -35, and -47 (for both planets). The long-term average frequency of tight transits (compared to typical transits) for Kepler-16, -34, and -35 are estimated to be several percent. Using full numerical integrations, the next tight transit for each system is predicted and the soonest example appears to be Kepler-47b and -47c, which are likely to have tight transits before 2025. These unique and valuable events often deserve special observational scrutiny., Comment: 10 pages, 5 figures, Accepted by ApJ, 2014, 790, 1

We present the results of our recent study on the interactions between a giant planet and a self-gravitating gas disk. We investigate how the disk's self-gravity affects the gap formation process and the migration of the giant planet. Two series of 1-D and 2-D hydrodynamic simulations are performed. We select several surface densities and focus on the gravitationally stable region. To obtain more reliable gravity torques exerted on the planet, a refined treatment of disk's gravity is adopted in the vicinity of the planet. Our results indicate that the net effect of the disk's self-gravity on the gap formation process depends on the surface density of the disk. We notice that there are two critical values, \Sigma_I and \Sigma_II. When the surface density of the disk is lower than the first one, \Sigma_0 < \Sigma_I, the effect of self-gravity suppresses the formation of a gap. When \Sigma_0 > \Sigma_I, the self-gravity of the gas tends to benefit the gap formation process and enlarge the width/depth of the gap. According to our 1-D and 2-D simulations, we estimate the first critical surface density \Sigma_I \approx 0.8MMSN. This effect increases until the surface density reaches the second critical value \Sigma_II. When \Sigma_0 > \Sigma_II, the gravitational turbulence in the disk becomes dominant and the gap formation process is suppressed again. Our 2-D simulations show that this critical surface density is around 3.5MMSN. We also study the associated orbital evolution of a giant planet. Under the effect of the disk's self-gravity, the migration rate of the giant planet increases when the disk is dominated by gravitational turbulence. We show that the migration timescale associates with the effective viscosity and can be up to 10^4 yr., Comment: 24 pages, 13 figures, accepted by RAA

Analysis of the transit timing variations (TTVs) of candidate pairs near mean-motion resonances (MMRs) is an effective method to confirm planets. Hitherto, 68 planets in 34 multi-planet systems have been confirmed via TTVs. We analyze the TTVs of all candidates from the most recent Kepler data with a time span as long as about 1350 days (Q0-Q15). The anti-correlations of TTV signals and the mass upper limits of candidate pairs in the same system are calculated, using an improved method suitable for long-period TTVs. If the false alarm probability (FAP) of a candidate pair is less than 10^{-3} and the mass upper limit for each candidate is less than 13 M_J, we confirm them as planets in the same system. Finally, 8 planets in 4 multi-planet systems are confirmed via analysis of their TTVs. All of the 4 planet pairs are near first-order MMRs, including KOI-2672 near 2:1 MMR, KOI-1236, KOI-1563 and KOI-2038 near 3:2 MMR. Four planets have relatively long orbital periods (> 35 day). KOI-2672.01 has a period of 88.51658 days and a fit mass of 17 M_\oplus. It is the longest-period planet confirmed, to date, near first-order MMR via TTVs., 34 pages, 12 figures, 3 tables; published in ApJ

Hitherto, six P-type planets are found around five binary systems, i.e. Kepler-16 b, 34 b, 35 b, 38 b, 47 b, c, which are all Neptune or Jupiter-like planets. The stability of planets and the habitable zones are influenced by the gravitational and radiative perturbations of binary companions. In this Letter, we check the stability of an additional habitable Earth-mass planet in each system. Based on our simulations in 10 Myr, a habitable "Earth" is hardly stable in Kepler-16 while a stable "Earth" in Kepler-47 close to the boundaries of the habitable zone is possible. In contrast, Kepler-34, 35 and 38 seem to have high probabilities of being able to tolerate a stable "Earth" in their habitable zones. The affects of transit time variations are quite small due to the small mass of an undetected "Earth", except that of Kepler-16 b. With a time precision of 0.001 day(~ 88 s), an "Earth" in the corotational resonance with Kepler-16 b can be detected in 3 years, while habitable "Earths" in Kepler-34 and 38 systems can be detected in 10 years. Habitable "Earths" in Kepler-35 and 47 are not likely to be detected in 10 years under this precision., Comment: 7 pages, 3 figures, 2 tables

The Chinese Small Telescope ARray (CSTAR) is the first Chinese astronomical instrument placed in Antarctica. It is a group of four identical, fully automatic $14.5\,\rm{cm}$ telescopes, with an field of view (FOV) of $20\,\rm{deg^2}$ centered on the South Celestial Pole. Placed at Antarctic Dome A, CSTAR is designed to provide high-cadence photometry for site monitoring and variable sources detection. During the 2008 observing season, CSTAR has taken high-precision photometric data for 18,145 stars around the South Celestial Pole. At $i\,=\,7.5$ and $12$, the photometric precision reaches $\sim 8$ mmag and $\sim 30$ mmag with a cadence of 20s or 30s, respectively. Using robust detection method, we have found 15 stellar flares on 13 sources, including two classified variables. We have also found a linear relation between the decay times and the total durations of the stellar flares. The details of all detected flares along with their stellar properties are presented in this work., Accepted for publication in AJ. 8 pages, 9 figures

GAIA leads us to step into a new era with a high astrometry precision of 10 uas. Under such a precision, astrometry will play important roles in detecting and characterizing exoplanets. Specially, we can identify planet pairs in mean motion resonances(MMRs) via astrometry, which constrains the formation and evolution of planetary systems. In accordance with observations, we consider two Jupiters or two super-Earths systems in 1:2, 2:3 and 3:4 MMRs. Our simulations show the false alarm probabilities(FAPs) of a third planet are extremely small while the real two planets can be good fitted with signal-to-noise ratio(SNR)> 3. The probability of reconstructing a resonant system is related with the eccentricities and resonance intensity. Generally, when SNR >= 10, if eccentricities of both planets are larger than 0.01 and the resonance is quite strong, the probabilities to reconstruct the planet pair in MMRs >= 80%. Jupiter pairs in MMRs are reconstructed more easily than super-Earth pairs with similar SNR when we consider the dynamical stability. FAPs are also calculated when we detect planet pairs in or near MMRs. FAPs for 1:2 MMR are largest, i.e., FAPs > 15% when SNR, 22 pages, 18 figures. Published in ApJ

We studied the sensing properties of stereo-SRRs metamaterials composed from two twisted split-ring resonators (SRRs). Due to the strong hybridization effect in the system, the polarization state of the transmitted wave is greatly changed at resonances. Since the stereo-SRRs structure is strongly coupled to the surrounding medium, the polarization change of the transmitted waves is quite sensitive to the refractive index change of the environment medium. The polarization ratio PRtran = Ty/Tx is used as sensing parameter and its figure of merit can reach 22.3 at the hybridized magnetic plasmon resonance. The results showed that the stereo-SRRs metamaterial can be applied to optical sensors an or other related field.

With the increasing number of detected exoplanet samples, the statistical properties of planetary systems have become much clearer. In this review, we summarize the major statistics that have been revealed mainly by radial velocity and transiting observations, and try to interpret them within the scope of the classical core-accretion scenario of planet formation, especially in the formation of different orbital architectures for planetary systems around main sequence stars. Based on the different possible formation routes for different planet systems, we tentatively classify them into three major catalogs: hot Jupiter systems, standard systems and distant giant planet systems. The standard system can be further categorized into three sub-types under different circumstances: solar-like systems, hot Super-Earth systems, sub-giant planet systems. We also review the planet detection and formation in binary systems as well as planets in star clusters., Comment: 27 pages, 2 figures, 1 table, published in "Research in Astron. Astrophysics." 2012, 12,1081

This paper mainly focus on the influence of N-body interaction in the later stage of planets formation, especially the gas depleted timescale. We want to interpret the distribution of eccentricity comparing with observations.

The Chinese Small Telescope ARray (CSTAR) has observed an area around the Celestial South Pole at Dome A since 2008. About $20,000$ light curves in the i band were obtained lasting from March to July, 2008. The photometric precision achieves about 4 mmag at i = 7.5 and 20 mmag at i = 12 within a 30 s exposure time. These light curves are analyzed using Lomb--Scargle, Phase Dispersion Minimization, and Box Least Squares methods to search for periodic signals. False positives may appear as a variable signature caused by contaminating stars and the observation mode of CSTAR. Therefore the period and position of each variable candidate are checked to eliminate false positives. Eclipsing binaries are removed by visual inspection, frequency spectrum analysis and locally linear embedding technique. We identify 53 eclipsing binaries in the field of view of CSTAR, containing 24 detached binaries, 8 semi-detached binaries, 18 contact binaries, and 3 ellipsoidal variables. To derive the parameters of these binaries, we use the Eclipsing Binaries via Artificial Intelligence (EBAI) method. The primary and the secondary eclipse timing variations (ETVs) for semi-detached and contact systems are analyzed. Correlated primary and secondary ETVs confirmed by false alarm tests may indicate an unseen perturbing companion. Through ETV analysis, we identify two triple systems (CSTAR J084612.64-883342.9 and CSTAR J220502.55-895206.7). The orbital parameters of the third body in CSTAR J220502.55-895206.7 are derived using a simple dynamical model., 41 pages, 12 figures; published online in ApJS

Goldfish Carassius auratus were exposed to 0.1 mg/l of 2,4-dichlorophenol (2,4-DCP), widely used as transportation power in China, for 2, 5, 10, 20 and 40 days, while one control group was designated for each exposure group. Antioxidant defenses consisting of contents of reduced glutathione (GSH) and glutathione disulfide (GSSG) and activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), selenium-dependent glutathione peroxidase (Se-GPx) and glutathione S-transferase (GST) in liver of freshwater fish were determined and the GSH–GSSG ratio and content of tGSH (total glutathione) were calculated. In the present study, the role of hepatic antioxidant defenses was evaluated and the possible poisoning mechanism of fish can be explained as an oxidative stress mechanism. In addition, hepatic SOD and GSH, especially tGSH, were sensitive to 2,4-DCP contamination and thus, can possibly be used in early assessment of 2,4-DCP-dominant polluted aquatic ecosystems.

The Chinese Small Telescope ARray (CSTAR) is a group of four identical, fully automated, static 14.5 cm telescopes. CSTAR is located at Dome A, Antarctica and covers 20 square degree of sky around the South Celestial Pole. The installation is designed to provide high-cadence photometry for the purpose of monitoring the quality of the astronomical observing conditions at Dome A and detecting transiting exoplanets. CSTAR has been operational since 2008, and has taken a rich and high-precision photometric data set of 10,690 stars. In the first observing season, we obtained 291,911 qualified science frames with 20-second integrations in the i-band. Photometric precision reaches about 4 mmag at 20-second cadence at i=7.5, and is about 20 mmag at i=12. Using robust detection methods, ten promising exoplanet candidates were found. Four of these were found to be giants using spectroscopic follow-up. All of these transit candidates are presented here along with the discussion of their detailed properties as well as the follow-up observations., 19 pages, 14 Figures, accepted by ApJ Supplement

Open clusters(OCs) are usually young and suitable for studying the formation and evolution of planetary systems. Hitherto, only four planets have been found with radial velocity measurements in OCs. Meanwhile, a lot of free-floating planets(FFPs) have been detected. We utilize N-body simulations to investigate the evolution and final configurations of multi-planetary systems in very young open clusters with an age 6%, and only 1% have planets in retrograde orbits. We also obtain a positive correlation between the survival planet number and the distance from the cluster center $r$: planetary systems with a larger $r$ tend to be more stable. Moreover, stars with a mass >2.5 $M_\odot$ are likely unstable and lose their planets. These results are roughly consistent with current observations. Planetary systems in binaries are less stable and we achieve a rough criterion: most of the binary systems with $a_{\rm b}(1-e_{\rm b}^2)$>100 AU can keep all the initial planets survived. Finally, 80% of the FFPs are ejected out of the clusters, while the rest (~20%) still stay in host clusters and most of them are concentrated in the center (, 18 pages, 13 figures, 2 tables, accepted to ApJ