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Ing-Guey Jiang

Publications and source records attributed to Ing-Guey Jiang.

At least 55 records · Page 3Linked to original sources

On the Scaling and Spacing of Extra-Solar Multi-Planet Systems

We investigate whether certain extra-solar multi-planet systems simultaneously follow the scaling and spacing rules of the angular-momentum-deficit model. The masses and semi-major axes of exoplanets in ten multi-planet systems are considered. It is found that GJ 667C, HD 215152, HD 40307, and Kepler-79 systems are currently close to configurations of the angular-momentum-deficit model. In a gas-poor scenario, GJ 3293, HD 141399, and HD 34445 systems are those which had a configuration of the angular-momentum-deficit model in the past and get scattered away due to post gaseous effects. In addition, no matter in gas-free or gas-poor scenario, 55 Cnc, GJ 876, and WASP-47 systems do not follow the angular-momentum-deficit model. Therefore, our results reveal important formation histories of these multi-planet systems.

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Are There Transit Timing Variations for the Exoplanet Qatar-1b ?

Motivated by the unsettled conclusion on whether there are any transit timing variations (TTVs) for the exoplanet Qatar-1b, 10 new transit light curves are presented and the TTV analysis with a baseline of 1400 epochs are performed. Because the linear model provides a good fitting with reduced chi-square = 2.59 and the false-alarm probabilities of possible TTV frequencies are as large as 35 %, our results are consistent with a null-TTV model. Nevertheless, a new ephemeris with the reference time T_0 = 2455647.63360\pm 0.00008 (BJD) and the period P= 1.4200236\pm 0.0000001 (day) is obtained. In addition, the updated orbital semi-major axis and planetary radius in unit of stellar radius are being provided, and the lower limit of modified stellar tidal quality factor is also determined.

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Non-Sinusoidal Transit Timing Variations for the Exoplanet HAT-P-12b

Considering the importance of investigating the transit timing variations (TTVs) of transiting exoplanets, we present a follow-up study of HAT-P-12b. We include six new light curves observed between 2011 and 2015 from three different observatories, in association with 25 light curves taken from the published literature. The sample of the data used, thus covers a time span of about 10.2 years with a large coverage of epochs (1160) for the transiting events of the exoplanet HAT-P-12b. The light curves are used to determine the orbital parameters and conduct an investigation of possible transit timing variations. The new linear ephemeris shows a large value of reduced chi-square = 7.93, and the sinusoidal fitting using the prominent frequency coming from a periodogram shows a reduced chi-square around 4. Based on these values and the corresponding O-C diagrams, we suspect the presence of a possible non-sinusoidal TTV in this planetary system. Finally, we find that a scenario with an additional non-transiting exoplanet could explain this TTV with an even smaller reduced chi-square value of around 2.

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A comprehensive analysis of NGC 2158 in Gaia era: photometric parameters, apex and orbit

We present an investigation of NGC 2158 using Gaia-DR2 data. We identified 800 most likely cluster members with membership probability higher than 90%. The mean proper motions of this object are determined as (mu_{x}=-0.203 \pm 0.003, mu_{y}=-1.99 \pm 0.004) mas yr^{-1}. The limiting radius, log(age), and distance of the cluster are obtained as 23.5 arcmin, 9.38 \pm 0.04 Gyr and 4.69 \pm 0.22 kpc, respectively. The overall mass function slope (0.93 \pm 0.14) is flatter than the Salpeter value (1.35) within the mass range 1.17-1.44 M_\odot. This cluster also shows the mass-segregation effect and our study demonstrates that NGC 2158 is a dynamically relaxed open cluster. Using the AD-diagram, the apex coordinates of the cluster are obtained in different ways and examined using (μ_{U},μ_{T}) diagram. The best value of apex coordinates is determined as A=87.24^\circ \pm 1.60^\circ, D=-36.61^\circ \pm 5.30 ^\circ. We also determined the orbit of the cluster and found that NGC 2158 moves almost in the Solar antapex direction. The resulting spatial velocity of NGC 2158 is 51 km s^{-1}. A significant oscillations along the Z-coordinate up to 529~pc is detected. Various scenarios regarding the origin of this cluster are also discussed.

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Investigating Extra-solar Planetary System Qatar-1 through Transit Observations

We report the results of the transit timing variation (TTV) analysis of the extra-solar planet Qatar-1b using thirty eight light curves. Our analysis combines thirty five previously available transit light curves with three new transits observed by us between June 2016 and September 2016 using the 2-m Himalayan Chandra Telescope (HCT) at the Indian Astronomical Observatory (Hanle, India). From these transit data, the physical and orbital parameters of the Qatar-1 system are determined. In addition to this, the ephemeris for the orbital period and mid-transit time are refined to investigate the possible TTV. We find that the null-TTV model provides the better fit to the (O-C) data. This indicates that there is no evidence for TTVs to confirm the presence of additional planets in the Qatar-1 system. The use of the 3.6-m Devasthal Optical Telescope (DOT) operated by the Aryabhatta Research Institute of Observational Sciences (ARIES, Nainital, India) could improve the photometric precision to examine the signature of TTVs in this system with a greater accuracy than in the present work.

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An investigation of poorly studied open cluster NGC 4337 using multi-color photometric and Gaia DR2 astrometric data

We present a comprehensive analysis (photometric and kinematical) of poorly studied open cluster NGC 4337 using 2MASS, WISE, APASS, and Gaia~DR2 database. By determining the membership probabilities of stars, we identified 624 most probable members with membership probability higher than $50\%$ by using proper motion and parallax data taken from Gaia~DR2. The mean proper motion of the cluster is obtained as $μ_{x}=-8.83\pm0.01$ and $μ_{y}=1.49\pm0.006$ mas yr$^{-1}$. We find the normal interstellar extinction towards the cluster region. The radial distribution of members provides a cluster radius of 7.75 arcmin (5.63 pc). The estimated age of $1600\pm180$ Myr indicates that NGC 4337 is an old open cluster with a bunch of red giant stars. The overall mass function slope for main-sequence stars is found as $1.46\pm0.18$ within the mass range 0.75$-$2.0 $M_\odot$, which is in fair agreement with Salpeter's value (x=1.35) within uncertainty. The present study demonstrates that NGC 4337 is a dynamically relaxed open cluster. Using the Galactic potential model, Galactic orbits are obtained for NGC 4337. We found that this object follows a circular path around the Galactic center. Under the kinematical analysis, we compute the apex coordinates $(A, D)$ by using two methods: (i) the classical convergent point method and (ii) the AD-diagram method. The obtained coordinates are: $(A_{conv}, D_{conv})$ = (96$^{\textrm{o}}$.27 $\pm$ 0$^{\textrm{o}}$.10, 13$^{\textrm{o}}$.14 $\pm$ 0$^{\textrm{o}}$.27) $\&$ $(A_\circ, D_\circ)$ = (100$^{\textrm{o}}$.282 $\pm$ 0$^{\textrm{o}}$.10, 9$^{\textrm{o}}$.577 $\pm$ 0$^{\textrm{o}}$.323) respectively. We also computed the Velocity Ellipsoid Parameters (VEPs), matrix elements ($μ_{ij}$), direction cosines ($l_j$, $m_j$, $n_j$) and the Galactic longitude of the vertex ($l_2$).

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Probing Transit Timing Variation and its Possible Origin with Twelve New Transits of TrES-3b

We present twelve new transit light curves of the hot-Jupiter TrES-3b observed during $2012-2018$ to probe the transit timing variation (TTV). By combining the mid-transit times determined from these twelve transit data with those re-estimated through uniform procedure from seventy one transit data available in the literature, we derive new linear ephemeris and obtain the timing residuals that suggest the possibility of TTV in TrES-3 system. However, the frequency analysis shows that the possible TTV is unlikely to be periodic, indicating the absence of an additional body in this system. To explore the other possible origins of TTV, the orbital decay and apsidal precession ephemeris models are fitted to the transit time data. We find decay rate of TrES-3b to be $\bf \dot{P_q}= -4.1 \pm 3.1$ $ms$ ${yr}^{-1}$ and the corresponding estimated modified tidal quality factor of ${Q}^{'}_{\ast}$ $\sim 1.11 \times {10}^{5}$ is consistent with the theoretically predicted values for the stars hosting the hot-Jupiters. The shift in the transit arrival time of TrES-3b after eleven years is expected to be ${T}_{shift}\sim 69.55 \ s$, which is consistent with the $RMS$ of the timing residuals. Besides, we find that the apsidal precession ephemeris model is statistically less probable than the other considered ephemeris models. It is also discussed that despite the linear ephemeris model appears to be the most plausible model to represent the transit time data, the possibility of the orbital decay cannot be completely ruled out in TrES-3 system. In order to confirm this, further high-precision and high-cadence follow-up observation of transits of TrES-3b would be important.

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The kinematical and space structures of IC 2391 open cluster and moving group with Gaia-DR2

The kinematical parameters, spatial shape and structure of the open cluster IC 2391 and the associated stellar stream are studied here using Gaia-DR2 (GDR2) astrometry data. The apex positions are determined for the open cluster IC 2391 (data taken from Cantat-Gaudin et al.) and for the kinematical streams stars mentioned in Montes et al. using both convergent point and AD-diagram methods. The values of apex coordinates identified. The results are in good agreement with the previously calculated values. The positions of the stars in the disk and the spatial dispersion velocities are determined. The paths of cluster and associated stream are traced in the disk by orbit calculation back in time to their places of formation. A possible genetic relationship between the cluster and the stream has been detected. The approximation of the spatial and kinematical shape of the stream and the cluster is made. According to this study, even though currently the cluster and the stream seem to have spatial difference in their locations but they appear to have formed in the same region of the Galactic disk.

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Long-term Hydrodynamic Simulations on the Planetesimals Trapped in the First-order Mean Motion Resonances

The resonant perturbations from planets are able to halt the drag-induced migration, and capture the inwardly drifting planetesimals into mean motion resonances. The equilibrium eccentricity of planetesimals in resonances, and the minimum size of planetesimal that can trigger resonance trapping, have been analyzed and formulated. However, the analytical works based on the assumption that the disk is axisymmetric, which is violated by the asymmetric structures developed by planets. We perform long-term 2D hydrodynamic simulations to study the dynamics of planetesimals in the $j:(j+1)$ first-order exterior resonances, and reexamine the theoretical expressions. We find the expression of equilibrium eccentricity underestimates the values for resonances with $j < 5$, in particular the 1:2 resonance that the underestimation can be $30 - 40\%$. Within the parameter space we explored, we find the equilibrium eccentricity and the minimum size are reduced in an asymmetric disk. The amount of discrepancy in eccentricity depends on the degree of asymmetric structures. For cases of Earth-sized planets, where the disk is less disturbed, the planetesimal's eccentricity can reach to the values predicted by our modified expression. For gaseous planets, however, the eccentricity can be $0.01 - 0.02$ smaller in value. We find the minimum size is 10 times smaller, and the factor seems to be independent of the planet's mass. The influences of asymmetric profiles on the eccentricity and the minimum size could affect the outcome of collisions between resonant and nonresonant planetesimals, and the amount of planetesimals migrated into the planet's feeding zone.

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Detecting Exoplanet Transits through Machine Learning Techniques with Convolutional Neural Networks

A machine learning technique with two-dimension convolutional neural network is proposed for detecting exoplanet transits. To test this new method, five different types of deep learning models with or without folding are constructed and studied. The light curves of the Kepler Data Release 25 are employed as the input of these models. The accuracy, reliability, and completeness are determined and their performances are compared. These results indicate that a combination of two-dimension convolutional neural network with folding would be an excellent choice for the future transit analysis.

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Studying Dynamical Models of the Core Galaxy NGC 1399 with Merging Remnants

An investigation on the possible dynamical models of the core galaxy NGC 1399 is performed. Because early-type galaxies are likely to be formed through merging events, remnant rings are considered in the modeling process. A numerical survey over three parameters is employed to obtain the best-fit models that are completely consistent with observations. It is found that the inner slope of dark matter profile is a cuspy one for this core galaxy. The existence of remnant rings in best-fit models indicates a merging history. The remnant ring explains the flatten surface brightness, and thus could be the physical counterpart of the core structure of NGC 1399.

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A Proper Motions Study of the Globular Cluster M12 (NGC 6218)

Using astrometric techniques developed by Anderson et al., we determine proper motions (PMs) in 14.60 arcmin X 16.53 arcmin area of the kinematically "thick-disk" globular cluster M12. The cluster's proximity and sparse nature makes it a suitable target for ground-based telescopes. Archive images with time gap of 11.1 years were observed with wide-field imager (WFI) mosaic camera mounted on ESO 2.2 m telescope. The median value of PM error in both components is 0.7 mas/yr for the stars having V less than or equal to 20 mag. PMs are used to determine membership probabilities and to separate field stars from the cluster sample. In electronic form, a membership catalog of 3725 stars with precise coordinates, PMs, BVRI photometry is being provided. One of the possible applications of the catalog was shown by gathering the membership information of the variable stars, blue stragglers and X-ray sources reported earlier in the cluster's region.

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The Pleiades apex and its kinematical structure

A study of cluster characteristics and internal kinematical structure of the middle-aged Pleiades open star cluster is presented. The individual star apexes and various cluster kinematical parameters including the velocity ellipsoid parameters are determined using both Hipparcos and Gaia data. Modern astrometric parameters were taken from the Gaia Data Release 1 (DR1) in combination with the Radial Velocity Experiment Fifth Data Release (DR5). The necessary set of parameters including parallaxes, proper motions and radial velocities are used for n=17 stars from Gaia DR1+RAVE DR5 and for n=19 stars from the Hipparcos catalog using SIMBAD data base. Single stars are used to improve accuracy by eliminating orbital movements. RAVE DR5 measurements were taken only for the stars with the radial velocity errors not exceeding $2$~km/s. For the Pleiades stars taken from Gaia, we found mean heliocentric distance as $136.8 \pm 6.4$~pc, and the apex position is calculated as: $A_{CP}=92^\circ.52\pm1^\circ.72$, $D_{CP}=-42^\circ.28\pm2^\circ.56$ by the convergent point method and $A_0=95^\circ.59\pm2^\circ.30$ and $D_0=-50^\circ.90\pm2^\circ.04$ using AD-diagram method (n=17 in both cases). The results are compared with those obtained historically before the Gaia mission era.

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A proper motions study of the globular cluster NGC 3201

With a high value of heliocentric radial velocity, a retrograde orbit, and being suspected to have an extragalactic origin, NGC 3201 is an interesting globular cluster for kinematical studies. Our purpose is to calculate the relative proper motions (PMs) and membership probability for the stars in the wide region of globular cluster NGC 3201. Proper motion based membership probabilities are used to isolate the cluster sample from the field stars. The membership catalogue will help address the question of chemical inhomogeneity in the cluster. Archive CCD data taken with a wide-field imager (WFI) mounted on the ESO 2.2m telescope are reduced using the high-precision astrometric software developed by Anderson et al. for the WFI images. The epoch gap between the two observational runs is $\sim$14.3 years. To standardize the $BVI$ photometry, Stetson's secondary standard stars are used. The CCD data with an epoch gap of $\sim$14.3 years enables us to decontaminate the cluster stars from field stars efficiently. The median precision of PMs is better than $\sim$0.8 mas~yr$^{-1}$ for stars having $V<$18 mag that increases up to $\sim$1.5 mas~yr$^{-1}$ for stars with $18<V<20$ mag. Kinematic membership probabilities are calculated using proper motions for stars brighter than $V\sim$20 mag. An electronic catalogue of positions, relative PMs, $BVI$ magnitudes and membership probabilities in $\sim$19.7$\times$17 arcmin$^2$ region of NGC 3201 is presented. We use our membership catalogue to identify probable cluster members among the known variables and $X$-ray sources in the direction of NGC 3201.

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Galaxies with Supermassive Binary Black Holes: (III) The Roche Lobes and Jiang-Yeh Lobe in a Core System

Three-dimensional equi-potential surfaces of a galactic system with supermassive binary black holes are discussed herein. The conditions of topological transitions for the important surfaces, i.e. Roche Lobes and Jiang-Yeh Lobe, are studied in this paper. In addition, the mathematical properties of the Jacobi surfaces are investigated analytically. Finally, a numerical procedure for determining the regions of the Roche Lobes and Jiang-Yeh Lobe is suggested.

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2MASS photometry and kinematical studies of open cluster NGC 188

In this paper, we present our results for the photometric and kinematical studies of old open cluster NGC 188. We determined various astrophysical parameters like limited radius, core and tidal radii, distance, luminosity and mass functions, total mass, relaxation time etc. for the cluster using 2MASS catalog. We obtained the cluster's distance from the Sun as 1721+/-41 pc and log (age)= 9.85+/-0.05 at Solar metallicity. The relaxation time of the cluster is smaller than the estimated cluster age which suggests that the cluster is dynamically relaxed. Our results agree with the values mentioned in the literature. We also determined the cluster's apex coordinates as (281.88 deg, -44.76 deg) using AD-diagram method. Other kinematical parameters like space velocity components, cluster center and elements of Solar motion etc. have also been computed.

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The Possible Orbital Decay and Transit Timing Variations of the Planet WASP-43b

Motivated by the previously reported high orbital decay rate of the planet WASP-43b, eight newly transit light curves are obtained and presented. Together with other data in literature, we perform a self-consistent timing analysis with data covering a timescale of 1849 epochs. The results give an orbital decay rate dP/dt = -0.02890795\pm 0.00772547 sec/year, which is one order smaller than previous values. This slow decay rate corresponds to a normally assumed theoretical value of stellar tidal dissipation factor. In addition, through the frequency analysis, the transit timing variations presented here are unlikely to be periodic, but could be signals of a slow orbital decay.

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On the Formation of Elliptical Rings in Disk Galaxies

N-body simulations of galactic collisions are employed to investigate the formation of elliptical rings in disk galaxies. The relative inclination between disk and dwarf galaxies is studied with a fine step of five degrees. It is confirmed that the eccentricity of elliptical ring is linearly proportional to the inclination angle. Deriving from the simulational results, an analytic formula which expresses the eccentricity as a function of time and inclination angle is obtained. This formula shall be useful for the interpretations of the observations of ring systems, and therefore reveals the merging histories of galaxies.

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