arXiv subjects

Ing-Guey Jiang

Publications and source records attributed to Ing-Guey Jiang.

At least 37 records · Page 2Linked to original sources

arXiv2023

Searching for Candidates of Orbital Decays among Transit Exoplanets

Transit observations have become an important technique to probe exoplanets. Therefore, there are many projects carrying on organized observations of transit events, which make a huge amount of light-curve and transit timing data available. We consider this as an excellent opportunity to search for possible orbital decays of exoplanets from this big number of mid-transit times through data-model fitting with both fixed-orbit and orbit-decay models. In order to perform this task, we collect mid-transit-time data from several sources and construct the most complete database up to date. Among 144 hot Jupiters in our study, HAT-P-51b, HAT-P-53b, TrES-5b, WASP-12b are classified as the orbit-decay cases. Thus, in addition to reconfirming WASP-12b as an orbit-decay planet, our results indicate that HAT-P-51b, HAT-P-53b, TrES-5b are potential orbit-decay candidates.

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arXiv2023

Revisiting the Transit Timing and Atmosphere Characterization of the Neptune-mass Planet HAT-P-26 b

We present the transit timing variation (TTV) and planetary atmosphere analysis of the Neptune-mass planet HAT-P-26~b. We present a new set of 13 transit light curves from optical ground-based observations and combine them with light curves from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), Transiting Exoplanet Survey Satellite (TESS), and previously published ground-based data. We refine the planetary parameters of HAT-P-26 b and undertake a TTV analysis using 33 transits obtained over seven years. The TTV analysis shows an amplitude signal of 1.98 $\pm$ 0.05 minutes, which could result from the presence of an additional $0.02 M_{Jup}$ planet at the 1:2 mean-motion resonance orbit. Using a combination of transit depths spanning optical to near-infrared wavelengths, we find that the atmosphere of HAT-P-26 b contains $2.4^{+2.9}_{-1.6}$% of H$_2$O with a derived temperature of $590^{+60}_{-50}$ K.

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arXiv2023

Anisotropic Ionizing Illumination from an M-type Pre-main Sequence Star, DM Tau

The powerful, high-energy magnetic activities of young stars play important roles in the magnetohydrodynamics in the innermost parts of the protoplanetary disks. In addition, the associated UV and X-ray emission dictates the photochemistry; moreover, the corona activities can affect the atmosphere of a newborn extra-solar planet. How the UV and X-ray photons are generated, and how they illuminate the disks, are not well understood. Here we report the analyses of the optical and infrared (OIR) photometric monitoring observations and the high angular-resolution centimeter band images of the low-mass (M1 type) pre-main sequence star, DM Tau. We found that the OIR photometric light curves present periodic variations, which is consistent with that the host young star is rotating in the same direction as the natal disk and is hosting at least one giant cold spot. In addition, we resolved that the ionized gas in the DM Tau disk is localized, and its spatial distribution is varying with time. All the present observations can be coherently interpreted, if the giant cold spot is the dominant anisotropic UV and/or X-ray source that illuminates the ambient cone-like region. These results indicate that a detailed theoretical model of the high-energy protostellar emission is essential in the understanding of the space weather around the extra-solar planets and the origin of life.

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arXiv2023

Characterising a World Within the Hot Neptune Desert: Transit Observations of LTT 9779 b with HST WFC3

We present an atmospheric analysis of LTT 9779 b, a rare planet situated in the hot Neptune desert, that has been observed with HST WFC3 G102 and G141. The combined transmission spectrum, which covers 0.8 - 1.6 $μ$m, shows a gradual increase in transit depth with wavelength. Our preferred atmospheric model shows evidence for H$_{\rm 2}$O, CO$_{\rm 2}$ and FeH with a significance of 3.1 $σ$, 2.4 $σ$ and 2.1 $σ$, respectively. In an attempt to constrain the rate of atmospheric escape for this planet, we search for the 1.083 $μ$m Helium line in the G102 data but find no evidence of excess absorption that would indicate an escaping atmosphere using this tracer. We refine the orbital ephemerides of LTT 9779 b using our HST data and observations from TESS, searching for evidence of orbital decay or apsidal precession, which is not found. The phase-curve observation of LTT 9779 b with JWST NIRISS should provide deeper insights into the atmosphere of this planet and the expected atmospheric escape might be detected with further observations concentrated on other tracers such as Lyman $α$.

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arXiv2023

Investigating Dynamical Properties of Globular Clusters through a Family of Lowered Isothermal Models

To investigate the dynamical properties of globular clusters, the surface brightness and kinematic data were collected and fitted to a family of lowered isothermal models called LIMEPY models. For 18 studied globular clusters, the amounts of concentration, truncation, and anisotropy were determined. In addition, the cluster mass, half-mass radius, distance, and mass-to-light ratio were also obtained. In general, LIMEPY models could describe these clusters well. Among these 18 clusters, NGC 5139, NGC 6388, and NGC 7078 were claimed to be candidates to host intermediate-mass black holes in literature. The models could not appropriately fit the central proper-motion velocity dispersion of NGC 5139 and the slope of proper-motion velocity-dispersion profile of NGC 6388. Thus, more dedicated models with intermediate-mass black holes or a group of stellar-mass black holes at cluster centers may need to be considered. Considering NGC 7078, our model with some degree of anisotropy can fit the data. Finally, the strong concentration-truncation anti-correlation and truncation-semimajor-axis correlation were revealed, which could be the observational imprint of the dynamical evolution of globular clusters.

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arXiv2023

A Possible Converter to Denoise the Images of Exoplanet Candidates through Machine Learning Techniques

The method of direct imaging has detected many exoplanets and made important contribution to the field of planet formation. The standard method employs angular differential imaging (ADI) technique, and more ADI image frames could lead to the results with larger signal-to-noise-ratio (SNR). However, it would need precious observational time from large telescopes, which are always over-subscribed. We thus explore the possibility to generate a converter which can increase the SNR derived from a smaller number of ADI frames. The machine learning technique with two-dimension convolutional neural network (2D-CNN) is tested here. Several 2D-CNN models are trained and their performances of denoising are presented and compared. It is found that our proposed Modified five-layer Wide Inference Network with the Residual learning technique and Batch normalization (MWIN5-RB) can give the best result. We conclude that this MWIN5-RB can be employed as a converter for future observational data.

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arXiv2022

A Gaia based analysis of open cluster Berkeley 27

In this paper, we have used the Gaia's Data Release-3 (DR3) data to study an intermediate-age open cluster Berkeley 27 (Be 27). A total of 131 most probable cluster members are picked within the cluster's radius based on the membership probability ($> 80\%$). The cluster's radius was estimated as 3.74 arcmin. The mean proper motion (PM) of Be 27 was determined to be ($μ_α cosδ$, $μ_δ$)= ($-1.076\pm0.008$, $0.152\pm0.007$)~mas~yr$^{-1}$. The blue straggler stars (BSS) of the cluster were found to be located in the central region. Theoretical isochrones of metallicity Z$_{metal}$= 0.008 were compared to the color-magnitude diagram (CMD) of Be 27. As a result, a heliocentric distance of 4.8$\pm$0.2 kpc and log (age) = 9.36$\pm$0.03 were determined for Be 27. The Galactic orbits are derived using the Galactic potential model which demonstrate that Be 27 follows a circular path around the Galactic center. The cluster does not seem to be affected much by the tidal forces from the Galactic thin disk.

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arXiv2022

Revisiting the Transit Timing Variations in the TrES-3 and Qatar-1 systems with TESS data

We present and analyze 58 transit light curves of TrES-3b and 98 transit light curves of Qatar-1b observed by Transiting Exoplanet Survey Satellite (TESS), plus two transit light curves of Qatar-1b observed by us using a ground-based 1.23\,m telescope. These light curves are combined with the best-quality light curves taken from the Exoplanet Transit Database (ETD) and literature. The precisely determined mid-transit times from these light curves enable us to obtain the refined orbital ephemerides with improved precision for both hot Jupiters. From the timing analysis, we find an indication for the presence of transit timing variations (TTVs) in both systems. Since the observed TTVs are unlikely to be short-term and periodic, the possibility of additional planets in the orbits close to TrES-3b and Qatar-1b are ruled out. Possible causes of long-term TTVs such as orbital decay, apsidal precession, the Applegate mechanism and line-of-sight acceleration are also examined. However, none of these possibilities are found to explain the observed TTV of TrES-3b. In contrast to this, the line-of-sight acceleration appears to be a plausible explanation for the observed TTV of Qatar-1b. In order to confirm these findings, further high-precision transit and RV observations of both systems would be worthwhile.

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arXiv2022

Twinkle -- a small satellite spectroscopy mission for the next phase of exoplanet science

With a focus on off-the-shelf components, Twinkle is the first in a series of cost competitive small satellites managed and financed by Blue Skies Space Ltd. The satellite is based on a high-heritage Airbus platform that will carry a 0.45 m telescope and a spectrometer which will provide simultaneous wavelength coverage from 0.5-4.5 $\rm{μm}$. The spacecraft prime is Airbus Stevenage while the telescope is being developed by Airbus Toulouse and the spectrometer by ABB Canada. Scheduled to begin scientific operations in 2025, Twinkle will sit in a thermally-stable, sun-synchronous, low-Earth orbit. The mission has a designed operation lifetime of at least seven years and, during the first three years of operation, will conduct two large-scale survey programmes: one focused on Solar System objects and the other dedicated to extrasolar targets. Here we present an overview of the architecture of the mission, refinements in the design approach, and some of the key science themes of the extrasolar survey.

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arXiv2022

A deep investigation of two poorly studied open clusters Haffner 22 and Melotte 71 in Gaia era

This paper presents a deep investigation of two open clusters, Haffner 22 and Melotte 71, using astrometric and photometric data from Gaia EDR3. We identified 382 and 597 most probable cluster members with membership probability higher than 50 percent. Mean proper motion in RA and DEC are estimated as -1.63 and 2.889 respectively for Haffner 22 and -2.398 and 4.210 for Melotte 71. A comparison of observed CMDs with theoretical isochrones leads to an age of 2.25 and 1.27 Gyr for these clusters. The distances 2.88 and 2.28 kpc based on parallax are comparable with the values derived by isochrone fitting method. Five and four blue straggler stars are identified as cluster members in Haffner 22 and Melotte 71 respectively. Based on the relative number of high velocity (binary) and single stars, we inferred binary fractions for both clusters. We found binary content is larger in core region. Mass function slope is in good agreement with the Salpeter's value while it is flat for Haffner 22. Evidence for the existence of mass segregation effect is observed in both clusters. Using the Galactic potential models, Galactic orbits are derived, indicating that both clusters follow a circular path around the Galactic center, evolving slowly.

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arXiv2021

The Effect of Impact Parameters on the Formation of Massive Black Hole Binaries in Galactic Mergers

By employing N-body simulations, we inestigate the formation of massive black hole binaries (MBHBs) through the sinking of two massive black holes (MBHs) during galaxy mergers. With different impact parameters and different central stellar density of the progenitor galaxies, we analyze the orbits of the MBHs from the beginning of the merger until the time when the bound MBHB forms. Contrary to the previous theory that the timing of the dual MBHs entering their dynamical radius is similar as the timing of the formation of the bound MBHB, we find that these two timings could deviate when the central stellar density of the progenitors galaxies are lower. On the other hand, when the central stellar density of the progenitor galaxies is higher and the mergers have small impact parameters, each MBHs would move directly into the core radius of the other progenitor galaxies, and therefore cause a variation in the timings of the MBHB formation.

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arXiv2021

The Transit Timing and Atmosphere of Hot Jupiter HAT-P-37b

The transit timing variation (TTV) and transmission spectroscopy analyses of the planet HAT-P-37b, which is a hot Jupiter orbiting an G-type star, were performed. Nine new transit light curves are obtained and analysed together with 21 published light curves from the literature. The updated physical parameters of HAT-P-37b are presented. The TTV analyses show a possibility that the system has an additional planet which induced the TTVs amplitude signal of 1.74 $\pm$ 0.17 minutes. If the body is located near the 1:2 mean motion resonance orbit, the sinusoidal TTV signal could be caused by the gravitational interaction of a sub-Earth mass planet with mass of 0.06 $M_\oplus$. From the analysis of an upper mass limit for the second planet, the Saturn mass planet with orbital period less than 6 days is excluded. The broad-band transmission spectra of HAT-P-37b favours a cloudy atmospheric model with an outlier spectrum in $B$-filter.

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arXiv2021

A Gaia based photometric and kinematic analysis of the old open cluster King 11

This paper presents an investigation of an old age open cluster King 11 using Gaia's Early Data Release 3 (EDR3) data. Considering the stars with membership probability ($P_μ$) $> 90\%$, we identified 676 most probable cluster members within the cluster's limiting radius. The mean proper motion (PM) for King 11 is determined as: $μ_{x}=-3.391\pm0.006$ and $μ_{y}=-0.660\pm0.004$ mas yr$^{-1}$. The blue straggler stars (BSS) of King 11 show a centrally concentrated radial distribution. The values of limiting radius, age, and distance are determined as 18.51 arcmin, 3.63$\pm$0.42 Gyr and $3.33\pm0.15$ kpc, respectively. The cluster's apex coordinates ($A=267.84^{\circ} \pm 1.01^{\circ}$, $D=-27.48^{\circ} \pm 1.03^{\circ}$) are determined using the apex diagram (AD) method and verified using the ($μ_U$,$μ_T$) diagram. We also obtained the orbit that the cluster follows in the Galaxy and estimated its tentative birthplace in the disk. The resulting spatial velocity of King 11 is 60.2 $\pm$ 2.16 km s$^{-1}$. A significant oscillation along the $Z$-coordinate up to 0.556$\pm$0.022~kpc is determined.

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arXiv2021

Detailed analysis of the poorly studied northern open cluster NGC 1348 using multi-color photometry and GAIA EDR3 astrometry

The membership determination for open clusters in noisy environments of the Milky Way is still an open problem. In this paper, our main aim is provide the membership probability of stars using proper motions and parallax values of stars using Gaia EDR3 astrometry. Apart from the Gaia astrometry, we have also used other photometric data sets like UKIDSS, WISE, APASS and Pan-STARRS1 in order to understand cluster properties from optical to mid-infrared regions. We selected 438 likely members with membership probability higher than $50\%$ and G$\le$20 mag. We obtained the mean value of proper motion as $μ_{x}=1.27\pm0.001$ and $μ_{y}=-0.73\pm0.002$ mas yr$^{-1}$. The cluster's radius is determined as 7.5 arcmin (5.67 pc) using radial density profile. Our analysis suggests that NGC 1348 is located at a distance of $2.6\pm0.05$ kpc. The mass function slope is found to be $1.30\pm0.18$ in the mass range 1.0$-$4.1 $M_\odot$, which is in fair agreement with Salpeter's value within the 1$σ$ uncertainty. The present study validates that NGC 1348 is a dynamically relaxed cluster. We computed the apex coordinates $(A, D)$ for NGC 1348 as $(A_\circ, D_\circ)$ = $(-23^{\textrm{o}}.815\pm 0^{\textrm{o}}.135$, $-22^{\textrm{o}}.228\pm 0^{\textrm{o}}.105)$. In addition, calculations of the velocity ellipsoid parameters (VEPs), matrix elements $μ_{ij}$, direction cosines ($l_j$, $m_j$, $n_j$) and the Galactic longitude of the vertex have been also conducted in this analysis.

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arXiv2021

On the Period-Ratio-Mass-Ratio Correlation of Extra-Solar Multi-Planet Systems

In order to gain possible hints for planet formation from the current data of known extra-solar planets, the period-ratios and mass-ratios of adjacent planet pairs in multi-planet systems are determined. A moderate period-ratio-mass-ratio correlation is found to have a correlation coefficient r=0.5779 with 99% confidence interval (0.464, 0.672). In contrast, for non-adjacent planet pairs, the correlation coefficient is r=0.2820 with 99% confidence interval (0.133, 0.419). Our results reveal the imprint of planet-planet interactions of the adjacent planet pairs in a certain fraction of the multi-planet systems during the stage of planet formation.

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arXiv2021

Multi-colour photometry and Gaia EDR3 astrometry of two couples of binary clusters (NGC 5617 and Trumpler 22) and (NGC 3293 and NGC 3324)

This paper presents a comprehensive analysis of two pairs of binary clusters (NGC 5617 and Trumpler 22) and (NGC 3293 and NGC 3324) located in the fourth quadrant of our Galaxy. For this purpose we use different data taken from VVV survey, WISE, VPHAS, APASS, GLIMPSE along with Gaia~EDR3 astrometric data. We identified 584, 429, 692 and 273 most probable cluster members with membership probability higher than 80 % towards the region of clusters NGC 5617, Trumpler 22, NGC 3293 and NGC 3324. We estimated the value of R as ~ 3.1 for clusters NGC 5617 and Trumpler 22, which indicates normal extinction law. The value of R ~ 3.8 and 1.9 represent the abnormal extinction law towards the clusters NGC 3293 and NGC 3324. Our Kinematical analysis show that all these clusters have circular orbits. Ages are found to be 90\pm10 and 12\pm3 Myr for the cluster pairs (NGC 5617 and Trumpler 22) and (NGC 3293 and NGC 3324), respectively. The distances of 2.43\pm0.08, 2.64\pm0.07, 2.59\pm0.1 and 2.80\pm0.2 kpc estimated using parallax are alike to the values calculated by using the distance modulus. We have also identified 18 and 44 young stellar object candidates present in NGC 5617 and Trumpler 22, respectively. Mass function slopes are found to be in fair agreement with the Salpeter's value. The dynamical study of these objects shows a lack of faint stars in their inner regions, which leads to the mass-segregation effect. Our study indicates that NGC 5617 and Trumpler 22 are dynamically relaxed but the other pair of clusters are not. Orbital alongwith the physical parameters show that the clusters in both pairs are physically connected.

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arXiv2021

A deep study of an intermediate age open cluster SAI 35 (Juchert 20) using ground based imaging and Gaia EDR3 astrometry

We present CCD $UBVI$ photometric study of poorly studied intermediate age open cluster SAI 35 (Juchert 20) for the first time. To accomplish this study, we also used LAMOST DR5, 2MASS, and Gaia EDR3 databases. We identified 214 most probable cluster members with membership probability higher than 50%. The mean proper motion of the cluster is found as μ_αcosδ=1.10 \pm 0.01 and μ_δ=-1.66 \pm 0.01 mas/yr. We find the normal interstellar extinction law using the various two-color diagrams. The age, distance, reddening, and radial velocity of the cluster are estimated to be 360 \pm 40 Myr, 2.9 \pm 0.15 kpc, 0.72 \pm 0.05 mag and -91.62 \pm 6.39 km/sec. The overall mass function slope for main-sequence stars is found to be 1.49\pm0.16 within the mass range 1.1-3.1 M_\odot, which is in agreement with Salpeter's value within uncertainty. The present study demonstrates that SAI 35 is a dynamically relaxed. Galactic orbital parameters are determined using Galactic potential models. We found that this object follows a circular path around the Galactic center.

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arXiv2020

Searching for Possible Exoplanet Transits from BRITE Data through a Machine Learning Technique

The photometric light curves of BRITE satellites were examined through a machine learning technique to investigate whether there are possible exoplanets moving around nearby bright stars. Focusing on different transit periods, several convolutional neural networks were constructed to search for transit candidates. The convolutional neural networks were trained with synthetic transit signals combined with BRITE light curves until the accuracy rate was higher than 99.7 $\%$. Our method could efficiently lead to a small number of possible transit candidates. Among these ten candidates, two of them, HD37465, and HD186882 systems, were followed up through future observations with a higher priority. The codes of convolutional neural networks employed in this study are publicly available at http://www.phys.nthu.edu.tw/$\sim$jiang/BRITE2020YehJiangCNN.tar.gz.

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