TNO Schedule

Cycle 13 (2025-2026)

ID	Title/PI	Abstract
TNTC013_001	Investigating the Interplay of Gas-Phase and Stellar Metallicities in Star-Forming Galaxies: Final Phase Ponlawat Yoifoi	Neutral hydrogen (HI) serves as the primary fuel for star formation in galaxies. Its abundance—regulated by gas inflows and outflows—has important implications for the formation of younger, more metal-rich generations of stars. In quiescent galaxies, the relationship between stellar metallicity and star formation activity has been extensively investigated in previous studies. However, there is a gap in understanding the relationship between gas-phase and stellar metallicities in star-forming galaxies, particularly in relation to gas fraction and star formation rate (SFR). This proposal aims to fill this gap by measuring both gas-phase and stellar-metallicities in star-forming galaxies with known HI gas fraction. We will apply the chemical evolution model from Leethochawalit et al. (2019) to constrain mass-loading factors of these galaxies. Moreover, we will investigate whether their positions on the stellar mass–metallicity relation are more strongly correlated with gas fraction or with star formation rate. For this phase, we propose observations of 158 galaxy targets with measured HI data from WALLABY DR2, focusing on the NGC 5044 group. Observations will be conducted using the Low-Resolution Spectrograph (LRS) at TNO during moon-free half-nights in early 2026. We request 135 hours of observation time to achieve the high signal-to-noise ratios necessary for accurate measurements. The results will provide deeper insights into the chemical evolution of galaxies and the factors driving the stellar mass–metallicity relation.
TNTC013_002	Long term monitoring of the long-period redback pulsar PSR J2129-0429 Sittippong Konkaew	PSR J2129-0429 is a "redback" pulsar binary that belongs to the more general class of "Spiders", in which a pulsar gradually ablates a low-mass companion orbiting at a close distance. Some redbacks called transitional millisecond pulsars have recently been found to occupy a key stage of binary evolution marking the transition from active accretion in a low-mass X-ray binary to a rotation-powered pulsar with an evolved companion. PSR J2129-0429 is the first and only formally identified Spider in which small secular optical changes have been detected so far and, while it is not a proper transitional system, it might give us significant clues about the evolution of these systems. Further investigation is warranted as there appears to be a relative flux change in the z band of TNT data from 2017 to 2021. We propose to initiate a bi-annual monitoring campaign in order to 1) track the future behavior of this system and 2) shed light on the physical mechanism responsible for these secular changes.
TNTC013_003	The astrophysical mechanisms of the peculiar variability in intermediate polars Zhongtao Han	Intermediate Polars (IPs) represent a key subclass of cataclysmic variables, bridging non-magnetic systems (e.g., dwarf novae, novae) and strongly magnetic polars. They provide unique laboratories to study truncated disk precession, magnetically controlled accretion, and localized thermonuclear bursts. Observations suggest that rapid outbursts in some IPs are linked with superhump-like signals, but their physical origins remain uncertain. Building on extensive photometric survey data and LAMOST spectroscopy, this project aims to systematically identify IPs and investigate their outbursts, superhumps, and related variability. By expanding the observational sample, we will conduct statistical studies to explore the connections between these phenomena and constrain the underlying physical processes. Complementary targeted monitoring with TNT 2.4m and TNO 1m telescopes will focus on key objects, combining analyses of light variability, magnetic fields of white dwarfs, and the activity of secondary stars. These studies will clarify the outburst mechanisms of IPs, establish their links with dwarf nova and nova eruptions, and provide empirical constraints for testing and refining accretion models. Ultimately, this project will deepen our understanding of magnetic white dwarfs, accretion dynamics, and time-domain behavior in compact binaries, contributing to the broader development of stellar astrophysics.
TNTC013_004	Search for the progenitors of stellar merger Liying Zhu	Stellar mergers are estimated to be common events in the Galaxy. However, those phenomena have not been efficiently probed by the Galactic surveys. Till now, V1309 Sco is the only confirmed non-compact stellar merger, which is identified mainly by its pre-outburst light curve. The modeling of the pre-outburst light curves of V1309 Sco reveals that its progenitor is a low mass-ratio contact binary with high fill-out factor. This link opens the window to investigate the stellar merger and the final fate of the contact binaries. In order to search for such progenitors of the stellar merger, we have investigated the LAMOST and TESS data and monitored a group of contact binaries for years photometrically and derived dozens of candidates of stellar merger progenitor with obvious period change. However, most of them are partial eclipsing binaries and show strong asymmetric light curves probably due to magnetic activities, which prevent us derive the reliable mass ratio based on the light curves only. So we need to combine the radial velocity curves to obtain the precise mass ratio. Furthermore, the third body orbiting around the binary may play an import role to the merger of the central binary. In this project, we apply the observational time of 2.4m telescope to do the spectroscopic observations for their radial velocity curves and the evidence of the third bodies.
TNTC013_005	SPEARNET Follow-Up Observations of Hot Jupiter Exoplanets in the TESS era Napaporn A-thano	To date, over 5,900 exoplanets have been discovered using various techniques. Among them, more than 2,300 were discovered by the Kepler mission and over 680 confirmed by TESS, primarily through the transit method. Beyond discovery, an important frontier in characterizing planetary atmospheres and system dynamics. Transmission spectroscopy is a key technique, measuring variations in transit depth across wavelengths to infer atmospheric composition. Transit light curves from these observations also enable detection of additional planets through transit timing variations (TTVs). This proposal is a fundamental part of the global initiative known as SPEARNET (Spectroscopy and Photometry of Exoplanet Atmospheres Research Network). This collaborative effort employs a distributed network of telescopes to analyze exoplanetary atmospheres. In this proposal, we focus on 11 selected targets: WASP-36b, WASP-143b, WASP-161b, WASP-183b, HAT-P-33b, HAT-P-36b, HAT-P-39b, HAT-P-43b, HAT-P-47b, HAT-P-48b, and NGTS-5b. These planets have been continuously observed since 2014 with NARIT facilities and partner observatories. In the upcoming cycle, we will employ the ULTRASPEC instrument on the 2.4 m TNT, the 1 m TNO telescope, and the Thai Robotic Telescopes Network (TRTN) to conduct transmission spectroscopy and TTV analyses. These coordinated observations aim to refine our understanding of exoplanetary atmospheres and their dynamical environments.
TNTC013_006	The Accurate Stellar Parameters of Eclipsing Binaries with Pulsating Components Kyeongsoo Hong	Eclipsing binaries (EBs) with pulsating components provide a unique opportunity to measure accurate stellar parameters and probe stellar interiors. δ Sct and γ Dor stars give complementary seismic constraints, while EL CVn-type binaries, consisting of a main-sequence star and a pre-He white dwarf, offer valuable insights into binary evolution. Empirical relations such as the large separation–mean density relation and the period–luminosity relation further improve stellar parameter precision, which is also critical for exoplanet host characterization. Despite many discoveries from Kepler and TESS, spectroscopic follow-up remains limited. We propose to obtain time-series spectra of selected pulsating EBs with the 2.4 m TNT and MRES to derive precise stellar properties and study their evolution through combined asteroseismology and binary modeling.
TNTC013_007	What blew up? Spectroscopic classifications and follow up observations of astronomical transients with TNT/LRS Samaporn Tinyanont	We propose for six classically scheduled nights on TNT, approximately once each month during the cycle, plus six Target of Opportunity triggers (one hour each) to obtain spectroscopic observations of astronomical transients with the Low-Resolution Spectrograph (LRS). LRS adds a critical capability to TNT to classify astronomical transients, discovered by TRT as part of the Distance Less Than 40 Mpc survey, or by other public all-sky surveys (e.g., ZTF, ATLAS, YSE etc.) The resolving power of R ~ 700 and the sensitivity is sufficient for this purpose. We will report all transients classified by this program publicly, and will use LRS to follow up interesting and nearby transients. TNT/LRS is one of a very few instrument capable of transient spectroscopic follow-up at this longitude, which could allow us to observe transients at a critical phase when it could not be reached by other observatories in North America, Hawaii, and Europe. In addition, the observing season at TNT is during the northern winter where California and Hawaii have poor weather; observations from TNT could be our only chance to capture transients in their critical phases. As part of the shared risk operation, we have already helped develop an observing manual for LRS, and develop a version of pypeit to reduce LRS data. We have extensive experience with spectroscopy on major telescopes worldwide (e.g., Lick/Kast, Keck/LRIS, Gemini/GMOS, SOAR/Goodman etc.), and will apply our experience to bring TNT/LRS up to speed and be ready for the next era of transient astronomy with the Rubin observatory.
TNTC013_008	Evolved planetary systems Amornrat Aungwerojwit	Close white dwarf binaries are a natural outcome of the evolution of main-sequence binaries containing two stars with initial masses >1Mⵙ. The shortest-period binaries of this population will eventually merge, as their orbit decays via the emission of gravitational wave radiation. The most massive among the mergers are extremely important in a wider context of astrophysics: a fraction of those will explode as type la supernovae. However, our current understanding of double white dwarf formation, evolution, and their ultimate fate as mergers is poorly understood. An important observational constraint is the fraction of massive merger remnants "hiding" among the population of massive white dwarfs that formed from single-star evolution. Within this project, we will use ULTRASPEC to probe for the short spin periods that are the unmistakable signature of a merger history among 36 white dwarfs that exhibit traces of carbon in their atmospheres. These systems are good merger remnant candidates, as the trace carbon can only be explained by a very thin hydrogen layer ontop of the carbon-rich core, too thin to have formed by single-star evolution. If successful, our project will allow the unambiguous identification of merger remnants based on spectroscopy alone.
TNTC013_009	Identifying merger remnants among massive white dwarfs Amornrat Aungwerojwit	Close white dwarf binaries are a natural outcome of the evolution of main-sequence binaries containing two stars with initial masses >1Mⵙ. The shortest-period binaries of this population will eventually merge, as their orbit decays via the emission of gravitational wave radiation. The most massive among the mergers are extremely important in a wider context of astrophysics: a fraction of those will explode as type la supernovae. However, our current understanding of double white dwarf formation, evolution, and their ultimate fate as mergers is poorly understood. An important observational constraint is the fraction of massive merger remnants "hiding" among the population of massive white dwarfs that formed from single-star evolution. Within this project, we will use ULTRASPEC to probe for the short spin periods that are the unmistakable signature of a merger history among 36 white dwarfs that exhibit traces of carbon in their atmospheres. These systems are good merger remnant candidates, as the trace carbon can only be explained by a very thin hydrogen layer ontop of the carbon-rich core, too thin to have formed by single-star evolution. If successful, our project will allow the unambiguous identification of merger remnants based on spectroscopy alone.
TNTC013_010	Searching for non-accreting compact objects in binaries Shengbang Qian	The demographic and physical properties of compact objects like neutron stars (NSs) and black holes (BHs) hold essential information about the stellar evolution and chemical enrichment history of our Galaxy. Most of the NSs and stellar-mass BHs have been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. Recently, a few nonaccreting stellar-mass BHs and NSs have been detected through radial-velocity (RV) measurements of the motion of the companion star, which indicates the optical time-domain surveys can unveil and characterize exciting but less explored nonaccreting NSs and stellar-mass BHs in binaries. Based on the LAMOST and TESS data, we have detected a group of variables with large radial velocities, high metallicity, ellipsoidal light curve, or even pulsating ellipsoidal light curve, which are potential candidates of non-accreting NSs and stellar-mass BHs. In this project, we apply to use medium resolution spectrograph of TNT to get the companions' RV curves of these potential candidates of non-accreting compact objects. Our purpose is searching for non-accreting NSs and stellar-mass BHs in binaries based on their companions 'RV curves and ellipsoidal light curves.
TNTC013_011	To see the unseen: a probe into the world of “cold” magnetospheres of Ap/Bp stars Eugene Semenko	The chemically peculiar (CP) Ap/Bp stars are famous for their strong magnetic fields and abnormal chemical abundances, which result in spots that cause photometric and spectroscopic variability. The proposed observational project aims to verify the hypothesis that the fine photometric variability recently detected in TESS observations for some CP stars is related to the presence of massive stellar photospheres, which cannot be directly observed otherwise due to their much cooler temperatures. In spectroscopic observations, such formations must cause line profile variability that mimics the photospheric spots commonly observed in chemically peculiar stars. Through the analysis of time-resolved spectroscopy, we aim to develop criteria that enable us to distinguish between these two distinct effects. The list of targets consists of five stars with well-known rotational periods and magnetic properties. Two of these stars are used as standards for calibration.
TNTC013_012	Hunting for Period Bouncers in Cataclysmic Variables Shengbang Qian	The evolution theory predicts that about 70% of Cataclysmic Variables（CV） should be period bouncers. However, until recently, only a few candidate period bouncers were known, which gives a serious challenge for the standard model. Consequently, short-period binaries near the period minimum have emerged as crucial objects for investigating CV evolution. In this project, we utilize the 2.4-m TNT telescope to conduct photometric monitoring of select short-period eclipsing CVs. Combining new observations with historical data, we will systematically analyze orbital period variations in these systems, searching specifically for potential period bouncers characterized by long-term period increases. Concurrently, systems displaying secular period decline will also be studied to explore angular momentum loss mechanisms. Furthermore, our dataset provides an opportunity to investigate period changes in candidate bouncers hosting sub-stellar donors and rigorously test the standard model. These findings aim to deepen our understanding of CV evolution and outburst mechanisms.
TNTC013_013	Doppler imaging of non-radial pulsations of TESS fast rotating A-type pulsators David Mkrtichian	The TNT telescope project aims to detect and study high-degree nonradial pulsations in bright, fast-rotating A-type stars using Doppler imaging of pulsations, as identified by our team from precise TESS light curves. We will obtain continuous, high-time-resolution spectroscopic time series with TNT for a new sample of very fast-rotating A-type star targets, and then apply 2D Fourier Transform (DFT) analysis to detect and identify the pulsation modes. This is a large-scale, long-term project with the goal of revolutionizing our understanding of the excitation of high-degree nonradial pulsations.
TNTC013_014	A new population of massive compact-object halo binaries? Pornisara Nuchvanichakul	This resubmission is for proposal ID: 010 in cycle 12. The Milky Way is expected to host between 10^3 and 10^8 stellar-mass black holes in binary systems, yet only about 30 have confirmed mass estimates, mainly in X-ray binaries. The recent discovery of Gaia-BH3, a 33 M⊙ black hole in a wide-orbit binary, suggests a larger population of massive black holes in low-metallicity, retrograde orbit systems, likely originating from the Galactic halo. This study proposes a Gaia targeted search for radial velocity (RV) variations in a set of new Gaia-BH3 candidate analogues. Selected based on retrograde space velocity, low metallicity ([Fe/H] < –1), and significant astrometric excess noise (AEN), these candidates are potential binaries hosting compact objects. By tracing radial velocity curves, we aim to confirm binarity, estimate orbital periods, and assess the binary fraction among these halo candidates. Additionally, we will search for weak luminous emissions from companion stars. This research marks an important step toward identifying and understanding massive stellar black holes in the Milky Way, particularly in halo, offering new insights into their formation, evolution, and broader population.
TNTC013_015	LRS Spectroscopy of potential spiral brightest cluster galaxies (BCGs) at z~0.4 Taweewat Somboonpanyakul	The brightest cluster galaxies (BCGs) are usually an elliptical galaxy, possibly caused by multiple dry merging processes. However, we found 14 BCGs out of 314 galaxy cluster at z=0.10-1.24 that show the spiral structure in their images. The spectra are required to check if these objects are truly spiral galaxies, but only 10 of them have publicly available spectra. We propose to observe the remaining 4 potential spiral brightest cluster galaxies (BCGs) at z=0.2-0.6 with LRS spectroscopy. The objectives of this proposal are 1) to confirm if the targets are indeed the BCGs and 2) to examine if the targets show the spectral signature for spiral galaxies. The first objective can be accomplished by just determining the spectroscopic redshift of the targets. We expect to detect [OII] 3727, Hbeta 4861, and [OIII] 4959, 5007 emission lines which are prominent evidence of star forming activities. We request 3 dark and 3 grey nights in April-May to achieve S/N>5 in g band so that we can calculate Dn4000 index in the case of no detected emission line. This observation will provide the complete sample for studying the spiral BCGs, which is crucial to make a constraint on the study of cluster formation and evolution.
TNTC013_016	SPEARNET Survey: Characterizing Five Hot Jupiters with TNT/LRS using SPARK-LRS Ida Janiak	With over 6,100 exoplanets detected, only a small fraction have had their atmospheres characterized, emphasizing the need for further studies. Transmission spectroscopy probes the absorption of elements and molecules in transiting exoplanet atmospheres. Given the expected discovery of hundreds of thousands of new exoplanets, reliable ground-based follow-up is essential. As part of the global SPEARNET (Spectroscopy and Photometry of Exoplanet Atmospheres Research Network) initiative, we propose observing transits of five exoplanets - WASP-49 b, WASP-50 b, WASP-104 b, WASP-149 b, and XO-2 N b - using the 2.4 m Thai National Telescope (TNT) and its Low-Resolution Spectrograph (LRS). Our objectives are to assess the feasibility of medium-sized telescopes for spectrophotometric observations and to test SPARK-LRS, a pipeline developed for TNT/LRS. By analyzing variations in planetary radius with wavelength, we will investigate atmospheric properties and validate transit parameters. WASP-49 b and XO-2 N b will serve as benchmarks, while WASP-50 b, WASP-104 b, and WASP-149 b will be observed spectroscopically for the first time, providing novel insights into their chemical composition. The data reduction pipeline combines standard techniques with spectrophotometric extensions and will be refined and made publicly available to streamline future TNT/LRS observations.
TNTC013_017	Optical Characterization of Satellite Body Brightness Using BRDF-Based Models and Earthshine Contributions Kanthanakorn Noysena	The growing number of satellites in Earth orbit necessitates accurate optical characterization to support both astronomical mitigation efforts and space situational awareness (SSA). This project aims to observe and model the brightness of artificial satellites using the 2.4 m telescope at the Thai National Observatory. Satellite brightness is influenced by multiple factors, including solar illumination geometry, Earthshine during twilight conditions, surface reflectivity, structural geometry, and satellite orientation. To quantify these effects, we will apply Bidirectional Reflectance Distribution Function (BRDF) models fitted to observational data, combined with light transport equations and earthshine simulations that discretize the Earth’s surface into radiating panels. Observations will be conducted across multiple wavelengths to determine apparent magnitudes and investigate spectral variability. The outcomes will include validated brightness estimates for different satellite components (e.g., solar panels, bus structures) and improved algorithms for predicting satellite visibility. These results will advance understanding of satellite impacts on ground-based astronomy and provide valuable inputs for SSA systems, including real-time tracking and brightness forecasting. In addition, the study will support the development of design guidelines for future satellite missions aimed at reducing their optical interference with scientific observations.
TNTC013_018	Follow-up LRS spectroscopy for four type-1 AGNs with variability in Hα emission line Kantapon Jensangjun	Due to poor weather conditions during Cycle 12, our previous observation was unsuccessful. We are therefore reproposing a follow-up LRS spectroscopic study of five type-1 AGNs at z∼0.1. These objects are classified as changing-look AGNs (CL-AGNs), exhibiting significant spectral variations in the broad component of the Hα λ6563 emission line over the past 10-12 years. The observed spectral changes are likely due to fluctuations in the accretion rate of the central supermassive blackhole. This study aims to investigate how these variations influence gas kinematics and outflows. Using LRS spectroscopy, we will analyze spectral variations in the Balmer lines (Hα λ6563 and Hβ λ4862), and probe gas kinematics and outflows via the [O III] λ5007 emission line. We expect to see enhanced gas kinematics or outflows in galaxies in which the broad component has recently emerged. If no outflow signatures are detected, we will be able to establish a lower limit for the time required to launch gas outflows after the central AGN shows an increase in the accretion rate. This work will improve our understanding of the fate of AGN-driven outflows and their impacts on both the central AGN and its host galaxy.
TNTC013_019	Study of variability on spectroscopic data of Wolf-Rayet stars Bakuh Danang Setyo Budi	The earliest generations of stars preserve the chemical fingerprints of the first supernovae and the transition from Population III to later stellar generations. Extremely and Very Metal-Poor (EMP/VMP; [Fe/H] < –2) stars, especially Carbon-Enhanced Metal-Poor (CEMP) stars, encode distinct nucleosynthesis pathways, including primordial enrichment, AGB mass transfer, and the intermediate (i-) neutron-capture process. Yet robust classification and detailed abundance studies are limited by survey-quality spectra. We propose medium-resolution (R ~18,000) spectroscopy with the Thai National Telescope (TNT) to confirm key light (C, O, Mg, Li, Na) and neutron-capture (Ba, Eu, Sr, La) element abundances. These measurements will enable precise classification of CEMP subgroups, identify potential very metal-poor binaries, and select the most promising targets for high-resolution follow-up with Subaru/HDS or other 8–10 m telescopes. Our targets are bright LAMOST candidates (V < 13.5 mag) with high carbon (A(C) > 6.9 dex) and barium ([Ba/Fe] > 0.5), observable in short exposures (<2 hours). By bridging wide-field surveys and high-resolution studies, this program maximizes the efficiency of valuable telescope time and provides critical insight into early nucleosynthesis, the origin of heavy elements, and the chemical evolution of the Galaxy.
TNTC013_020	Establishing a Spectral-Range Atmospheric Extinction Database for Improving Astronomical Observation Quality at the Thai National Observatory Somsawat Rattanasoon	Ground-based astronomical observations are limited by atmospheric extinction, which arises from the scattering and absorption of light by air molecules, aerosols, and water vapor. These processes alter the brightness and spectra of celestial objects, introducing systematic errors that compromise the accuracy of quantitative measurements such as stellar fluxes, galaxy luminosities, and atmospheric signatures of exoplanets. To address this challenge, a spectral-range atmospheric extinction database is proposed for the Thai National Observatory (TNO). Observations will be conducted with the 2.4-meter telescope equipped with the Medium-Resolution Echelle Spectrograph, targeting standard stars across different sky positions and seasonal conditions. From these data, wavelength-dependent extinction curves will be constructed over the range of 370–1100 nm, allowing contributions from Rayleigh scattering, ozone and oxygen absorption, and water vapor to be quantified. These curves will then be integrated to derive spectroscopic corrections and photometric coefficients applicable across observing programs. The resulting database will serve as a reusable calibration tool, improving the reliability and precision of both photometric and spectroscopic research carried out at TNO. In addition, participation of undergraduate students will be integrated into the project, providing training in observational techniques, data reduction, and atmospheric analysis while strengthening the long-term research capacity of the observatory.
TNTC013_021	Developing and validating a novel non-axisymmetric accretion flow model with the ideal dataset: MRES plus TESS Caeley Pittman	Understanding accretion onto low-mass pre-main-sequence stars (T Tauri stars, TTS) is vital for establishing the evolution of the planet-forming environment around Sun-like stars. However, characterizing the accretion has historically required observationally- and computationally-expensive resources, which limits the sample sizes that can be studied. Therefore, we propose to develop an accretion model that can be applied to easily-obtainable observations and requires significantly less computing power than more complicated magnetohydrodynamic models. To do so, we will use MRES to observe H-alpha, a prime tracer of the accretion flow, in a target that is known to show evidence of non-axisymmetric accretion flows with a well-established period of variability of 5.7 days. We will schedule the multi-epoch MRES observations to coincide with TESS observations in order to simultaneously characterize the accretion flow and hotspot on the stellar surface, building a coherent picture of the structure of the accretion flow from the disk, along the magnetic field lines, and onto the star itself. This dataset will enable the first application of a non-axisymmetric accretion flow model to TTS. Once developed and validated, it will enable sophisticated accretion modeling of a large sample of TTS at a fraction of the observational and computational cost as required in the past.
TNTC013_022	Long-Term Optical Monitoring of Redback Pulsars: Probing Irradiation and Mass Transfer Adipol Phosrisom	Spider pulsars are compact binary systems containing a millisecond pulsar and a low-mass irradiated companion. The optical variability can be seen due to the irradiation and ellipsoidal modulation, while some redback systems (a sub-type of spiders) also exhibit long-term variability and signs of ongoing companion evolution. These behaviors provide key insights into binary interactions, mass transfer, and the late stages of pulsar recycling. Therefore, we propose to observe four redback pulsars: PSRs J0212+5321, J1723-2837, J1306-4035, and J1816+4510 with the Thai National Telescope. We aim to obtain at least 2 cycles of these redbacks a year. This strategy is designed to capture both short-term variability and long-term evolutionary changes.