TNO Schedule

Cycle12 (2024-2025)

ID	Title/PI	Abstract
TNTC012_001	Investigating the Interplay of Gas-Phase and Stellar Metallicities in Star-Forming Galaxies: A Pilot Study   Nicha Leethochawalit	The metallicity of gas and stars in galaxies offers crucial insights into their chemical evolution, influenced by processes such as star formation, gas inflows, and outflows. While previous studies have focused on stellar metallicity in quiescent galaxies, 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 seeks to fill this gap through a pilot study using LRS to measure both gas-phase and stellar metallicities in star-forming galaxies with known HI gas fractions. By applying the chemical evolution model from Leethochawalit et al. (2019), we aim to constrain mass-loading factors in these galaxies and explore whether their positions in the stellar mass-metallicity relation depends on gas fraction. We will target 16 galaxies from the WALLABY pilot survey, focusing on the Hydra cluster, with observations planned using the TNO during moon-free half-nights in early 2025. We request a total of 16 hours of observation time to ensure the necessary signal-to-noise ratio for accurate measurements. The results will contribute to a deeper understanding of galaxy evolution and the factors driving stellar mass metallicity relations.
TNTC012_002	Evolved planetary systems   Amornrat Aungwerojwit	The study of evolved planetary systems is an emerging research field with considerable potential, and our aim is to carry out the first dedicated study of the full range of these systems. This project will significantly contribute to our overall understanding of the formation, architecture, and evolution of planets. We will in particular investigate the tidal disruption of rocky planetesimals and the subsequent formation and evolution of debris discs around white dwarfs through intensive follow-up of WD1145+017, the first white dwarf with detected transits. Our previous TNT observations of this system demonstrate a rapid evolution of the debris field at this white dwarf, providing real-time insight into the physical processes at work.. We then propose here (a) extend the photometric monitoring to all known eight debris systems accessible from the TNT (10 nights required), and (b) Obtain follow-up photometry of variable white dwarfs selected of 70 (out of 356) white dwarfs (35 nights required).
TNTC012_003	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 Ia 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.
TNTC012_004	Optical Counterparts and Follow Up Gravitational Wave Events through RUN O4   Kanthanakorn Noysena	The groundbreaking detection of gravitational waves (GWs) through GW150914 confirmed both the existence of GWs and the occurrence of binary black hole (BBH) mergers. The subsequent observation of the binary neutron star (BNS) merger GW170817, associated with a short Gamma-Ray Burst (sGRB) and a Kilonova (KN), inaugurated the multi-messenger era of astrophysics. Although GW170817 provided many answers, it also raised numerous new questions. Therefore, it is crucial to observe more counterparts and follow-up GW events during the second period of the fourth scientific observing run (O4b) of LIGO-Virgo. The first period of the O4 observing run (O4a), from May 24, 2023, to January 16, 2024, yielded 81 BBH detection candidates without evidence of optical transient detection. The second period, which began on March 27, 2024, and will conclude on June 9, 2025, is currently underway, with expectations of significant neutron star-black hole (NSBH) mergers. We propose several strategies to achieve this, including wide-field surveys, sGRB associations, and GW observations during O4b. While LIGO-Virgo detected NSBH mergers during O4a, no clear connection with optical transients was established, as seen with supernova S2023wrk. To address this, we propose a multi-observatory campaign utilizing Thai National Telescopes (TNT) in conjunction with the GRANDMA and GOTO networks. GRANDMA will analyze alerts from GWs, sGRBs, and GOTO surveys to identify the most promising KN candidates. TNT will then measure outflow geometry and constrain the KN's r-process, enhancing scientific output through tailored photometry. This ongoing campaign is essential for advancing this remarkably dynamic field.
TNTC012_005	Spectroscopic observations of astronomical transients with the new Low-Resolution Spectrograph   Samaporn Tinyanont	We propose for six nights on TNT, approximately once each month during the cycle, 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 and Einstein Probe X-ray transient counterpart search, or by other public all-sky surveys (e.g., ZTF, ATLAS, YSE etc.) The resolving power of R ~ 700 is sufficient for this purpose. Its sensitivity also allows us to classify all transients discovered by TRT and ATLAS, and most discovered by ZTF and YSE. We will work with our international collaboration to coordinate our observations. 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. As part of the shared risk operation, we will help develop an observing manual for LRS, and finalize the development of the data reduction pipeline. 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.
TNTC012_006	Estimating the Black Hole Mass and Jet Power for Fermi-Detected Active Galactic Nuclei with Optical Spectroscopy   Zhi-Yuan Pei	Based on the observation, active galactic nuclei (AGNs) can be described by a so-called unified model, namely central black hole + accretion disk + jet. Thus probing the properties of black hole and jet are rather important for us to understand the radiation mechanism of AGNs. In this project, we would like to use the Low-Resolution Spectrograph (LRS) at the 2.4-m Thai National Telescope for spectroscopic study on our selected gamma-ray-loud AGNs, which are detected by the Fermi-LAT telescope. Obtaining and fitting the optical spectrum are our main purpose. We can conduct the calculations of the board line region luminosity via emission lines, e.g., Hα, Hβ, Mg II, and C IV lines, and determine the black hole mass by adopting efficient approach presented from our previous work. Besides, the jet power can also be estimated by means of the analysis on continuum spectrums for our targets.
TNTC012_007	Long-term monitoring of the long-period redback pulsar PSR J2129-0429   Sittipong 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.
TNTC012_008	Search for the progenitors of the 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 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.
TNTC012_009	SPEARNET Follow-Up Observations of Hot Jupiter Exoplanets in the TESS era   Napaporn A-thano	Currently, over 5,700 planets have been identified using various techniques. Among these, more than 2,300 were discovered through the Kepler mission, and over 500 have been confirmed by TESS, primarily using the transit method. Beyond detecting new exoplanets, a rapidly advancing field focuses on characterizing the atmospheres and properties of these celestial bodies. One technique employs for studying planetary atmospheres is transmission spectroscopy, which measure changes in transit depth across different wavelengths (Seager & Deming, 2010). Through transmission spectroscopy, scientists can infer the absorption spectrum and compositional makeup of a planet's atmosphere. Additionally, transit light curves from these observations can be used to detect other planets within a system via the transit timing variations (TTVs) technique. 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 plan to focus on observing 13 specific targets: WASP-11b, 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, NGTS-5b and K2-237b. These targets have been continuously observed since 2014 using both NARIT facilities and our collaborative telescope network. In the upcoming observational cycle, we plan to use the TNT for transmission spectroscopy and TTVs analyses with the ULTRASPEC instrument on the 2.4-meter telescope and the 1-meter telescope at TNO, as well as the Thai Robotic Telescopes Network (TRTN). These observations will be focused on conducting transmission spectroscopy and monitor TTVs of the aforementioned exoplanets. This effort is aimed at enhancing our understanding of exoplanetary atmospheres and their surrounding environments.
TNTC012_010	A new population of massive compact-object halo binaries?   Pornisara Nuchvanichakul	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 (vr) 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, and estimate orbital periods. 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.
TNTC012_011	Observational study on evolution of the ultrashort-period cataclysmic variables   Shengbang Qian	The minimum period cut-off of cataclysmic binaries (CVs) is the unsolved problem in the field of stellar astrophysics. The standard model proposes that the donor will transit from a star to a degenerate brown dwarf after reaching the period minimum. The change in the structure of the donor leads to a reversal in the direction of orbital period evolution. The systems evolving back towards longer periods are referred to as period bouncers. The evolution theory also predicts that about 70% of CVs should be period bouncers. However, until recently, only a few candidate period bouncers were known, which gives a serious challenge for the standard model. This also make the ultrashort-period cataclysmic binaries around the period minimum into the important objects for studying the evolution of CVs. In this project, our scientific purposes are to monitor some eclipsing CVs photometrically with the 2.4-m TNT telescope. Based on those observations, coupled with the historical data, we plan to analyze systematically the law of orbital period changes in these binaries, and search for the potential period bouncers with long-term period increase. Meanwhile, the systems with secular period decrease will be studied and the angular momentum loss mechanisms will be discussed. Our data can also be used to study the period changes of the candidate bouncers with sub-stellar donors and to test the standard model. These results can enrich our understanding and knowledge on the evolution and outburst of CVs.
TNTC012_012	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 non-accreting 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 non-accreting 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.
TNTC012_013	SPEARNET Transmission Spectroscopy of HAT-P-16 b and HAT-P-32 b with TNT/LRS   Ida Janiak	With over 5,700 exoplanets detected to date, only a limited number have had their atmospheres measured and characterized, underscoring the urgent need for further atmospheric studies. Transmission spectroscopy is a key technique in this field, enabling the determination of the absorption spectra of elements and molecules in the atmospheres of transiting exoplanets. Given the anticipated discovery of hundreds of thousands of new exoplanets, establishing reliable ground-based follow-up observatories is crucial. As part of the global initiative known as SPEARNET (Spectroscopy and Photometry of Exoplanet Atmospheres Research Network), we propose observing transits of two exoplanets, HAT-P-16b and HAT-P-32b, using the 2.4 m Thai National Telescope (TNT) and its Low-Resolution Spectrograph (LRS). Our goal is to assess the feasibility and limitations of medium-sized telescopes for ground-based spectrophotometric observations of transiting exoplanets. By analyzing variations in planetary radius as a function of wavelength, we aim to investigate the atmospheric properties of both planets and validate their parameters through transit flux measurements. HAT-P-32b, which has been previously studied with large telescopes, serves as a benchmark for our observations, allowing us to evaluate the performance of the TNT/LRS. In contrast, HAT-P-16b has not been subjected to prior spectroscopic studies, enabling us to provide novel insights into its chemical composition. To enhance the reliability of our results, we will employ a custom-built data reduction pipeline that integrates standard reduction techniques with specialized spectrophotometric extensions. This pipeline will be refined based on our findings and made publicly available to streamline future data reductions for TNT/LRS observations.
TNTC012_014	LRS Spectroscopy of potential spiral brightest cluster galaxies (BCGs) at z~0.4   Taweewat Somboonpanyakul	Brightest cluster galaxies (BCGs) are typically elliptical galaxies, likely formed through multiple dry mergers. However, we have identified 14 BCGs out of 314 galaxy cluster at z=0.10-1.24 that show spiral structures in their images. Spectroscopic confirmation is necessary to determine 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 BCGs at z=0.2-0.6 with LRS spectroscopy. The objectives of this proposal are to 1) confirm if the targets are indeed the BCGs and 2) access if the targets show the spectral signature for spiral galaxies. The first objective can be achieved by determining the spectroscopic redshift of the targets. We expect to detect [OII] λ3727, Hβ λ4861, and [OIII] λ4959,5007 emission lines, which are prominent evidence of star forming activities. We request 2 dark and 2 grey nights in April-May to achieve a S/N>5 in the g-band, allowing us to calculate the Dn4000 index in the case of no detected emission line. This observation will complete our sample for studying the spiral BCGs, which is crucial for constraining models of cluster formation and evolution. Additionally, this program will pushing the sensitivity and stability of the LRS to its limits, offering valuable insights for the engineering and development of this spectrograph.
TNTC012_015	Verifying LRES Capabilities with SEA OtTeRS   Krittapas Chanchaiworawit	We propose to utilize LRS in its long-slit spectroscopy mode to observe the bright AGN and BCG of the intermediate redshift-rich cluster, MACSJ1149 as well as its member galaxies. The observation will reveal time-variation of the AGN continuum levels and board components of the emission features originating from the accretion disk and corona of the central supermassive black hole. This study will shed light on the geometry of the accretion disk as well as its entangled behavior with the corona. Furthermore, the observed BCG, member galaxies, and fillers will reveal the stellar populations, levels of star-formation, and AGN activities in the member galaxies of the cluster, paving a way to understand the role of overdensity in nurturing evolution of its members. Nevertheless, the proposed observation will put the sensitivities and stabilities in terms of spectroscopy and temporal repeatability of LRS to the test, yielding valuable data for the next stage of development of the instrument and its commissioning at the Thai National Telescope.
TNTC012_016	Follow-up LRS spectroscopy for four type-1 AGNs with variability in Hαemission line   Kantapon Jensangjun	We propose LRS spectroscopy of six type-1 AGNs at z∼0.1 showing significant spectral variation in Hα λ6563 emission line during the past 10-12 years. The spectral variation is usually linked to the change in the accretion rate or possibly due to changes in obscuration by the inflowing/outflowing gas. Our objective is to investigate the effect of spectral variations to the gas outflows. With LRS spectroscopy, we will study the gas kinematics as traced by strong [O III] λ5007 emission line. The spectral variations are studied through Balmer lines (Hα λ6563 and Hβ λ4862). From the observations, we might identify galaxies with outflow signatures that have emerged within the past ~10 years. If no sign of outflow is found, we could set the lower limit of the time required to launch gas outflow after the central AGN switches on (higher accretion rate). This should enable us to better understand the fate of AGN-driven outflow and their impacts to the central AGN and host galaxy.
TNTC012_017	Doppler imaging of non-radial pulsations of the fast-rotating A-type pulsators in the solar neighborhood   David Mkrtichian	The project for the TNT telescope is aimed to detect and study high-degree nonradial pulsations using the Doppler imaging of pulsations in A-type fast rotating pulsators close to the Sun. The survey is ongoing and successful, we discovered 42 new non-radially-pulsating rapidly-rotating A-type stars. We plan to continue project and to get during a winter-spring 2024/25 at TNT+MRES continuous and high-time resolution spectral time series for the new samples of fainter (and more distant) fast-rotating A-type stars. The photometric variability of selected targets will be investigated using precise light curves from the TESS space telescope. The spectroscopic series will be analyzed using the 2D DFT analysis of spectral line profiles and identification of modal degree and azimuthal number will be obtained.
TNTC012_018	Linking Accretion and near-IR Variability in Peculiar Protoplanetary Disks   Thanawuth Thanathibodee	Accretion is one of the most fundamental processes in star and planet formation. The intricate link between accretion and protoplanetary disks cannot be understated. For low-mass, pre-main sequence stars (T Tauri stars; TTS), accretion from planet-forming disk onto the star follows the magnetospheric accretion paradigm, where stellar magnetic fields truncate the disk and mass flow along the field lines toward the star. High-energy radiation from the accretion process, in turn, irradiates the disk and affects its properties, including the physical and chemical structures. Variability in accretion and (inner) disk tracers has been observed, but the connection between accretion and disk emission variability remains unclear despite their physical link. Here, we propose to use TNT/MRES to observe accretion tracers of two T Tauri stars with substantial near-IR variability at the same time as approved NASA IRTF/SpeX observations to probe the inner disks. Multi-epoch, contemporaneous observations from the two facilities will help to identify the mechanism responsible for the near-IR variability of these systems. The results will provide a better understanding of the processes in the inner region of protoplanetary disks, where rocky planets are thought to form.
TNTC012_019	Follow up Spectroscopic Observation of Eclipsing Binary TYC 5405-3070-1   Bakuh Danang Setyo Budi	We aim to observe TYC 5405-3070-1, an eclipsing binary star that is located in the Puppis constellation, observable from the southern hemisphere from around October-March. Through our initial estimation, the target star is expected to be a totally detached binary active stars, with their light curve indicating the spots experiencing dynamic change over time, possibly due to either differential rotation or spots evolution. Thus, we would like additional observation spectroscopy data which hopefully may aid in more detailed modelling of the binary system. This target star also shows a slight possibility of having a third body in its system based on the O-C data. Currently, with its limited Time of Minima (ToM) data, there’s no firm conclusion that can be drawn on this matter. By adding more complete ToM data from this observation, we hope that we can make a more definite confirmation.
TNTC012_020	Is MRI Responsible for Accretion in T Tauri Disks?   Thanawuth Thanathibodee	While accretion from protoplanetary disks onto the stars is well understood, it is still unclear how accretion works in the disk itself. Theoretical works have shown that magnetorotational instability (MRI) may be responsible for accretion within protoplanetary disks. For MRI to operate, the disk needs to be sufficiently ionized. We have an approved joint HST-JWST-Chandra program to observe a representative sample of protoplanetary disks to measure their ionization levels and determine if MRI can activate in those disks. JWST/MIRI will provide molecular and atomic lines for thermochemical modeling, and HST and Chandra will provide high-energy radiation measurement as input for the model. A key assumption is that the (non-observable) EUV emission from the star can reach the disk surface. However, a recent observation suggests that EUV can be suppressed or modulated by the star's accretion flows and MHD winds, which can be probed with accretion/wind tracers such as the H-alpha/beta line. Here, we propose to use MRES to observe the H-alpha/beta lines of one object in our sample to complete our multi-wavelength observational campaign. The results of our program will help shed light on accretion processes in protoplanetary disks and give insight into the process in other accretion disks.
TNTC012_021	Stellar occultation by binary asteroids   Puji Irawati	We propose to observe stellar occultations by binary asteroids using the 2.4m telescope with ULTRASPEC. Binary asteroids, unlike single asteroids, offer unique opportunities to study many fundamental processes in the Solar System. These processes are collisional dynamics, gravitational interactions, and, most importantly, the formation and evolution of planetary bodies. Furthermore, using the stellar occultation technique, we can accurately derive the size of these bodies, allowing us to get information on their shapes and densities. Our goals in this proposal is to use fast photometry (milliseconds) (1) to improve the orbit for these objects through positive or negative detection; (2) to measure the size of some of the binary asteroid candidates at km-accuracy and to derive density for the components (3) confirm the binarity and discover additional/multiple bodies. The drastic improvement provided by the Gaia DR3 catalogue (Liberato et al. 2024) will make predictions 3-4 times more accurate than previously done.
TNTC012_022	Absolute Properties of Eclipsing Binaries with Pulsating Components   Kyeongsoo Hong	Eclipsing binaries (EBs) allow for direct and independent determination of the absolute dimensions of each component without any assumptions from time-series photometry and spectroscopy, while pulsating stars are capable of probing their interiors from cores to envelopes and placing rigorous constraints on stellar theory through their pulsation features. Most stars in binary and multiple systems are born almost simultaneously and evolved by interaction between their components. The pulsating variables such as δ Sct and γ Dor stars in such systems are very useful for probing the impacts of mass transfer and tides on stellar evolution and interior structure. Recently, the EB stars with multiple pulsations have increased significantly in number thanks to space missions such as Transiting Exoplanet Survey Satellite (TESS). However, accurate physical properties have been only determined for about 20 pulsating EBs. Therefore, medium-resolution accurate spectroscopic observations for these stars are needed. We will investigate the evolutionary history of selected EBs by comparing their physical parameters with stellar models. For this, we propose to perform follow-up spectroscopic observations of interesting oscillating EBs using the 2.4m Thai National Telescope (TNT) with Medium Resolution Echelle Spectrograph (MRES), and to study their structure and evolution through asteroseismology and binary properties.