1 November 2023 to 15 May 2024
Asia/Bangkok timezone

Cycle 10 (2022-2023)


ID Title, PI Abstract

Are rapidly rotating M dwarfs flare inactive or are those objects dominated by UV micro-flaring?

PI: Dr. Puji Irawati

Observations made using TESS have revealed that the majority of low mass stars which have rotation periods shorter than 0.3d show very few (if any) flares. Given that rapid rotation is the usual sign for high levels of stellar activity this is a surprise. Various explanations have been put forward for this discrepancy but it is currently unresolved. Here we propose to observe a small selection of these low mass stars with a rotation period <0.2 d and show fewer than 1 flare every 27 days (the duration of a TESS sector). Our observations would allow us to determine whether micro-flaring (and/or ultra-violet dominated events) are present which can not be seen by TESS due to their short duration and emission in the ultra-violet. This will allow us to better constrain the interplay between the magnetic energy, stellar rotation, activity level and underlying dynamo action.

Spectroscopic portrait of the Orion Nebula foreground population

PI: Dr. Eugene Semenko

Orion OB1 is one of the closest to the Sun associations with active star formation. It was believed that the division of this association into four subgroups reflected their sequential formation, though analysis of the GAIA data revealed a more complex picture with a stellar population of different ages mixed within the same volume. Meantime, deep spectroscopic surveys show that the association is chemically homogeneous, doubting the sequential scenario with multiple supernovae explosions. The most complicated situation is in a direction toward the Orion Nebula, where the stellar ages dispersed between 1 and 10 Myr. Our observational project is aimed at the searches for a chemical enrichment caused by supernovae in older and poorly studied stars, which form a foreground population of the Orion nebula complex. From medium-resolution spectra obtained with MRES for 21 stars, we plan to draw a chemical portrait of this population and answer the question about its similarity in terms of chemical composition, kinematics, and origin to the rest of the nebula stars.

Search for the contact binaries under the short period limit

PI: Prof. Liying Zhu

W UMa-type contact binaries are containing two late-type stars, where both components are filling their critical Roche Lobes and sharing a common convective envelope. Their formation and evolution are unsolved problems in Astrophysics. There is a short period limit of W UMa-type contact binaries at about 0.22 days. According to the period-color relation, the contact binaries under this limit should be K or M type binaries. Recently, a few contact binaries under this short-period limit were discovered, which is the challenge of the theory and may suggest a different way to form the contact binaries. However, the rarity of the extremely short period contact binary prevents the further study. Thanks to some surveys in the world (e.g., SDSS, SuperWASP, TESS), some short-period (P < 0.22 days) close binaries with EW-type light variations were discovered. Together with the LAMOST spectral data, we found more than 30 such contact binary candidates. Our scientific purposes are to search for such ultra short-period contact binaries and investigate their physical properties. These results will shed light on the formation and evolution of contact binary stars, and will help us to reveal the physical reasons of this short-period limit.

Triton Stellar Occultation of 6 October 2022

PI: Dr. Puji Irawati

A stellar occultation by Triton, the largest of Neptune’s moon, will occur on 6 October 2022. This event can be observed across the Asian continent and the middle east, including the northern part of Thailand. While there are plenty of stellar occultations by solar system bodies, Triton occultation is very rare. The last two occurrences happened in 2008 and 2017, with the nearest future events in 2022 and 2029. Light curves obtained from various observation sites will help to constrain Triton’s atmospheric profile and the changes in atmospheric pressure in different seasons. Here we apply for 5 hours of TNT time to observe the Triton occultation using the ULTRASPEC instrument. This observation is part of a global campaign and NARIT is collaborating with the groups from Planetary Science Institute/MIT/Lowell Observatory and Observatoire de Paris. As a note, we want to mention that the observation requested in this proposal will be outside the normal observing season (16 Nov 2022 to 15 May 2023). In addition, we will also use the TNO-1m telescope and the 0.7m telescope at AstroPark to observe this event simultaneously.

Optical Counterparts to Gravitational Wave Events during the fourth observing run of Advanced LIGO and Advanced Virgo

PI: Dr. Kanthanakorn Noysena

The first detection of gravitational waves (GWs) GW150914, proved the existence of both gravitation waves and binary black hole (BBH) mergers. The detection of the binary neutron star (BNS) merger GW170817, associated with both a short Gamma-Ray Burst (sGRB) and a Kilonova (KN) led to the beginning of the multi-messenger era of astrophysics. GW170817 answered many questions, but still left many open and gave rise to a large number of new ones. Therefore, more counterparts and follow-up GW events will need to be observed in the fourth scientific observing run (O4) of LIGO and Virgo. The 2.4-meter Thai national telescope (TNT) can play an important role in the field by following-up optical transients discovered by wide-field telescopes, such as the Thai Robotic Telescope (TRT), the Gravitational-Wave Optical Transient Observer (GOTO), and the Global Rapid Advanced Network Devoted to the Multi-messenger Addicts (GRANDMA) in all of which the PI of this proposal is an active member. Here we propose to use TNT for a multi-observatory campaign that will be coordinated with observations from TRT, GOTO, GRANDMA. The trigger for ToO programme will only respond to significant alerts from GWs, sGRBs, and optical transients discovered during the O4 run and will aim at the characterization of the counterparts using multi-band photomety.

Prominences and their connection to the circumstellar material formation in white dwarf main sequence binaries (continued)

PI: Dr. Puji Irawati
This is a continuation of proposal TNTC08_009 and TNTC09_006 with the same title. In white dwarf binaries, evidence of slingshot prominences has been recorded spectroscopically, but the limited time resolution, compared to their rapid evolution makes them hard to study in detail. We have found what we believe to be the signature of the circumstellar materials (formed by the materials ejected in the prominences) in a white dwarf / M dwarf binary star through persistent dips in flux caused by obscuration of the white dwarf in the binary system SDSS J1021+1744. This feature was first detected in 2014 (TNO-Cycle 1), but a similar feature was again observed during the regular monitoring of WDMS binaries in Cycle 6. The goal of this project, together with the simultaneous observation effort using DOT-3.6m, is to investigate the origin of the dips and whether the prominences are feeding the formations of these extraneous eclipses. Therefore, in this cycle, we plan to do a further follow-up (15hrs) on this system.

Doppler imaging of non-radial pulsations of TESS fast rotating A-type pulsators. Part II:

PI: Dr. David Mkrtichian

The project for TNT telescope is aimed to detect and study high-degree nonradial pulsations using the Doppler imaging of pulsations in A-type fast rotating pulsators detected by us using precise TESS light curve. We are going to get continuous and high-time resolution spectral time series using TNT for the sample of five very fast rotating bright A-type stars in winter 2022/23 and apply the 2D DFT analysis for identification of pulsation modes

Observational study on evolution of the ultrashort-period cataclysmic variables

PI: Prof. 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.

Searching for the Orbital Decays of Exoplanets through Transit Observations

PI: Ms. Napaporn A-thano

The exoplanet discovery through transit events has become an emerging science in recent years. More than 3000 exoplanets have been detected using this technique, and more than 200 planets were confirmed by the TESS mission. The Transit Timing Variations (TTVs) of transiting exoplanets was introduced as one of the successful methods for the discoveries of new exoplanets. In addition, the study of TTVs can lead to the constraints on exoplanets’ masses and orbital evolution. We propose to use the ULTRASPEC 2.4-meter TNT observing facilities to monitor the transits of five close-in giant planets. We hope to monitor the transit events, thus determine the orbital characteristics, and investigate the possible orbital decays. These results could help us to advance the understanding of the planet formation and evolution processes.

Time series spectroscopic monitoring of ULLYSES targets with MRES on TNT

PI: Mr. Tirthendu Sinha

The proposed observations are complementary to our ongoing 3 yrs (2020 - 2022) HST observing program “Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS)” of classical T Tauri stars. ODYSSEUS is an international community effort of multi-wavelength photometric and spectroscopic monitoring of ULLYSES (Hubble UV Legacy Library of Young Stars as Essential Standards) sources in synergy with HST spectroscopic observations. This campaign is intended to revolutionize our understanding of the physics of disk evolution and planet formation; and the intricate relationships between mass accretion, mass outflow, and disk structure, thanks to our ongoing and upcoming simultaneous ground and space multi-band observations. Our team of 60 young star experts from around the world will bring their combined knowledge to bear on the ULLYSES FUV spectral database, ensuring a uniform and systematic approach in order to (1) measure how the accretion flow depends on the accretion rate and magnetic structures, (2) determine where winds and jets are launched and how mass loss rates compare to accretion, and (3) establish the influence of UV radiation on the chemistry of the warm inner regions of planet-forming disks. In this context, we propose the optical spectroscopic observations of 3 bright ULLYSES targets. These observations, in part, will be carried out in synergy with HST, 3.6m DOT and ARIES 1.04m and 1m TNO telescope.

A comprehensive analysis of the extended Main Sequence Turn-Offs in the Galactic open clusters

PI: Mr. Jayanand Maurya

With this proposal, we plan to carry out spectroscopic observations of 24 stars brighter than V = 11.5 mags belonging to extended Main-Sequence Turn Off (eMSTO) of the open cluster NGC 2423 using the medium resolution spectrograph (MRES) mounted on 2.4-m TNT telescope. The main objective of this study is to investigate the origin of eMSTO in the colour-magnitude diagram of the Galactic open clusters. The presence of eMSTO in the Galactic open clusters has been attributed to various reasons such as multiple stellar populations, spread in rotational velocities, the presence of binary stars, metallicity spread, and differential reddening. However, the comprehensive analysis exploring all these possibilities based on the homogeneous sample is still lacking. The spectroscopic estimation of rotation rates, metallicity, luminosity, and effective temperature will enrich our understanding of the existence of eMSTO in the open clusters. In addition, the spectra of these stars will also be helpful in the determination of the physical properties of the parent cluster.

A test for the single degenerate channel towards type Ia supernovae (continued)

PI: Ms. Pakakaew Rittipruk

This is a continuation of proposals TNTC08_007 and TNTC09_005 with the same title. The progenitors of type Ia supernovae are close binaries containing white dwarfs. Of crucial importance to the evolution of these systems is how much material the white dwarf can stably accrete and grow in mass. This occurs during the super-soft source (SSS) phase. The short duration of this phase means that only a handful of SSS is known. Far more can be learned from the underlying SSS progenitor population of close white dwarf plus A, F, G, K type binaries. Using the GALEX survey, combined with data from LAMOST, RAVE, TGAS, and Gaia DR2, we have now identified the first large sample of A, F, G, K stars with significant UV excesses typical of white dwarfs. Follow-up observations at the TNT using MRES (C2-C7) have led to the discovery of 24 close binaries among our sample (Rebassa-Mansergas+2017) and the identification of four more systems (Werner+2020, Hernandez+2020, Ren+2020). Further observation (C8-C9) uncovers additional 9 close binaries with significant radial velocity variations. However, a few more TNT nights are needed to confirm this finding. Here we apply for 5.0 nights of observations at the TNT with MRES to measure radial velocities of these WD+AFGK binaries.

Transmission spectroscopy and transit timing variations analyses of Jovian planets in the TESS era

PI: Dr. Supachai Awiphan

Todate, more than 5,000 planets have been confirmed by various methods, including over 2,300 by Kepler using the transit method (Morton et al. 2016). In addition to the discovery of new exoplanets, the characterization of planetary atmospheres and environments is a rapidly developing area. One method that is used to study planetary atmospheres is transmission spectroscopy, which measures the variation of transit depth with wavelength (Seager & Deming 2010). Using the transmission spectroscopy technique, the absorption spectrum and the composition of the planetary atmosphere can be deduced. This method has been applied to several transiting exoplanets. Moreover, the obtained transit light curves can be used to search for additional bodies in planetary systems using the transit timing variations technique. This proposal is a part of an international project SPEARNET (Spectroscopy and Photometry of Exoplanet Atmospheres Research Network) which is a globally distributed network of telescopes to study the exoplanet atmospheres. In this proposal, we propose to observe 11 targets: WASP-11b, WASP-143b, HAT-P-33b, HAT-P-36b, HAT-P-39b, HAT-P-43b, HAT-P-47b, HAT-P-48b, NGTS-5b, WASP-36b and WASP-183b. They have been monitored since 2014 with NARIT facilities and our collaborative telescopes. In this cycle, we plan to use the TNT with ULTRASPEC, 1.0-m telescope at TNO and the Thai Robotic Telescopes Network (TRTN) to perform transmission spectroscopy and transit timing variations observation of exoplanets in order to provide a better understanding of exoplanet atmospheres and enviroments.

A study on the structure and evolution of eclipsing binaries with a pulsating star

PI: Ms. Pakakaew Rittipruk

The pulsating variables such as δ Scuti and γ Doradus stars located in the lower part of the classical instability region of the Hertzsprung-Russell (H-R) diagram are very interesting targets for asteroseismology. In addition, the accurate fundamental stellar parameters of eclipsing binaries (EBs) with pulsating stars can give us useful information on stellar internal structure and evolution. Recently, the EB stars with 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 systems. Therefore, medium to high-resolution 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 study, we propose to perform follow-up spectroscopic observations for interesting pulsating EBs with a medium resolution echelle spectrograph (MRES) mounted on the 2.4m Thai National Telescope (TNT) and to study their structure and evolution through asteroseismology and binary properties.

Space density of Cataclysmic Variables

PI: Dr. Amornrat Aungwerojwit

Cataclysmic variables are an excellent benchmark population to test, calibrate, and develop binary population synthesis models. The Sloan Digital Sky Survey (SDSS) produced the deepest and most homogenous CV sample to date, highlighting the importance of the faintest systems to confirm and calibrate models. The spectroscopic completeness of SDSS plummets below i=19.1. However, it is exactly in this range that the composition of the Galactic CV population undergoes a major change. Towards fainter magnitudes the fraction of low-luminosity systems increase and probably dominate the space density of CVs. We propose here to extend the depth of the SDSS CV sample by obtaining TNT observations of faint CV candidates in the SDSS footprint and to measure their orbital periods with the ultimate goal of establishing a statistically representative sample which can be used to test and further develop the theory of compact binary evolution

Identifying white dwarf-pulsators in interacting binaries

PI: Dr. Amornrat Aungwerojwit

The study of stellar pulsations, asteroseismology, has the potential to probe the entire interior structure of a star, and very accurate asteroseismological parameter studies have been carried out for single stars. The same method offers an enormous potential to determine the effect that the accretion of mass, angular momentum, and energy has in interacting binaries, and to infer how common envelope evolution affects the stellar structure of the white dwarf that is left behind. However, so far we only know a handful of pulsating white dwarfs in binary stars. Here we propose to use ULTRASPEC on the TNT to increase the number of non-radial pulsators in cataclysmic variables (CVs). This exploratory study is a necessary first step that will be followed by detailed asteroseismological studies once suitable targets have been identified.

Evolved planetary systems

PI: Dr. 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. In addition in cycle 8, we obtained the light curves of two debris disc systems, ZTF J0328–0129, and ZTF J0923+4236 which reveal very diverse behaviour compared to WD 1145+017. We then propose here (a) to obtain intense high-speed follow-up of both systems, during Cycle 9 to characterise in detail the morphology, and temporal variability of the light curves, including (9 nights required), and (b) to carry out a detailed search for additional systems with photometric transits by obtaining high-time resolution light curves of ~3-4 (out of ~20) white dwarfs with dusty debris discs (9 nights required).

Observations of selected special binary stars at key evolutionary stages

PI: Prof. Shengbang Qian

Close binaries usually have strong interaction between two components. For early-type stars, because their main sequence lifetime is much shorter than less massive stars, they will start mass transfer very quickly and thus enter into key evolutionary stages. Various interesting phenomena may be triggered and found, such as enhanced stellar wind, fast mass transfer and possible mass outflow, special stellar pulsation and etc. However, many details of these processes are not been well investigated so far. The research of the binaries at key evolutionary stages is important for understanding these astrophysical processes, especially in the large sky survey era which could provide us with special candidates among numerous objects. This observation project will also facilitate the research of the structure and evolution of massive stars.

Constraining Mass of an IMBH in the Comet-Like HII Galaxy: NGC 4861

PI: Dr. Krittapas Chanchaiworawit

We propose to utilize ULTRASPEC at the 2.4-m TNT to monitor MRK 59 (a suspect), an intermediate-mass-black-hole-powering AGN hidden in the HII complex of NGC 4861, a local blue compact dwarf with high specific star formation rate. This aims to settle the decade-long debate on the nature of MRK 59 and provide insight into the mass and accretion mechanism of this potential IMBH. We aim to monitor variability in the 5 optical bands, namely u'g'r'i'z' to perform Reverberation Mapping (RM) by assessing the time lags between wavelength bands (using discrete correlation function). This RM technique will provide a mass-accretion disk size scaling relation, which after being combined with the recently obtained GTC IFU spectroscopy of Balmer broad line emissions, we can untangle the mass, accretion rate, and disk size of this AGN in one go. The 60 hours (20 epochs) observation will also yield unprecedented photometric 5-sigma depth of r~26 mag (AB), granting the ability to recover the previously obscured optical counterparts of HI clouds, X-Ray bright background AGN, ULXs, and HII knots within the same field. Combining with the rich spectroscopic data from GTC, this program will yield multi-prong scientific returns, not only including the first confirmed IMBH-driven AGN in metal-poor compact dwarf; but also stellar populations, progenitor of ULXs, and host candidates of X-ray bright AGN in the background, and interaction and star formation history of this complex systems!

Investigation of Extraneous Eclipses in the Light Curves of Binary and Multiple Systems

PI: Mr. Supattra Wongsriya

In this work which is a re-submission of proposal TNT09_01, we are requesting 13.6 nights (136 hours) to investigate triple system candidates of which light curves show extraneous eclipses. To begin with, the Kepler space telescope and Transiting exoplanet survey satellite (TESS) report a comprehensive search for eclipsing binaries that are relatively short-period Algol systems (P < 3 days). Light curves (LC) and ETV (Eclipse time variation) analyses, including the light-travel time effect (LTTE) and short-term dynamical from third body perturbations resulted in consistent third body solutions. Therefore, we are proposing to investigate triple system candidates in which light curves show extraneous eclipses on earth, their light components, as well as to find physical properties in order to understand the evolution of eclipsing multiple systems. In this observation, we will use both the ULTRASPEC CCD photometer (e.g. u', g', r', i', z', and KG5 filters) and the MRES spectrograph.