TNT Schedule

Cycle 9 (2021-2022)

ID	Title, PI	Abstract
TNTC09_001	Investigation of extraneous eclipses in binary and multiple system light curves Mr. Supattra Wongsriya	In this work that is re-submission of proposal TNT08_016, we are requesting to get 14.4 TNT nights (144 hours) to investigate triple system candidates of which light curves show extraneous eclipses. The aim of this research is to investigate eclipsing multiple systems, 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 the ULTRASPEC CCD photometer (e.g. u’, g’, r’, i’ filters) and MRES spectrograph. The data will be analyzed by using photometry technique using dedicated pipelines, to create light curves and spectral profile. After that, we will analyze the light curve to derive the parameters of the third body which is causing the extraneous eclipses in these systems.
TNTC09_002	Deep spectroscopic survey of chemically peculiar stars in the Orion OB1 association Dr. Eugene Semenko	This observational project is aimed to help the study of the evolution of chemical composition and parameters of young chemically peculiar (CP) stars located in the Orion OB1 association. Rich in CP-stars, Orion OB1 is among the closest stellar associations and it has a distinctive and well-determined fragmentation of different parts by their age. Recent researches based on GAIA and TESS gave important insights into stellar evolution in Orion, but the medium to high-resolution spectroscopy even for the stars with V≈8m is still rare. As the spectroscopic observation is vital for determining of membership of the stars and it is the only way to deduce the information about the chemical composition, we decided to compensate this gap with a uniform analysis of spectra obtained with MRES of the 2.4-m telescope of TNO.
TNTC09_003	Doppler imaging of non-radial pulsations of TESS fast-rotating A-type pulsators 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 4 very fast rotating bright A-type stars targets Tau3 Eri, 71 Tau, Beta Eri, and 18 UMa in winter 2022 and apply the 2D DFT analysis for identification of pulsation modes.
TNTC09_004	Peculiar Velocity Distribution Analysis of Galactic High-mass X-ray Binaries in Gaia DR2 Ms. Pornisara Nuchvanichakul	This is resubmission proposal ID: 20 in cycle 8. High-mass X-ray Binaries (HMXBs) consist of a massive OB-type star bound with a compact object which is either a neutron star or a black hole. Companion typically have masses more than 10 solar mass. As a result of their brightness, HMXBs are excellent tools for probing galactic star formation and compact object physics. Since both components of the binary are massive, HMXBs represent very interesting phases of stellar evolution. HMXB can be classified into two groups according to the nature of the massive star is the OB-supergiant systems, and the Be/X-ray binaries. Interestingly, previous studies with the Hipparcos mission found very high transverse (vt) sky velocities for the OB supergiant binaries (Chevalier & Ilovaisky 1998) of order vt~60 km s-1, much larger than for Be systems. This suggests distinct formation channel for these most massive binary systems which may originate in distinct fractional Helium core masses between the two groups (van den Heuvel et al. 2000). This variation results in large runaway velocities (also known as ‘peculiar velocities’) for the former group. This refers to the motion relative to a Galactic rest frame, in excess of Galactic rotation. We are now extending this work to 3d velocities by adding in the third (radial) component of velocities (vr). We are also utilizing the latest precise measurements of stellar kinematics from the Gaia mission DR2 catalogue (Gaia Collaboration 2018). Remarkably, we are finding peculiar velocities of up to ~100 km s-1, and a potential clear bimodal separation with respect to lower velocity systems. Such high velocities for these massive systems are surprising, and have great power to constrain their stellar evolutionary models. However, vr are not available for all systems, and this is what we would like to measure with the observations proposed.
TNTC09_005	A test for the single degenerate channel towards type Ia supernovae (continued) Dr. Puji Irawati	This is a continuation of proposal TNTC08_007 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 are 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-C8) and several other telescopes have led us to the discovery of 24 binaries among our sample displaying significant radial velocity variations (Rebassa-Mansergas+2017), as well as identification of four more systems (Werner+2020, Hernandez+2020, Ren+2020). Here we apply for 8.0 nights of observations at the TNT with MRES to measure radial velocities of 9 WD+AFGK binaries suspected to have short orbital period and to confirm the periods of these systems
TNTC09_006	Prominences and their connection to the circumstellar material formation in white dwarf main-sequence binaries (continued) Dr. Puji Irawati	This is a continuation of proposal TNTC08_009 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 spectroscopic observation 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 (20hrs) on this system.
TNTC09_007	Unravelling the sub-luminous accretion states in tMSPs with ULTRASPEC Dr. Kaustubh Rajwade	Transitional Millisecond Pulsars (tMSPs) are neutron star binary systems that are believed to bridge the evolutionary gap between low-mass X-ray binary systems and radio emitting neutron star binaries. In spite of significant progress made in the field, there are still many questions about the evolution of the spin-period and accretion in these systems that remain unanswered. Typically, tMSPs transition from a LMXB phase that is dominated by accretion to a radio pulsar state where the accretion ceases and the MSP emits radio pulses. tMSPs tend to show a unique accretion mode with distinct changes in the rate characterised by high and low modes in the X-ray/optical light curves. Studying these modes is extremely important in order to form a coherent theory of LMXB evolution. The only way forward is to observe known tMSPs and tMSP candidates simultaneously at multiple wavelengths. Here, we propose to observe a sample of tMSP candidates with the ULTRASPEC high speed camera. The goal is to look for high and low modes in the optical light curves for these sources, telltale signs of a sub-luminous accretion state that will confirm their tMSP nature and to study moding at a high time resolution to unravel information about the underlying accretion. The observations will be shadowed by simultaneous NICER observations at X-ray wavelengths that will provide insights into the physics of accretion during this phase.
TNTC09_008	Unravelling the mysteries of Magnetars with ULTRASPEC Dr. Kaustubh Rajwade	Fast Radio Bursts (FRBs) are mysterious bright, extragalactic radio bursts of as yet unidentified origins. Theory predicts prompt optical emission from FRBs but none has been detected to date. A recent detection of a bright radio burst associated with an X-ray burst from an active Galactic magnetar has provided strong credence to the connection between magnetars and FRBs. Moreover, Magnetars are known to exhibit optical pulsations while one of them has shown bright optical flaring correlated with an X-ray active phase. Hence, it is important to promptly observe magnetars at optical wavelengths in their active period. To that end, we propose triggered optical observations of active magnetars using the ULTRASPEC high-speed camera. These observations will not only help in answering fundamental questions about the origins of FRBs but also provide us with an opportunity to study and characterise optical emission from an active magnetar.
TNTC09_009	IDENTIFYING THE FIRST BROAD ABSORPTION LINES FROM A “MISALIGNED” BLAZAR Dr. Pak-Hin Thomas Tam	Sudden GeV flares (the transient dubbed “Fermi J1544-0649”) emerge from a -ray quiet galaxy in 2017. All observation evidences from X-ray to GeV indicate a blazar characteristic of Fermi J1544-0649 during its GeV flares. Unidentified Broad absorption lines are discovered with Lijiang 2.4m in 2018, which is a typical quasar feature. Recent VLBI observations discovered a jet structure, with a viewing angle ~7.4 deg, which indeed lies near the boundary of a blazar and a quasar. We apply for further optical observations using TNT to identify the BAL from this unique galaxy.
TNTC09_010	Observational study on evolution of the ultrashort-period cataclysmic variables 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.
TNTC09_011	Search for the contact binaries under the short period limit 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 futher study. Thanks to some surveys in the world (e.g., SDSS and SuperWASP), 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 thant 30 such contact binary candidates. Our scientific purposes are to search for such ultral 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.
TNTC09_012	TNT dome turbulence characterisation Mr. Somsawat Rattanasoon	Measurements of the atmospheric turbulence profile derived from the TNT SLODAR instrument have shown that a significant fraction of the seeing observed by the TNT is due to a slowly-evolving turbulent layer found close to the ground. Such results usually indicate of the presence of dome turbulence, but the root causes of dome turbulence are difficult to identify and characterise from SLODAR data alone. If we can identify the causes of dome turbulence at the TNT, we have the possibility of reducing their impact and improving observing quality for all TNT instrumentation. Through the STFC-NARIT Newton Fund we have assembled a suite of local profiling instrumentation that we will install in the TNT dome, to operate simultaneously with the TNT SLODAR. The SLODAR measurements are required to identify situations where the TNT observes dome turbulence, and then the local turbulence instrumentation will be used to identify and isolate any internal sources of this turbulence. For this experiment we require an initial commissioning period where we can test various locations within the telescope dome, and then a longer monitoring campaign where we can investigate dome turbulence under the full range of operating conditions.
TNTC09_013	High time resolution measurements of asteroid occultations with ULTRASPEC Dr. Tarek Hassan	When a solar-system object, such as an asteroid, occults a star, it provides a powerful tool for studying both the occulting object and the occulted star. Occultations of stars by asteroids have generally been used to extract information of the shape and structure of asteroids, by detecting the time of occultation at different points along the shadow path over the Earth. The diffraction pattern fitting technique has been successfully exploited with lunar occultation measurements to measure stellar angular diameters down to the ~1 mas level. Three scientific objectives will be attained by applying diffraction analysis to asteroid occultations with ULTRASPEC: 1) use the diffraction pattern in the shadow generated by asteroid occultations of stars to measure their angular size at the sub-milliarcsecond (mas) level; 2) measure the impact of differential heating of the asteroid surface on their orbital dynamics (Yarkovsky effect) and 3) serendipitous discovery of close binary systems. As proven by observations carried out during last two observing cycles, ULTRASPEC has the potential to achieve these goals.
TNTC09_014	Searching for circumbinary bodies in eclipsing binary systems. Mr. Ronnakrit Rattanamala	Nowadays, searching circumbinary planets is an interested field in exoplanetary and binary researches as there are a number of binary systems and exoplanet have been detected. The study can be conducted via the period variation curve on O-C diagram of the binary system due to the third body orbit around the system. The technique is successfully detected exoplanets, third bodies with mass less than 13 Jupiter mass. To date, more than 20 circumbinary exoplanets have been detected, including DP Leo, HU Aqr, RR Cae, UZ For, NN Ser. In order to detect circumbinary exoplanet with this technique, the high precession and high-time resolution photometry from the instrument such as ULTRASPEC on the TNT is required. In this work, we will use ULTRASPEC to observe eclipse timing of three circumbinary planet candidates: EC10246-2707, V470 Cam and GSC00196-00617, and a confirmed circumbinary system: NN Aqr. From observed light curves, not only eclipse timing should be obtained, but also the physical parameters of the star components in the eclipsing binary system should be analyzed.
TNTC09_015	Transmission spectroscopy of exoplanets Dr. Supachai Awiphan	Todate, more than 4,000 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 interiors and atmospheres 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. 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 13 targets: WASP-11b, WASP-143b, HAT-P-26b, HAT-P-33b, HAT-P-36b, HAT-P-39b, HAT-P-43b, HAT-P-47b, HAT-P-48b, KELT-3b, NGTS-5b, WASP-36b and WASP-183b. All of them have been monitor since 2014 with NARIT facilities and our collaborated 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 observation of exoplanets in order to provide a better understanding of exoplanet atmospheres and statistics of planetary atmosphere.
TNTC09_016	Transmission spectroscopy of exoplanets (LRES) Dr. Supachai Awiphan	Todate, more than 4,000 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 interiors and atmospheres 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. 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 3 targets: WASP-50b, WASP-104b and KELT-3b. All of them have been monitor since 2014 with NARIT facilities and our collaborated telescopes. In this cycle, we plan to use the TNT with LRES, 1.0-m telescope at TNO and the Thai Robotic Telescopes Network (TRTN) to perform transmission spectroscopy observation of exoplanets in order to provide a better understanding of exoplanet atmospheres and statistics of planetary atmosphere.
TNTC09_017	Space density of Cataclysmic Variables 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
TNTC09_018	Identifying white dwarf-pulsators in interacting binaries 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.
TNTC09_019	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).