National Astronomical Research Institute of Thailand (NARIT) has a manifold network of small telescopes installed worldwide. These telescopes serve educational and research purposes and are equipped ...mainly with CCD detectors for direct imaging and photometry. To extend the possible field of applications, several telescopes were fitted with commercially available medium resolution spectrographs eShel from Shelyak. With these devices, researchers in NARIT obtained a versatile tool for stellar spectroscopy. Here we describe the current status of available equipment, possible ways of upgrading, and briefly introduce the achieved results of the asteroseismologic study of fast-rotating stars.
Based on the data of the State of Global Air (2020), air quality deterioration in Thailand has caused ~32,000 premature deaths, while the World Health Organization evaluated that air pollutants can ...decrease the life expectancy in the country by two years. PM2.5 was collected at three air quality observatory sites in Chiang-Mai, Bangkok, and Phuket, Thailand, from July 2020 to June 2021. The concentrations of 25 elements (Na, Mg, Al, Si, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Sr, Ba, and Pb) were quantitatively characterised using energy-dispersive X-ray fluorescence spectrometry. Potential adverse health impacts of some element exposures from inhaling PM2.5 were estimated by employing the hazard quotient and excess lifetime cancer risk. Higher cancer risks were detected in PM2.5 samples collected at the sampling site in Bangkok, indicating that vehicle exhaust adversely impacts human health. Principal component analysis suggests that traffic emissions, crustal inputs coupled with maritime aerosols, and construction dust were the three main potential sources of PM2.5. Artificial neural networks underlined agricultural waste burning and relative humidity as two major factors controlling the air quality of Thailand.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
ABSTRACT Luminous debris disks of warm dust in the terrestrial planet zones around solar-like stars were recently found to vary, which is indicative of ongoing large-scale collisions of rocky ...objects. We use Spitzer 3.6 and 4.5 m time-series observations in 2012 and 2013 (extended to 2014 in one case) to monitor five more debris disks with unusually high fractional luminosities ("extreme debris disk"), including P1121 in the open cluster M47 (80 Myr), HD 15407A in the AB Dor moving group (80 Myr), HD 23514 in the Pleiades (120 Myr), HD 145263 in the Upper Sco Association (10 Myr), and the field star BD+20 307 ( 1 Gyr). Together with the published results for ID8 in NGC 2547 (35 Myr), this makes the first systematic time-domain investigation of planetary impacts outside the solar system. Significant variations with timescales shorter than a year are detected in five out of the six extreme debris disks we monitored. However, different systems show diverse sets of characteristics in the time domain, including long-term decay or growth, disk temperature variations, and possible periodicity.
The final assembly of terrestrial planets occurs via massive collisions, which can launch copious clouds of dust that are warmed by the star and glow in the infrared. We report the real-time ...detection of a debris-producing impact in the terrestrial planet zone around a 35-million-year-old solar-analog star. We observed a substantial brightening of the debris disk at a wavelength of 3 to 5 micrometers, followed by a decay over a year, with quasi-periodic modulations of the disk flux. The behavior is consistent with the occurrence of a violent impact that produced vapor out of which a thick cloud of silicate spherules condensed that were then ground into dust by collisions. These results demonstrate how the time domain can become a new dimension for the study of terrestrial planet formation.
Abstract
The evanescent wave coronagraph uses the principle of frustrated total internal reflection (FTIR) to suppress the light coming from the star and study its close environment. Its focal plane ...mask is composed of a lens and a prism placed in contact with each other to produce the coronagraphic effect. In this paper, we present the experimental results obtained using an upgraded focal plane mask of the Evanescent Wave Coronagraph (EvWaCo). These experimental results are also compared to the theoretical performance of the coronagraph obtained through simulations. Experimentally, we reach a raw contrast equal to a few 10
−4
at a distance equal to 3
λ
/
D
over the full
I
band (
λ
c
= 800 nm, Δ
λ
/
λ
≈ 20%) and equal to 4
λ
/
D
over the full
R
band (
λ
c
= 650 nm, Δ
λ
/
λ
≈ 23%) in unpolarized light. However, our simulations show a raw contrast close to 10
−4
over the full
I
band and
R
band at the same distance, thus confirming the theoretical achromatic advantage of the coronagraph. We also verify the stability of the mask through a series of contrast measurements over a period of 8 months. Furthermore, we measure the sensitivity of the coronagraph to the lateral and longitudinal misalignment of the focal plane mask and to the lateral misalignment of the Lyot stop.
This study investigated atmospheric particulate matter (PM) with an aerodynamic diameter of ＜ 2.5 μm (PM_(2.5)) observed at the Prince of Songkla University (Phuket Campus) in southern Thailand. All ...samples (n = 75) were collected using MiniVol^(TM) portable air samplers from March 2017 to February 2018. Carbonaceous aerosol compositions, i.e., organic carbon (OC) and elemental carbon (EC), water-soluble ionic species (WSIS), and polycyclic aromatic hydrocarbons (PAHs) in the PM_(2.5) samples were identified and quantified. We found that the average PM_(2.5) concentration was 42.26 ± 13.45 μg m^(-3), while the average concentrations of OC and EC were 3.05 ± 1.70 and 0.63 ± 0.58 μg m^(-3), respectively. The OC/EC ratio was in the range of 2.69-16.9 (mean: 6.05 ± 2.70), and the average concentration of 10 selected ions was 6.91 ± 3.54 μg m^(-3). The average concentration of SO_4^(2-) was the highest throughout the entire study period (2.33 ± 1.73 μg m^(-3)); the average contribution of SO_4^(2-) to the major ionic components was 34%. Surprisingly, the average concentrations of NO_3^- and NH_4^+ were relatively low. The mean ratio of NO_3^-/SO_4^(2-) was 0.33 ± 0.24. Strong positive correlation was found between K^+ and both OC and EC (r = 0.90 and r = 0.93, respectively). It is also precious to highlight that biomass burning (BB) is the major source of OC, EC and K^+, which multiple studies have confirmed that the role of K^+ as a biomass marker. Results showed that BB episodes might play a major role in producing the observed high levels of OC. The relatively high abundance of both Bg,h,iP and Ind suggests that motor vehicles, petroleum/oil combustion, and industrial waste burning are the primary emission sources of PAHs in the ambient air of Phuket. Interestingly, principal component analysis (PCA) indicated that vehicular exhausts are the main source of carbonaceous aerosol compositions found in the ambient air of Phuket, whereas the contributions of biomass burning, diesel emissions, sea salt aerosols and industrial emissions were also important.
Abstract NARIT initiated a national flagship project in 2017 for development of radio astronomy and geodesy in Thailand. In this project, a 40-m Thai National Radio Telescope (TNRT) and a 13-m VLBI ...Global Observing System radio telescope are constructed in Chiang Mai. The 40-m TNRT is the largest telescope for radio astronomy in South-East Asia. Its flexible operation with a wide-frequency coverage 0.3-115 GHz will allow us to uniquely contribute to the time-domain astronomy as well as carry out unbiased surveys for a wide variety of research fields, which were published in a white paper. Within the framework of collaboration with VLBI arrays in the world, TNRT will drastically improve the imaging quality and performances based on its unique geographical location. Through commissioning of the L-band system, the 1st Call for Proposals of the 40-m TNRT in the L-band 1 has been internationally announced on 10th October 2023, TST 10 am. Future vision for establishment of forthcoming regional VLBI networks based on TNRT is also introduced: Thai National VLBI Array and South-East Asian VLBI Network in collaboration with Indonesia, Malaysia, and Vietnam.
ABSTRACT
We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from 2018 July ...to December using broad-bandB-,R-, and narrow-band H α and S ii filters. The B band traces the continuum emission from the accretion disc, the R band encompasses both the continuum emission from the accretion disc and the redshifted H α line from the broad-line region (BLR), the S ii band contains the redshifted H α emission and the H α band traces the continuum emission underneath the S ii band. All the light curves showed strong variation with a fractional root-mean-square variation of 0.132 ± 0.001 in the B band and 0.321 ± 0.001 in H α line. From cross-correlation function analysis, we obtained a delayed response of H α line emission to the opticalB-band continuum emission of $21.44^{+1.49}_{-2.11}$ d in the rest frame of the source, corresponding to a linear size of the BLR of 0.018 pc. This is consistent with previous estimates using H β. By combining the BLR size with the H α line full width at half-maximum of 6478 ± 240 km s−1 measured from a single-epoch spectrum obtained with the Subaru telescope, we derived a black hole mass of $1.96^{+0.15}_{-0.21}\times 10^8 {\rm M}_{\odot }$.
New light curves in B, V, R, and I bands for the B-type contact binary V593 Cen were obtained, and another V-band light curve was collected from All Sky Automated Survey data. We analyzed these two ...sets of light curves using the Wilson-Devinney code. It was found that V593 Cen is a deep-contact binary with a fill-out factor of more than 45%. The mass ratio, derived to be nearly one from light curves, indicates that this system contains two twin components. Together with the higher temperature of the less-massive component, it is inferred that the system has just passed the mass-reversal stage during the mass-transfer evolution. Therefore, at present it has the shortest period and deepest-contact configuration. By analyzing all available eclipse times, it is found that the O − C curve of V593 Cen shows a cyclic variation with a period of 50.9 yr. This can be explained as the light-travel time effect via the presence of a third body. The mass of the third body is derived to be larger than 4.3 ( 0.3) M , and it should contribute to the total light of the system. However, no third light is detected during the photometric analyses. This indicates that it may be a black hole candidate orbiting the central mass-transferring binary in a triple system. During the evolution of this hierarchical triple-star system, the "eccentric Kozai-Lidov" mechanism may play a major role in the formation of the inner contact binary. This system seems a perfect candidate to be one of "merged" systems mentioned by Naoz & Fabrycky.
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