Spectroscopic Devices for Asteroseismology With Small Telescopes in NARIT

The 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.Comment: This paper was submitted as a contribution to the proceedings of the third Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, which was held in Bhimtal, Uttarakhand (India) on 22-24 March 2023. The final, peer-reviewed version will be published in Bulletin de la Soci\'et\'e Royale des Sciences de Li\`ege. The manuscript contains 5 pages, 3 figures, and 4 reference

Planetary Collisions outside the Solar System: Time Domain Characterization of Extreme Debris Disks

Luminous debris disks of warm dust in the terrestrial planet zones around solar-like stars are recently found to vary, indicative of ongoing large-scale collisions of rocky objects. We use Spitzer 3.6 and 4.5 {\mu}m time-series observations in 2012 and 2013 (extended to 2014 in one case) to monitor 5 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 have 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.Comment: 50 pages, 14 figures, 9 tables; Accepted for publication in the Astrophysical Journa

Large Impacts around a Solar Analog Star in the Era of Terrestrial Planet Formation

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 3-5 {\mu}m, 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 ground into dust by collisions. These results demonstrate how the time domain can become a new dimension for the study of terrestrial planet formation.Comment: 25 pages, 7 figures (fixed a typo in name

RW Doradus: A solar-type shallow contact binary with a new orbital period investigation

New CCD photometric light curves of the short-period (P = 0.285 d) eclipsing binary RW Dor are presented. The observations were performed with the PROMPT-8 robotic telescope at CTIO in Chile between 2015 March and 2017 March. Other eclipse timings were obtained from the 2.15 m JS telescope at CASLEO, San Juan, Argentina in 2011 December. Based on a light curve analysis, it is found that RW Dor is a W-type shallow contact binary with a fill-out factor f ∼ 11% and a high mass ratio q ∼ 1.587 (1/q = 0.63), where the hotter component is the less massive one (M1 ∼ 0.52 M and M2 ∼ 0.82 M). For orbital-period investigation, 15 new eclipse times and those previously published were compiled. O − C analysis with very weak evidence suggests that a long-term decrease in period with a rate of dP/dt = −9.61 × 10−9 d yr−1 is superimposed on a cyclic variation(A3 = 0.0054 d and P3 = 49.9 yr). The long-term decrease can be interpreted as mass transfer from the more massive component to the less massive one, or combined with angular momentum loss via magnetic braking. In addition, the marginal contact phase, high mass ratio (1/q > 0.4), and long-term decrease in period all suggest that RW Dor is a newly formed contact binary via Case A mass transfer, and it will evolve into a deepernormal contact binary. If the cyclic change is correct, the light travel-time effect via the presence of a cool third body will be a more plausible explanation for this.Fil: Sarotsakulchai, Thawicharat. University of Chinese Academy of Sciences; China. National Astronomical Research Institute of Thailand; Tailandia. Chinese Academy of Sciences; República de ChinaFil: Qian, Sheng Bang. Chinese Academy of Sciences; República de China. University of Chinese Academy of Sciences; ChinaFil: Soonthornthum, Boonrucksar. National Astronomical Research Institute of Thailand; TailandiaFil: Fernandez Lajus, Eduardo Eusebio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Liu, Nian Ping. Chinese Academy of Sciences; República de ChinaFil: Zhou, Xiao. Chinese Academy of Sciences; República de ChinaFil: Zhang, Jia. Chinese Academy of Sciences; República de ChinaFil: Liao, Wen Ping. Chinese Academy of Sciences; República de ChinaFil: Reichart, Daniel E.. University of North Carolina; Estados UnidosFil: Haislip, Joshua B.. University of North Carolina; Estados UnidosFil: Kouprianov, Vladimir V.. University of North Carolina; Estados UnidosFil: Poshyachinda, Saran. National Astronomical Research Institute of Thailand; Tailandi

RW Doradus: a solar-type shallow contact binary with a new orbital period investigation

New CCD photometric light curves of the short-period (P = 0.285 d) eclipsing binary RW Dor are presented. The observations were performed with the PROMPT-8 robotic telescope at CTIO in Chile between 2015 March and 2017 March. Other eclipse timings were obtained from the 2.15 m JS telescope at CASLEO, San Juan, Argentina in 2011 December. Based on a light curve analysis, it is found that RW Dor is a W-type shallow contact binary with a fill-out factor f ∼ 11% and a high mass ratio q ∼ 1.587 (1/q = 0.63), where the hotter component is the less massive one (M₁ ∼ 0.52 M⊙ and M₂ ∼ 0.82 M⊙). For orbital-period investigation, 15 new eclipse times and those previously published were compiled. O − C analysis with very weak evidence suggests that a long-term decrease in period with a rate of dP/dt = −9.61 × 10⁻⁹ d yr⁻¹ is superimposed on a cyclic variation (A₃ = 0.0054 d and P₃ = 49.9 yr). The long-term decrease can be interpreted as mass transfer from the more massive component to the less massive one, or combined with angular momentum loss via magnetic braking. In addition, the marginal contact phase, high mass ratio (1/q >0.4), and long-term decrease in period all suggest that RW Dor is a newly formed contact binary via Case A mass transfer, and it will evolve into a deeper normal contact binary. If the cyclic change is correct, the light travel-time effect via the presence of a cool third body will be a more plausible explanation for thisInstituto de Astrofísica de La Plat

Design and performance estimate of a focal reducer for the 23 m Thai National Telescope

International audienc

BM UMa: A middle shallow contact binary at pre-transition stage of evolution from W-type to A-type

International audienceAbstract In this study, all unpublished time series photometric data of BM UMa (q ∼ 2.0, P = 0.2712 d) from available archives were re-investigated together with new data taken from the 2.4-m Thai National Telescope of the Thai National Observatory. Based on period analysis, there is a short-term variation superimposed on the long-term period decrease. The trend of period change can be fitted with a downward parabolic curve indicating a period decrease at a rate of dP/dt = −3.36(±0.02) × 10−8 d yr−1. This long-term period decrease can be explained by mass transfer from the more massive component (M2 ∼ 0.79M⊙) to the less-massive one (M1 ∼ 0.39M⊙), in combination with angular momentum loss. For photometric study, we found that the binary consists of K0 V stars and at the intermediate shallow of contact configuration with evolution of fill-out factor from 8.8% (in 2007) to 23.2% (in 2020). Those results suggest that the binary is at the pre-transition stage of evolution from W-type to A-type, agreeing with the results of statistical study of W-type contact binaries. The mass of M2 will be decreased close to or below M1 and the mass ratio will be decreased (q < 1.0). In this way, the binary will evolve into an A-type as a deeper normal over-contact system with period increase. Finally, the binary will become a merger or a rapid-rotating single star when the mass ratio meets the critical value (q < 0.094), and produce a red nova