Fu.J.N., Khokhuntod, P., Rodriguez, E., Boonyarak, C., Marak, K., Lopez-Gonzalez, M.J., Zhu, L.Y., Qian, S.B. and Jiang, Y. (2008). Detection of a Degenerate Companion of the SX Phoenicis Star KZ Hydrae by Studying its Long-Term Variability. The Astronomical Journal. Vol.135 : 1958-1967. (Impact Factor 2007 : 4.854)

Samerjai T, Tamaekong N, Liewhiran C, Wisitsoraat A, Phanichphant S. NO2 gas sensing of flame-made Pt-loaded WO3 thick films. Journal of Solid State Chemistry2014;214:47-52.

Boonyarak, C., Khokhuntod, P. & Jiang, SY. The period variation of the double mode high amplitude δ Scuti variable VZ Cnc. Astrophys Space Sci 324, 5 (2009). https://doi.org/10.1007/s10509-009-0147-y

Kanokwan Marak1*, Chayan Boonyarak1 and Shi-yang Jiang2.UY Camelopardalis Possibly Has an Unseen Companion.NU Science Journal 2009; 6(1): 33 - 39 .

We present 83 new times of maximum light of the SX Phoenicis (SX Phe) star DY Pegasi (DY Peg), based mainly on our new time-series photometric observations from the years 2004–2008. Together with the times of maximum light in the literature, a comprehensive study of the O - C diagram with the data spanning over seven decades leads to a new general ephemeris formula and the determination of a new value of the updated period 0.072926187( ± 3)d. The available times of maximum light can be well modeled with either a triple linear fit, or a fit concerning a continuously increasing period change combined with the light-time effect of an orbital motion. On the contrary, the decreasing period hypothesis suggested by some previous investigators appears to be rejected. The frequency analyses of the data collected in 2004 and 2006 provide the radial pulsation frequency 13.713 c d^-1 and its four harmonics …

In this paper the researchers collected 28 times of maximum light including 4 times of those observed at the Xinglong station, the National Astronomical Observation of China between May 27, 2004 and June 1, 2004 and 1 time of maximum light from a 60 cm telescope on May 4, 1984. It found that the O-C point distribution was more completely compared than in any papers published before. The period is decreasing at the rate of about (1.4±0.1)×10⁻⁸ per year, which should not be caused by stellar evolution. It might be only part of a binary orbital light-time variation or other unknown reason. The time scale is longer than Pocs and Szeidl’s suggestion; the star needs more observations before we can be certain of the exact light-time variation.

We present 109 new times of maximum light of the SX Phoenicis (SX Phe) star KZ Hydrae (KZ Hya) based mainly on our extensive photometric observations for two decades, leading to determination of a general ephemeris combined with the data in the literature. The O–C diagram reveals a continuously increasing period change combined with the light traveling time effect of the orbital motion of KZ Hya in a binary system with an orbital period of 26.8±0.2 years. The deduced mass of the companion cannot be smaller than 0.83 M☉. Since no sign of the companion has ever been observed spectroscopically and the observed color index b–y excludes the possibility of the companion being a late-type main-sequence or dwarf star, KZ Hya becomes the first SX Phe star for which a degenerate companion is detected. The pulsation properties are studied by analyzing the Fourier spectra of the observed light curves while …

New time-series photometric observations of BL Cam in the V band and white light were made during 2005 to 2007 at the Xinglong Station of China. The frequency analysis confirms two closely separated frequencies, 25.181 d− 1 and 25.571 d− 1, but the frequency of 31–32 d− 1 reported in the literature was not detected in the new data. New times of maximum light were determined from both our light curves and those available on Internet, allowing a more comprehensive study of the O− C diagram, together with the times of maximum light in the literature. A new interpretation, including the period increasing before 1988 and decreasing since 1992 of BL Cam and the light-time effect in a binary system, looks plausible.

Time-series photometry was made for the large-amplitude δ Scuti star AD CMi in 2005 and 2006. High-quality photometric data provided in the literature were used to analyze the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics, one low frequency (2.27402 c d− 1) is discovered, which provides a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima determined from the new data with the 64 times collected from the literature, we analyzed the long-term variability of AD CMi with the O− C technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and light-time effect of a binary system, of which some parameters are hereby deduced.

Boonyarak, C. and Yang Jiang, S. The period variation of DY Hercules. Astrophysics and Space Science. Vol. 310, (2007).:285-291. (Impact Factor 2005 : 0.771)

Seeing test based on DIMM method was employed to investigate the atmospheric turbulence at Samorkraeng Mountain, Wangtong district, Phitsanulok province. The latitude and the longitude of the selected site for an observatory are 16 50. 59′ D N and 100 24. 08′ D E, respectively; the altitude is about 180 meters above the sea level; and the distance is about 15 kilometers north east from the downtown of Phitsanulok. The statistics of the seeing in FWHM, temperature, and humidity which measured and calculated for 20 nights during December 8, 2004 to January 4, 2006 are as follows: maximum FWHM, minimum FWHM, and average FWHM are 3.6, 0.8, and 1.7 arc seconds, respectively; maximum temperature, minimum temperature, and average temperature are 29.2, 17.4, and 22.8 C, respectively; and maximum humidity, minimum humidity, average humidity are 80, 55, and 68.8 percent, respectively. The average seeing value at Samorkraeng Mountain is not much different from the average values at Siding Springs in Australia, Kitt Peak in the United States of America, Devasthal in India, and South Pole in Antarctica which are the famous observatories in the world.

We found in the published literature the rotational velocities for 162 B0-B9. 5, 152 A0-A5, and 86 A6-F0 stars, all of luminosity classes V or IV, that are in spectroscopic or visual binaries with known orbital elements. The data show that stars in binaries with periods of less than about 4 days have synchronized rotational and orbital motions. Stars in binaries with periods of more than about 500 days have the same rotational velocities as single stars. However, the primaries in binaries with periods of between 4 and 500 days have substantially smaller rotational velocities than single stars, implying that they have lost one-third to two-thirds of their angular momentum, presumably because of tidal interactions. The angular momentum losses increase with decreasing binary separations or periods and increase with increasing age or decreasing mass.

Helmut A. Abt and Chayan Boonyarak. What Kinds of Astronomical Papers are Still Referenced 50 Years after Publication?, Jouranal : BAAS, Vol 36, 5/2004. 868-870

Helmut A.Abt and Chayan Boonyarak. The Scientific Output of the International Ultraviolet Explorer during Its Lifetime, Journal : BAAS, Vol. 35, 1446-1447, 2003

A.-Y. Zhou, S.-Y. Jiang, C. Boonyarak, and B.-T. Du. Amplitude and Period Changes in the SX Phoenics star XXCygni, Astrophysics and Space Science 281: 699-714, 2002.

 From observation one finds the periods of pulsating variables are always changing along with time. Now one need to know what the reasons are and how they are caused. On the HR diagram, when a star evolves, its position will change following an evolving trap. That means its luminosity and surface temperature are changing continuously, then from the period-luminosity-color relation of the pulsating star, its periods must change continuously also. Could we find it or have we already found it from the real observation? From the 1980 till recent year, many authors had made discussions about the period variations of δ Scuti variables quite carefully but had not got a reasonable explanation. This paper discusses it again in some different point of view.

Chayan Boonyarak. Observation of Active Galactic Nuclei (AGN) at Landessternwarte Heidelberg- Koenigstuhl, Germany, Naresuan University Journal, ISSN 0858-7418 Vol.6 No.2 July-Dec. 1998 pp.52-58.

Chayan Boonyarak and Others. Basic Research in Total Solar Eclipse on October 24, 1995, Bangkok Planetarium, Science Center for Education, The Ministry of Education, Thailand 1996 pp.47-48

. Chayan Boonyarak. Statistical Characteristics of Solar Radiation for Phitsanulok Province, Naresuan University Journal, ISSN 0858-7418. Vol.6 No.1 Jan-Jun, 1998 pp.1-The study was supported by National Research Council of Thailand (NRCT) in the academic year of 1995

Chayan Boonyarak and Others. Development of Production Process in Drying Seasonal Fruits at Industrial Scale Using Solar Energy Dryer, Physics Department, Naresuan University, Phitsanulok, 275p. The study was supported by National Research Council of Thailand (NRCT) in the academic year of 1995.

W. Rakwichan, C. Boonyarak, and S. Sukjai. The Data of Thermal-Energy Comsumption in Industrial Drying in Lower Northern Area, Naresuan University, Phitsanulok, 43p.The study was supported by NRCT in the academic year of 1992.

C. Boonyarak. A Study of Science Teaching Problems in Secondary Schools in Lower Northern Region of Thailand. Physics Department, Naresuan University Phitsanulok,77p. The study was supported by NRCT in the academic year of 1992.

W. Rakwichian, C. Boonyarak and Others. Developing of Solar Fruit Dryer at Industrial Scale, Naresuan University, Phitsanulok, 319p. The study was supported by NRCT in the academic year of 1992.

Chayan Boonyarak, Sangwal Pengpad, and Sombat Saithon. Producing Software for Computer Assisted Instruction in Nuclear Physics at University Level, Naresuan University, Phitsanulok , 87p. The study was supported by NRCT in the academic year of 1991.

Time-scries photometry for the high-amplitude S Scuti star AD CMi was made in 2005 and 2006. The high-quality photometric data provided in the literatures were used to analyse the pulsation of the star, with the derived multiple frequencies fitted to our new data. Besides the dominant frequency and its harmonics resolved, one low frequency (2.27402 c/d) is discovered, providing a reasonable interpretation for the long-noticed luminosity variation at the maximum and minimum light. Combining the nine new times of light maxima, determined from the new data, with the 64 times collected from the literatures, we analyzed the long-term variability of AD CMi with the OC technique. The results provide the updated value of period of 0.122974478 days, and seem to be in favor of the model of combination of the evolutionary effect and the light-time effect of a binary system for AD CMi. Some parameters of the binary system …