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PSR J10203+0038 is a transitional millisecond pulsar (tMSP) in an eclipsing binary system, which has been observed to switch between the radio loud millisecond pulsar (MSP) and low-mass-X-ray binary (LMXB) states. This behavior offers a great opportunity to study the origin of MSPs and confirming the 'recycling' scenario, a theoretical model of MSP's origin. We develop an automated pipeline to monitor the system using Python programming language and Source-Extractor software for detecting the objects and measuring its magnitude. We obtain a series of observations with the 0.6m PROMPT-8 telescope at Cerro Tololo in Chile. The magnitude threshold for alert has been set 16.884 mag in R filter. When the magnitude of the system increases over the limit, 16.884 mag in filter R, the pipeline will alert us about the next possible switching of this system. The pipeline has been running on server at National Astronomical Research of Thailand (NARIT) since January 2018. We have found that, during January and February 2018, the system still remains in LMXB state.

We demonstrate how a small, robotically controlled telescope can be used to monitor bright, long-period variable stars in dense stellar systems like Galactic globular clusters. Observations of NGC 1851 gathered with the No. 5 PROMPT 0.4 m telescope in BVRI B V R I yielded quality color-magnitude diagrams to well below the horizontal branch at V = 16.1 mag V = 16.1     mag . We recovered many of the known RR Lyrae variables, clarified the nature of the three known bright variables in the cluster, detected two new long-period variables, and flagged seven more suspected variables. We describe methods that should yield good results in variable star searches and monitoring using this and other small telescopes.

We present spectroscopic and photometric observations of the emission-line star MWC 930 (V446 Sct) during its long-term optical brightening in 2006–2013. Based on our earlier data we suggested that the object has features found in Luminous Blue Variables (LBV), such as a high luminosity (~3 105 L⊙), a low wind terminal velocity (~140 km s−1), and a tendency to show strong brightness variations (~1 mag over 20 years). For the last ~7 years it has been exhibiting a continuous optical and near-IR brightening along with a change of the emission-line spectrum appearance and cooling of the star’s photosphere. We present the object’s V-band light curve, analyze the spectral variations, and compare the observed properties with those of other recognized Galactic LBVs, such as AG Car and HR Car. Overall we conclude the MWC 930 is a bona fide Galactic LBV that is currently in the middle of an S Dor cycle.

We present follow-up photometry and spectroscopy of the rapidly pulsating subdwarf B star EC 22221-3152. Using the SAAO 1.0-m telescope and the 0.4-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) at the Cerro Tololo Inter-American Observatory (CTIO), we monitored the star photometrically for one week. By combining data from both telescopes, we were able to resolve 18 significant periodicities in the light curve. Seven of these signals consist of combination frequencies, a first harmonic, and possible rotational splittings that would be indicative of an 8.2-d rotation period. The remaining 11 periodicities appear to represent independent oscillation modes, including three not originally detected in the discovery work. Time series spectroscopy obtained with the Goodman spectrograph on the 4.1-m SOAR telescope reveals possible velocity variations corresponding to two of the observed pulsation modes. From atmospheric model fits to the spectra, we derive Teff = 35600\\pm 600$ K, log g = 5.86 ± 0.15, and log N(He)/N(H) = -1.4 ± 0.3 and confirm the star's status as one of the hottest sdBV r stars currently known.

Blazar OJ287 exhibits large thermal flares at least twice every 12 years. The times of these flares have been predicted successfully using the model of a quasi-Keplerian eccentric black hole binary where the secondary impacts the accretion disk of the primary, creating the thermal flares. New measurements of the historical light curve have been combined with the observations of the 2015 November/December flare to identify the impact record since year 1886, and to constrain the orbit of the binary. The orbital solution shows that the binary period, now 12.062 years, is decreasing at the rate of 36 days per century. This corresponds to an energy loss to gravitational waves that is 6.5 ± 4 % less than the rate predicted by the standard quadrupolar gravitational wave (GW) emission. We show that the difference is due to higher order gravitational radiation reaction terms that include the dominant order tail contributions.

We conducted a search for luminous outbursts prior to the explosion of Type IIn Supernovae (SNe IIn). We built a sample of 27 objects spectroscopically classified as SNe IIn, all located at \\(z<0.015\\). Using deep archival SN fields images taken up to nearly 20 years prior from transient surveys (PTF, ZTF, DES, CHASE) and major astronomical observatories (ESO and NOAO), we found at least one outburst years to months before the explosion of seven SNe IIn, the earliest precursor being 10 years prior to the explosion of SN 2019bxq. The maximum absolute magnitudes of the outbursts range between -11.5 mag and -15 mag, and the eruptive phases last for a few weeks to a few years. The \\(g-r\\) colour measured for three objects during their outburst is relatively red, with \\(g-r\\) ranging between 0.5 and 1.0 mag. This is similar to the colour expected during the eruptions of Luminous Blue Variables. We noticed that the SNe with pre-SN outbursts have light curves with faster decline rates than those that do not show pre-SN outbursts. SN 2011fh is remarkable, as it is still visible 12 years after the luminous SN-like event, indicating that the progenitor possibly survived, or that the interaction is still on-going. We detect precursor activity in 29% of bona-fide SNe~IIn in our sample. However, a quantitative assessment of the observational biases affecting the sample suggests that this fraction underestimates the intrinsic precursor occurrence rate.

We present an analysis of the \\(BVRI\\) photometry of the blazar BL Lacertae on diverse timescales from mid-July to mid-September 2020. We have used 11 different optical telescopes around the world and have collected data over 84 observational nights. The observations cover the onset of a new activity phase of BL Lacertae started in August 2020 (termed as the August 2020 flare by us), and the analysis is focused on the intra-night variability. On short-term timescales, (i) flux varied with ~2.2\\,mag in \\(R\\) band, (ii) the spectral index was found to be weakly dependent on the flux (i.e., the variations could be considered mildly chromatic) and (iii) no periodicity was detected. On intra-night timescales, BL Lacertae was found to show bluer-when-brighter chromatism predominantly. We also found two cases of significant inter-band time lags of the order of a few minutes. The duty cycle of the blazar during the August 2020 flare was estimated to be quite high (~90\\% or higher). We decomposed the intra-night light curves into individual flares and determined their characteristics. On the basis of our analysis and assuming the turbulent jet model, we determined some characteristics of the emitting regions: Doppler factor, magnetic field strength, electron Lorentz factor, and radius. The radii determined were discussed in the framework of the Kolmogorov theory of turbulence. We also estimated the weighted mean structure function slope on intra-night timescales, related it to the slope of the power spectral density, and discussed it with regard to the origin of intra-night variability.

The origin of the diverse light-curve shapes of Type II supernovae (SNe), and whether they come from similar or distinct progenitors, has been actively discussed for decades. Here we report spectropolarimetry of two fast declining Type II (Type IIL) SNe: SN 2013ej and SN 2017ahn. SN 2013ej exhibited high continuum polarization from very soon after the explosion to the radioactive tail phase with time-variable polarization angles. The origin of this polarimetric behavior can be interpreted as the combination of two different aspherical structures, namely an aspherical interaction of the SN ejecta with circumstellar matter (CSM) and an inherently aspherical explosion. Aspherical explosions are a common feature of slowly declining Type II (Type IIP) SNe. By contrast, SN 2017ahn showed low polarization not only in the photospheric phase but also in the radioactive tail phase. This low polarization in the tail phase, which has never before been observed in other Type IIP/L SNe, suggests that the explosion of SN 2017ahn was nearly spherical. These observations imply that Type IIL SNe have, at least, two different origins: they result from stars that have different explosion properties and/or different mass-loss processes. This fact might indicate that 13ej-like Type IIL SNe originate from a similar progenitor to those of Type IIP SNe accompanied by an aspherical CSM interaction, while 17ahn-like Type IIL SNe come from a more massive progenitor with less hydrogen in its envelope.

We present follow-up photometry and spectroscopy of the rapidly pulsating subdwarf B star EC 22221-3152. Using the SAAO 1.0-m telescope and the 0.4-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) at the Cerro Tololo Inter-American Observatory (CTIO), we monitored the star photometrically for one week. By combining data from both telescopes, we were able to resolve 18 significant periodicities in the light curve. Seven of these signals consist of combination frequencies, a first harmonic, and possible rotational splittings that would be indicative of an 8.2-d rotation period. The remaining 11 periodicities appear to represent independent oscillation modes, including three not originally detected in the discovery work. Time series spectroscopy obtained with the Goodman spectrograph on the 4.1-m SOAR telescope reveals possible velocity variations corresponding to two of the observed pulsation modes. From atmospheric model fits to the spectra, we derive T eff = 35600 ± 600 K, log g = 5.86 ± 0.15, and log N(He)/N(H) = −1.4 ± 0.3 and confirm the star’s status as one of the hottest sdBV r stars currently known.

We present follow-up photometry and spectroscopy of the rapidly pulsating subdwarf B star EC 22221-3152. Using the SAAO 1.0-m telescope and the 0.4-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) at the Cerro Tololo Inter-American Observatory (CTIO), we monitored the star photometrically for one week. By combining data from both telescopes, we were able to resolve 18 significant periodicities in the light curve. Seven of these signals consist of combination frequencies, a first harmonic, and possible rotational splittings that would be indicative of an 8.2-d rotation period. The remaining 11 periodicities appear to represent independent oscillation modes, including three not originally detected in the discovery work. Time series spectroscopy obtained with the Goodman spectrograph on the 4.1-m SOAR telescope reveals possible velocity variations corresponding to two of the observed pulsation modes. From atmospheric model fits to the spectra, we derive T eff = 35600 600 K, log g = 5.86 0.15, and log N(He)/N(H) = −1.4 0.3 and confirm the star's status as one of the hottest sdBVr stars currently known.