Related papers: The Irregular Variable Ku Her: The Light And Perio…

Long-term, uniform series of UBVR observations of T Tauri and Herbig Ae stars obtained over 20 yr at the Maidanak Observatory as part of the ROTOR program are analyzed. We find a linear relationship between the characteristic variability…

The star CoRoT102781750 reveals a puzzle, showing a very complex and altering variation in different `CoRoT colours'. We established without doubt that more than a single star was situated within the CoRoT mask. Using a search for…

Magnetic chemically peculiar stars of the main sequence can present rotational periods as long as many decades. Here we report the results of an observational campaign started in 2001 aimed at establishing these very long periods from the…

We have observed S4 0954+658 in the BVRI bands in 2001, and in the BI bands in 2002. The observations resulted in almost evenly sampled light curves, 3-8 hours long, with an average sampling interval of ~5-15 min. Because of the dense…

We present photometric observations of the BL Lacertae object S5 0716+714 with a temporal resolution of 120 s in the Sloan i' and r' bands. These observations were conducted using the Comet Search Program telescope at Xingming Observatory…

We present photometric light curves for a sample of 21 ultra cool M and L dwarfs in the field and in the young open clusters sigma Orionis and the Pleiades. Evidence for variability with RMS amplitudes (in the I band) of 0.01 to 0.055…

(abridged) Variability is a key property of stars on the asymptotic giant branch (AGB). Their pulsation period is related to the luminosity and mass-loss rate (MLR) of the star. Long-period variables (LPVs) and Mira variables are the most…

We present a detailed lightcurve analysis for a sample of bright semiregular variables based on long-term (70--90 years) visual magnitude estimates carried out by amateur astronomers. Fundamental changes of the physical state (amplitude…

We monitored BL Lacertae simultaneously in the optical B, V, R and I bands for 13 nights during the period 2012-2016. The variations were well correlated in all bands and the source showed significant intraday variability (IDV). We also…

Context. RU Lup is a Classical T Tauri star with unusually strong emission lines, which has been interpreted as manifestations of accretion. Recently, evidence has accumulated that this star might have a variable radial velocity. Aims. We…

We report CCD photometric monitoring of the nonemission ultracool dwarf BRI 0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in 1996 August, with CCD cameras at 1 m class telescopes on the observatories of the Canary…

We report results based on the monitoring of the BL Lac object Mrk 501 in the optical (B, V and R) passbands from March to May 2000. Observations spread over 12 nights were carried out using 1.2 meter Mount Abu Telescope, India and 61 cm…

The NASA Kepler spacecraft data revealed a large number of multimode nonradially pulsating gamma Dor and delta Sct variable star candidates. The high precision long time-series photometry makes it possible to study amplitude variations of…

OI 090.4 was monitored on 21 nights from 2006 to 2012 for studying the variability. Strong variations occurred during the past 6 years. The long-term variability amplitude is consistent with previous results. Microvariability was analyzed…

T Tauri stars exhibit variability on all timescales, whose origin is still debated. On WTTS the variability is fairly simple and attributed to long-lived, ubiquitous cool spots. We investigate the long term variability of WTTS, extending up…

We present HAWK-I J-band light curves of five late-type T dwarfs (T6.5-T7.5) with a typical duration of four hours, and investigate the evidence for quasi-periodic photometric variability on intra-night timescales. Our photometry reaches…

We investigate the period changes of 13 short-period Type II Cepheids using the O-C method over a century-long data baseline. The O-C diagrams for these stars exhibit a parabolic trend, indicating both increasing and decreasing period…

Nova Her 2021 or V1674 Her was one of the fastest novae to be observed so far. We report here the results from our timing and spectral studies of the source observed at multiple epochs with AstroSat. We report the detection of a periodicity…

Using the 1.56m telescope at the Shanghai Observatory (ShAO), China, we monitored two sources, BL Lac object S5 0716+714 and Flat Spectrum Radio Quasar (FSRQ) 3C 273. For S5 0716+714, we report 4969 sets of CCD (Charge-coupled Device)…

The VIIRS Day Night Band sensor on the Suomi NPP satellite provides almost a decade of observations of night light. The daily frequency of sampling, without the temporal averaging of annual composites, requires the distinction between…