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This paper presents the photometric and spectroscopic analysis of a long-period totally eclipsing contact binary (HAT 307-0007476) for the first time. This system is a low mass ratio ($q\sim0.114$) and medium contact binary ($f\sim37.1\%$).…
The classical T Tauri star RW Aur A is an irregular variable with a large amplitude in all photometric bands. In an extended series of photometric data we found small-amplitude periodic variations in the blue colours of the star, with a…
UW Coronae Borealis (UW CrB) is a low mass X-ray binary that shows both Type 1 X-ray and optical bursts, which typically last for 20 s. The system has a binary period of close to 2 hours and is thought to have a relatively high inclination…
Studying the periodic flux-variation behavior of blazars is vital for probing supermassive black hole binaries and the kinematics of relativistic jets. In this work, we report the detection of the multi-band possible periodic variations of…
We report the discovery of a compact, coplanar, quadruply-lined, eclipsing quadruple star system from TESS data, TIC 454140642, also known as TYC 0074-01254-1. The target was first detected in Sector 5 with 30-min cadence in Full-Frame…
We present the results of an intensive campaign of spectroscopic and photometric monitoring of the peculiar Wolf-Rayet star WR 134 from 1989 to 1997. This unprecedentedly large data set allows us to confirm unambiguously the existence of a…
Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD93162 (=WR25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the…
We report the discovery in $TESS$ Sectors 3 and 4 of a compact triply eclipsing triple star system. TIC 209409435 is a previously unknown eclipsing binary with a period of 5.717 days, and the presence of a third star in an outer eccentric…
V907 Scorpii is a unique triple system in which the inner binary component has been reported to have switched on and off eclipses several times in modern history. In spite of its peculiarity, observational data on this system are…
The recently discovered eclipsing binary system TYC 2675-663-1 is a X-ray source, and shows properties in the optical that are similar to the W UMa systems, but are somewhat unusual compared to what is seen in other contact binary systems.…
A new ephemeris has been determined for the supersoft X-ray binary CAL 83 using MACHO photometry. With an improved orbital period of 1.047568 days, it is now possible to phase together photometric and spectroscopic data obtained over the…
A sample of contact binaries discovered by the OGLE project in Baade's Window, with orbital periods longer than one day and with available color and light-curve data, has been analyzed. It consists of only 32 systems, in contrast to 388…
Detecting planets within protoplanetary disks around young stars is essential for understanding planet formation and evolution. However, planet detection using the radial velocity method faces challenges due to strong stellar activity in…
The millisecond pulsar PSR B1259-63 and the Be star SS2883 are situated in a highly eccentric binary system, with orbital period ~3.4 years. We report on hard X-ray observations obtained with the INTEGRAL satellite close to the 2004…
The high-mass X-ray binary LS I +61{\deg}303 is composed of a Be-type star and a compact object. The emission is variable and periodic across the electromagnetic spectrum, from radio to very high-energy gamma rays. The orbital period is…
We present an update of the lunar occultation program which is routinely carried out in the near-IR at the Calar Alto Observatory. A total of 350 events were recorded since our last report (Fors et al. 2004). In the course of eight runs we…
PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multi-frequency study of the pulsed radio flux variability which suggests that this phenomenon is extrinsic to the pulsar and…
We present optical spectrophotometric monitoring of four active T Tauri stars (DG Tau, RY Tau, XZ Tau, RW Aur A) at high spectral resolution ($R \ga 1 \times 10^4$), to investigate the correlation between time variable mass ejection seen in…
We have obtained 48 high resolution echelle spectra of the pre-main sequence eclipsing binary system KH~15D (V582 Mon, P = 48.37 d, $e$ $\sim$ 0.6, M$_{A}$ = 0.6 M$_{\odot}$, M$_{B}$ = 0.7 M$_{\odot}$). The eclipses are caused by a…
Determinations of stellar mass and radius with realistic uncertainties at the level of 1% provide important constraints on models of stellar structure and evolution. We present a high-precision light curve of the A0IV star Psi Centauri,…