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PV Tel variables are extreme helium (EHe) stars known to be intrinsic light and velocity variable on characteristic timescales 0.1 - 2 d. With two exceptions, they are best described as irregular. Light curves have invariably been obtained…

A study is presented regarding the nature of several variable stars sampled during a campaign of photometric monitoring from the Abbey Ridge Observatory: 3 eclipsing binaries, 2 semiregulars, a luminous Be star, and a star of uncertain…

Observations using the Australia Telescope Compact Array at a wavelength of 6 cm have uncovered the radio counterpart to the compact X-ray nebula surrounding the Vela pulsar. Two lobes were found oriented about the spin axis of the pulsar,…

Multiwavelength monitoring of Be/X-ray binaries is crucial to understand the mechanisms producing their outbursts. H 1145-619 is one of these systems, which has recently displayed X-ray activity. We investigate the correlation between the…

Close binary systems often show linear polarization varying over the binary period, usually attributed to light scattered from electrons in circumstellar clouds. One of the brightest close binary systems is Spica (Alpha Virginis) consisting…

We present the results of a 2-epoch variability survey in the Hubble Deep Field with the goal of investigating the population of AGN to z=1. The primary data sets analyzed for galactic variability are the original HDF observations obtained…

Eight planetary nebulae have been identified as `born-again', a class of object typified by knotty secondary ejecta having low masses ($\sim$$10^{-4}$ M$_{\odot}$) with nearly no hydrogen. Abell 30, the archetype of the class, also belongs…

V Hya, an evolved carbon star with a complex circumstellar envelope, has two variability periods, 530d and 6000d (17 years). We analyze recent light curve data and show that both variations have benn present for at least 100 years and have…

Spectra of planetary nebulae (PNe) are characterised by strong forbidden emission lines and often also by an infrared (IR) excess. A few PNe show dust obscuration events and/or harbour long-period binaries. Some post-asymptotic giant branch…

Abell 14 is a poorly studied object despite being considered a born again planetary nebula. We performed a detailed study of its 3D morphology and ionization structure using the SHAPE and MOCASSIN codes. We found that Abell 14 is a highly…

We study the outflow activity, photometric variability and morphology of three very young stellar objects in the Serpens NW star forming region: OO Serpentis, EC 37 (V370 Ser) and EC 53 (V371 Ser). High spatial resolution Keck/NIRC2 laser…

We present spectrophotometric imaging mid-IR observations of the reflection nebula Ced201. Ced201 is a part of a molecular cloud illuminated by a B9.5V star moving through it at more than 12 km/s. The spectra of Ced201 give evidence for…

Stars with B[e] phenomenon comprise a very diverse group of objects in a different evolutionary status. These objects show common spectral characteristics, including presence of Balmer lines in emission, forbidden lines, and strong infrared…

The central part of the globular cluster NGC 288 was surveyed in a search for short-period variable stars. We obtained the V-band light curves for 4 SX Phe stars and 2 RR Lyrae variables, five of which are new discoveries. All SX Phe stars…

One of the principal scientific objectives of the upcoming Constellation-X mission is to attempt to map the inner regions of accretion disks around black holes in Seyfert galaxies by reverberation mapping of the Fe K fluorescence line. This…

We examine the long-term light curve, optical spectrum, spectral energy distribution, and Galactic location of V1117 Her in order to establish its nature. V1117 Her is most probably a young intermediate-mass star whose cyclic brightness…

We have monitored a 3 deg2 area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11,000 stars in each band were obtained, and 143 variables have been identified. Among those,…

We summarize results from flux density monitoring campaigns performed with the 100 meter radio-telescope at Effelsberg and the VLA during the past 15 yrs. We briefly discuss some of the statistical properties of the rapid variability from…

A previously faint young stellar object (YSO), V557 Mon, rapidly brightened in late 2024 and is currently at least $\Delta G=3.3$ magnitudes brighter than its typical pre-outburst brightness. The ongoing outburst is identified in the Gaia…

We present recent contemporaneous X-ray and optical observations of the Be/X-ray binary system A\,0535+26 with the \textit{Fermi}/Gamma-ray Burst Monitor (GBM) and several ground-based observatories. These new observations are put into the…