Related papers: Bolometric luminosity variations in the Luminous B…

The luminosities and periods of obscured AGB stars in the LMC are discussed using a combination of ISO and ground-based infrared photometry. The bolometric luminosities of these stars fall close to an extrapolation of the period-luminosity…

The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We…

We present photometric and spectroscopic analysis of the Hubble Sandage variable AF And in M31. The data has been taken under the Nainital Microlensing Survey during 1998-2002 and follow-up observations were carried out until 2011. During…

Context. The post-main-sequence evolution of massive stars remains poorly understood, particularly for blue supergiants. These objects play a crucial role in the dynamical and chemical evolution of galaxies and exhibit pronounced…

This study presents an investigation of nearly two dozen candidate Luminous Blue Variables (cLBVs) in the galaxies M31 and M33. Eight stars have been studied in detail, while an additional sixteen objects are briefly mentioned. Multi-epoch…

We present the results of a near-infrared monitoring programme of a selected sample of stars, initially suspected to be Mira variables and OH/IR stars, covering more than a decade of observations. The objects monitored cover the typical…

We investigate a suspected very massive star in one of the most metal-poor dwarf galaxies, PHL~293B. Excitingly, we find the sudden disappearance of the stellar signatures from our 2019 spectra, in particular the broad H lines with P~Cygni…

We present an investigation of a large sample of confirmed (N=233) and candidate (N=54) Galactic classical Be stars (mean V magnitude range of 6.4 to 12.6 mag), with the main aim of characterizing their photometric variability. Our sample…

We perform a study on the optical and infrared photometric properties of known luminous blue variables (LBVs) in M31 using the sample of LBV candidates from the Local Group Galaxy Survey (Massey et al. 2007). We find that M31 LBV candidates…

In the standard view of massive star evolution, luminous blue variables (LBVs) are transitional objects between the most massive O-type stars and Wolf-Rayet (WR) stars. With short lifetimes, these stars should all be found near one another.…

As shown by Mennickent, et al(2003), a subset of the blue variable stars in the Large Magellanic Cloud exhibit brightness variability of small amplitude in the period range 2.4 to 16 days as well as larger amplitude variability with periods…

We present a detailed spectroscopic analysis of the luminous blue variable AG Carinae during the last two visual minimum phases of its S-Dor cycle (1985-1990 and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a…

We report the results of a 3 year-long dedicated monitoring campaign of a restless Luminous Blue Variable (LBV) in NGC 7259. The object, named SN 2009ip, was observed photometrically and spectroscopically in the optical and near-infrared…

Recent IR surveys of the Galactic plane have revealed a large number of candidate Luminous Blue Variables. In order to verify these classifications we have been undertaking a long term spectroscopic and photometric monitoring campaign…

We aim to explore the variable photometric and stellar properties of four yellow hypergiants (YHGs), HR8752, HR 5171A, $\rho$ Cas, and HD 179821, and their pulsations of hundreds of days, and long-term variations (LTVs) of years. We tackled…

Context. Luminous blue variables (LBVs) are rare massive stars with very high luminosity. They are characterized by strong photo-metric and spectroscopic variability related to transient eruptions. The mechanisms at the origin of these…

Luminous Blue Variables (LBVs) are massive stars that show strong spectral and photometric variability. The question of what evolutionary stages they represent and what exactly drives their instability is still open, and thus is it…

We consider the luminous blue variable (LBV) star V532 in M33, also known as Romano's star, in two different spectral states: in the optical minimum of 2007/2008 and during a local brightening in 2005. Optical spectra of low and moderate…

We present the results of spectroscopic and photometric observations for three hot southern-hemisphere post-AGB objects, Hen 3-1347 = IRAS 17074-1845, Hen 3-1428 = IRAS17311-4924, and LSS 4634 = IRAS 18023-3409. In the spectrograms taken…

We continue to search for LBV stars in galaxies outside the Local Group. In this work, we have investigated four luminous stars in NGC 4449. Multiple spectral observations carried out for J122810.94+440540.6, J122811.70+440550.9, and…