Context. The lack of high-precision long-term continuous photometric data for large samples of stars has impeded the large-scale exploration of pulsational variability in the OB star regime. As a result, the candidates for in-depth asteroseismic modelling have remained limited to a few dozen dwarfs. The TESS nominal space mission has surveyed the southern sky, including parts of the galactic plane, yielding continuous data across at least 27 d for hundreds of OB stars. Aims. We aim to couple TESS data in the southern sky with ground-based spectroscopy to study the variability in two dimensions, mass and evolution. We focus mainly on the presence of coherent pulsation modes that may or may not be present in the predicted theoretical instability domains and unravel all frequency behaviour in the amplitude spectra of the TESS data. Methods. We compose a sample of 98 OB-type stars observed by TESS in Sectors 1–13 and with available multi-epoch, high-resolution spectroscopy gathered by the IACOB and OWN surveys. We present the short-cadence 2 min light curves of dozens of OB-type stars, which have one or more spectra in the IACOB or OWN database. Based on these light curves and their Lomb–Scargle periodograms, we performed variability classification and frequency analysis. We placed the stars in the spectroscopic Hertzsprung–Russell diagram to interpret the variability in an evolutionary context. Results. We deduce the diverse origins of the mmag-level variability found in all of the 98 OB stars in the TESS data. We find among the sample several new variable stars, including three hybrid pulsators, three eclipsing binaries, high frequency modes in a Be star, and potential heat-driven pulsations in two Oe stars. Conclusions. We identify stars for which future asteroseismic modelling is possible, provided mode identification is achieved. By comparing the position of the variables to theoretical instability strips, we discuss the current shortcomings in non-adiabatic pulsation theory and the distribution of pulsators in the upper Hertzsprung–Russell diagram.

Context. LB-1 has recently been proposed to be a binary system at 4 kpc consisting of a B-type star of 8 M and a massive stellar black hole (BH) of 70 M . This finding challenges our current theories of massive star evolution and formation of BHs at solar metallicity. Aims. Our objective is to derive the effective temperature, surface gravity and chemical composition of the B-type component in order to determine its nature and evolutionary status and, indirectly, to constrain the mass of the BH. Methods. We use the non-LTE stellar atmosphere code FASTWIND to analyse new and archival high resolution data. Results. We determine (T eff , log g) values of (14 000±500 K, 3.50±0.15 dex) that, combined with the Gaia parallax, implies a spectroscopic mass, from log g, of 3.2 +2.1 −1.9 M and an evolutionary mass, assuming single star evolution, of 5.2 +0.3 −0.6 M . We determine an upper limit of 8 km s −1 for the projected rotational velocity and derive the surface abundances, finding the star to have a silicon abundance below solar, to be significantly enhanced in nitrogen and iron, and depleted in carbon and magnesium. Complementary evidence derived from a photometric extinction analysis and Gaia yields similar results for T eff and log g and a consistent distance around 2 kpc. Conclusions. We propose that the B-type star is a slightly evolved main sequence star of 3 -5 M with surface abundances reminiscent of diffusion in late B/A chemically peculiar stars with low rotational velocities. There is also evidence for CN-processed material in its atmosphere. These conclusions rely critically on the distance inferred from the Gaia parallax. The goodness of fit of the Gaia astrometry also favours a high-inclination orbit. If the orbit is edge-on and the B-type star has a mass of 3 -5 M , the mass of the dark companion would be 4 -5 M , which would be easier to explain with our current stellar evolutionary models.

The INT Galactic Plane Survey (IGAPS) is the merger of the optical photometric surveys, IPHAS and UVEX, based on data from the Isaac Newton Telescope (INT) obtained between 2003 and 2018. Here, we present the IGAPS point source catalogue. It contains 295.4 million rows providing photometry in the filters, i, r, narrow-band Hα, g and U RGO . The IGAPS footprint fills the Galactic coordinate range, |b| < 5 • and 30 • < < 215 • . A uniform calibration, referred to the Pan-STARRS system, is applied to g, r and i, while the Hα calibration is linked to r and then is reconciled via field overlaps. The astrometry in all 5 bands has been recalculated on the Gaia DR2 frame. Down to i ∼ 20 mag. (Vega system), most stars are also detected in g, r and Hα. As exposures in the r band were obtained within the IPHAS and UVEX surveys a few years apart, typically, the catalogue includes two distinct r measures, r I and r U . The r 10σ limiting magnitude is ∼21, with median seeing 1.1 arcsec. Between ∼13th and ∼19th magnitudes in all bands, the photometry is internally reproducible to within 0.02 magnitudes. Stars brighter than r = 19.5 have been tested for narrow-band Hα excess signalling line emission, and for variation exceeding |r I − r U | = 0.2 mag. We find and flag 8292 candidate emission line stars and over 53000 variables (both at > 5σ confidence). The 174-column catalogue will be available via CDS Strasbourg.Article number, page 3 of 28 A&A proofs: manuscript no. main filters at each pointing should be observed consecutivelyusually within an elapsed time of ∼5 min. All included exposure sets meet this criterion. Article number, page 20 of 28 M. Monguió et al.: IGAPS