Related papers: A dwarf nova in the globular cluster M13

We used a set of archived HST/WFPC2 images to probe the stellar population in the core of the nearby Galactic Globular Cluster (GGC) 47 Tuc. From the ultraviolet (UV) Color Magnitude Diagrams (CMDs) obtained for ~4,000 stars detected within…

We report on the spectroscopic confirmation of 68 new bright ($G=13.5-17.2$ mag) and blue (pre-)white dwarfs (WDs). This finding has allowed us to almost double the number of the hottest ($T_{\mathrm{eff}} \geq 60$kK) known WDs brighter…

We have used public data from the Next Generation Virgo Survey (NGVS) to investigate the dwarf galaxy population of the Virgo cluster beyond what has previously been discovered. We initially mask and smooth the data, and then use the object…

Ultra-compact dwarf galaxies (UCDs) were serendipitously discovered by spectroscopic surveys in the Fornax cluster twenty years ago. Nowadays, it is commonly accepted that many bright UCDs are the nuclei of galaxies that have been stripped.…

We redetermine the relationship between absolute magnitude and orbital period for dwarf novae, based on 46 stars with good distance estimates. This improves upon Warner's previous relation, building upon today's improved estimates of…

(Abridged) We have surveyed four globular clusters in the Fornax dwarf galaxy for RR Lyrae stars, using archival HST observations. We identify 197 new RR Lyrae stars in these four clusters. Despite the short observational baseline, we…

Using a 12 ks archival Chandra X-ray Observatory ACIS-S observation on the massive globular cluster (GC) M14, we detect a total of 7 faint X-ray sources within its half-light radius at a 0.5-7 keV depth of $2.5\times…

Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations…

Galactic globular clusters harbour binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core…

We report the discovery of 271 previously undetected dwarf galaxies in the outer Fornax cluster regions at radii $r_{\rm vir}/4<\!r\!<r_{\rm vir}/2$ using data from the Next Generation Fornax Survey (NGFS) with deep coadded $u'$, $g'$ and…

In order to characterize 22 new globular cluster (GC) candidates in the Galactic bulge, we present their colour-magnitude diagrams (CMDs) and Ks-band luminosity functions (LFs) using the near-infrared VVV database as well as Gaia-DR2 proper…

The nature of the dwarf galaxy population as a function of location in the cluster and within different environments is investigated. We have previously described the results of a search for low surface brightness objects in data drawn from…

Aims - We present the first results of a large spectroscopic survey of globular clusters and candidate globular clusters in the nearby M~31 galaxy. The survey is aimed at the classification of known candidate M~31 clusters and at the study…

Our VLT (FLAMES) observations near NGC1399 investigate the connection between ultra-compact dwarf galaxies (UCDs), NGC1399 globular clusters and intra-cluster globulars. We have uncovered 30 faint compact stellar systems in the Fornax…

We present ultraviolet (UV) photometry of M31 globular clusters (GCs) found in 23 Galaxy Evolution Explorer (GALEX) images covering the entirety of M31. We detect 485 and 273 GCs (and GC candidates) in the near-ultraviolet (NUV; 2267 A) and…

Globular clusters at the distance of M31 have apparent angular sizes of a few arcseconds. While many M31 GCs have been detected and studied from ground-based images, the high spatial resolution of HST allows much more robust detection and…

We present preliminary results obtained from the comparison of the specific frequencies of Blue Straggler Stars (BSS) detected so far in a sample of 26 Galactic globular clusters. The number of BSS seems to increase almost linearly with…

We have followed up on the results of a 65 square degree CFHT/MegaCam imaging survey of the nearby M81 Group searching for faint and ultra-faint dwarf galaxies. The original survey turned up 22 faint candidate dwarf members. Based on…

[Abridged] Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M31. We performed a dedicated monitoring of the M31 central region, aimed to detect SSS…

The mysterious high galactic latitude cometary globule CG12 has been observed with the ACIS detector on board the Chandra X-ray Observatory. We detect 128 X-ray sources; half are likely young stars formed within the globule's head. This new…