TY - JOUR A1 - Giesers, Benjamin David A1 - Kamann, Sebastian A1 - Dreizler, Stefan A1 - Husser, Tim-Oliver A1 - Askar, Abbas A1 - Göttgens, Fabian A1 - Brinchmann, Jarle A1 - Latour, Marilyn A1 - Weilbacher, Peter Michael A1 - Wendt, Martin A1 - Roth, Martin M. T1 - A stellar census in globular clusters with MUSE: Binaries in NGC 3201 JF - Astronomy and astrophysics : an international weekly journal N2 - We utilise multi-epoch MUSE spectroscopy to study binary stars in the core of the Galactic globular cluster NGC 3201. Our sample consists of 3553 stars with 54 883 spectra in total comprising 3200 main-sequence stars up to 4 magnitudes below the turn-off. Each star in our sample has between 3 and 63 (with a median of 14) reliable radial velocity measurements within five years of observations. We introduce a statistical method to determine the probability of a star showing radial velocity variations based on the whole inhomogeneous radial velocity sample. Using HST photometry and an advanced dynamical MOCCA simulation of this specific cluster we overcome observational biases that previous spectroscopic studies had to deal with. This allows us to infer a binary frequency in the MUSE field of view and enables us to deduce the underlying true binary frequency of (6.75 +/- 0.72)% in NGC 3201. The comparison of the MUSE observations with the MOCCA simulation suggests a large portion of primordial binaries. We can also confirm a radial increase in the binary fraction towards the cluster centre due to mass segregation. We discovered that in the core of NGC 3201 at least (57.5 +/- 7.9)% of blue straggler stars are in a binary system. For the first time in a study of globular clusters, we were able to fit Keplerian orbits to a significant sample of 95 binaries. We present the binary system properties of eleven blue straggler stars and the connection to SX Phoenicis-type stars. We show evidence that two blue straggler formation scenarios, the mass transfer in binary (or triple) star systems and the coalescence due to binary-binary interactions, are present in our data. We also describe the binary and spectroscopic properties of four sub-subgiant (or red straggler) stars. Furthermore, we discovered two new black hole candidates with minimum masses (M sin i) of (7.68 +/- 0.50)M-circle dot, (4.4 +/- 2.8)M-circle dot, and refine the minimum mass estimate on the already published black hole to (4.53 +/- 0.21)M-circle dot, These black holes are consistent with an extensive black hole subsystem hosted by NGC 3201. KW - binaries: general KW - blue stragglers KW - stars: black holes KW - techniques: radial velocities KW - techniques: imaging spectroscopy KW - globular clusters: individual: NGC 3201 Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201936203 SN - 0004-6361 SN - 1432-0746 VL - 632 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Göttgens, Fabian A1 - Weilbacher, Peter Michael A1 - Roth, Martin M. A1 - Dreizler, Stefan A1 - Giesers, Benjamin A1 - Husser, Tim-Oliver A1 - Kamann, Sebastian A1 - Brinchmann, Jarle A1 - Kollatschny, Wolfram A1 - Monreal-Ibero, Ana A1 - Schmidt, Kasper Borello A1 - Wendt, Martin A1 - Wisotzki, Lutz A1 - Bacon, Roland T1 - Discovery of an old nova remnant in the Galactic globular cluster M 22 JF - Astronomy and astrophysics : an international weekly journal N2 - A nova is a cataclysmic event on the surface of a white dwarf in a binary system that increases the overall brightness by several orders of magnitude. Although binary systems with a white dwarf are expected to be overabundant in globular clusters compared with in the Galaxy, only two novae from Galactic globular clusters have been observed. We present the discovery of an emission nebula in the Galactic globular cluster M 22 (NGC 6656) in observations made with the integral-field spectrograph MUSE. We extracted the spectrum of the nebula and used the radial velocity determined from the emission lines to confirm that the nebula is part of NGC 6656. Emission-line ratios were used to determine the electron temperature and density. It is estimated to have a mass of 1-17 x 10(-5) M-circle dot. This mass and the emission-line ratios indicate that the nebula is a nova remnant. Its position coincides with the reported location of a "guest star", an ancient Chinese term for transients, observed in May 48 BCE. With this discovery, this nova may be one of the oldest confirmed extra-solar events recorded in human history. KW - globular clusters: individual: NGC 6656 KW - novae, cataclysmic variables KW - techniques: imaging spectroscopy Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201935221 SN - 1432-0746 VL - 626 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Göttgens, Fabian A1 - Husser, Tim-Oliver A1 - Kamann, Sebastian A1 - Dreizler, Stefan A1 - Giesers, Benjamin A1 - Kollatschny, Wolfram A1 - Weilbacher, Peter Michael A1 - Roth, Martin M. A1 - Wendt, Martin T1 - A stellar census in globular clusters with MUSE: A spectral catalogue of emission-line sources JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. Globular clusters produce many exotic stars due to a much higher frequency of dynamical interactions in their dense stellar environments. Some of these objects were observed together with several hundred thousand other stars in our MUSE survey of 26 Galactic globular clusters. Assuming that at least a few exotic stars have exotic spectra (i.e. spectra that contain emission lines), we can use this large spectroscopic data set of over a million stellar spectra as a blind survey to detect stellar exotica in globular clusters. Methods. To detect emission lines in each spectrum, we modelled the expected shape of an emission line as a Gaussian curve. This template was used for matched filtering on the di fferences between each observed 1D spectrum and its fitted spectral model. The spectra with the most significant detections of H alpha emission are checked visually and cross-matched with published catalogues. Results. We find 156 stars with H alpha emission, including several known cataclysmic variables (CV) and two new CVs, pulsating variable stars, eclipsing binary stars, the optical counterpart of a known black hole, several probable sub-subgiants and red stragglers, and 21 background emission-line galaxies. We find possible optical counterparts to 39 X-ray sources, as we detected H alpha emission in several spectra of stars that are close to known positions of Chandra X-ray sources. This spectral catalogue can be used to supplement existing or future X-ray or radio observations with spectra of potential optical counterparts to classify the sources. KW - globular clusters: general KW - stars: emission-line, Be KW - novae KW - cataclysmic variables KW - catalogs KW - techniques: imaging spectroscopy Y1 - 2019 U6 - https://doi.org/10.1051/0004-6361/201936485 SN - 0004-6361 SN - 1432-0746 VL - 631 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Muster, Sina A1 - Riley, William J. A1 - Roth, Kurt A1 - Langer, Moritz A1 - Aleina, Fabio Cresto A1 - Koven, Charles D. A1 - Lange, Stephan A1 - Bartsch, Annett A1 - Grosse, Guido A1 - Wilson, Cathy J. A1 - Jones, Benjamin M. A1 - Boike, Julia T1 - Size distributions of arctic waterbodies reveal consistent relations in their statistical moments in space and time JF - Frontiers in Earth Science N2 - Arctic lowlands are characterized by large numbers of small waterbodies, which are known to affect surface energy budgets and the global carbon cycle. Statistical analysis of their size distributions has been hindered by the shortage of observations at sufficiently high spatial resolutions. This situation has now changed with the high-resolution (<5 m) circum-Arctic Permafrost Region Pond and Lake (PeRL) database recently becoming available. We have used this database to make the first consistent, high-resolution estimation of Arctic waterbody size distributions, with surface areas ranging from 0.0001 km(2) (100 m(2)) to 1 km(2). We found that the size distributions varied greatly across the thirty study regions investigated and that there was no single universal size distribution function (including power-law distribution functions) appropriate across all of the study regions. We did, however, find close relationships between the statistical moments (mean, variance, and skewness) of the waterbody size distributions from different study regions. Specifically, we found that the spatial variance increased linearly with mean waterbody size (R-2 = 0.97, p < 2.2e-16) and that the skewness decreased approximately hyperbolically. We have demonstrated that these relationships (1) hold across the 30 Arctic study regions covering a variety of (bio)climatic and permafrost zones, (2) hold over time in two of these study regions for which multi-decadal satellite imagery is available, and (3) can be reproduced by simulating rising water levels in a high-resolution digital elevation model. The consistent spatial and temporal relationships between the statistical moments of the waterbody size distributions underscore the dominance of topographic controls in lowland permafrost areas. These results provide motivation for further analyses of the factors involved in waterbody development and spatial distribution and for investigations into the possibility of using statistical moments to predict future hydrologic dynamics in the Arctic. KW - permafrost KW - hydrology KW - waterbodies KW - size distribution KW - thermokarst KW - statistical moments KW - ponds KW - lakes Y1 - 2019 U6 - https://doi.org/10.3389/feart.2019.00005 SN - 2296-6463 VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER -