102,990 research outputs found
The AM Canum Venaticorum binary SDSS J173047.59+554518.5
No full textThe AM Canum Venaticorum (AM CVn) binaries are a rare group of hydrogen-deficient, ultrashort period, mass-transferring white dwarf binaries and are possible progenitors of Type Ia supernovae. We present time-resolved spectroscopy of the recently discovered AM CVn binary SDSS J173047.59+554518.5. The average spectrum shows strong double-peaked helium emission lines, as well as a variety of metal lines, including neon; this is the second detection of neon in an AM CVn binary, after the much brighter system GP Com. We detect no calcium in the accretion disc, a puzzling feature that has been noted in many of the longer period AM CVn binaries. We measure an orbital period, from the radial velocities of the emission lines, of 35.2 ± 0.2 min, confirming the ultracompact binary nature of the system. The emission lines seen in SDSS J1730 are very narrow, although double-peaked, implying a low-inclination, face-on accretion disc; using the measured velocities of the line peaks, we estimate i ≤ 11°. This low inclination makes SDSS J1730 an excellent system for the identification of emission lines
The impact of the FMR and starburst galaxies on the (low metallicity) cosmic star formation history
No full textsponsorship: We thank Karina Caputi and Jarle Brinchmann for helpful discussions. We thank the anonymous referee for their thoughtful comments that helped to improve this paper. MC and GN acknowledge support from the Netherlands Organisation for Scientific Research (NWO). ALandLBare supported by PRINMIUR 2017 prot. 20173ML3WW, `Opening the ALMA window on the cosmic evolution of gas, stars and supermassive black holes', and by the EU H2020-MSCA-ITN2019 Project 860744 'BiD4BESt: Big Data applications for black hole Evolution STudies.' (Netherlands Organisation for Scientific Research (NWO), PRINMIUR|20173ML3WW, EU H2020-MSCA-ITN2019|860744)status: Publishe
Optical spectroscopy of (candidate) ultracompact X-ray binaries : constraints on the composition of the donor stars
No full textWe present optical spectroscopy of several (candidate) ultracompact X-ray binaries (UCXBs) obtained with the European Southern Observatory Very Large Telescope and Gemini-North telescopes. In only one of five observed UCXB candidates did we find evidence for H in its spectrum (4U 1556−60). For XB 1905+00 the optical counterpart is not detected. For the known UCXBs 4U 1626−67 and XB 1916−05 we find spectra consistent with a C/O and a He/N accretion disc, respectively, the latter is the first optical spectrum of a He-rich donor in an UCXB. Interestingly, the C/O spectrum of 4U 1626−67 shows both similarities as well as marked differences from the optical C/O spectrum of 4U 0614+09. We obtained phase-resolved spectroscopy of 4U 0614+09 and the 44-min transient XTE J0929−314. In neither object were we able to detect clear orbital periodicities, highlighting the difficulties of period determinations in UCXBs. We reanalysed the spectra of XTE J0929−314 that were taken close to the peak of its 2003 X-ray outburst and do not confirm the detection of Hα emission as was claimed in the literature. The peak spectra do show strong C or N emission around 4640 Å, as has also been detected in other UCXBs. We discuss the implications of our findings for our understanding of the formation of UCXBs and the Galactic population of UCXBs. At the moment all studied systems are consistent with having white dwarf donors, the majority being C/O rich
arXiv:astro-ph/9911054 v1 4 Nov 1999
No full textConstraints on mass ejection in black hole formation derived from black hole x-ray binaries Nelemans, G.A.; Tauris, Th.M.; van den Heuvel, E.P.J
XMM-Newton observations of AM CVn binaries : V396 Hya and SDSS J1240–01
No full textWe present the results of XMM-Newton observations of two AM CVn systems - V396 Hya and SDSS J1240-01. Both systems are detected in X-rays and in the UV: neither shows coherent variability in their light curves. We compare the rms variability of the X-ray and UV power spectra of these sources with other AM CVn systems. Apart from ES Cet, AM CVn sources are not strongly variable in X-rays, while in the UV the degree of variability is related to the systems apparent brightness. The X-ray spectra of V396 Hya and SDSS J1240-01 show highly non-solar abundances, requiring enhanced nitrogen to obtain good fits. We compare the UV and X-ray luminosities for 7 AM CVn systems using recent distances. We find that the X-ray luminosity is not strongly dependent upon orbital period. However, the UV luminosity is highly correlated with orbital period with the UV luminosity decreasing with increasing orbital period. We expect that this is due to the accretion disk making an increasingly strong contribution to the UV emission at shorter periods. The implied luminosities are in remarkably good agreement with predictions
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
The UV-excess survey of the Northern Galactic Plane
No full textThe UV-Excess survey of the northern Galactic plane images a 10 degrees x 185 degrees wide band, centred on the Galactic equator using the 2.5-m Isaac Newton Telescope in four bands (U, g, r, He 15875) down to similar to 21-22 mag (similar to 20 in He 15875). The setup and data reduction procedures are described. Simulations of the colours of main-sequence stars, giant, supergiants, DA and DB white dwarfs and AM Canum Venaticorum stars are made, including the effects of reddening. A first look at the data of the survey (currently 30 per cent complete) is given
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