1,723,742 research outputs found
The puzzling Luminous Blue Variable-like object HD 5980 in the Small Magellanic Cloud.
Get PDFpeer reviewedWe have observed the exceptional SMC star HD 5980 during several runs from 1989 to 1995 at ESO La Silla. CASPEC at the 3.6m telescope and EMMI in echelle and long slit modes at NTT were used for spectroscopy. Sub-arcsecond images were obtained using SUSI at NTT and also an adaptive optics system at the 3.6m telescope. In all our spectra taken before 1994 September HD 5980 shows a spectral type of WN6. The 1994 September spectra were taken shortly after the maximum of the visual light-curve of the LBV-like phenomenon (Bateson & Jones, 1993PVSS...19...50B) and about one month before the observations of Barba et al. (1995ApJ...446L..23B). Near maximum visual brightness, HD 5980 displays a WN11-like spectrum with the HeI lines and the Balmer lines Hdelta and Hgamma showing well-developed PCyg profiles. The sub-arcsecond images (0.17" FWHM), through the near infrared bands J, H, and K, obtained in 1993 and 1996, show no stellar components down to 6.7 mag fainter than HD 5980 in K at a separation of 1.0" and the 3sigma level. For a separation of 0.3" this upper bound is 4.1mag fainter than HD 5980. The observed behavior of this object raises serious problems for our comprehension of the LBV phenomenon in the conventional scenarios of massive star evolution. The present observations cover a crucial period in the evolution of HD 5980 and will therefore be helpful for better understanding this peculiar object especially during its outburst as well as the evolution of W-R stars in general
Linked collectors and determiners for: Estudios bióticos: Plantas, edafofauna epígea, anfibios y aves de los Complejos de Páramos de Sonsón y Urrao.
No full textNatural history specimen data linked to collectors and determiners held within, "Estudios bióticos: Plantas, edafofauna epígea, anfibios y aves de los Complejos de Páramos de Sonsón y Urrao". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="http://bionomia.net/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123">https://bionomia.net/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123">https://gbif.org/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123</a>. Formatted as a Frictionless Data package
Linked collectors and determiners for: Estudios bióticos: Plantas, edafofauna epígea, anfibios y aves de los Complejos de Páramos de Sonsón y Urrao.
No full textNatural history specimen data linked to collectors and determiners held within, "Estudios bióticos: Plantas, edafofauna epígea, anfibios y aves de los Complejos de Páramos de Sonsón y Urrao". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="http://bionomia.net/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123">https://bionomia.net/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123">https://gbif.org/dataset/5dfaf2ac-5980-4ec5-8490-4607fcd59123</a>. Formatted as a Frictionless Data package
Aspectos ecofisiológicos da cultivar de soja BRS 5980 IPRO em Planaltina-DF.
Get PDFO objetivo desse estudo foi avaliar fenologia, crescimento, desenvolvimento, fotoperíodo e grupo de precocidade da cultivar de soja BRS 5980 IPRO, em função de duas épocas de semeadura, na região de Planaltina ? DF. Ressalta-se que a BRS 5980 IPRO é uma nova cultivar com a tecnologia Intacta RR2 Pro®, que confere proteção das principais lagartas que atacam a cultura e tolerância ao herbicida glifosato. A cultivar será lançada em 2018 pela Embrapa Cerrados
Rapid Evolutionary Changes in the WR Binary HD 5980
Get PDFObservations of the optical spectrum of the Wolf-Rayet eclipsing binary HD 5980 in the Small Magellanic Cloud show how one component of this binary system unexpectedly underwent an eruption transforming its spectral type from a hot WN3 to a cooler and more luminous WN11 type. Radial velocity analysis of the preoutburst spectra indicates that both components of the binary are massive stars with emission lines in their spectra. The component that erupted is found to be the one in front of the system during the light curve phase zero. Differential analysis of the H Balmer and He ii Pickering emission line strengths indicates that the hydrogen content changes with the cooling of the spectrum. The maximum light of the eruption of HD 5980 had a duration of a few months, but the slow change from a WNE spectrum to WNL type took about 10 years. The similarity of the present spectrum of HD 5980 to the galactic WR binary system WR 12 is noticed.Facultad de Ciencias Astronómicas y Geofísica
The WR/LBV system HD 5980: wind-velocity – brightness correlations
Get PDFThe massive eclipsing system HD 5980 in the Small Magellanic Cloud presented sudden ~1–3 mag eruptive events in 1993-1994, the nature of which is still unexplained. We recently showed that these brief eruptions occurred at the beginning of an extended high state of activity which is characterized by large emission-line intensities and that this high state is currently ending (Koenigsberger et al . 2010). Star A , the more massive member of the 19-day binary, is responsible for the spectacular spectral variations observed over the past 3 decades (see Figure 1). It has a He-enriched stellar wind and is over-luminous for its mass, implying an advanced evolutionary state (Koenigsberger et al . 1998). Data obtained over the past 3 decades show that Star A's wind speed slowed down as the system brightened. Also present in these data is a correlated increase in emission-line strength, visual and UV brigthness. The latter suggests that the high activity state in HD 5980 may be attributed to a bolometric luminosity increase, consistent with the results of Drissen et al . (2001). Hence, HD 5980 may be providing the important clues needed for understanding the behavior of other luminous blue variables and for understainding the evolutionary transition between massive O-type stars and Wolf-Rayet stars.Facultad de Ciencias Astronómicas y Geofísica
The WR/LBV system HD 5980: wind-velocity – brightness correlations
No full textAbstractThe massive eclipsing system HD 5980 in the Small Magellanic Cloud presented sudden ~1–3 mag eruptive events in 1993-1994, the nature of which is still unexplained. We recently showed that these brief eruptions occurred at the beginning of an extended high state of activity which is characterized by large emission-line intensities and that this high state is currently ending (Koenigsberger et al. 2010). Star A, the more massive member of the 19-day binary, is responsible for the spectacular spectral variations observed over the past 3 decades (see Figure 1). It has a He-enriched stellar wind and is over-luminous for its mass, implying an advanced evolutionary state (Koenigsberger et al. 1998). Data obtained over the past 3 decades show that Star A's wind speed slowed down as the system brightened. Also present in these data is a correlated increase in emission-line strength, visual and UV brigthness. The latter suggests that the high activity state in HD 5980 may be attributed to a bolometric luminosity increase, consistent with the results of Drissen et al. (2001). Hence, HD 5980 may be providing the important clues needed for understanding the behavior of other luminous blue variables and for understainding the evolutionary transition between massive O-type stars and Wolf-Rayet stars.</jats:p
THE EXTRAORDINARY LBV/WR SYSTEM HD 5980
No full textRESUMEN Presentamos resultados de los cálculos para HD 5980 efectuados con nuestro modelo de interacción por fuerzas de marea. El modelo predice una mayor actividad atmosférica después del paso por el periastro, así como una mayor actividad ocasional en zonas intermedias entre el ecuador y el polo. ABSTRACT The LBV/WR system HD 5980 contains a short-period, eccentric binary system with interacting stellar winds. In this paper we summarize results from model calculations of the tidal flows on the LBV component showing that energy dissipation rates,Ė, associated with turbulent viscosity are orbital-phase dependent as well as variable over the stellar surface. We speculate that ifĖ contributes towards driving mass-loss, the strongest wind-wind interaction effects may occur after periastron passage. In addition, the model suggests the presence of stronger outflows localized at polar angles θ ∼30-50 • than over the rest of the stellar surface during part of the orbital cycle. Thus, the analysis of wind-wind interactions in this system requires a modified model in which non-stationary and asymmetric wind structures are incorporated
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