Model atmosphere fits to high-resolution optical spectra of Wray 977 confirm the B hypergiant classification of the massive companion to the X-ray pulsar GX301−2. The models give a radius of 62 R , an effective temperature of 18 100 K and a luminosity of 5 × 10 5 L . These values are somewhat reduced compared to the stellar parameters of Wray 977 measured previously. The deduced mass-loss rate and terminal velocity of the stellar wind are 10 −5 M yr −1 and 305 km s −1 , respectively. The interstellar Na i D absorption indicates that Wray 977 is located behind the first intersection with the Sagittarius-Carina spiral arm (1-2.5 kpc) and probably belongs to the stellar population of the Norma spiral arm at a distance of 3−4 kpc. The luminosity derived from the model atmosphere is consistent with this distance (3 kpc). The luminosity of the wind-fed X-ray pulsar (L X ∼ 10 37 erg s −1 ) is in good accordance with the Bondi-Hoyle mass accretion rate. The spectra obtained with UVES on the Very Large Telescope (VLT) cover a full orbit of the system, including periastron passage, from which we derive the radial-velocity curve of the B hypergiant. The measured radial-velocity amplitude is 10 ± 3 km s −1 yielding a mass ratio q = M X /M opt = 0.046 ± 0.014. The absence of an X-ray eclipse results in a lower limit to the mass of Wray 977 of 39 M . An upper limit of 68 or 53 M is derived for the mass of Wray 977 adopting a maximum neutron star mass of 3.2 or 2.5 M , respectively. The corresponding lower limit to the system inclination is i > 44• , supporting the view that the dip in the X-ray lightcurve is due to absorption by the dense stellar wind of Wray 977 (Leahy 2002). The "spectroscopic" mass of Wray 977 is 43 ± 10 M , consistent with the range in mass derived from the binarity constraints. The mass of the neutron star is 1.85 ± 0.6 M . Time series of spectral lines formed in the dense stellar wind (e.g. He i 5876 Å and Hα) indicate the presence of a gas stream trailing the neutron star in its orbit. The long-term behaviour of the Hα equivalent width exhibits strong variations in wind strength; the sampling of the data is insufficient to conclude whether a relation exists between wind mass-loss rate and pulsar spin period.
We present spectroscopy of the microquasar SS 433 obtained near primary eclipse and disk precessional phase Ψ = 0.0, when the accretion disk is expected to be most "face-on". The likelihood of observing the spectrum of the mass donor is maximized at this combination of orbital and precessional phases since the donor is in the foreground and above the extended disk believed to be present in the system. The spectra were obtained over four different runs centered on these special phases. The blue spectra show clear evidence of absorption features consistent with a classification of A3-7 I. The behavior of the observed lines indicates an origin in the mass donor. The observed radial velocity variations are in anti-phase to the disk, the absorption lines strengthen at mid-eclipse when the donor star is expected to contribute its maximum percentage of the total flux, and
Detection of Diffuse Interstellar Bands in the Magellanic Clouds Ehrenfreund, P.; Cami, J.; Jimenez-Vicente, J.; Foing, B.H.; Kaper, L.; van der Meer, A.; Cox, N.L.J.; d' Hendecourt, L.; Maier, J.P.; Salama, F.ABSTRACT With the Ultraviolet Visual Echelle Spectrograph mounted at the Very Large Telescope, we have observed at unprecedented spectral resolution the absorption spectrum toward reddened stars in the Magellanic Clouds over the wavelength range of 3500-10500 Å . This range covers the strong transitions associated with neutral and charged large carbon molecules of varying sizes and structures. We report the first detection of diffuse interstellar bands (DIBs) at 5780 and 5797 Å in the Small Magellanic Cloud and the variation of the 6284 Å DIB toward several targets in the Large Magellanic Cloud. The variation of DIBs in the Magellanic Clouds compared with Galactic targets may be governed by a combination of the different chemical processes prevailing in low-metallicity regions and the local environmental conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.