Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000mnras.313..789w&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 313, Issue 4, pp. 789-799.
Astronomy and Astrophysics
Astronomy
9
Binaries: Close, Binaries: Eclipsing, Stars: Individual: V Sge, Stars: Mass-Loss, Ultraviolet: Stars
Scientific paper
In this paper we present the first phase-resolved, high-resolution, UV spectroscopy of V Sge. HST GHRS observations were obtained covering 1.5 orbital cycles of V Sge in a low state. We covered the Heii 1640 line and the Civ 1550 doublet alternately, and also obtained one spectrum covering Mgii 2800. We create continuum and line flux light curves for the Heii and Civ spectra. A secular decrease in continuum and line strength occurs throughout our observation. The continuum light curves show a deep primary eclipse but no obvious secondary eclipse. The line fluxes show no significant changes during primary or secondary eclipses. The Heii line shows dramatic orbital variations in shape, but it is always purely an emission line, i.e., it shows no sign of a P Cygni profile. The Civ doublet shows a P Cygni profile in which the absorption vanishes at primary mid-eclipse. This locates the source of the P Cygni line in the primary star wind. The maximum velocity of absorption in the P Cygni profile is 700kms-1, much smaller than the HWZI of the Civ emission which is 1500kms-1. We attribute this to the presence of a broad Civ emission component underlying the primary star P Cygni profile. The Civ line also varies with orbital phase. In particular, the velocity at the blue edge of the absorption varies between -700 and -250kms-1 as a function of orbital phase. The red and blue peaks of the profile also vary around the orbit, with the red peak at maximum strength near phases 0.5-0.7. The blue peak is at maximum strength near phases 0.1-0.2. We can explain the detailed behaviour of the Heii and Civ line profiles in the context of a colliding wind model. Here the winds from each star collide, forming a shock which, due to the rapid rotation of the binary, is wrapped around both stars. The Civ P Cygni line comes from the primary star wind, which has a terminal velocity of ~700kms-1. We attribute the Heii line and the broad Civ emission to a fast, optically thin wind from the secondary star. This wind has a terminal velocity of ~1500kms-1. Interstellar lines due to Ci, Ci*, Civ, Mgii and Pii are detected. Column densities are measured for Ci and Pii. The Ci column density is used to estimate the hydrogen column density. We find that nH is of order 1019atomcm-2.
Lockley J. J.
Wood Janet H.
No associations
LandOfFree
UV spectroscopy of the peculiar binary V Sagittae in a low state does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with UV spectroscopy of the peculiar binary V Sagittae in a low state, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and UV spectroscopy of the peculiar binary V Sagittae in a low state will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1621897