Showing papers by "Lee Hartmann published in 1988"
TL;DR: In this article, the authors calculate du spectre theorique du disque d'accretion and comparaisons des resultats avec les observations of FU Ori and V1057 Cyg.
Abstract: Calcul du spectre theorique du disque d'accretion et comparaisons des resultats avec les observations de FU Ori et V1057 Cyg afin de tester l'hypothese du disque pour ces objets
125 citations
TL;DR: In this article, the results of an optical spectroscopic and photometric study of the star formation region Lynds 1551 and the young stellar object IRS 5 and a high-resolution spectra of the Herbig-Haro (HH) objects associated with the outflow from this region are reported.
Abstract: The results of an optical spectroscopic and photometric study of the star formation region Lynds 1551 and the young stellar object IRS 5 and a high-resolution spectroscopic study of the Herbig-Haro (HH) objects associated with the outflow from this region are reported. The results further establish IRS 5 as the source of the reflected light in the region. Spectral studies suggest that the spectrum of IRS 5 is dominated by the light from an accretion disk analogous to those characterizing objects of the rare class of FU Orionis objects. Analysis of high and medium resolution spectra of the optical jet emanating from IRS 5 strongly suggest that the jet HH objects are the bow shock interfaces between two winds coming from the IRS 5 region. The high-velocity wind is inferred to have a velocity of 440 km/s, and is identified as the stellar wind. High-density clumps in the stellar wind shock a lower-density, but much more pervasive second wind which has an inferred velocity of about 160 km/s. 69 references.
61 citations
TL;DR: In this article, IUE observations of five blue, low-metallicity, star-forming galaxies sufficiently redshifted to permit detection of Lyman-alpha are reported.
Abstract: IUE observations of five blue, low-metallicity, star-forming galaxies sufficiently redshifted to permit detection of Lyman-alpha are reported. The galaxies with metallicities 0.1 time solar or more have weak or absent Lyman-alpha emission. There is evidence for increasing Lyman-alpha emission with decreasing metallicity. The reduction of Lyman-alpha fluxes from recombination values is attributed to absorption of multiply scattered Lyman-alpha by dust.
51 citations
TL;DR: An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented in this paper, which provides a more accurate calculation of the ionization state of material entering the bow.
Abstract: An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented. The modifications provide a more accurate calculation of the ionization state of material entering the bow shock. The revised preionization does not drastically affect the emission-line predictions for a 200 km/s bow shock model, though the effects will be more severe for slower shock velocities. The line profiles of the new models resemble the observed profiles somewhat more closely, and the relative emission-line intensities typically differ by 30 percent from those predicted by the older models. The models agree well with new IUE spectra and existing optical data for HH 2A-prime.
26 citations
01 Jan 1988
TL;DR: In this paper, observational constraints on disk accretion in young stellar objects were reviewed and implications of this phenomenon for early stellar evolution were discussed, and the implications of the observed constraints were discussed.
Abstract: This article reviews observational constraints on disk accretion in young stellar objects, and discusses implications of this phenomenon for early stellar evolution.
15 citations
TL;DR: In this paper, the observed total luminosity is compared quantitatively with an estimate of the stellar luminosity for a sample of 59 low-mass young stellar objects (YSOs) in the Taurus-Auriga complex.
Abstract: This paper presents a statistical study in which the observed total luminosity is compared quantitatively with an estimate of the stellar luminosity for a sample of 59 low-mass young stellar objects (YSOs) in the Taurus-Auriga complex. In 13 of the analyzed YSOs, luminosity excesses greater than 0.20 are observed together with greater than 0.6 IR excesses, which typically contribute the bulk of the observed excess luminosity and are characterized by spectral energy distributions which are flat or rise toward long wavelengths. The analysis suggests that YSOs showing the largest luminosity excesses typically power optical jets and/or molecular outflows or have strong winds, as evidenced by the presence of O I emission, indicating a possible correlation between accretion and mass-outflow properties.
15 citations
01 Jan 1988
TL;DR: In this paper, the authors summarize the evidence that pre-main sequence stars accreting material at high rates from a circumstellar disk, and describe estimates for mass loss rates derived from Hα and Na I D line profiles.
Abstract: This article reviews recent observations of the FU Orionis variables. We summarize the evidence that these systems are pre-main sequence stars accreting material at high rates from a circumstellar disk, and describe estimates for mass loss rates derived from Hα and Na I D line profiles.
2 citations