Ultraviolet photometry from the orbiting astronomical observatory. XVI. The stellar Lyman-alpha absorption line.
1974; IOP Publishing; Volume: 191; Linguagem: Inglês
10.1086/153007
ISSN1538-4357
Autores Tópico(s)Astronomical Observations and Instrumentation
Resumoview Abstract Citations (47) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Ultraviolet photometry from the Orbiting Astronomical Observatory. XVI. The stellar Lyman-alpha absorption line. Savage, B. D. ; Panek, R. J. Abstract The Wisconsin far-ultraviolet spectrometer on OAO-2 has observed the stellar La line at 1216 A in 29 lightly reddened stars ranging in spectral type from B2.5 to B9. For these stars, La equivalent widths have been derived by fitting synthetic profiles to the observed spectra. This procedure corrects for a small amount of blending between the stellar La line and a stellar Si "`line at 1206.5 A. The final equivalent widths, which include a small correction for interstellar La absorption, range from 15 A at spectral type B2. 5 to 65 A at spectral type B8. For the late-B stars the La line removes 2 to 3 percent of the total stellar flux. For our sample of stars (24 dwarfs, four giants, and one supergiant) the strength of La correlates quite well with measures of the Balmer discontinuity and Balmer line strengths. With the exception of the one supergiant, luminosity classification does not appear to strongly influence the La line strength. The observed La equivalent widths have been compared with the predictions of Mihalas's grid of non-LTE model atmospheres. With the possible exception of the stars of high luminosity, the calculations and observations are in basic agreement over their range of overlap (T6 = 1 5, ,000 K). We have shown that in a number of cases the stellar La line influences the interstellar column densities reported in the OAO-2 interstellar La survey. Because of this contamination the OAO-2 interstellar column densities toward lightly reddened B2 and B1 .5 stars should be regarded as only upper limits. Subject headings: early-type stars - interstellar matter - line profiles - spectra, ultraviolet Publication: The Astrophysical Journal Pub Date: August 1974 DOI: 10.1086/153007 Bibcode: 1974ApJ...191..659S full text sources ADS | data products SIMBAD (90) Related Materials (37) Part 1: 1970ApJ...161..377C Part 2: 1972ApJ...171..293B Part 3: 1972ApJ...172..755W Part 4: 1972ApJ...178..727D Part 5: 1972ApJ...178..189B Part 6: 1972ApJ...178..495D Part 7: 1973ApJ...179..527M Part 8: 1973ApJ...185..577L Part 9: 1973ApJ...185..921E Part 10: 1974ApJ...189..303G Part 11: 1974ApJ...187..521D Part 12: 1973ApJ...186..939H Part 13: 1974ApJ...187..197S Part 14: 1974ApJ...187..243J Part 15: 1974ApJ...190..319L Part 17: 1975ApJ...195..121D Part 18: 1975ApJ...197..379E Part 19: 1975ApJ...199...92S Part 20: 1976ApJ...203..410B Part 21: 1976Ap&SS..41..121K Part 22: 1976ApJ...206..167P Part 23: 1976ApJ...208..135L Part 24: 1976ApJ...208...64L Part 25: 1979ApJ...228...95C Part 26: 1977ApJ...211..207H Part 27: 1978ApJ...219..947L Part 28: 1978ApJ...222..909W Part 29: 1978ApJ...220..582E Part 30: 1979ApJS...39..195C Part 31: 1979ApJ...229..994G Part 32: 1980ApJS...43..501C Part 33: 1979ApJ...228..419W Part 34: 1980ApJ...236..798W Part 35: 1980ApJS...42..283M Part 36: 1984ApJ...281..774C Part 37: 1982ApJ...256....1C Part 38: 1982AJ.....87..849D
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