Spectroscopic observations of the eclipse of 31 Cygni.

Abstract

view Abstract Citations (2) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic observations of the eclipse of 31 Cygni. McLaughlin, Dean B. Abstract The eclipse of 31 Cygni in 1951 showed absorption effects as spectacular as those of Aurigae, and practically identical in appearance. Numerous spectrograms were obtained during ingress in August and a continuous run for 12 days during egress in October. From spectrograms taken August 12.1 and October 13.0 UT, it was first estimated that second contact occurred Aug. 12.2 and third contact Oct. 12.8, the eclipse being certainly deeper at the ingress observation. Data communicated by E. F. Carpenter, however, suggest the time of third contact may need revision to Oct. 12.5. The atmosphere was unsymmetrical in the same direction as that of Aurigae.' The absorption effects were stronger at a given time interval before second contact than at an equal interval after third contact. The maximum difference, at 7 days from totality, corresponded to nearly two days' motion of the companion. Spectrograms during egress were measured in an attempt to determine rotation of the giant K star. During the first five days, most lines had negative residuals of about 6 km$sec, while Caii had negative residuals of 12 km sec for seven days. However, after the first few days, the velocities quickly increased algebraically, showing positive residuals of about the same amount for several days. The duration of the positive displacements was different for different lines, being longest for Cali. Apparently the observations are strongly affected by atmospheric currents, and no conclusions should be drawn concerning rotation. By October 25.2 UT, the measured lines, with the exception of Caii, were nearly all free of eclipse absorption effects and agreed with the orbital velocity. Cail showed positive residuals as great as i8 km sec from November 28 to December 8. This is attributed to high prominences. Curves of "atmospheric eclipse intensity" were determined for 31 Cygni, 32 Cygni and VV Cephei by direct comparison with a standard set of Aurigae, eclipse of 1947-48. Except for VV Cephei, the spectra and forms of curves are similar, indicating nearly identical atmospheric structure. When the time scales of 31 and 32 Cygni are divided by 3.3 and 5.25 respectively, their curves are almost superimposed on that of Aurigae for intensities of 3 and greater. For lesser intensities the duration of atmospheric eclipse was about 30 per cent longer for 32 Cygni and 50 per cent longer for 31 Cygni, corresponding to proportionally greater extent of the outer chromospheres of these stars as compared with Aurigae. VV Cephei had an irregular curve. A time-scale factor of 55 reduces it to roughly the scale of Aurigae, but the outer chromosphere had enormously greater extent. I.Ap. J. io8, 237, 1948. Michigan University Observatory, Ann Arbor, Michigan. Publication: The Astronomical Journal Pub Date: April 1952 DOI: 10.1086/106687 Bibcode: 1952AJ.....57...18M full text sources ADS | data products SIMBAD (4)