The periodicity of the η Carinae events

• Autores: Damineli, A.; Hillier, D. J.; Corcoran, M. F.; Stahl, O.; Levenhagen, R. S.; Leister, N. V.; Groh, J. H.; Teodoro, M.; Albacete Colombo, Juan Facundo; Gonzalez, F.; Arias, Julia Inés; Levato, Orlando Hugo; Grosso, M.; Morrell, Nidia Irene; Gamen, Roberto Claudio; Wallerstein, G.; Niemelä, Virpi Sinikka
• Año de publicación: 2008
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Astronómicas; Stars: binary; Stars: general; Stars: individual: eta Carinae
• Institución: Universidad Nacional de La Plata

Extensive spectral observations of η Carinae over the last cycle, and particularly around the 2003.5 low-excitation event, have been obtained. The variability of both narrow and broad lines, when combined with data taken from two earlier cycles, reveal a common and well-defined period. We have combined the cycle lengths derived from the many lines in the optical spectrum with those from broad-band X-rays, optical and near-infrared observations, and obtained a period length of P_pres = 2022.7 ± 1.3 d. Spectroscopic data collected during the last 60 yr yield an average period of P_avg = 2020 ± 4 d, consistent with the present-day period. The period cannot have changed by more than ΔP/P = 0.0007 since 1948. This confirms the previous claims of a true, stable periodicity, and gives strong support to the binary scenario. We have used the disappearance of the narrow component of He I 6678 to define the epoch of the Cycle 11 minimum, T₀ = JD 245 2819.8. The next event is predicted to occur on 2009 January 11 (±2 d). The dates for the start of the minimum in other spectral features and broad-bands are very close to this date, and have well-determined time-delays from the He I epoch.
Facultad de Ciencias Astronómicas y Geofísicas