The periodicity of the eta Carinae events

DAMINELLI, A.; HILLIER, D. J; CORCORAN, M. F.; STAHL, O.,; LEVENHAGEN, R. S.,; LEISTER, N. V.,; GROH, J. H.,; TEODORO, M.,; ALBACETE COLOMBO, J. F.,; GONZALEZ, F.,; ARIAS, J.; LEVATO, H.,

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Blackwell

Lugar: Cambridge; Año: 2008 vol. 384 p. 1649 - 1656

0035-8711

Extensive spectral observations of ç Carinae over the lastcycle, and particularly around the 2003.5 low-excitationevent, have been obtained. The variability of both narrow andbroad lines, when combined with data taken from two earliercycles, reveal a common and well-defined period. We havecombined the cycle lengths derived from the many lines in theoptical spectrum with those from broad-band X-rays, opticaland near-infrared observations, and obtained a period lengthof Ppres = 2022.7 +/- 1.3 d.Spectroscopic data collected during the last 60 yr yield anaverage period of Pavg = 2020 +/- 4 d, consistent with thepresent-day period. The period cannot have changed by morethan ÄP/P = 0.0007 since 1948. This confirms the previousclaims of a true, stable periodicity, and gives strongsupport to the binary scenario. We have used thedisappearance of the narrow component of HeI 6678 to definethe epoch of the Cycle 11 minimum, T0 = JD2452819.8. The nextevent is predicted to occur on 2009 January 11 (+/-2 d). Thedates for the start of the minimum in other spectral featuresand broad-bands are very close to this date, and have well-determined time-delays from the HeI epoch.