No abstract

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 Ppres= 2022.7 ± 1.3 d. Spectroscopic data collected during the last 60 yr yield an average period of Pavg= 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.

A full description of the 5.5‐yr low excitation events in η Carinae is presented. We show that they are not as simple and brief as previously thought, but a combination of two components. The first, the slow variation component, is revealed by slow changes in the ionization level of circumstellar matter across the whole cycle and is caused by gradual changes in the wind–wind collision shock‐cone orientation, angular opening and gaseous content. The second, the collapse component, is restricted to around the minimum, and is due to a temporary global collapse of the wind–wind collision shock. High‐energy photons (E > 16 eV) from the companion star are strongly shielded, leaving the Weigelt objects at low‐ionization state for more than six months. High‐energy phenomena are sensitive only to the collapse, low energy only to the slow variation and intermediate energies to both components. Simple eclipses and mechanisms effective only near periastron (e.g. shell ejection or accretion on to the secondary star) cannot account for the whole 5.5‐yr cycle. We find anti‐correlated changes in the intensity and the radial velocity of P Cygni absorption profiles in Fe iiλ6455 and He iλ7065 lines, indicating that the former is associated to the primary and the latter to the secondary star. We present a set of light curves representative of the whole spectrum, useful for monitoring the next event (2009 January 11).

FS CMa stars form a group of objects with the B[e] phenomenon that were previously known as unclassified B[e] stars or B[e] stars with warm dust (B[e]WD) until recently. They exhibit strong emission-line spectra and strong IR excesses, most likely due to recently formed circumstellar dust. These properties have been suggested to be due to ongoing or recent rapid mass exchange in binary systems with hot primaries and various types of secondaries. The first paper of this series reported an analysis of the available information about previously known Galactic objects with the B[e] phenomenon, the initial selection of the FS CMa group objects, and a qualitative explanation of their properties. This paper reports the results of our new search for more FS CMa objects in the IRAS Point Source Catalog. We present new photometric criteria for identifying FS CMa stars as well as the first results of our observations of nine new FS CMa group members. With this addition, the FS CMa group has now 40 members, becoming the largest among the dust-forming hot star groups. We also present nine objects with no evidence for the B[e] phenomenon, but with newly discovered spectral line emission and/or strong IR excesses.

In this paper we present radial velocity measurements &probable members of Trumpler 14, a very young open cluster associated with the Carina Nebula. We have found 4 double-line spectroscopic binaries and 2 single-line spectroscopic binaries. We have succeeded in deriving orbital elements for the SBIs. All the binaries are of potential astrophysical interest and are worth further observational efforts.