Long-term Optical Monitoring of Eta Carinae. Multiband light curves for a complete orbital period

E. FERNÁNDEZ LAJÚS; C. FARIÑA; A.F. TORRES; M.A. SCHWARTZ; N. SALERNO; J.P. CALDERÓN; C. VON ESSEN; L.M. CALCAFERRO; F. GIUDICI; C. LLINARES; V. NIEMELA.

ASTRONOMY AND ASTROPHYSICS

EDP Sciences

Lugar: Les Ulis; Año: 2009 vol. 493 p. 1093 - 1097

0004-6361

The periodicity of 5.5 years of some observational events that occur in Eta Carinae is manifested in a wide wavelength range and has been associated to its binary nature. These events are supposed to take place when the binary components are near periastron. To record the previous periastron passage of Eta Car in 2003, we started an intensive ground-based optical photometric observing campaign. We continued observing the object with the intention of monitoring the photometric behavior and variability along the whole orbital cycle. Our observation program consists of daily differential photometry from CCD images, which are acquired using a 0.8 m telescope and a standard BVRI filter set at La Plata Observatory. The photometry includes the central object and the surrounding Homunculus nebula. We present in this paper the up-to-date results of our observing program, including homogeneous photometric data collected since 2003 to 2008. Our observations show that Eta Car continued increasing its brightness at the same rate since 1998. In 2006 it reached the brightest magnitude (V ~ 4.7) since about 1860s. The object suddenly reverted the brightening trend, fading to V = 5.0 at the beginning of 2007, and keeps in a quite steady state since then. Currently we continue with the photometric monitoring of Eta Carexpecting the next periastron passage, predicted for the beginning of 2009.