A photometric survey of stars with circumstellar material

Abstract

Abstract. We present the result of a follow-up Strömgren photometric survey of sixteen southern bright stars with circumstellar material, in order to detect possible weak photometric variations. We found new variations of the β Pictoris brightness from 1999 to 2002 with a weak long-term variation of ∼−0.8 × 10 −3 mag per year, over about 3 years. These variations look similar to those seen from 1975 to 1981 and from 1995 to 1998(Nitschelm et al. 2000. They can be due to differential occultation by dust inhomogeneities transiting the star through the years. We detected new periodic variations for HD 256 (HR 10) with periods ranging from 0.35 day to 6.69 days during several months. These variations may also be interpreted in terms of variable obscuration due to structures in the circumstellar disk suspected to be surrounding this star.

Morphology of the very inclined debris disk around HD 32297

“…To be consistent with the slopes shown in Fig. 6, we adopt α out = −5 in H. This value is consistent with the predictions of Lecavelier des Etangs et al (1996) for a circular ring of planetesimals producing dust with collisions and expelled by the radiation pressure. It is also similar to the slopes measured in the debris disk around β Pic (Golimowski et al 2006).…”

Is β Pictoris b the transiting planet of November 1981?

“…Because the northeast side of the gas disk is receding (Olofsson et al 2001;Brandeker et al 2004), one can guess that if observed in 2003 in quadrature, the planet should have passed in front of the star in the years around 1999 and 1983. This is an attractive coincidence with the possible observation of a planetary transit on November 10, 1981 (Lecavelier des Etangs et al 1994Etangs et al , 1995 which might have been caused by the same planet.…”

“…The β Pic disk is constrained to be inclined by only a few degrees (Lecavelier des Etangs et al 1993;Kalas et al 1995;Heap et al 2000;Golimowski et al 2006). If a planet is located within the disk, the transit probability is enhanced by this favorable configuration.…”

“…In the photometric measurements obtained by Geneva observatory between 1975 and1982, the light curve of β Pic showed significant photometric variations in November 1981 with a transit-like event on November 10 (Lecavelier des Etangs et al 1994Etangs et al , 1995. The probability that these variations are produced by statistical noise is less than 10 −5 (Lecavelier des Etangs et al 1995).…”

“…The probability that these variations are produced by statistical noise is less than 10 −5 (Lecavelier des Etangs et al 1995). These photometric variations were attributed to the transit of a giant comet (Lamers et al 1997) or a planet orbiting at several AUs (Lecavelier des Etangs et al 1994Etangs et al , 1995Etangs et al , 1997a. From analysis of the transit light curve, Lecavelier des Etangs et al (1997a) obtained the following constraints on the possible transiting planet: 1) the period of the planet must be less than about 19 year to be compatible with measurements of November 10 and 11; 2) the radius of the transiting object must be 2.3 to 4.0 times the radius of Jupiter to be compatible with the transit ingress in the light curve.…”