Massimiliano Grosso

The periodicity of the η Carinae events

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 AP/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, To = 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.

Spectroscopy of the growing circumstellar disk in the Delta Scorpii Be binary

We present the results of a spectroscopic monitoring program of the binary system Delta Scorpii, whose primary became a Be star after the last periastron encounter in the Summer of 2000. The observations cover a period of 2 years (March 2001–June 2003) and are a continuation of our previous campaign reported in Miroshnichenko et al. (2001). We found that the emission-line spectrum was gradually strengthening over the whole monitoring period.

Properties of galactic B[e] supergiants - IV. Hen 3–298 and Hen 3–303

We present the results of optical and near-IR spectroscopic and near-IR photometric observations of the emission-line stars Hen3–298 and Hen3–303. Strong emission in the Ha line is found in both objects. The presence of Fe II and [O I] emission lines in the spectrum of Hen3–298 indicates that it is a B[e] star. The double-peaked CO line profiles, found in the infrared spectrum of Hen3–298, along with the optical line profiles suggest that the star is surrounded by a rotating circumstellar disc. Both objects also show infrared excesses, similar to those of B[e] stars. The radial velocities of the absorption and emission lines as well as a high reddening level suggest that the objects are located in the Norma spiral arm at a distance of 3–4.5 kpc. We estimated a luminosity of log L/L? 5.1 and a spectral type of no earlier than B3 for Hen 3–298. Hen3–303 seems to be a less luminous B-type object (log L/L? 4.3), located in the same spiral arm.

Properties of galactic B[e] supergiants II. HDE 327083

The emission-line object HDE 327083 has long been considered to be one of the most luminous stars in the Milky Way. Nevertheless, no reliable physical parameters have been published for it. Our high-resolution optical spectroscopy revealed the presence of photospheric lines of a cool luminous companion. We detected significant antiphased radial velocity variations of the emission and absorption lines. The data obtained are still insufficient to derive a reliable orbital solution; however, the orbital period is most likely of the order of 6 months. We conclude that HDE 327083 is a binary system consisting of an early B-type primary and early F-type secondary, with luminosities log L/L� = 5.0 ± 0.4 and 4.2 ± 0.4, respectively, and whose orbital plane is viewed nearly edge-on. We also obtained new multicolour optical and infrared photometry of HDE 327083. From both the photometric and spectroscopic data, we found that the system is located at a distance of 1.5 ± 0.5 kpc. Most of the circumstellar gas seems to be orbiting the primary and is distributed in a mildly flattened envelope with a height scale and velocity decreasing outward from the star. We suggest that HDE 327083 represents an advanced evolutionary stage of a β Lyrae type binary.

The massive double-lined O-type binary HD 165052

We present a new optical spectroscopic study of the O-type binary HD 165052 based on high-and intermediate-resolution CCD observations. We re-investigated the spectral classification of the binary components, obtaining spectral types of 06.5 V and 07.5 V for the primary and secondary, respectively, finding that both stars display weak CIII A5696 emission in their spectra. We also determined a radial-velocity orbit for HD 165052 with a period of 2.95510 ′ 0.00001 d, and semi-amplitudes of 94.8 and 104.7 ′ 0.5 kms - 1 , resulting in a mass ratio Q = 0.9. From a comparison with previous radial-velocity determinations, we found evidence of apsidal motion in the system. Several signatures of wind-wind collision, such as phase-locked variability of the X-ray flux and the Struve-Sahade effect, are also considered. It was also found that the reddening in the region should be normal, in contrast with previous determinations.

Elemental abundance study of the CP star HD 206653

An analysis of the abundances of the Silicon star HD 206653 is presented using an ATLAS9 model atmosphere and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are solar or deficient except silicon which is overabundant by a factor of 5. The iron peak elements are all overabundant by factors between 10 and 50. Sr and Y are around 1000 times the solar values. Among the Rare Earths only Ce and Eu are identified; both are overabundant by large factors.

Confirmation of the Luminous Blue Variable Status of MWC 930

We present spectroscopic and photometric observations of the emission-line star MWC 930 (V446 Sct) during its long-term optical brightening in 2006–2013. Based on our earlier data we suggested that the object has features found in Luminous Blue Variables (LBV), such as a high luminosity (~3 105 ), a low wind terminal velocity (~140 km s−1), and a tendency to show strong brightness variations (1 mag over 20 years). For the last 7 years it has been exhibiting a continuous optical and near-IR brightening along with a change of the emission-line spectrum appearance and cooling of the star’s photosphere. We present the object’s -band light curve, analyze the spectral variations, and compare the observed properties with those of other recognized Galactic LBVs, such as AG Car and HR Car. Overall we conclude the MWC 930 is a bona fide Galactic LBV that is currently in the middle of an S Dor cycle.