HIGH-RESOLUTION SPECTROSCOPY OF THE B[e] STAR MWC 645

Optical high-resolution spectroscopic observations of the emission-line star MWC645 are presented. The spectrum exhibits strong variable double-peaked Balmer emission lines as well as low-excitation emission lines of FeII, [FeII], and [OI] which are signatures of the B[e] phenomenon, while lines of helium have not been found. In addition to the emission lines, for the first time we identified absorption lines of neutral metals (e.g., LiI 6708 A, CaI 6717 A, and a number of FeI and TiI lines) that indicate the presence of a cool component in the system. The heliocentric radial velocity measured in our best spectrum was found to be −65.1±1.0 kms −1 for the emission lines and −23.2±0.4 kms −1 for the absorption lines. Using a combination of photometric and spectroscopic data as well as the Gaia EDR3 distance (D=6.5±0.9 kpc), we disentangled the component contributions and estimated their temperatures and luminosities (∼15000 K and ∼4000 K, log L/L ? = 3.8±0.2 and 2.8±0.2 for the hot and cool component, respectively).

Details of the Classification of Symbiotic Stars: The Case of the Symbiotic Nova AG Peg

We analyze archival and modern spectroscopic and photometric observations of the oldest known symbiotic nova AG Peg. Its new outburst (which began in 2015 June) differs greatly from the first one (which occurred in the mid-1850s). Fast photometric evolution of the new outburst is similar to that of Z And-type outbursts. However, the SED of AG Peg during the 2015 outburst, as well as during the quiescence, can be fitted by a standard three-component model (cool component + hot component + nebula), which is not common for an Z And-type outburst.

Two-temperature Debris Disks: Signposts for Directly Imaged Planets?

This work considers debris disks whose spectra can be modelled by dust emission at two different temperatures. These disks are typically assumed to be a sign of multiple belts, but only a few cases have been confirmed via high resolution observations. We derive the properties of a sample of two-temperature disks, and explore whether this emission can arise from dust in a single narrow belt. While some two-temperature disks arise from single belts, it is probable that most have multiple spatial components. These disks are plausibly similar to the outer Solar System's configuration of Asteroid and Edgeworth-Kuiper belts separated by giant planets. Alternatively, the inner component could arise from inward scattering of material from the outer belt, again due to intervening planets. For either scenario, the ratio of warm/cool component temperatures is indicative of the scale of outer planetary systems, which typically span a factor of about ten in radius.

Symbiotic Nova PU Vul - 33 Years of Observations

We present UBVRI light curves of the symbiotic nova PU Vul after its outburst in 1978. Three observed eclipses of the hot component by the cool one were used to determine the ephemeris of the binary system as JD (Min I) = 2444550(15) + 4897(10) × E days. the 194-day shift of the secondary minimum from its expected positions in 2001 suggests the eccentricity of the binary orbit. Period analysis of the VRI photometry improved the pulsation period of the cool AGB variable in the system to P = 217.7 days. Pulsation of the cool component is detected only in the phases around the primary minimum, when the visible hemisphere of the AGB star is not influenced by the interaction with the hot component.

Spectroscopic Monotoring of the Symbiotic Star BX Monocerotis

Low resolution optical spectra of the symbiotic star BX Monocerotis in the 3500-9000 Å range obtained during 1999–2010 are described. the spectrum of BX Mon at all phases is dominated by the cool component, with a red continuum and TiO absorption. Emission lines, predominantly due to HI, He I, He II, Fe II, Ca II and [O III] are seen superimposed on the spectrum of the M5III star, with variable intensities. the observed variations in the spectra seem to be correlated with the orbital phases.

Modeling of the IR Light Curves of the Symbiotic Recurrent Nova T CrB

We analyze the results of our IR photometric monitoring of T CrB during 1987-2003 and describe the ellipsoidal variability of the Roche lobe filling cool component. We obtain limits to the binary inclination of i ∈ [50,60] deg and binary mass ratio q ∈ [0.4,2] (90 per cent confidence). The mass of the hot component is therefore 1.3-3 M⊙. If the hot component of T CrB is a white dwarf, its mass will be near the Chandrasekhar limit.