Spectral synthesis of circumstellar disks - application to white dwarf debris disks

Gas and dust disks are common objects in the universe and can be found around various objects, e.g. young stars, cataclysmic variables, active galactic nuclei, or white dwarfs. The light that we receive from disks provides us with clues about their composition, temperature, and density. In order to better understand the physical and chemical dynamics of these disks, self-consistent radiative transfer simulations are inevitable. Therefore, we have developed a 1+1D radiative transfer code as an extension to the well-established model atmosphere code \verb!PHOENIX!. We will show the potential of the application of our code to model the spectra of white dwarf debris disks.Comment: 4 pages, 4 figures, to appear in: Proceedings of the 16th European Workshop on White Dwarf

Ideals and finiteness conditions for subsemigroups

In this paper we consider a number of finiteness conditions for semigroups related to their ideal structure, and ask whether such conditions are preserved by sub- or supersemigroups with finite Rees or Green index. Specific properties under consideration include stability, D=J and minimal conditions on ideals.Comment: 25 pages, revised according to referee's comments, to appear in Glasgow Mathematical Journa

A multi-wavelength view on the dusty Wolf-Rayet star WR 48a

We present results from the first attempts to derive various physical characteristics of the dusty Wolf-Rayet star WR 48a based on a multi-wavelength view of its observational properties. This is done on the basis of new optical and near-infrared spectral observations and on data from various archives in the optical, radio and X-rays. The optical spectrum of WR 48a is acceptably well represented by a sum of two spectra: of a WR star of the WC8 type and of a WR star of the WN8h type. The strength of the interstellar absorption features in the optical spectra of WR 48a and the near-by stars D2-3 and D2-7 (both members of the open cluster Danks 2) indicates that WR 48a is located at a distance of ~4 kpc from us. WR 48a is very likely a thermal radio source and for such a case and smooth (no clumps) wind its radio emission suggests a relatively high mass-loss rate of this dusty WR star (dM/dt = a few x 10^(-4) solar masses per year). Long timescale (years) variability of WR 48a is established in the optical, radio and X-rays. Colliding stellar winds likely play a very important role in the physics of this object. However, some LBV-like (luminous blue variable) activity could not be excluded as well.Comment: Accepted for publication in MNRAS; 16 pages, 16 figures, 6 table

Uji Aktivitas Anti Jamur Ekstrak Kayu Manis (Cinnamomum Burmanii Blume) terhadap Jamur Candida Albicans

Cinnamon contains essential oils those can act as anti-fungal. This study aims to determine the inhibition of fungal growth of cinnamon extract against candida albicans. The study was conducted using a sample of cinnamon extract in some solvents those were distilled water, ethanol, and hexane, and the suspension of the fungus candida albicans which has been synchronized with the MC.Farland standard solution, and performed with pitting method. The results showed that the inhibition of cinnamon extract in hexane against candida albicans fungus was greater than in distilled water and ethanol. Hexane was the most dominant solvent to extract oil contained in cinnamon and some seeds, and also easy to evaporate and separate to produce more essential oils. Based on the observations the percentage of fungal inhibition of cinnamon extracts in distilled water, ethanol, and hexane solvents were, 3.19%, 0% and 100%, respectively

New observations of cool carbon stars in the halo

We report new results of our search for rare, cool carbon stars located at large distances from the galactic plane. Eighteen new C stars were discovered. Six are remarkable by showing the two peculiarities of a strong infrared excess at 12 microns and a large height above the Galactic plane, from 1.7 to 6 kpc. The number of C stars with these properties has been increased to 16. Mass-loss rates were tentatively estimated by assuming that all these 16 stars are Miras and by using the correlation between Mdot and the K-12 colour index. It is found that several stars have large mass loss, with median Mdot around 4E-06 solar mass per year. It would be desirable to detect their CO emission ... Eight stars might be at more than 30 kpc from the Sun, and two at the unprecedented distance of 150 kpc (this abstract has been abridged).Comment: 15 pages; accepted by Astronomy and Astrophysic

Identifikasi Zat Warna Rhodamin B pada Lipstik yang Beredar di Pasar Kota Palu

Rhodamine B is a synthetic dye used for colouring of paper, textiles and inks. Rhodamine B is able to cause an irritation of the respiratory tract, liver damage and as a carcinogenic substance. The use of dyes aims to obtain more attractive colour. This study aims to identify the rhodamine B on lipsticks in the market in Palu City. The dye was determined using thin layer chromatography (TLC) through qualitative and quantitative tests. The results showed that all lipstick samples were negative containing rhodamine B. Based on qualitative test by TLC did not found similar Rf 0.72 cm confirming the reference solution for rhodamine B, where the value of Rf on consecutive samples were 1A code samples obtained value Rf = 0.58 cm, the sample code 2A obtained value Rf = 0.46 cm, the sample code 3A Rf value = 0.68 cm, the sample code 4A obtained Rf = 0.65 cm, code samples obtained 1B Rf = 0.49 cm, and the sample code 2B obtained value Rf = 0.50 cm. Based on this study it can be concluded that all 6 lipstick samples tested did not contain rhodamine B

Spectral modeling of gaseous metal disks around DAZ white dwarfs

We report on our attempt for the first non-LTE modeling of gaseous metal disks around single DAZ white dwarfs recently discovered by Gaensicke et al. and thought to originate from a disrupted asteroid. We assume a Keplerian rotating viscous disk ring composed of calcium and hydrogen and compute the detailed vertical structure and emergent spectrum. We find that the observed infrared CaII emission triplet can be modeled with a hydrogen-deficient gas ring located at R=1.2 R_sun, inside of the tidal disruption radius, with Teff about 6000 K and a low surface mass density of about 0.3 g/cm**2. A disk having this density and reaching from the central white dwarf out to R=1.2 R_sun would have a total mass of 7 10**21 g, corresponding to an asteroid with about 160 km diameter.Comment: Proceedings, 16th European White Dwarf Workshop, Barcelona, 200

The Mid-Infrared Emitting Dust Around AB Aur

Using the Keck I telescope, we have obtained 11.7 micron and 18.7 micron images of the circumstellar dust emission from AB Aur, a Herbig Ae star. We find that AB Aur is probably resolved at 18.7 micron with an angular diameter of 1.2" at a surface brightness of 3.5 Jy/arcsec^2. Most of the dust mass detected at millimeter wavelengths does not contribute to the 18.7 micron emission, which is plausibly explained if the system possesses a relatively cold, massive disk. We find that models with an optically thick, geometrically thin disk, surrounded by an optically thin spherical envelope fit the data somewhat better than flared disk models.Comment: ApJ in press, 4 color figure