The Discovery of the Most Metal-Rich White Dwarf: Composition of a Tidally Disrupted Extrasolar Dwarf Planet

Cool white dwarf stars are usually found to have an outer atmosphere that is practically pure in hydrogen or helium. However, a small fraction have traces of heavy elements that must originate from the accretion of extrinsic material, most probably circumstellar matter. Upon examining thousands of Sloan Digital Sky Survey spectra, we discovered that the helium-atmosphere white dwarf SDSS J073842.56+183509.6 shows the most severe metal pollution ever seen in the outermost layers of such stars. We present here a quantitative analysis of this exciting star by combining high S/N follow-up spectroscopic and photometric observations with model atmospheres and evolutionary models. We determine the global structural properties of our target star, as well as the abundances of the most significant pollutants in its atmosphere, i.e., H, O, Na, Mg, Si, Ca, and Fe. The relative abundances of these elements imply that the source of the accreted material has a composition similar to that of Bulk Earth. We also report the signature of a circumstellar disk revealed through a large infrared excess in JHK photometry. Combined with our inferred estimate of the mass of the accreted material, this strongly suggests that we are witnessing the remains of a tidally disrupted extrasolar body that was as large as Ceres.Comment: 7 pages in emulateapj, 5 figures, accepted for publication in Ap

Non-LTE models for the gaseous metal component of circumstellar discs around white dwarfs

Gaseous metal discs around single white dwarfs have been discovered recently. They are thought to develop from disrupted planetary bodies. Spectroscopic analyses will allow us to study the composition of extrasolar planetary material. We investigate in detail the first object for which a gas disc was discovered (SDSS J122859.93+104032.9). Therefor we perform non-LTE modelling of viscous gas discs by computing the detailed vertical structure and line spectra. The models are composed of carbon, oxygen, magnesium, silicon, calcium, and hydrogen with chemical abundances typical for Solar System asteroids. Line asymmetries are modelled by assuming spiral-arm and eccentric disc structures as suggested by hydrodynamical simulations. The observed infrared Ca II emission triplet can be modelled with a hydrogen-deficient metal gas disc located inside of the tidal disruption radius, with an effective temperature of about 6000 K and a surface mass density of 0.3 g/cm^2. The inner radius is well constrained at about 0.64 Solar radii. The line profile asymmetry can be reproduced by either a spiral-arm structure or an eccentric disc, the latter being favoured by its time variability behaviour. Such structures, reaching from 0.64 to 1.5 Solar radii, contain a mass of about 3 to 6*10^21 g, the latter equivalent to the mass of a 135-km diameter Solar System asteroid.Comment: 7 pages, 10 figures, accepted for publication in A&

Discovery of shocked H2 around OH 231.8+4.2

We present K-band integral field observations of the circumstellar envelope of the evolved star OH 231.8+4.2. Spatial and spectral information were simultaneously acquired using the Sinfoni integral field unit, with adaptive optics, on the Very Large Telescope. The observations reveal the discovery of H2 emission (1) around the centre of the nebula and (2) located in clumps along the Western side of the Northern lobe, presumably associated with the strong shocks that stimulate the previously reported H-alpha emission at the same location. An observed H2 1-0/2-1S(1) line ratio of 8.3+/-1.9 was calculated for the central field, a value consistent with shock excitation.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter

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

Pengaruh Ekstrak Tanaman Putri Malu (Mimosa Pudica Linn) terhadap Penurunan Kadar Glukosa Darah pada Mencit (Mus Musculus)

The research aim is to determine the effect of mimosa plant (mimosa pudica Linn) to reduce blood sugar levels in mice and determining the effective concentration of mimosa plant extracts as an alternative to decrease blood sugar levels. The extract is produced by the infusion method. The animal test used is male mice with amount 18 mice that induced by EDTA (ethylene diamine tetraacetic acid). Mice are divided into 6 groups randomly with different treatment. The group I, II, III and IV were given the mimosa plant extract with a concentration of 10, 20, 30, and 40% (w/v) respectively while group V is given glibenclamide suspension as positive control (+) and group VI is given Na-CMC 1% as negative control (-). Data were analyzed using the statistical test analysis of variance (ANOVA) and then followed by Duncan test. The results showed that the mimosa plant extract contains flavonoids, alkaloids, and tannins. In preclinical testing of mimosa plant extract proven to reduce blood sugar levels in mice and the most effective concentration is a concentration of 20% (w/v) with significantly α = 0.05

Uji Aktivitas Antioksidan Ekstrak Daun Patikan Kebo (Euphorbia Hirta L.)

Patikan kebo (euphorbia hirta L.) is a plant commonly found in the tropical regions. The objectiveof this research was to determine the antioxidant activity of Patikan kebo leaves extract and tocategorize the strength of the extract in blocking free radicals. This research was conducted by laboratoryexperiment using maceration extraction techniques. Antioxidant activity of the extract was tested using1,1-diphenyl-2-pikrilhidrazil (DPPH). Variation concentrations of the used of Patikan kebo leavesextract and vitamin c as a positive control used for analysis were of 20 ppm, 40 ppm, 60 ppm, and 80ppm. Analysis of the sample was conducted using spectronic UV-Vis. The result showed that Patikankebo leaves extract was a very strong antioxidant. It was proved by the number of IC50 less then 50. Thecalculation of IC50 of patikan kebo leaves extract was 11.50 mg/L

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

High angular resolution N-band observation of the silicate carbon star IRAS08002-3803 with the VLTI/MIDI instrument

We present the results of N-band spectro-interferometric observations of the silicate carbon star IRAS08002-3803 with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO). The observations were carried out using two unit telescopes (UT2 and UT3) with projected baseline lengths ranging from 39 to 47 m. Our observations of IRAS08002-3803 have spatially resolved the dusty environment of a silicate carbon star for the first time and revealed an unexpected wavelength dependence of the angular size in the N band: the uniform-disk diameter is found to be constant and ~36 mas (72 Rstar) between 8 and 10 micron, while it steeply increases longward of 10 micron to reach ~53 mas (106 Rstar) at 13 micron. Model calculations with our Monte Carlo radiative transfer code show that neither spherical shell models nor axisymmetric disk models consisting of silicate grains alone can simultaneously explain the observed wavelength dependence of the visibility and the spectral energy distribution (SED). We propose that the circumstellar environment of IRAS08002-3803 may consist of two grain species coexisting in the disk: silicate and a second grain species, for which we consider amorphous carbon, large silicate grains, and metallic iron grains. Comparison of the observed visibilities and SED with our models shows that such disk models can fairly -- though not entirely satisfactorily -- reproduce the observed SED and N-band visibilities. Our MIDI observations and the radiative transfer calculations lend support to the picture where oxygen-rich material around IRAS08002-3803 is stored in a circumbinary disk surrounding the carbon-rich primary star and its putative low-luminosity companion.Comment: 15 pages, 8 figures, accepted for publication in A&