Detection of the Red Giant Branch Stars in M82 Using the Hubble Space Telescope

We present color-magnitude diagrams and luminosity functions of stars in two halo regions of the irregular galaxy in M82, based on F555W and F814W photometry taken with the Hubble Space Telescope and Wide Field Planetary Camera 2. The I-band luminosity function shows a sudden jump at I~23.95 mag, which is identified as the tip of the red giant branch (TRGB). Adopting the Lee et al. (1993) calibration of the TRGB based on the RR Lyrae distances to Galactic globular clusters, we obtain the distance modulus of (m-M)_0=27.95 +- 0.14 (random) +- 0.16 (systematic) mag. This corresponds to a linear distance of 3.9 +- 0.3 (random) +- 0.3 (systematicf) Mpc, which agrees well with the distance of M81 deteremined from the HST observations of the Cepheid variable stars. In addition, we observe a significant number of stars apparently brighter than the TRGB. However, with the current data, we cannot rule out whether these stars are blends of fainter stars, or are indeed intermediate-age asymptotic giant branch stars.Comment: 8 figure

Unusual cavity shapes resulting from multistep mass transport controlled dissolution: Numerical simulation and experimental investigation with titanium using oxide film laser lithography

The shape evolution of cavities produced by multistep electrochemical micromachining is investigated both theoretically and experimentally. A boundary element code is used for 2D simulation of the shape evolution as a function of applied charge. A two-step process is simulated by assuming that metal dissolves from a small area at the bottom of a hemicylindrical groove protected by an insulating film. Similarly, the shape evolution in a three-step process is numerically simulated. The simulation shows that multistep isotropic etching can yield buried cavities with a narrow opening as well as large aspect ratio cavities. It also permits one to achieve aspect ratios larger than one. Electrochemical micromachining experiments were carried out with titanium using oxide film laser lithography (OFLL) for patterning the surface. Metal dissolution from the irradiated line features on the oxide was carried out in an electropolishing electrolyte starting from a flat surface or from preformed grooves. The resulting cavity shapes observed with a microscope corresponded well to the theoretical predictions. The experiments thus confirmed that isotropic etching involving two or three subsequent anodization-irradiation-dissolution steps can yield high aspect ratio cavities and partly occluded cavities. Possible implications of the present results for the shape evolution of corrosion pits are discusse

Neutrinos and Energetics of the Earth

We estimate terrestrial antineutrino and neutrino fluxes according to different models of Earth composition. We find large variations, corresponding to uncertainties on the estimated $U$, $Th$ and $K$ abundances in the mantle. Information on the mantle composition can be derived from antineutrino flux measurements after subtracting the crust contribution. This requires a good description of the crust composition in the region of the detector site. Measurements of terrestrial antineutrinos will provide a direct insight on the main sources of Earth's heat flow.Comment: 11 pages, RevTeX file. To appear on Phys. Lett. B. Addendum contains comparison with KamLAND result

Positive effective Q12 electrostrictive coefficient in perovskites

It is demonstrated that for classical perovskites such as BaTiO3, SrTiO3 and PbTiO3 electrostrictive strain induced by an electric field may not obey traditionally considered "extension along the field, contraction perpendicular to it" behavior if a sample is cut obliquely to the cubic crystallographic directions

Cepheid and Tip of the Red Giant Branch Distances To the Dwarf Irregular Galaxy IC10

We present color-magnitude diagrams and luminosity functions of stars in the nearby galaxy IC 10, based on VI CCD photometry acquired with the COSMIC prime-focus camera on the Palomar 5m telescope. The apparent I-band luminosity function of stars in the halo of IC 10 shows an identifiable rise at I~21.7 mag. This is interpreted as being the tip of the red giant branch (TRGB) at M_V~-4 mag. Since IC 10 is at a very low Galactic latitude, its foreground extinction is expected to be high and the uncertainty associated with that correction is the largest contributor to the error associated with its distance determination. Multi-wavelength observations of Cepheid variable stars in IC 10 give a Population I distance modulus of 24.1 +- 0.2 mag, which corresponds to a linear distance of 660 +- 66 kpc for a total line-of-sight reddening of E(B-V) = 1.16 +- 0.08 mag, derived self-consistently from the Cepheid data alone. Applying this Population I reddening to the Population II halo stars gives a TRGB distance modulus of 23.5 +- 0.2 mag, corresponding to 500 +- 50 kpc. We consider this to be a lower limit on the TRGB distance. Reconciling the Cepheid and TRGB distances would require that the reddening to the halo is $\Delta$E(B-V) = 0.31 mag lower than that into the main body of the galaxy. This then suggests that the Galactic extinction in the direction of IC10 is (B-V) ~ 0.85

The Extinction Towards the GRB970228 Field

We determine the local galactic extinction towards the field of gamma-ray burst GRB970228 using a variety of methods. We develop a maximum likelihood method for measuring the extinction by comparing galaxy counts in the field of interest to those in a field of known extinction, and apply this method to the GRB970228 field. We also measure the extinction by comparing the observed stellar spectral energy distributions of stars in the GRB970228 field to the spectral energy distribution of library spectra of the same spectral type. Finally we estimate the extinction using the Balmer emission line ratios of a galaxy in the GRB970228 field, and the neutral hydrogen column density and amount of infrared dust emission toward this field. Combining the results of these methods, we find a best-fit galactic extinction in the optical of $A_V=1.19^{+0.10}_{-0.17}$, which implies a a substantial dimming and change of the spectral slope of the intrinsic GRB970228 afterglow.Comment: 22 pages, including 7 figures. Submitted to Ap

Surface finish control by electrochemical polishing in stainless steel 316 pipes

Electrochemical machining (ECM) is a non-conventional machining process which is based on the localised anodic dissolution of any conductive material. One of the main applications of ECM is the polishing of materials with enhanced characteristics, such as high strength, heat-resistance or corrosion-resistance, i.e. electrochemical polishing. The present work presents an evaluation of the parameters involved in the ECM of Stainless Steel 316 (SS316) with the objective of predicting the resulting surface finish on the sample. The interest of studying ECM on SS316 resides on the fact that a repeatable surface finish is not easily achieved. ECM experimental tests on SS316 pipes of 1.5" (0.0381 m) diameter were conducted by varying machining parameters such as voltage, interelectrode gap, electrolyte inlet temperature, and electrolyte flow rate. The surface finish of the samples was then evaluated in order to find the significance of each of these parameters on the surface quality of the end product. Results showed that overvoltage, which is dependent on the interelectrode gap and the electrolyte temperature, is one of the main parameters affecting the surface finish; additionally there is a strong relationship between the resulting surface finish and the electrolyte flow. The interelectrode gap and inlet electrolyte temperature also affect the resulting surface finish but their influence was not so evident in this work. Finally, the variation of the electrolyte temperature during the process was found to have a great impact on the uniformity of the surface finish along the sample. We believe that this contribution enables the tailoring of the surface finish to specific applications while reducing manufacturing costs and duration of the ECM process

Properties, evolution and morpho-kinematical modelling of the very fast nova V2672 Oph (Nova Oph 2009), a clone of U Sco

V2672 Oph reached maximum brightness V=11.35 on 2009 August 16.5. With observed t2(V)=2.3 and t3(V)=4.2 days decline times, it is one of the fastest known novae, being rivalled only by V1500 Cyg (1975) and V838 Her (1991) among classical novae, and U Sco among the recurrent ones. The line of sight to the nova passes within a few degrees of the Galactic centre. The reddening of V2672 Oph is E(B-V)=1.6 +/-0.1, and its distance ~19 kpc places it on the other side of the Galactic centre at a galacto-centric distance larger than the solar one. The lack of an infrared counterpart for the progenitor excludes the donor star from being a cool giant like in RS Oph or T CrB. With close similarity to U Sco, V2672 Oph displayed a photometric plateau phase, a He/N spectrum classification, extreme expansion velocities and triple peaked emission line profiles during advanced decline. The full width at zero intensity of Halpha was 12,000 km/s at maximum, and declined linearly in time with a slope very similar to that observed in U Sco. We infer a WD mass close to the Chandrasekhar limit and a possible final fate as a SNIa. Morpho-kinematical modelling of the evolution of the Halpha profile suggests that the overall structure of the ejecta is that of a prolate system with polar blobs and an equatorial ring. The density in the prolate system appeared to decline faster than that in the other components. V2672 Oph is seen pole-on, with an inclination of 0+/-6 deg and an expansion velocity of the polar blobs of 4800 +900/-800 km/s. On the basis of its remarkable similarity to U Sco, we suspect this nova may be a recurrent. Given the southern declination, the faintness at maximum, the extremely rapid decline and its close proximity to the Ecliptic, it is quite possible that previous outbursts of V2672 Oph have been missed.Comment: in press in MNRA

Critical boron-doping levels for generation of dislocations in synthetic diamond

Defects induced by boron doping in diamond layers were studied by transmission electron microscopy. The existence of a critical boron doping level above which defects are generated is reported. This level is found to be dependent on the CH4 /H2 molar ratios and on growth directions. The critical boron concentration lied in the 6.5–17.0 X 10 20 at/cm3 range in the direction and at 3.2 X 1021 at/cm 3 for the one. Strain related effects induced by the doping are shown not to be responsible. From the location of dislocations and their Burger vectors, a model is proposed, together with their generation mechanism.6 page

UBVRI twilight sky brightness at ESO-Paranal

Twilight studies have proved to be important tools to analyze the atmospheric structure with interesting consequences on the characterization of astronomical sites. Active discussions on this topic have been recently restarted in connection with the evaluation of Dome C, Antarctica as a potential astronomical site and several site-testing experiments, including twilight brightness measurements, are being prepared. The present work provides for the first time absolute photometric measurements of twilight sky brightness for ESO-Paranal (Chile), which are meant both as a contribution to the site monitoring and as reference values in the analysis of other sites, including Dome C. The UBVRI twilight sky brightness was estimated on more than 2000 FORS1 archival images, which include both flats and standard stars observations taken in twilight, covering a Sun zenith distance range 94-112 deg. The comparison with a low altitude site shows that Paranal V twilight sky brightness is about 30% lower, implying that some fraction of multiple scattering has to take place at an altitude of a few km above the sea level.Comment: 11 pages, 13 figures, accepted for publication in A&