32,455 research outputs found
TMCalc - A fast code to derive Teff and [Fe/H] for FGK stars
We present a new direct spectroscopic calibration for a fast estimation of
the stellar metallicity [Fe/H]. These calibrations were computed using a large
sample of 451 solar-type stars for which we have precise spectroscopic
parameters derived from high quality spectra. The new [Fe/H] calibration is
based on weak Fe I lines, which are expected to be less dependent on surface
gravity and microturbulence, and require only a pre-determination of the
effective temperature. This temperature can be obtained using a previously
presented line-ratio calibration. We also present a simple code that uses the
calibrations and procedures presented in these works to obtain both the
effective temperature and the [Fe/H] estimate. The code, written in C, is
freely available for the community and may be used as an extension of the ARES
code. We test these calibrations for 582 independent FGK stars. We show that
the code can be used as a precise and fast indicator of the spectroscopic
temperature and metallicity for dwarf FKG stars with effective temperatures
ranging from 4500 K to 6500 K and with [Fe/H] ranging from -0.8 dex to 0.4 dex.Comment: 10 pages, 8 Figures, published in A&
Microwave oven fabricated hybrid memristor devices for non-volatile memory storage
© 2014 IOP Publishing Ltd. Novel hybrid non-volatile memories made using an ultra-fast microwave heating method are reported for the first time. The devices, consisting of aligned ZnO nanorods embedded in poly (methyl methacrylate), require no forming step and exhibit reliable and reproducible bipolar resistive switching at low voltages and with low power usage. We attribute these properties to a combination of the high aspect ratio of the nanorods and the polymeric hybrid structure of the device. The extremely easy, fast and low-cost solution based method of fabrication makes possible the simple and quick production of cheap memory cells
Two new bright Ae stars
Two newly identified Ae stars, nu Cyg and kappa UMa, were discovered in the
course of the Magnetic Survey of Bright MS stars (Monin et al. 2002). We pre
sent their Halpha profiles along with measurements of their equivalent width
and parameters of emission features. Emission in the Halpha line of nu Cyg is
variable on a time scale of 3 years. kappa UMa exhibits weak emission which is
rather stable. The emission is thought to arise from a circumstellar disk, and
we have estimated the size of that disk.Both new emission stars are IRAS
sources. Their IR color excesses are consistent with those of classical Ae
stars. Thus, nu Cyg and kappa UMa appear not to belong to the class of Herbig
Ae/Be stars. We argue that the frequency of Ae stars may be underestimated due
to the difficulty of detection of weak emission in some A stars.Comment: 6 pages,3 figures, submitted to A&
The behaviour of Sal’nikov’s reaction, P → A → B, in a spherical batch reactor with the diffusion of heat and matter
- …