Turbine blade metal temperature measurement with a sputtered thin film chromel-alumel thermocouple

A technique for fabricating Chromel and Alumel thin film thermocouples was developed. Turbine blade metal temperatures measured with the thin film thermocouple installation were compared with those of a reference sheathed (wire) thermocouple. Good agreement was obtained, and the results are encouraging

Discovery of a Magnetic DZ White Dwarf with Zeeman-Split Lines of Heavy Elements

A spectroscopic survey of previously-unstudied Luyten Half Second proper motion stars has resulted in the discoveries of two new cool magnetic white dwarfs. One (LHS 2273) is a routine DA star, T= 6,500K, with Zeeman-split H alpha and H beta, for which a simple model suggests a polar field strength of 18.5 MG viewed close to equator-on. However, the white dwarf LHS 2534 proves to be the first magnetic DZ showing Zeeman-split Na I and Mg I components, as well as Ca I and Ca II lines for which Zeeman components are blended. The Na I splittings result in a mean surface field strength estimate of 1.92 MG. Apart from the magnetic field, LHS 2534 is one of the most heavily-blanketed and coolest DZ white dwarfs at T ~ 6,000K.Comment: 7 pages, Astrophysical Journal (Letters), in pres

The Ages of the Thin Disk, Thick Disk, and the Halo from Nearby White Dwarfs

We present a detailed analysis of the white dwarf luminosity functions derived from the local 40 pc sample and the deep proper motion catalog of Munn et al (2014, 2017). Many of the previous studies ignored the contribution of thick disk white dwarfs to the Galactic disk luminosity function, which results in an erronous age measurement. We demonstrate that the ratio of thick/thin disk white dwarfs is roughly 20\% in the local sample. Simultaneously fitting for both disk components, we derive ages of 6.8-7.0 Gyr for the thin disk and 8.7 $\pm$ 0.1 Gyr for the thick disk from the local 40 pc sample. Similarly, we derive ages of 7.4-8.2 Gyr for the thin disk and 9.5-9.9 Gyr for the thick disk from the deep proper motion catalog, which shows no evidence of a deviation from a constant star formation rate in the past 2.5 Gyr. We constrain the time difference between the onset of star formation in the thin disk and the thick disk to be $1.6^{+0.3}_{-0.4}$ Gyr. The faint end of the luminosity function for the halo white dwarfs is less constrained, resulting in an age estimate of $12.5^{+1.4}_{-3.4}$ Gyr for the Galactic inner halo. This is the first time ages for all three major components of the Galaxy are obtained from a sample of field white dwarfs that is large enough to contain significant numbers of disk and halo objects. The resultant ages agree reasonably well with the age estimates for the oldest open and globular clusters.Comment: ApJ, in pres

Mutated Measles Virus Matrix and Fusion Protein Influence Viral Titer In Vitro and Neuro-Invasion in Lewis Rat Brain Slice Cultures

Measles virus (MV) can cause severe acute diseases as well as long-lasting clinical deteriorations due to viral-induced immunosuppression and neuronal manifestation. How the virus enters the brain and manages to persist in neuronal tissue is not fully understood. Various mutations in the viral genes were found in MV strains isolated from patient brains. In this study, reverse genetics was used to introduce mutations in the fusion, matrix and polymerase genes of MV. The generated virus clones were characterized in cell culture and used to infect rat brain slice cultures. A mutation in the carboxy-terminal domain of the matrix protein (R293Q) promoted the production of progeny virions. This effect was observed in Vero cells irrespective of the expression of the signaling lymphocyte activation molecule (SLAM). Furthermore, a mutation in the fusion protein (I225M) induced syncytia formation on Vero cells in the absence of SLAM and promoted viral spread throughout the rat brain slices. In this study, a solid ex vivo model was established to elucidate the MV mutations contributing to neural manifestation

No Neutron Star Companion To The Lowest Mass SDSS White Dwarf

SDSS J091709.55+463821.8 (hereafter J0917+4638) is the lowest surface gravity white dwarf (WD) currently known, with log g = 5.55 +/- 0.05 (M ~ 0.17 M_sun; Kilic et al. 2007a,b). Such low-mass white dwarfs (LMWDs) are believed to originate in binaries that evolve into WD/WD or WD/neutron star (NS) systems. An optical search for J0917+4638's companion showed that it must be a compact object with a mass >= 0.28 M_sun (Kilic 2007b). Here we report on Green Bank Telescope 820 MHz and XMM-Newton X-ray observations of J0917+4638 intended to uncover a potential NS companion to the LMWD. No convincing pulsar signal is detected in our radio data. Our X-ray observation also failed to detect X-ray emission from J0917+4638's companion, while we would have detected any of the millisecond radio pulsars in 47 Tuc. We conclude that the companion is almost certainly another WD.Comment: 4 pages, 1 table; to appear in the Astrophysical Journal Letter

Multiwavelength Observations of the Hot DB Star PG 0112+104

We present a comprehensive multiwavelength analysis of the hot DB white dwarf PG 0112+104. Our analysis relies on newly-acquired FUSE observations, on medium-resolution FOS and GHRS data, on archival high-resolution GHRS observations, on optical spectrophotometry both in the blue and around Halpha, as well as on time-resolved photometry. From the optical data, we derive a self-consistent effective temperature of 31,300+-500 K, a surface gravity of log g = 7.8 +- 0.1 (M=0.52 Msun), and a hydrogen abundance of log N(H)/N(He) < -4.0. The FUSE spectra reveal the presence of CII and CIII lines that complement the previous detection of CII transitions with the GHRS. The improved carbon abundance in this hot object is log N(C)/N(He) = -6.15 +- 0.23. No photospheric features associated with other heavy elements are detected. We reconsider the role of PG 0112+104 in the definition of the blue edge of the V777 Her instability strip in light of our high-speed photometry, and contrast our results with those of previous observations carried out at the McDonald Observatory.Comment: 10 pages in emulateapj, 9 figures, accepted for publication in Ap

Simultaneous Multi-Wavelength Observations of Magnetic Activity in Ultracool Dwarfs. I. The Complex Behavior of the M8.5 Dwarf TVLM513-46546

[Abridged] We present the first simultaneous radio, X-ray, ultraviolet, and optical spectroscopic observations of the M8.5 dwarf TVLM513-46546, with a duration of 9 hours. These observations are part of a program to study the origin of magnetic activity in ultracool dwarfs, and its impact on chromospheric and coronal emission. Here we detect steady quiescent radio emission superposed with multiple short-duration, highly polarized flares; there is no evidence for periodic bursts previously reported for this object, indicating their transient nature. We also detect soft X-ray emission, with L_X/L_bol~10^-4.9, the faintest to date for any object later than M5, and a possible weak X-ray flare. TVLM513-46546 continues the trend of severe violation of the radio/X-ray correlation in ultracool dwarfs, by nearly 4 orders of magnitude. From the optical spectroscopy we find that the Balmer line luminosity exceeds the X-ray luminosity by a factor of a few, suggesting that, unlike in early M dwarfs, chromospheric heating may not be due to coronal X-ray emission. More importantly, we detect a sinusoidal H-alpha light curve with a period of 2 hr, matching the rotation period of TVLM513-46546. This is the first known example of such Balmer line behavior, which points to a co-rotating chromospheric hot spot or an extended magnetic structure, with a covering fraction of about 50%. This feature may be transitory based on the apparent decline in light curve peak during the four observed maxima. From the radio data we infer a large scale steady magnetic field of ~100 G, in good agreement with the value required for confinement of the X-ray emitting plasma. The radio flares, on the other hand, are produced in a component of the field with a strength of ~3 kG and a likely multi-polar configuration.Comment: 13 pages, 4 figure

Blue Horizontal Branch Stars in Old, Metal-Rich Stellar Systems

Twenty years ago, Burstein et al. (1984)suggested that strong CN and Hbeta absorption meant younger ages among globular clusters in the Andromeda galaxy (M31), unless blue stars above the main-sequence turnoff or on the horizontal branch were uncommonly prominent. Here we test these suggestions by fitting the detailed mid-ultraviolet (2280-3120A) and optical (3850-4750A) spectra of one moderately metal-rich M31 globular cluster, G1. We explore the effects of a wide range of non-solar temperatures and abundance ratios, by combining a small set of theoretical stellar spectra like those of Peterson et al. (2001) that were calculated using extensively updated atomic-line constants. To match the mid-UV fluxes of G1, we find that hot components with Teff >= 8000K must be included. We obtain a very good fit with cool and hot blue horizontal branch (BHB) stars, but less satisfactory fits for blue straggler stars, those hotter than the main-sequence turnoff. The G1 color-magnitude diagram does show cool BHB stars, and the color of its giant branch supports the metallicity of one-sixth the solar value that we deduce. The turnoff temperature of the best-fit model is consistent with that of turnoff stars in galactic globular clusters and the field halo, indicating G1 is comparably old. Because metal-rich cool BHB and extremely blue HB stars have now been found within our own Galaxy, we suggest that these hot horizontal-branch stars be considered in fitting spectra of metal-rich populations such as the Andromeda globular clusters, to avoid possible underestimates of their ages. We plan to make the relevant spectral calculations available as part of our Hubble Treasury Program