A new magnetic white dwarf : PG2329+267

We have discovered that the white dwarf PG 2329+267 is magnetic, and assuming a centered dipole structure, has a dipole magnetic field strength of approximately 2.3MG. This makes it one of only approximately 4% of isolated white dwarfs with a detectable magnetic field. Linear Zeeman splitting as well as quadratic Zeeman shifts are evident in the hydrogen Balmer sequence and circular spectropolarimetry reveals 10% circular polarisation in the two displaced sigma components of Halpha. We suggest from comparison with spectra of white dwarfs of known mass that PG 2329+267 is more massive than typical isolated white dwarfs, in agreement with the hypothesis that magnetic white dwarfs evolve from magnetic chemically peculiar Ap and Bp type main sequence stars.Comment: 5 pages, with 2 encapsulated postscipts figures include

Publications of the JPL Solar Thermal Power Systems Project 1976 Through 1985

Bibliographical listings are documentation products associated with the Solar Thermal Power Systems Project carried out by the Jet Propulsion Laboratory from 1976 to 1986. Documents are categorized as conference and journal papers, JPL external reports, JPL internal reports, or contractor reports (i.e., deliverable documents produced under contract to JPL). Alphabetical listings by titles are used in the bibliography itself to facilitate location of the document by subject. Two indexes are included for ease of reference; an author index; and a topical index

Low Luminosity Companions to White Dwarfs

This paper presents results of a near-infrared imaging survey for low mass stellar and substellar companions to white dwarfs. A wide field proper motion survey of 261 white dwarfs was capable of directly detecting companions at orbital separations between $\sim100$ and 5000 AU with masses as low as 0.05 $M_{\odot}$, while a deep near field search of 86 white dwarfs was capable of directly detecting companions at separations between $\sim50$ and 1100 AU with masses as low as 0.02 $M_{\odot}$. Additionally, all white dwarf targets were examined for near-infrared excess emission, a technique capable of detecting companions at arbitrarily close separations down to masses of 0.05 $M_{\odot}$. No brown dwarf candidates were detected, which implies a brown dwarf companion fraction of $<0.5$% for white dwarfs. In contrast, the stellar companion fraction of white dwarfs as measured by this survey is 22%, uncorrected for bias. Moreover, most of the known and suspected stellar companions to white dwarfs are low mass stars whose masses are only slightly greater than the masses of brown dwarfs. Twenty previously unknown stellar companions were detected, five of which are confirmed or likely white dwarfs themselves, while fifteen are confirmed or likely low mass stars. Similar to the distribution of cool field dwarfs as a function of spectral type, the number of cool unevolved dwarf companions peaks at mid-M type. Based on the present work, relative to this peak, field L dwarfs appear to be roughly 2-3 times more abundant than companion L dwarfs. Additionally, there is no evidence that the initial companion masses have been altered by post main sequence binary interactions.Comment: 149 pages, 59 figures, 11 tables, accepted to ApJ Supplement

A Radial Velocity Study of CTCV J1300-3052

We present time-resolved spectroscopy of the eclipsing, short period cataclysmic variable CTCV J1300-3052. Using absorption features from the secondary star, we determine the radial velocity semi-amplitude of the secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These parameters are found to be in excellent agreement with previous mass determinations found via photometric fitting techniques, supporting the accuracy and validity of photometric mass determinations in short period CVs.Comment: Accepted for publication in MNRAS (24th January 2012). 10 pages, 9 figures (black and white

Searching for nova shells around cataclysmic variables

We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using Halpha images taken with the 4.2-m William Herschel Telescope (WHT) and the 2.5-m Isaac Newton Telescope Photometric Halpha Survey of the Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. We concentrated our WHT search on nova-like variables, whilst our IPHAS search covered all CVs in the IPHAS footprint. We found one shell out of the 24 nova-like variables we examined. The newly discovered shell is around V1315 Aql and has a radius of approx.2.5 arcmin, indicative of a nova eruption approximately 120 years ago. This result is consistent with the idea that the high mass-transfer rate exhibited by nova-like variables is due to enhanced irradiation of the secondary by the hot white dwarf following a recent nova eruption. The implications of our observations for the lifetime of the nova-like variable phase are discussed. We also examined 4 asynchronous polars, but found no new shells around any of them, so we are unable to confirm that a recent nova eruption is the cause of the asynchronicity in the white dwarf spin. We find tentative evidence of a faint shell around the dwarf nova V1363 Cyg. In addition, we find evidence for a light echo around the nova V2275 Cyg, which erupted in 2001, indicative of an earlier nova eruption approx.300 years ago, making V2275 Cyg a possible recurrent nova.Comment: 14 pages, 50 figures, 3 Table

The Future is Now: the Formation of Single Low Mass White Dwarfs in the Solar Neighborhood

Low mass helium-core white dwarfs (M < 0.45 Msun) can be produced from interacting binary systems, and traditionally all of them have been attributed to this channel. However, a low mass white dwarf could also result from a single star that experiences severe mass loss on the first ascent giant branch. A large population of low mass He-core white dwarfs has been discovered in the old metal-rich cluster NGC 6791. There is therefore a mechanism in clusters to produce low mass white dwarfs without requiring binary star interactions, and we search for evidence of a similar population in field white dwarfs. We argue that there is a significant field population (of order half of the detected systems) that arises from old metal rich stars which truncate their evolution prior to the helium flash from severe mass loss. There is a consistent absence of evidence for nearby companions in a large fraction of low mass white dwarfs. The number of old metal-rich field dwarfs is also comparable with the apparently single low mass white dwarf population, and our revised estimate for the space density of low mass white dwarfs produced from binary interactions is also compatible with theoretical expectations. This indicates that this channel of stellar evolution, hitherto thought hypothetical only, has been in operation in our own Galaxy for many billions of years. One strong implication of our model is that single low mass white dwarfs should be good targets for planet searches because they are likely to arise from metal-rich progenitors. We also discuss other observational tests and implications, including the potential impact on SN Ia rates and the frequency of planetary nebulae.Comment: ApJ published versio

First Lunar Occultation Results from the 2.4 m Thai National Telescope equipped with ULTRASPEC

The recently inaugurated 2.4\,m Thai National Telescope (TNT) is equipped, among other instruments, with the ULTRASPEC low-noise, frame-transfer EMCCD camera. At the end of its first official observing season, we report on the use of this facility to record high time resolution imaging using small detector subarrays with sampling as fast as several $10^2$\,Hz. In particular, we have recorded lunar occultations of several stars which represent the first contribution to this area of research made from South-East Asia with a telescope of this class. Among the results, we discuss an accurate measurement of $\alpha$~Cnc, which has been reported previously as a suspected close binary. Attempts to resolve this star by several authors have so far met with a lack of unambiguous confirmation. With our observation we are able to place stringent limits on the projected angular separation (<0\farcs003) and brightness ($\Delta{\rm m} > 5$) of a putative companion. We also present a measurement of the binary {HR~7072}, which extends considerably the time coverage available for its yet undetermined orbit. We discuss our precise determination of the flux ratio and projected separation in the context of other available data. We conclude by providing an estimate of the performance of ULTRASPEC at TNT for lunar occultation work. This facility can help to extend the lunar occultation technique in a geographical area where no comparable resources were available until now.Comment: Accepted for publication in Astronomical Journa

Dissipative Particle Dynamics with energy conservation

Dissipative particle dynamics (DPD) does not conserve energy and this precludes its use in the study of thermal processes in complex fluids. We present here a generalization of DPD that incorporates an internal energy and a temperature variable for each particle. The dissipation induced by the dissipative forces between particles is invested in raising the internal energy of the particles. Thermal conduction occurs by means of (inverse) temperature differences. The model can be viewed as a simplified solver of the fluctuating hydrodynamic equations and opens up the possibility of studying thermal processes in complex fluids with a mesoscopic simulation technique.Comment: 5 page