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The impact of climate change on three small- to medium-sized river catchments (Ammer, Mulde, and Ruhr) in Germany is investigated for the near future (2021–50) following the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario. A 10-member ensemble of hydrological model (HM) simulations, based on two high-resolution regional climate models (RCMs) driven by two global climate models (GCMs), with three realizations of ECHAM5 (E5) and one realization of the Canadian Centre for Climate Modelling and Analysis version 3 (CCCma3; C3) is established. All GCM simulations are downscaled by the RCM Community Land Model (CLM), and one realization of E5 is downscaled also with the RCM Weather Research and Forecasting Model (WRF). This concerted 7-km, high-resolution RCM ensemble provides a sound basis for runoff simulations of small catchments and is currently unique for Germany. The hydrology for each catchment is simulated in an overlapping scheme, with two of the three HMs used in the project. The resulting ensemble hence contains for each chain link (GCM–realization–RCM–HM) at least two members and allows the investigation of qualitative and limited quantitative indications of the existence and uncertainty range of the change signal. The ensemble spread in the climate change signal is large and varies with catchment and season, and the results show that most of the uncertainty of the change signal arises from the natural variability in winter and from the RCMs in summer.

Despite considerable progress in recent years, output of both global and regional circulation models is still afflicted with biases to a degree that precludes its direct use, especially in climate change impact studies. This is well known, and to overcome this problem, bias correction (BC; i.e. the correction of model output towards observations in a post-processing step) has now become a standard procedure in climate change impact studies. In this paper we argue that BC is currently often used in an invalid way: it is added to the GCM/RCM model chain without sufficient proof that the consistency of the latter (i.e. the agreement between model dynamics/model output and our judgement) as well as the generality of its applicability increases. BC methods often impair the advantages of circulation models by altering spatiotemporal field consistency, relations among variables and by violating conservation principles. Currently used BC methods largely neglect feedback mechanisms, and it is unclear whether they are time-invariant under climate change conditions. Applying BC increases agreement of climate model output with observations in hindcasts and hence narrows the uncertainty range of simulations and predictions without, however, providing a satisfactory physical justification. This is in most cases not transparent to the end user. We argue that this hides rather than reduces uncertainty, which may lead to avoidable forejudging of end users and decision makers. We present here a brief overview of state-of-the-art bias correction methods, discuss the related assumptions and implications, draw conclusions on the validity of bias correction and propose ways to cope with biased output of circulation models in the short term and how to reduce the bias in the long term. The most promising strategy for improved future global and regional circulation model simulations is the increase in model resolution to the convection-permitting scale in combination with ensemble predictions based on sophisticated approaches for ensemble perturbation. With this article, we advocate communicating the entire uncertainty range associated with climate change predictions openly and hope to stimulate a lively discussion on bias correction among the atmospheric and hydrological community and end users of climate change impact studies.

We identify seven new ultracool white dwarfs discovered in the Sloan Digital Sky Survey (SDSS). The SDSS photometry, spectra, and proper motions are presented, and additional BVRI data are given for these and other previously discovered ultracool white dwarfs. The observed colors span a remarkably wide range, qualitatively similar to colors predicted by models for very cool white dwarfs. One of the new stars (SDSS J1251+44) exhibits strong collision-induced absorption (CIA) in its spectra, while the spectra and colors of the other six are consistent with mild CIA. Another of the new discoveries (SDSS J2239+00A) is part of a binary system -- its companion is also a cool white dwarf, and other data indicate that the companion exhibits an infrared flux deficiency, making this the first binary system composed of two CIA white dwarfs. A third discovery (SDSS J0310-00) has weak Balmer emission lines. The proper motions of all seven stars are consistent with membership in the disk or thick disk., Comment: Accepted for Astrophysical Journal. 16 pages (includes 3 figures)

[Abridged] As part of our on-going investigation of magnetic activity in ultracool dwarfs we present simultaneous radio, X-ray, UV, and optical observations of LSR1835+32 (M8.5), and simultaneous X-ray and UV observations of VB10 (M8), both with a duration of about 9 hours. LSR1835+32 exhibits persistent radio emission and H-alpha variability on timescales of ~0.5-2 hr. The detected UV flux is consistent with photospheric emission, and no X-ray emission is detected to a deep limit of L_X/L_bol2x10^4. Similarly, L_Halpha/L_X>10 is at least 30 times larger than in early M dwarfs, and eliminates coronal emission as the source of chromospheric heating. The lack of radio variability during four rotations of LSR1835+32 requires a uniform stellar-scale field of ~10 G, and indicates that the H-alpha variability is dominated by much smaller scales, 25 km/s., Submitted to ApJ

[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 figures

On behalf of and in close collaboration with the institution of environment, measurements and conservation of the federal state of Baden-Württemberg (Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg/LUBW/ see http://www.lubw.baden-wuerttemberg.de/) an innovative regionnalisation concept has been developed. This concept allows the supply of flood, mean or low flow parameters for 10 790 sites in Baden-Württemberg and an evaluation of the predicted impact of climate change on the flood situation. The extensive data basis for this regionalisation concept with numerous input parameters and varied result reporting made it necessary to select an appropriate database structure. New software was developed to help with the calculations, notably for: – upgrading the official areal water system register (Gewässerkundliches Flächenverzeichnis/GKFV) – proofing tools to maintain consistency – automatic parameter derivation with the software ESRI© ArcInfo. The results were published in electronic form and included a stand-alone geo-information software for easy and fast retrieval of data and results. The objective of this article is to describe the implementation of these new concepts for coupling Geographic Information System (GIS) and database needs to reach the identified requirements.

We present the first simultaneous, multi-wavelength observations of an L dwarf, the L3.5 candidate brown dwarf 2MASS J00361617+1821104, conducted with the Very Large Array, the Chandra X-ray Observatory, and the Kitt Peak 4-m telescope. We detect strongly variable and periodic radio emission (P=3 hr) with a fraction of about 60% circular polarization. No X-ray emission is detected to a limit of L_X/L_{bol}, Submitted to ApJ; 26 pages, 15 figures

Early data taken during commissioning of the SDSS have resulted in the discovery of a very cool white dwarf. It appears to have stronger collision induced absorption from molecular hydrogen than any other known white dwarf, suggesting it has a cooler temperature than any other. While its distance is presently unknown, it has a surprisingly small proper motion, making it unlikely to be a halo star. An analysis of white dwarf cooling times suggests that this object may be a low-mass star with a helium core. The SDSS imaging and spectroscopy also recovered LHS 3250, the coolest previously known white dwarf, indicating that the SDSS will be an effective tool for identifying these extreme objects., 15 pages, including 5 figures. Accepted for Astrophysical Journal Letters

Within the PWR safety analyses, attention has increasingly focused in recent years on boron dilution events which could potentially lead to reactivity transients. In Germany, the current discussion concerning boron dilution events is focused on small break loss of coolant accident (SB-LOCA) scenarios with reflux-condenser mode and restart of natural circulation (NC). The investigation of this topic was the subject of experiments performed in the Primarkreislauf (PKL) test facility and in the upper plenum test facility (UPTF). The two test facilities represent a typical western-type pressurized water reactor (PWR) and are/were operated by Siemens/KWU in Germany. While the restart of NC was investigated in the PKL system test facility (volume 1:145, height 1:1), the UPTF experiments dealt with the mixing of water flows with different boron concentration in the cold legs, reactor pressure vessel (RPV) downcomer and the lower plenum (all these components were full-scale models). The results from the PKL test facility demonstrate that in case of a postulated SB-LOCA (30 cm 2 -break in the cold leg; two out of four high pressure safety injection pumps (HP-SIPs) available) NC does not start up simultaneously in all loops. This means, that plugs of non-borated condensate, that might have accumulated in the pump seal during reflux condenser mode of operation, would reach the RPV at different points in time. The UPTF tests showed an almost ideal mixing of water flows with different boron concentration in the RPV downcomer. The most important results from PKL and UPTF tests which concern boron dilution events following the restart of NC are presented in this paper.

To investigate the flow phenomena in the primary system of a pressurized water reactor (PWR) during a loss-of-coolant accident (LOCA) occurring with a small or intermediate break, experiments were performed at the full-scale Upper Plenum Test Facility (UPTF). Within the Transient and Accident Management (TRAM) program integral and separate effect tests were carried out to study loop seal clearing and to provide data for the further improvement of computer codes concerning the reactor safety analysis. This paper describes the UPTF tests that focus on the sequence of loop seal clearance in a four-loop operation for two different cold leg break sizes and the residual water levels, the flow patterns in, and the pressure drops across a single loop seal during the clearing. The UPTF results obtained from a single-loop seal operation are compared with experimental data and correlations available in the literature. Two correlations are proposed which allow the quantification of residual water levels in the loop seal under PWR conditions. It is shown that the steam–water test results gained from the full-scale UPTF with realistic PWR loop seal geometry differ from those obtained from the full or small-scale test facilities under air–water conditions. The UPTF experiments indicate the substantial need for steam-water test data from a full-scale facility with realistic PWR geometries in order to validate PWR LOCA thermal-hydraulic system codes to predict loop seal clearing correctly.

Precise trigonometric parallax measurements orders of magnitude more accurate than a milliarcsecond will contribute greatly to our understanding of peculiar, low luminosity stellar objects of several types. First, the volume of space out to which luminosities may be determined to the accuracy of the best, very-nearby stars will be increased greatly. For the relatively rare field Population II stars, this will lead to the first accurate empirical calibrations of the main sequence at the low mass end, for comparison with globular clusters of various metallicities. Parallaxes at 1 kpc or farther will be adequate to help in the discovery or confirmation of the rare carbon dwarfs - main sequence stars with carbon-rich atmospheres. For cool white dwarfs, luminosities accurate to a few per cent or better will identify unresolved binaries, and objects of unusually high and low mass. For our most numerous solar neighbors, the M dwarfs and especially those near the stellar mass limit, accurate luminosities can help in the determinations of the chemical composition and age distributions.

A total of 34 tests were performed at upper plenum test facility (UPTF, a 1:1 scale test facility) to investigate the thermal-hydraulic phenomena in a pressurized water reactor (PWR) primary system during end-of-blowdown, refill and reflood phases of a loss-of-coolant accident (LOCA). Separate effect tests as well as integral tests were carried out. After the completion of the program a summary of the basic findings from the full-scale tests is given, focusing on thermal-hydraulic issues related to: two-phase flow phenomena at the ECC injection ports for cold or hot leg injection; the ECC delivery into core area via the downcomer or the tie plate; entrainment de-entrainment phenomena during reflood (i.e. the “steam binding” and driving water head reduction problems).

We present a preliminary analysis of the recently discovered carbon‐dominated atmosphere white dwarfs (“Hot DQ”) based on HST/COS observations. We also present a summary of the recent findings that emerged from our ongoing campaign aimed at obtaining high signal‐to‐noise optical spectroscopic observations of these objects.

[Abridged] As part of our on-going investigation into the magnetic field properties of ultracool dwarfs, we present simultaneous radio, X-ray, and H-alpha observations of three M9.5-L2.5 dwarfs (BRI0021-0214, LSR060230.4+391059, and 2MASSJ052338.2-140302). We do not detect X-ray or radio emission from any of the three sources, despite previous detections of radio emission from BRI0021 and 2M0523-14. Steady and variable H-alpha emission are detected from 2M0523-14 and BRI0021, respectively, while no H-alpha emission is detected from LSR0602+39. Overall, our survey of nine M8-L5 dwarfs doubles the number of ultracool dwarfs observed in X-rays, and triples the number of L dwarfs, providing in addition the deepest limits to date, log(L_X/L_bol)M6. In the radio band, however, the luminosity remains relatively unchanged from M0 to L4, leading to a substantial increase in L_rad/L_bol. Our survey also provides the first comprehensive set of simultaneous radio/X-ray/H-alpha observations of ultracool dwarfs, and reveals a clear breakdown of the radio/X-ray correlation beyond spectral type M7, evolving smoothly from L_{\nu,rad}/L_X ~ 10^-15.5 to ~10^-11.5 Hz^-1 over the narrow spectral type range M7-M9. This breakdown reflects the substantial reduction in X-ray activity beyond M7, but its physical origin remains unclear since, as evidenced by the uniform radio emission, there is no drop in the field dissipation and particle acceleration efficiency., Comment: Submitted to ApJ; 19 pages, 10 figures, 5 tables

[Abridged] We present an 8.5-hour simultaneous radio, X-ray, UV, and optical observation of the L dwarf binary 2MASSW J0746+20. We detect strong radio emission, dominated by short-duration periodic pulses at 4.86 GHz with P=124.32+/-0.11 min. The stability of the pulse profiles and arrival times demonstrates that they are due to the rotational modulation of a B~1.7 kG magnetic field. A quiescent non-variable component is also detected, likely due to emission from a uniform large-scale field. The H-alpha emission exhibits identical periodicity, but unlike the radio pulses it varies sinusoidally and is offset by exactly 1/4 of a phase. The sinusoidal variations require chromospheric emission from a large-scale field structure, with the radio pulses likely emanating from the magnetic poles. While both light curves can be explained by a rotating mis-aligned magnetic field, the 1/4 phase lag rules out a symmetric dipole topology since it would result in a phase lag of 1/2 (poloidal field) or zero (toroidal field). We therefore conclude that either (i) the field is dominated by a quadrupole configuration, which can naturally explain the 1/4 phase lag; or (ii) the H-alpha and/or radio emission regions are not trivially aligned with the field. Regardless of the field topology, we use the measured period along with the known rotation velocity (vsini=27 km/s), and the binary orbital inclination (i=142 deg), to derive a radius for the primary star of 0.078+/-0.010 R_sun. This is the first measurement of the radius of an L dwarf, and along with a mass of 0.085+/-0.010 M_sun it provides a constraint on the mass-radius relation below 0.1 M_sun. We find that the radius is about 30% smaller than expected from theoretical models, even for an age of a few Gyr., Comment: Submitted to ApJ

We present analysis of Hubble Space Telescope images of 82 nearby field late-M and L dwarfs. We resolve 13 of these systems into double M/L dwarf systems and identify an additional possible binary. Combined with previous observations of 20 L dwarfs, we derive an observed binary fraction for ultracool dwarfs of 17+4-3%, where the statistics included systems with separations in the range 1.6-16 A.U. We argue that accounting for biases and incompleteness leads to an estimated binary fraction 15+-5% in the range 1.6-16 A.U. No systems wider than 16 A.U. are seen, implying that the wide companion frequency is less than 1.7%; the distribution of orbital separation is peaked at ~2-4 A.U. and differs greatly from the G dwarf binary distribution. Indirect evidence suggests that the binary fraction is ~5+-3% for separations less than 1.6 A.U. We find no evidence for differences in the binary fraction between stellar late-M and L dwarfs and substellar L dwarfs. We note, however, that the widest (>10 A.U.) systems in our sample are all of earlier (M8-L0) spectral type; a larger sample is needed determine if this is a real effect. One system with a spectral type of L7 has a secondary that is fainter in the HST F814W filter but brighter in F1042M; we argue that this secondary is an early-T dwarf., To appear in June 2003 Astronomical Journal

An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees), observed much like the full survey will be, 269 white dwarfs and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and 5 hot subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and DB (helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C_2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12000 K, and the density of these stars for 15, Comment: Accepted for AJ; 43 pages, including 12 figures and 5 tables

Trigonometric parallax determinations are presented for 28 late type dwarfs and brown dwarfs, including eight M dwarfs with spectral types between M7 and M9.5, 17 L dwarfs with spectral types between L0 and L8, and three T dwarfs. Broadband photometry at CCD wavelengths (VRIz) and/or near-IR wavelengths (JHK) are presented for these objects and for 24 additional late-type dwarfs. Supplemented with astrometry and photometry from the literature, including ten L and two T dwarfs with parallaxes established by association with bright, usually HIPPARCOS primaries, this material forms the basis for studying various color-color and color-absolute magnitude relations. The I-J color is a good predictor of absolute magnitude for late-M and L dwarfs. M_J becomes monotonically fainter with I-J color and with spectral type through late-L dwarfs, then brightens for early-T dwarfs. The combination of zJK colors alone can be used to classify late-M, early-L, and T dwarfs accurately, and to predict their absolute magnitudes, but is less effective at untangling the scatter among mid- and late-L dwarfs. The mean tangential velocity of these objects is found to be slightly less than that for dM stars in the solar neighborhood, consistent with a sample with a mean age of several Gyr. Using colors to estimate bolometric corrections, and models to estimate stellar radii, effective temperatures are derived. The latest L dwarfs are found to have T_eff ~ 1360 K., Comment: 48 pages, including 7 figures and 6 tables. Accepted for AJ

The three papers presented in this section on model atmospheres of brown dwarfs raise several common themes. I discuss three of these from an observational viewpoint — the temperature scale for L dwarfs, the role of the alkali elements, and the liely “weather” in brown dwarf atmospheres.

The session was brief and quite informal as there were only six participants. The agenda included my report on organizational activities of the Commission during the 2003-2006 term and Virginia Trimble's presentation Presence of binary stars in the current astronomical literature. I summarize below the most important part of my report.

We present initial results of an all-sky search for cool, low-mass stars and brown dwarfs within 20 pc. We have used the near-infrared photometry provided by the 2-Micron All Sky Survey (2MASS) Second Incremental Data Release to create a target list of 1793 candidates with 6 < J < 17 and J – K > 1. Follow-up observations and existing data have enabled over 85% of the sample to be classified. Spectral types and distances have been derived for over 250 nearby dwarfs, including 39 newly discovered L dwarfs. In this poster, we discuss our selection methods and present preliminary results.

Results are presented from an X-ray survey of ∼50 square degrees of the high galactic latitude sky at sensitivities in the range 7·10−14–5·10−12 erg/cm2 sec (0.3–3.5 keV) carried out with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. The extragalactic sample consists of 48 sources which have been used to determine the number flux relation. The content of the sample is analyzed in terms of types of sources and is found to be significantly different from the content of similar samples selected at higher fluxes.

Determinants of grant getting are explored for a national sample of over 5,000 faculty in all types of fields and senior institutions of higher education. The pattern of grant getting by individual...

The recent discovery that the cool DA white dwarf L870-2 (EG11, WD0135-052) is a double-lined spectroscopic binary composed of a detached pair of DA white dwarfs (Saffer, Liebert, and Olszewski 1988, SLO hereafter) has raised some challenging problems for stellar evolution theories of such binary systems. One first important step in the understanding of this short-period system is to establish the atmospheric parameters of each component. SLO have argued from previous determinations of the effective temperature and absolute magnitude of the system, and also from their own study of the composite Hα profile, that the two components should be similar. We wish here to reexamine this assertion by taking a new look at the constraints on the two components brought about by the available observational data.

We have used optical and UV spectroscopy to determine He abundances and upper limits to He abundances in the photospheres of a selected sample of very hot hydrogen-rich white dwarfs. He abundances in the range log(He/H) -3 to -1.5 are observed in several of these DAs and upper limits of -3 determined for the remainder. In apparent contradiction to the relatively large He abundances inferred from soft X-ray observations for the hot DA G191 B2B, we find no evidence of He in the optical and UV.

Resume La distribution de la polyploidie dans 163 clones du Phragmites australis de la region mediterraneenne, comme celle des flavonoides dans 41 d'entre eux, montrent que le polymorphisme de cette espece est plus en rapport avec sa grande faculte d'accommodation et sa forte heterozygotie, qu'avec ses differents niveaux de ploidie. Si, d'une maniere generale, le complexe du P.a. atteint un etat de maturite avancee, la differenciation de cette espece est moins variee dans la region mediterraneenne que dans les regions ouest- et centre- asiatiques.

Research grants are resources in academic stratification that may be distributed by performance criteria or by particularism or favor. This paper explores determinants of grant getting, using a subsample draw from a 1972-73 general national survey of faculty in higher education. The findings show that grant getting depends primarily on productivity, secondarily on the inequalities in favor shown to specific fields, and very little on particularistic situational and personal status factors. The inevitable inequality of this meritocracy apparently is lessned by broad participation in grantsmanship.

The cool white dwarf stars G 128-7 and G 165-7 have a quite different character: While the line spectrum of G 165-7 is the richest of all white dwarfs known, G 128-7 shows only a strong Hα line (Wλ ≈ 5.5 Å) and a much weaker Hβ line (Wλ ≈ 1 Å).

Observations a haute dispersions de la region spectrale Hα pour un echantillon d'etoiles naines M tres avancees. On en derive les vitesses radiales et les mouvements spatiaux. On examine les resultats par rapport a l'appartenance a une population cinematique

UBVR observations and image-tube spectra of the faint blue star LP182-44 are analyzed. It is shown that this star is a high-space-velocity non-DA white dwarf with probable weak carbon features in its spectrum. An absolute visual magnitude of about 13.0 and a tangential velocity of approximately 190 km/s are estimated. Properties of the group of high-velocity C2 degenerates are discussed.

The spectrum of GD 190 (EG 193), a strong-lined DB white dwarf, is shown to contain an absorption feature at 4517 A in the redward wing of the He I lambda 4471 line. This feature, which is believed to be due to the forbidden 2 /sup 3/P--4 /sup 3/P transition in He I, has not been detected previously in DB white dwarfs. While its presence is predicted from model atmosphere calculations, agreement between theory and observation remains qualitative. It is possible that the lambda 4517 feature may provide a valuable gravity discriminant at least for hot DB white dwarfs. (auth)

The temperature, radius, and other atmospheric parameters are derived for the cool DC white dwarf Stein 2051B (=G175-34B=EG 180), whose mass was recently determined by Strand. New spectrophotometric scans of this star and its dwarf M companion are discussed; these and existing Stroemgren photometry are fitted to model atmospheres with hydrogen/metal deficient compositions, and a temperature of 7050 +- 400 K is determined. The resulting radius of 0.0111 +- 0.0015 R/sub sun/ is marginally smaller than that of 40 Eri B. (AIP)

The three X-ray selected mid-K stars with the highest values of optical flux ratios in the Einstein Medium Sensitivity Survey have been studied spectroscopically at moderate and high spectral resolution. One of these objects (1E1548.7 + 1125) is presented as a binary-star system with characteristics similar to the RS CVn class of binaries. A second of these stars (1E1751.0 + 7046) is a rapid rotator, while the third star (1E1339.9 + 6030) has not been shown to be either a binary system or a rapid rotator. The presence of both Ca II H and K emission core and high X-ray flux is attributed to chromospheric and coronal activity, but no single underlying cause is indicated.

Results of an investigation of the X-ray properties of quasars conducted using the Einstein Observatory (HEAO 2) are reported. The positions, fluxes and luminosities of 35 known quasars were observed by the Einstein high-resolution imaging detector and the imaging proportional counter. Assuming optical redshifts as valid distance indicators, 0.5-4.5 keV X-ray luminosities ranging from 10 to the 43rd to 10 to the 47 ergs/sec are obtained, with evidence of very little cold gas absorption. Flux variability on a time scale of less than 10,000 sec is observed for the quasar OX 169, which implies a mass between 8 x 10 to the 5th and 2 x 10 to the 8th solar masses for the black hole assumed to be responsible for the emission. Preliminary results of the quasar survey also indicate that quasars contribute significantly to the diffuse X-ray background.

Broad-band circular polarization measurements for 32 white dwarfs are presented, part of a continuing program to assess the magnetic field distribution and stellar parameters of magnetic white dwarfs. None of the stars discussed here represent statistically significant detections, though a few are marginal, and one in particular (LP777-1) deserves closer study. The null results for cool degenerates include the very low luminosity stars LP701-29, LP131-66, and Ross 193B (VB11), and support the hypothesis that the temperature distribution of magnetic stars is not signficantly different from the distribution of all white dwarfs. G35-26, a likely low-field case with Zeeman-split lines, does not show significant continuum circular polarization.

The triple radio source 3C 154 is centered on a 17.5 mag QSO with z=0.580. The optical spectrum is Seyfert-like. The outer radio lobes are separated by 43'', or about 375 kpc (for H/sub 0/=50, q/sub 0/=0) in projection, making 3C 154 among the larger sources in linear size. We have used a simple expansion model to determine that the characteristic outburst time scale is longer than 6 million years. (AIP)

Image-tube scans are presented for three white dwarfs known to be magnetic from polarization measurements and for the polarized recurrent nova DQ Her. Five separate scans of short duration were obtained of GD229, G240-72, and G195-19. No convincing evidence for spectral variability was found for these stars, even for the detailed band structure of GD229. The very broad (A > 1000 A) depression found by Creenstein in G240-72 is confirmed. However, for A> 4400 A no other features previously reported for G195-19 and G240-72 are confirmed by these data. The two scans of DQ Her revealed emission features reported many years ago; the underlying absorption spectrum at maximum light was featureless to A7200. Key words: white-dwarf stars - magnetic stars - novae - spectrophotometry