Is IRAS 03134 + 5958 a Herbig-Haro object?

The source IRAS 03134 + 5958 identified by Iyengar & Verma (1984) on the Palomar Observatory Sky Survey (POSS) prints with a nonstellar optical object with [P – R]≃ 5.3 ± 1.5 is near the edge of Lynds dark cloud No. 1384 and is either embedded in or behind the cloud. The galactic latitude of this source (b ^II = 2‡.3), its positionvis-a-vis the Lynds dark cloud, its nonstellar appearance, high [P – R] colour and its far-infrared spectrum, all suggest the possibility of its being a Herbig-Haro (HH) object. To test this possibility we undertook measurements of its proper motion and variability (two of the characteristic properties of HH objects). These yield μ_a = (3.6 ± 2.3) arcsec/century and μ_δ= (−1.2 ± 2.0) arcsec/century for its proper motion. The source reveals large variation in brightness between 1950 and 1954. Optical line studies of the source are required to confirm its classification as an HH object.     

BATSE/OSSE rapid burst response

The BATSE and OSSE instrument teams have modified flight software to promptly (within 2 min of trigger) slew the OSSE detectors to burst locations determined on-board by BATSE. This enables OSSE to make sensitive searches for prompt and delayed post-burst line and continuum emission above 50 keV. In the best cases our sensitivity will be more than an order of magnitude better than any other search in this energy range. We expect to slew to 1–2 bursts per month, based on the OSSE FOV and BATSE event rate. Detections or limits from continued operation of this system may provide significant constraints on burst models. As an example of the observations made using this system, we present preliminary limits for post-burst emission from GRB 950223 on several time scales.     

Comet P/Shoemaker-Levy 9 Collision with Jupiter: A Model of G-Site Dust Composition

Scattering models of aerosol particles at the G-impact site (18 July1994) are presented for a number of likely compositional candidates. Two differing dust particle population distribution functions are taken, along with varying aerosol cloud densities, leading to differing optical depths. A number of models including graphite, amorphous carbon, astrophysical silicate, water ice and a number of organic compounds are discussed, but no single material provides a fully satisfactory fit to the published observations. A porous silicate/graphite composite is found to provide a good fit to the spectral data. This revised version was published online in July 2006 with corrections to the Cover Date.     

A kinetic model of gas flow in a porous cometary mantle

A numerical study of gas flow through a porous cometary mantle is presented. A kinetic model based on the well-known Test Particle Monte Carlo Method for the solution of rarefied gas dynamics problems is proposed. The physical model consists of two spatial plane regions: the condensed ice phase and a porous dust mantle. The structure of the porous dust layer is described as a bundle of cylindrical inclined channels not crossing each other. A vertical temperature gradient may exist across the dust mantle. The aim is to investigate how the characteristics of molecular flow depend on the capillary length, inclination angle, and temperature gradient. Examples illustrating a significant deviation of some results from equilibrium values are shown. In particular, the gas velocity distribution at both ends of the pore is strongly non-Maxwellian if there is an important temperature contrast across the pore. The emergent gas flow rate is found to vary with the pore length/radius ratio in excellent agreement with Clausing's empirical formula. The degree of collimation of the flow is quantitatively studied as a function of the length/radius ratio, and consequences for the jet force of outgassing through a dust mantle or, indeed, a rough surface are estimated.     

Simultaneous five color (UBVRI) polarimetry of EF Eri

We present the first observations of the AM Her type object EF Eri where both the polarization and the photometric data are recorded simultaneously in five color bands (UBVRI). The position angle rotates strongly (30°) vs. wavelength from U to I, probably due to Faraday rotation or due to fact that the polarized radiation seen in the different wavelength bands comes from different parts of the accretion region. The phase dependence of the position angle requires field and accretion geometry more complicated than a simple centered dipole and a second emitting region producing weaker intermediate pulses in the infrared seems to be present. We derive the value of the inclination of the system i=55°±5°, the colatitude of the active pole ₁,= 38° ±5° and the second emitting region = 115° ± 5°, both of which are nearly at the same longitude facing the main accretion stream.Based on observations made at the European Southern Observatory, La Silla, Chile.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

A survey of nova remnants

Exnovae and nova shells are generally faint and difficult to observe. Only a few have been studied, and even less of them in sufficient detail. We give a progress report on our survey of exnovae and nova shells, especially on the results of a spectral survey of novae in the southern Milky Way. The three-dimensional structure in the light of H derived for the nebula of GK Per is displayed.Based on observations obtained at the European Southern Observatory, La Silla, Chile, and at the Centro Astronomico Hispano-Aleman Calar Alto, Spain, operated by the Max-Planck-Institut für Astronomie, Heidelberg.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Simultaneous five color (UBVRI) polarimetry of VV Puppis

Observations of linear and circular polarization in five colour bands during a highly active state of VV Puppis in January-86 are reported. A strong linear polarization pulse with the maximum in the blue, P_B22 %, is observed at the end of the bright phase when the active pole is at the limb and a weaker secondary pulse, P_B7 %, is seen in the beginning of the bright phase, when the active pole reappears. Strong positive circular polarization is also observed in the blue and the ultraviolet, P_UP_B18 %, P_V10 % during the bright phase. The circular polarization reverses the sign in the B and V bands during the faint phase and a negative polarization hump is seen when the active pole crosses the limb. The circular polarization in the V band reaches the value P_V–10% at the hump, after which it remains near P_V–5% during the faint phase. This is probably due to radiation coming from the second, less active pole and accretion thus takes place onto both poles. The wavelength dependences of the positive and negative parts of the circular polarization curve are different and no polarization reversal is seen in the U band. The position angle of the linear polarization is well determined during a large portion of the cycle, especially in the V band, thanks to the activity from both poles. A best fit to the position angle curve, taking into account also the duration of the positive circular polarization phase interval =0.40 (in the V band), yields the values of orbital inclination i=78°±2° and the colatitude of the active magnetic pole =146°±2°. The relatively good fit to the position angle data indicates that the simple dipole model is nearly correct in the case of VV Puppis. Some wavelength dependence is, however, seen in the position angle curves, especially in the I band where the slope / at the main pulse is considerably smaller than in the other bands. The shape of the position angle curves changes also in the blue and the ultraviolet around the middle of the bright phase. This is probably due to optical thickness effects as the side of the accretion column which is toward the observer changes near this phase.Based on observations made at the European Southern Observatory, La Silla, Chile.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.On leave from University of Helsinki Observatory     

Atomic data relevant to line formation in strongly magnetized white dwarf stars

The discovery of magnetic field strengths in the range of 500 million Gauss in the objects Grw+70°8247 and PG1031+224 has given enormous impetus to investigations of magnetic white dwarf stars. We have determined intensities of Balmer transitions for B>10⁸ Gauss as a function of field and find strong oscillations of the transitions strengths, which are of importance to the quantitative analysis of the observed spectra and the interpretation of polarimetric measurements in these objects.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

The energy distributions of magnetic variables: The effects of inhomogeneous accretion columns

Previous shock models for the AM Herculis-type magnetic variables have assumed homogeneous accretion columns, with constant infall densities out to a characteristic column radius. The resulting energy distributions are strongly peaked in the visible to ultraviolet and are in disagreement with observations. We report the preliminary results of calculations with more general radial functions of the infall density. Exponential and gaussian profiles yield continua profiles produce continua which are flatter and in better agreement with observations. Comparisons are made to data for AM Her and E2003+225.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Age distribution of open clusters as a function of their linear diameter and age-dependence of cluster masses

From the well-observed data of star clusters, the age distribution of galactic clusters is obtianed as a function of their linear diameter and it is concluded that the observed age distribution of clusters for different linear diameter intervals within 1500 pc, is not seriously affected by the selection effects. If we assume that the rate of formation of clusters is constant, the lifetimes _1/2 of the clusters for different linear diameter intervals have been obtained and it is found that the clusters with a linear diameter in the range 0–1.9 pc have longer lifetimes than the clusters having linear diameters larger than 2.0 pc.Total masses of 57 clusters have been obtained using the catalogues of Piskunov (1983) and Myakutinet al. (1984). A study of age-dependence of cluster masses, based on the total masses of the clusters obtained in the present study and the cluster masses given by Bruch and Sanders (1983) and Lynga (1983b), shows that there is a decreasing trend in the total mass with the age, however, there is an increasing trend after the age of about 10⁸ yr. It is also concluded that the initial rate of formation of rich clusters was relatively higher than the present rate of formation.