A Sward Based Method to Estimate Herbage Selection of Grazing Dairy Cows

Diet selection of grazing animals is influenced by sward composition and vertical sward structure. Grazing studies were established in northern Germany (Kiel, Schleswig - Holstein state) to determine if selective grazing behaviour in a mixed sward can be measured by a sward based method. The hypothesis that active selection of different functional groups of forages can be documented by using the selection index (Figure 1, Hodgson, 1990) and regressive approaches vs time was tested

A spectropolarimetric view on the nature of the peculiar Type I SN 2005hk

We report two spectropolarimetric observations of SN 2005hk, which is a close copy of the "very peculiar" SN 2002cx, showing low peak luminosity, slow decline, high ionization near peak and an unusually low expansion velocity of only about 7,000 km s^-1. Further to the data presented by Chornock et al., (2006), at -4 days before maximum, we present data of this object taken on 9 November 2005 (near maximum) and 23 November (+ two weeks) that show the continuum and most of the spectral lines to be polarized at levels of about 0.2-0.3%. At both epochs the data corresponds to the Spectropolarimetric Type D1. The general low level of line polarization suggests that the line forming regions for most species observed in the spectrum have a similar shape to that of the photosphere, which deviates from a spherical symmetry by <10%. In comparison with spectropolarimetry of Type Ia and Core-collapse SNe at similar epochs, we find that the properties of SN 2005hk are most similar to those of Type Ia SNe. In particular, we find the low levels of continuum and line polarization to indicate that the explosion mechanism is approximately spherical, with homogeneous ejecta (unlike the chemically segregated ejecta of CCSNe). We discuss the possibility that SN 2005hk was the result of the pure deflagration of a white dwarf and note the issues concerning this interpretation.Comment: ApJ accepted, uses emulateapj, 16 pages, 10 figures, figures 3 and 4 update

Spectropolarimetry of the Type Ia SN 2007sr Two Months After Maximum Light

We present late time spectropolarimetric observations of SN 2007sr, obtained with the VLT telescope at ESO Paranal Observatory when the object was 63 days after maximum light. The late time spectrum displays strong line polarization in the CaII absorption features. SN 2007sr adds to the case of some normal Type Ia SNe that show high line polarization or repolarization at late times, a fact that might be connected with the presence of high velocity features at early times

Spectroscopic and photometric oscillatory envelope variability during the S Doradus outburst of the Luminous Blue Variable R71

To better understand the LBV phenomenon, we analyze multi-epoch and multi-wavelength spectra and photometry of R71. Pre-outburst spectra are analyzed with the radiative transfer code CMFGEN to determine the star's fundamental stellar parameters. During quiescence, R71 has an effective temperature of $T_\mathrm{{eff}} = 15\,500~K$ and a luminosity of log$(L_*/L_{\odot})$ = 5.78 and is thus a classical LBV, but at the lower luminosity end of this group. We determine its mass-loss rate to $4.0 \times 10^{-6}~M_{\odot}~$yr$^{-1}$. We present R71's spectral energy distribution from the near-ultraviolet to the mid-infrared during its present outburst. Mid-infrared observations suggest that we are witnessing dust formation and grain evolution. Semi-regular oscillatory variability in the star's light curve is observed during the current outburst. Absorption lines develop a second blue component on a timescale twice that length. The variability may consist of one (quasi-)periodic component with P ~ 425/850 d with additional variations superimposed. During its current S Doradus outburst, R71 occupies a region in the HR diagram at the high-luminosity extension of the Cepheid instability strip and exhibits similar irregular variations as RV Tau variables. LBVs do not pass the Cepheid instability strip because of core evolution, but they develop comparable cool, low-mass, extended atmospheres in which convective instabilities may occur. As in the case of RV Tau variables, the occurrence of double absorption lines with an apparent regular cycle may be due to shocks within the atmosphere and period doubling may explain the factor of two in the lengths of the photometric and spectroscopic cycles.Comment: 18 pages, 14 figures, submitted to A&

Properties of extragalactic dust inferred from linear polarimetry of Type Ia Supernovae

Aims: The aim of this paper is twofold: 1) to investigate the properties of extragalactic dust and compare them to what is seen in the Galaxy; 2) to address in an independent way the problem of the anomalous extinction curves reported for reddened Type Ia Supernovae (SN) in connection to the environments in which they explode. Methods: The properties of the dust are derived from the wavelength dependence of the continuum polarization observed in four reddened Type Ia SN: 1986G, 2006X, 2008fp, and 2014J. [...] Results: All four objects are characterized by exceptionally low total-to-selective absorption ratios (R_V) and display an anomalous interstellar polarization law, characterized by very blue polarization peaks. In all cases the polarization position angle is well aligned with the local spiral structure. While SN~1986G is compatible with the most extreme cases of interstellar polarization known in the Galaxy, SN2006X, 2008fp, and 2014J show unprecedented behaviours. The observed deviations do not appear to be connected to selection effects related to the relatively large amounts of reddening characterizing the objects in the sample. Conclusions: The dust responsible for the polarization of these four SN is most likely of interstellar nature. The polarization properties can be interpreted in terms of a significantly enhanced abundance of small grains. The anomalous behaviour is apparently associated with the properties of the galactic environment in which the SN explode, rather than with the progenitor system from which they originate. For the extreme case of SN2014J, we cannot exclude the contribution of light scattered by local material; however, the observed polarization properties require an ad hoc geometrical dust distribution.Comment: 10 pages, 6 figures, accepted for publication in Astronomy and Astrophysic

Updated Information on the Local Group

The present note updates the information published in my recent monograph on \underline{The Galaxies of the Local Group}. Highlights include (1) the addition of the newly discovered Cetus dwarf spheroidal as a certain member of the Local Group, (2) an improved distance for SagDIG, which now places this object very close to the edge of the Local Group zero-velocity surface, (3) more information on the evolutionary histories of some individual Local Group members, and (4) improved distance determinations to, and luminosities for, a number of Local Group members. These data increase the number of certain (or probable) Local Group members to 36. The spatial distribution of these galaxies supports Hubble's claim that the Local Group ``is isolated in the general field.'' Presently available evidence suggests that star formation continued much longer in many dwarf spheroidals than it did in the main body of the Galactic halo. It is suggested that ``young'' globular clusters, such as Ruprecht 106, might have formed in now defunct dwarf spheroidals. Assuming SagDIG, which is the most remote Local Group galaxy, to lie on, or just inside, the zero-velocity surface of the Local Group yields a dynamical age \gtrsim 17.9 \pm 2.7 Gyr.Comment: 19 pages, 1 figure, to be published in the April 2000 issue of PAS

Spectropolarimetry of the 2012 outburst of SN 2009ip: A bi-polar explosion in a dense, disc-like CSM

We present a sequence of eight spectropolarimetric observations monitoring the geometric evolution of the late phase of the major 2012 outburst of SN 2009ip. These were acquired with the Focal Reducer and Low Dispersion Spectrograph polarimeter mounted on European Southern Observatory VLT. The continuum was polarized at 0.3-0.8 per cent throughout the observations, showing that the photosphere deviated substantially from spherical symmetry by 10-15 per cent. Significant line polarization is detected for both hydrogen and helium at high velocities. The similarity in the polarized signal between these elements indicates that they form in the same location in the ejecta. The line polarization (p ~ 1-1.5 per cent) at low velocities revealed the presence of a highly aspherical hydrogen- and helium-rich circumstellar medium (CSM). Monte Carlo simulations of the observed polarimetry were performed in an effort to constrain the shape of the CSM. The simulations imply that the polarimetry can be understood within the framework of a disc-like CSM inclined by 14° ± 2° out of the line of sight, obscuring the photosphere only at certain epochs. The varying temporal evolution of polarization at high and low velocities indicated that the fast-moving ejecta expanded with a preferred direction orthogonal to that of the CSM

Uncovering the kiloparsec-scale stellar ring of NGC5128

We reveal the stellar light emerging from the kiloparsec-scale, ring-like structure of the NGC5128 (Centaurus A) galaxy in unprecedented detail. We use arcsecond-scale resolution near infrared images to create a "dust-free" view of the central region of the galaxy, which we then use to quantify the shape of the revealed structure. At the resolution of the data, the structure contains several hundreds of discreet, point-like or slightly elongated sources. Typical extinction corrected surface brightness of the structure is K_S = 16.5 mag/arcsec^2, and we estimate the total near infrared luminosity of the structure to be M = -21 mag. We use diffraction limited (FWHM resolution of ~ 0.1", or 1.6 pc) near infrared data taken with the NACO instrument on VLT to show that the structure decomposes into thousands of separate, mostly point-like sources. According to the tentative photometry, the most luminous sources have M_K = -12 mag, naming them red supergiants or relatively low-mass star clusters. We also discuss the large-scale geometry implied by the reddening signatures of dust in our near infrared images.Comment: 5 pages, 4 figures, accepted for publication in A&A Letters. A version with high resolution images can be downloaded from http://www.helsinki.fi/~jtkainul/CenALette

Pre-Maximum Spectropolarimetry of the Type Ia SN 2004dt

We report observations of SN 2004dt obtained with the Very Large Telescope of the European Southern Observatory on August 13.30, 2004 when the supernova was more than a week before optical maximum. SN 2004dt showed strong lines of \ion{O}{1}, \ion{Mg}{2}, \ion{Si}{2}, and \ion{Ca}{2} with typical velocities of absorption minimum around 17,000 \kms. The line profiles show material moving at velocities as high as 25,000 \kms in these lines. The observations also reveal absorption lines from \ion{S}{2} and \ion{Si}{3} with a velocity of only 11,000 \kms. The highest velocity in the \ion{S}{2} features can be traced no higher than 15,000 \kms, much lower than those of O, Mg, Si, and Ca. SN 2004dt has a polarization spectrum unlike any previously observed. The variation of the polarization across some \ion{Si}{2} lines approaches 2%, making SN 2004dt the most highly polarized SN Ia ever observed. In contrast, the strong line of O I at 777.4 nm shows little or no polarization signature. The degree of polarization points to a richly-structured partially burned silicon layer with substantial departure from spherical symmetry. A geometry that would account for the observations is one in which the distribution of oxygen is essentially spherically symmetric, but with bubbles of intermediate-mass elements with significant opacity within the oxygen substrate.Comment: Submitted to Ap