SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Lundqvist Peter) srt2:(2010-2013)"

Sökning: WFRF:(Lundqvist Peter) > (2010-2013)

  • Resultat 1-10 av 116
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Wang, Xiaofeng, et al. (författare)
  • Evidence for type ia supernova diversity from ultraviolet observations with the hubble space telescope
  • 2012
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:2, s. 126-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 angstrom. Significant diversity is seen in the near-maximum-light spectra (similar to 2000-3500 angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminositiesmeasured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Delta m(15)(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., similar to 0.4 mag versus similar to 0.2 mag for those with 0.8 mag < Delta m(15)(B) < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by similar to 0.9 mag and similar to 2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
  •  
2.
  • France, Kevin, et al. (författare)
  • HST-COS Observations of Hydrogen, Helium, Carbon, and Nitrogen Emission from the SN 1987A Reverse Shock
  • 2011
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 743:2, s. 186-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (Δv ~ 300 km s-1) emission lines from the circumstellar ring, broad (Δv ~ 10-20 × 103 km s-1) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Lyα emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at λ > 1350 Å can be explained by H I two-photon (2s 2 S 1/2-1s 2 S 1/2) emission from the same region. We confirm our earlier, tentative detection of N V λ1240 emission from the reverse shock and present the first detections of broad He II λ1640, C IV λ1550, and N IV] λ1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 ± 0.06. The N V/Hα line ratio requires partial ion-electron equilibration (Te /Tp ≈ 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expulsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expulsion of the circumstellar ring. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
  •  
3.
  • France, Kevin, et al. (författare)
  • Observing Supernova 1987A with the Refurbished Hubble Space Telescope
  • 2010
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 329:5999, s. 1624-1627
  • Tidskriftsartikel (refereegranskat)abstract
    • Observations with the Hubble Space Telescope (HST), conducted since 1990, now offer an unprecedented glimpse into fast astrophysical shocks in the young remnant of supernova 1987A. Comparing observations taken in 2010 with the use of the refurbished instruments on HST with data taken in 2004, just before the Space Telescope Imaging Spectrograph failed, we find that the Ly alpha and H alpha lines from shock emission continue to brighten, whereas their maximum velocities continue to decrease. We observe broad, blueshifted Ly alpha, which we attribute to resonant scattering of photons emitted from hot spots on the equatorial ring. We also detect N v lambda lambda 1239, 1243 angstrom line emission, but only to the red of Ly alpha. The profiles of the N v lines differ markedly from that of H alpha, suggesting that the N4+ ions are scattered and accelerated by turbulent electromagnetic fields that isotropize the ions in the collisionless shock.
  •  
4.
  • Pinzke, Stefan, et al. (författare)
  • Tractor Incidence on Swedish roads
  • 2012
  • Ingår i: Nordic Meeting on Agricultural Occupational Health & Safety August 27-29 Ystad Sweden.
  • Konferensbidrag (refereegranskat)abstract
    • Compared with other industries, agriculture is the most dangerous branch in Sweden. In 2004,at least one injury occurred on 8% of Swedish farms that resulted in body impairments andconstituted obstacle at work. Beside the injuries that occured on the farms farmers also areinvolved in incidents with tractors and other slow-moving vehicles (SMVs) on the roadsoutside the farms.
  •  
5.
  • Fransson, Claes, et al. (författare)
  • Late spectral evolution of the ejecta and reverse shock in SN 1987a
  • 2013
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 768:1, s. 88-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present observations with the Very Large Telescope and Hubble Space Telescope (HST) of the broad emission lines from the inner ejecta and reverse shock of SN 1987A from 1999 February until 2012 January (days 4381-9100 after explosion). We detect broad lines from H alpha, H beta, Mg I], Na I, [O I], [Ca II], and a feature at similar to 9220 angstrom. We identify the latter line with Mg II lambda lambda 9218, 9244, which is most likely pumped by Ly alpha fluorescence. H alpha and H beta both have a centrally peaked component extending to similar to 4500 km s(-1) and a very broad component extending to greater than or similar to 11,000 km s(-1), while the other lines have only the central component. The low-velocity component comes from unshocked ejecta, heated mainly by X-rays from the circumstellar environment, whereas the very broad component comes from faster ejecta passing through the reverse shock, created by the collision with the circumstellar ring. The flux in H alpha from the reverse shock has increased by a factor of four to six from 2000 to 2007. After that there is a tendency of flattening of the light curve, similar to what may be seen in the optical lines from the shocked ring. The core component seen in H alpha, [Ca II], and Mg II has experienced a similar increase, which is consistent with that found from HST photometry. The energy deposition of the external X-rays is calculated using explosion models for SN 1987A and we predict that the outer parts of the unshocked ejecta will continue to brighten because of this. The external X-ray illumination also explains the edge-brightened morphology of the ejecta seen in the HST images. We finally discuss evidence for dust in the ejecta from line asymmetries.
  •  
6.
  • Lundqvist, Natalia, 1974-, et al. (författare)
  • Spectral evolution and polarization of variable structures in the pulsar wind nebula of PSR B0540-69.3
  • 2011
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 413:1, s. 611-627
  • Tidskriftsartikel (refereegranskat)abstract
    • We present high spatial resolution optical imaging and polarization observations of the PSR B0540-69.3 and its highly dynamical pulsar wind nebula (PWN) performed with Hubble Space Telescope, and compare them with X-ray data obtained with the Chandra X-ray Observatory. In particular, we have studied the bright region south-west of the pulsar where a bright 'blob' is seen in 1999. In a recent paper by De Luca et al. it was argued that the 'blob' moves away from the pulsar at high speed. We show that it may instead be a result of local energy deposition around 1999, and that the emission from this then faded away rather than moved outward. Polarization data from 2007 show that the polarization properties show dramatic spatial variations at the 1999 blob position arguing for a local process. Several other positions along the pulsar-'blob' orientation show similar changes in polarization, indicating previous recent local energy depositions. In X-rays, the spectrum steepens away from the 'blob' position, faster orthogonal to the pulsar-'blob' direction than along this axis of orientation. This could indicate that the pulsar-'blob' orientation is an axis along where energy in the PWN is mainly injected, and that this is then mediated to the filaments in the PWN by shocks. We highlight this by constructing an [S ii]-to-[O iii]-ratio map, and comparing this to optical continuum and X-ray emission maps. We argue, through modelling, that the high [S ii]/[O iii] ratio is not due to time-dependent photoionization caused by possible rapid X-ray emission variations in the 'blob' region. We have also created a multiwavelength energy spectrum for the 'blob' position showing that one can, to within 2 Sigma, connect the optical and X-ray emission by a single power law. The slope of that power law (defined from ) would be alpha(nu) = 0.74 +/- 0.03, which is marginally different from the X-ray spectral slope alone with alpha(nu) = 0.65 +/- 0.03. A single power law for most of the PWN is, however, not be possible. We obtain best power-law fits for the X-ray spectrum if we include 'extra' oxygen, in addition to the oxygen column density in the interstellar gas of the Large Magellanic Cloud and the Milky Way. This oxygen is most naturally explained by the oxygen-rich ejecta of the supernova remnant. The oxygen needed likely places the progenitor mass in the 20-25 M(circle dot) range, i.e. in the upper mass range for progenitors of Type IIP supernovae.
  •  
7.
  • Mattila, Seppo, et al. (författare)
  • Abundances and Density Structure of the Inner Circumstellar Ring Around SN 1987A
  • 2010
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 717:2, s. 1140-1156
  • Tidskriftsartikel (refereegranskat)abstract
    • We present optical spectroscopic data of the inner circumstellar ring around supernova (SN) 1987A from the Anglo-Australian Telescope and the Very Large Telescope (VLT) between ~1400 and ~5000 days post-explosion. We also assembled the available optical and near-infrared line fluxes from the literature between ~300 and ~2000 days. These line light curves were fitted with a photoionization model to determine the density structure and the elemental abundances for the inner ring. We found densities ranging from 1 × 103 to 3 × 104 atoms cm-3 and a total mass of the ionized gas of ~5.8 × 10-2 M sun within the inner ring. Abundances inferred from the optical and near-infrared data were also complemented with estimates of Lundqvist & Fransson based on ultraviolet lines. This way we found an He/H ratio (by number of atoms) of 0.17 ± 0.06 which is roughly 30% lower than previously estimated and twice the solar and the Large Magellanic Cloud (LMC) value. We found an N/O ratio of 1.5 ± 0.7, and the total (C+N+O)/(H+He) abundance about 1.6 times its LMC value or roughly 0.6 times the most recent solar value. An iron abundance of 0.20 ± 0.11 times solar was found which is within the range of the estimates for the LMC. We also present late time (~5000-7500 days) line light curves of [O III], [Ne III], [Ne IV], [Ar III], [Ar IV], and [Fe VII] from observations with the VLT. We compared these with model fluxes and found that an additional 102 atoms cm-3 component was required to explain the data of the highest ionization lines. Such low-density gas is expected in the H II-region interior to the inner ring which likely extends also to larger radii at higher latitudes (out of the ring plane). At epochs later than ~5000 days, our models underproduce the emission of most of these lines as expected due to the contribution from the interaction of the SN ejecta with the ring.
  •  
8.
  • Sandin, Christer, et al. (författare)
  • Properties of the three-dimensional structure in the central region of the supernova remnant SNR 0540−69.3
  • 2013
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 432:4, s. 2854-2868
  • Tidskriftsartikel (refereegranskat)abstract
    • We present and discuss new visual wavelength-range observations of the inner regions of the supernova remnant SNR 0540−69.3 that is located in the Large Magellanic Cloud (LMC). These observations provide us with more spatial and spectral information than were previously available for this object. We use these data to create a detailed three-dimensional model of the remnant, assuming linear expansion of the ejecta. With the observations and the model, we study the general three-dimensional structure of the remnant, and the influence of an active region in the remnant – a ‘blob’ – that we address in previous papers. We used the fibre-fed integral-field Visual Multi-Object Spectrograph at the Very Large Telescope of the European Southern Observatory. The observations provide us with three-dimensional data in [O iii] λ5007 and [S ii] λλ6717, 6731 at a 0.33 arcsec × 0.33 arcsec spatial sampling and a velocity resolution of about 35 km s− 1. We decomposed the two, partially overlapping, sulphur lines and used them to calculate electron densities across the remnant at a high signal-to-noise ratio. In our study, we recover results of previous studies, but we are more importantly able to obtain more detailed information than before. Our analysis reveals a structure that stretches from the position of the ‘blob’, and into the plane of the sky at a position angle of PA ≃ 60°. Assuming a remnant age of 1000 yr and the usual LMC distance, the structure has an inclination angle of about 65° to the line of sight. The position angle is close to the symmetry axis with present and past activity in the visual and the X-ray wavelength ranges. We speculate that the pulsar is positioned along this activity axis, where it has a velocity along the line of sight of a few hundred  km s− 1. The ‘blob’ is most likely a region of shock activity, as it is mainly bright in [S ii]; future observations of [O ii] λλ3726, 3729 would be useful to test whether the S/O abundance ratio is higher than average for that location in the remnant. The striking resemblance in X-rays between the pulsar wind nebula (PWN) of SNR 0540−69.3 and the Crab, in combination with our findings in this paper, suggests that the symmetry axis is part of a torus in the PWN. This is in agreement with the original suggestion by Gotthelf & Wang.
  •  
9.
  •  
10.
  • Alwall Svennefelt, Catharina, et al. (författare)
  • Barn och ungdomars säkra arbete (BUSA) : råd för medverkan i arbetet på häst-, gris- och mjölkgården
  • 2011
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Lantbruket är på många sätt unikt - inte minst då det inte bara är en arbetsplats utan även hem- och uppväxtmiljö för barn och ungdomar. Barn och ungdomar på landsbygden börjar hjälpa till i lantbruksarbetet från tidig ålder. Föreliggande projekt avsåg att utarbeta råd och riktlinjer för barn och ungdomars medverkan i lantbruksarbete. Dessa råd skulle anpassas till gällande svensk arbetsmiljölagstiftning och baseras på lämpliga arbetsuppgifter i relation till barn och ungdomars ålder, fysiska och psykiska mognad osv. En referensgrupp inrättades och ett internationellt samarbete etablerades med the National Children’s Center for Rural and Agricultural Health and Safety i USA som utvecklat rekommendationer för barns medverkan i lantbruksarbete. Projektet inleddes med en enkätundersökning gällande barns medverkan i lantbruksarbete och eventuella olycksfallsrisker. Studien visade att av de familjer som hade barn i åldrarna 7–18 var det nära 87 % av dessa där barnen deltog i lantbruksarbetet. Resultaten från enkätstudien redovisades och diskuterades i referensgruppen och med enkäten som underlag togs beslut om att utarbeta rekommendationer för barn & ungdomar med tyngdpunkt på gårdar med djurproduktion. Barn och ungdomars säkra arbete (BUSA) är det gemensamma koncept som rekommendationerna följer och i denna skrift förmedlas råd till lantbrukarfamiljerna gällande barn och ungdomars medverkan i arbetet på hästgården, grisgården och mjölkgården. Materialet är avsett att vara till inspirerande underlag för diskussioner och beslut om, hur och när barn och ungdomar ska medverka i gårdens sysslor med djurskötsel
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 116
Typ av publikation
tidskriftsartikel (38)
konferensbidrag (33)
rapport (28)
annan publikation (10)
doktorsavhandling (2)
forskningsöversikt (2)
visa fler...
bokkapitel (2)
proceedings (redaktörskap) (1)
visa färre...
Typ av innehåll
refereegranskat (54)
övrigt vetenskapligt/konstnärligt (51)
populärvet., debatt m.m. (11)
Författare/redaktör
Lundqvist, Peter (100)
Pinzke, Stefan (21)
Alwall Svennefelt, C ... (20)
Lunner Kolstrup, Chr ... (17)
Fransson, Claes (10)
Sollerman, Jesper (9)
visa fler...
Nilsson, Kerstin (7)
Larsson, Josefin (5)
Svensson, Måns (5)
Albin, Maria (5)
Kirshner, Robert P. (5)
Svennefelt, Wiveca (5)
Lindahl, Cecilia (5)
Atar, Dan (4)
Lundqvist, Hans (4)
Widimsky, Petr (4)
Bohgard, Mats (4)
Blomström-Lundqvist, ... (4)
Rivinoja, Peter (4)
Alkan Olsson, Johann ... (4)
Mattila, Seppo (4)
Spyromilio, Jason (4)
Leibundgut, Bruno (4)
Wheeler, J. Craig (4)
Leonardsson, Kjell (4)
McCray, Richard (4)
Nilsson, Ulla (4)
Tendera, Michal (3)
Kolh, Philippe (3)
Dean, Veronica (3)
McDonagh, Theresa (3)
Jerkstrand, Anders (3)
Challis, Peter (3)
Bouchet, Patrice (3)
Sonneborn, George (3)
Littorin, Margareta (3)
Reiner, Zeljko (3)
Kirchhof, Paulus (3)
Rydén, Nils (3)
Sechtem, Udo (3)
Ceconi, Claudio (3)
Funck-Brentano, Chri ... (3)
Popescu, Bogdan A (3)
Vahanian, Alec (3)
Sirnes, Per Anton (3)
Panagia, Nino (3)
Garnavich, Peter M. (3)
Urinboyev, Rustamjon (3)
Kozma, Cecilia (3)
Gröningsson, Per (3)
visa färre...
Språk
Engelska (84)
Svenska (32)
Forskningsämne (UKÄ/SCB)
Lantbruksvetenskap (69)
Medicin och hälsovetenskap (36)
Samhällsvetenskap (36)
Naturvetenskap (16)
Teknik (8)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy