| 1. |
- Pastorello, A., et al.
(författare)
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A giant outburst two years before the core-collapse of a massive star
- 2007
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 829-832
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Tidskriftsartikel (refereegranskat)abstract
- The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars(1,2). The detection of several precursor stars of type II supernovae has been reported ( see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient(4) that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf - Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60 - 100 solar masses(5), but the progenitor of SN 2006jc was helium- and hydrogen-deficient ( unlike LBVs). An LBV-like outburst of a Wolf - Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf - Rayet star exploding as SN 2006jc, could explain the observations.
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| 2. |
- Kotak, R., et al.
(författare)
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Dust and The Type II-Plateau Supernova 2004et
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 704:1, s. 306-323
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Tidskriftsartikel (refereegranskat)abstract
- We present mid-infrared (MIR) observations of the Type II-plateau supernova (SN) 2004et, obtained with the Spitzer Space Telescope between 64 and 1406 days past explosion. Late-time optical spectra are also presented. For the period 300-795 days past explosion, we argue that the spectral energy distribution (SED) of SN 2004et comprises (1) a hot component due to emission from optically thick gas, as well as free-bound radiation; (2) a warm component due to newly formed, radioactively heated dust in the ejecta; and (3) a cold component due to an IR echo from the interstellar-medium dust of the host galaxy, NGC 6946. There may also have been a small contribution to the IR SED due to free-free emission from ionized gas in the ejecta. We reveal the first-ever spectroscopic evidence for silicate dust formed in the ejecta of a supernova. This is supported by our detection of a large, but progressively declining, mass of SiO. However, we conclude that the mass of directly detected ejecta dust grew to no more than a few times 10-4 M sun. We also provide evidence that the ejecta dust formed in comoving clumps of fixed size. We argue that, after about two years past explosion, the appearance of wide, box-shaped optical line profiles was due to the impact of the ejecta on the progenitor circumstellar medium and that the subsequent formation of a cool, dense shell was responsible for a later rise in the MIR flux. This study demonstrates the rich, multifaceted ways in which a typical core-collapse supernova and its progenitor can produce and/or interact with dust grains. The work presented here adds to the growing number of studies that do not support the contention that SNe are responsible for the large mass of observed dust in high-redshift galaxies.
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| 3. |
- Mazzali, P. A., et al.
(författare)
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High-Velocity Features : A Ubiquitous Property of Type Ia Supernovae
- 2005
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 623, s. L37-L40
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Tidskriftsartikel (refereegranskat)abstract
- Evidence of high-velocity features (HVFs) such as those seen in the near-maximum spectra of some Type Ia supernovae (SNe Ia; e.g., SN 2000cx) has been searched for in the available SN Ia spectra observed earlier than 1 week before B maximum. Recent observational efforts have doubled the number of SNe Ia with very early spectra. Remarkably, all SNe Ia with early data (seven in our Research Training Network sample and 10 from other programs) show signs of such features, to a greater or lesser degree, in Ca II IR and some also in the Si II λ6355 line. HVFs may be interpreted as abundance or density enhancements. Abundance enhancements would imply an outer region dominated by Si and Ca. Density enhancements may result from the sweeping up of circumstellar material (CSM) by the highest velocity SN ejecta. In this scenario, the high incidence of HVFs suggests that a thick disk and/or a high-density companion wind surrounds the exploding white dwarf, as may be the case in single degenerate systems. Large-scale angular fluctuations in the radial density and abundance distribution may also be responsible: this could originate in the explosion and would suggest a deflagration as the more likely explosion mechanism. CSM interaction and surface fluctuations may coexist, possibly leaving different signatures on the spectrum. In some SNe, the HVFs are narrowly confined in velocity, suggesting the ejection of blobs of burned material.
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| 4. |
- Meikle, W. P. S., et al.
(författare)
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A Spitzer Space Telescope Study of SN 2002hh : An Infrared Echo from a Type IIP Supernova
- 2006
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 649, s. 332-344
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Tidskriftsartikel (refereegranskat)abstract
- We present late-time (590-994 days) mid-IR photometry of the normal but highly reddened Type IIP supernova SN 2002hh. Bright, cool, slowly fading emission is detected from the direction of the supernova. Most of this flux appears not to be driven by the supernova event but instead probably originates in a cool, obscured star formation region or molecular cloud along the line of sight. We also show, however, that the declining component of the flux is consistent with an SN-powered IR echo from a dusty progenitor CSM. Mid-IR emission could also be coming from newly condensed dust and/or an ejecta/CSM impact, but their contributions are likely to be small. For the case of a CSM-IR echo, we infer a dust mass of as little as 0.036 Msolar with a corresponding CSM mass of 3.6(0.01/rdg) Msolar, where rdg is the dust-to-gas mass ratio. Such a CSM would have resulted from episodic mass loss whose rate declined significantly about 28,000 years ago. Alternatively, an IR echo from a surrounding, dense, dusty molecular cloud might also have been responsible for the fading component. Either way, this is the first time that an IR echo has been clearly identified in a Type IIP supernova. We find no evidence for or against the proposal that Type IIP supernovae produce large amounts of dust via grain condensation in the ejecta. However, within the CSM-IR echo scenario, the mass of dust derived implies that the progenitors of the most common of core-collapse supernovae may make an important contribution to the universal dust content.
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| 5. |
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| 6. |
- Dahlen, Tomas, et al.
(författare)
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The Stockholm Vimos Supernova Survey (SVISS) - First Results From An Intermediate Redshift Sn Survey
- 2009
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Konferensbidrag (refereegranskat)abstract
- The aim of the Stockholm VIMOS Supernova Survey is to find and characterize supernovae in the redshift range 0.1 to 1.2 and to derive accurate supernova rate densities for this redshift range. A preliminary analysis show that we have 14 prime SN candidates and an additional 23 less secure detections in one of our search fields. A sample of R+I light curves for the prime candidates will be presented. We will also show some results from testing of our supernova search pipeline and our supernova typing method.
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| 7. |
- Hernberg, Micaela, et al.
(författare)
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The prognostic role of blood lymphocyte subset distribution in patients with resected high-risk primary or regionally metastatic melanoma.
- 2007
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Ingår i: Journal of immunotherapy (Hagerstown, Md. : 1997). - 1524-9557. ; 30:7, s. 773-9
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate whether the profile of peripheral blood lymphocyte subsets of patients with high-risk malignant melanoma is associated with prognosis. Blood samples were systematically obtained from 31 patients with high-risk melanoma eligible for the Nordic Melanoma Cooperative Group adjuvant interferon study. The frequencies of peripheral blood lymphocyte subsets were monitored by flow cytometry using CD3, CD4, CD8, CD56, and CD69 monoclonal antibodies. Patients with low proportions of CD3+CD4+CD69+ cells and of CD3+CD56+ cells before treatment had an improved disease-free survival compared to those with high proportions [77.7 vs. 16.8 mo, hazard ratio (HR) 0.25, confidence interval (CI) 0.09-0.71, P=0.005 and 77.2 vs. 16.0 mo, HR: 0.25, CI 0.086-0.73, P=0.001, respectively]. Low pretreatment levels of these cell populations also correlated with a better overall survival (79.2 vs. 22.6 mo, HR: 0.17, CI 0.05-0.52, P=0.0005 and 78.2 vs. 21.4 mo, HR: 0.2, CI 0.07-0.59, P=0.001, respectively). In the multivariate analysis both the pretreatment proportion of CD3+CD4+CD69+ cells (P=0.01, HR: 0.21, CI 0.07-0.67) and CD3+CD56+ cells (P=0.01, HR: 0.22, CI 0.062-0.65) were independent prognostic factors for overall survival. Our data show that both the proportions of CD3+CD4+CD69+ cells and of CD3+CD56+ cells seem to have a prognostic potential in the natural course of melanoma. These results need to be confirmed in larger studies.
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| 8. |
- Laukkanen, P, et al.
(författare)
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Electronic and structural properties of GaAs(100)(2x4) and InAs(100)(2x4) surfaces studied by core-level photoemission and scanning tunneling microscopy
- 2005
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 72:4
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and structural properties of GaAs(100)(2x4), InAs(100)(2x4), and Sb/InAs(100)(2x4) reconstructed surfaces have been studied by synchrotron-radiation photoelectron spectroscopy and scanning tunneling microscopy (STM). Based on the difference spectrum of As 3d core-level spectra of III-As(100)(2x4), measured in different surface-sensitivity conditions, as well as the line shape of the As 3d emission from the Sb-induced (2x4) surface, we give evidence that the As 3d spectra of GaAs(100)(2x4) and InAs(100)(2x4) consist of two surface-core-level-shifted components. One of them is shifted about 0.2 eV to the lower kinetic energy from the bulk component. On the basis of the relative component intensities, this surface-shifted As 3d component is assigned to the emission from the first-layer As dimers in the established model of the (2x4) surface. The other component, shifted about 0.3 eV to the higher kinetic energy, is connected to the third-layer As-dimer site. The comparison of the core-level results between GaAs(100)(2x4) and InAs(100)(2x4) suggests that the alpha 2 phase, which has one As dimer in both the first and third atomic layers per unit cell, exists on GaAs(100)(2x4), similarly to the case of InAs(100)(2x4), as predicted in theory but not observed to date. Furthermore, the STM observation of the GaAs(100)(2x4)alpha 2 phase is reported.
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| 9. |
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| 10. |
- Mattila, Seppo, et al.
(författare)
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Adaptive Optics Discovery of Supernova 2004ip in the Nuclear Regions of the Luminous Infrared Galaxy IRAS 18293-3413
- 2007
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 659:1, s. L9-L12
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Tidskriftsartikel (refereegranskat)abstract
- We report a supernova discovery in Ks-band images from the NAOS CONICA adaptive optics (AO) system on the ESO Very Large Telescope. The images were obtained as part of a near-infrared search for highly obscured supernovae in the nuclear regions of luminous and ultraluminous infrared galaxies. SN 2004ip is located within a circumnuclear starburst at 1.4" (or 500 pc) projected distance from the K-band nucleus of the luminous infrared galaxy IRAS 18293-3413. The supernova luminosity and light curve are consistent with a core-collapse event suffering from a host galaxy extinction of up to about 40 mag in the V band, which is as expected for a circumnuclear starburst environment. This is the first supernova to be discovered making use of AO correction and demonstrates the potential of the current 8 m-class telescopes equipped with AO in discovering supernovae from the innermost nuclear regions of luminous and ultraluminous infrared galaxies.
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