| 1. |
- Gerardy, Christopher L., et al.
(författare)
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Signatures of Delayed Detonation, Asymmetry, and Electron Capture in the Mid-Infrared Spectra of Supernovae 2003hv and 2005df
- 2007
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 661:2, s. 995-1012
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Tidskriftsartikel (refereegranskat)abstract
- We present mid-infrared (5.2-15.2 μm) spectra of the Type Ia supernovae (SNe Ia) 2003hv and 2005df observed with the Spitzer Space Telescope. These are the first observed mid-infrared spectra of thermonuclear supernovae, and show strong emission from fine-structure lines of Ni, Co, S, and Ar. The detection of Ni emission in SN 2005df 135 days after the explosion provides direct observational evidence of high-density nuclear burning forming a significant amount of stable Ni in a SN Ia. The SN 2005df Ar lines also exhibit a two-pronged emission profile, implying that the Ar emission deviates significantly from spherical symmetry. The spectrum of SN 2003hv also shows signs of asymmetry, exhibiting blueshifted [Co III], which matches the blueshift of [Fe II ] lines in nearly coeval near-infrared spectra. Finally, local thermodynamic equilibrium abundance estimates for the yield of radioactive 56Ni give M56Ni~0.5 Msolar, for SN 2003hv, but only M56Ni~0.13-0.22 Msolar for the apparently subluminous SN 2005df, supporting the notion that the luminosity of SNe Ia is primarily a function of the radioactive 56Ni yield. The observed emission-line profiles in the SN 2005df spectrum indicate a chemically stratified ejecta structure, which matches the predictions of delayed detonation (DD) models, but is entirely incompatible with current three-dimensional deflagration models. Furthermore, the degree that this layering persists to the innermost regions of the supernova is difficult to explain even in a DD scenario, where the innermost ejecta are still the product of deflagration burning. Thus, while these results are roughly consistent with a delayed detonation, it is clear that a key piece of physics is still missing from our understanding of the earliest phases of SN Ia explosions.
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| 2. |
- Gröningsson, Per, et al.
(författare)
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High resolution spectroscopy of the inner ring of SN 1987A
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 479:3, s. 761-777
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Tidskriftsartikel (refereegranskat)abstract
- We discuss high resolution VLT/UVES observations (FWHM similar to 6 kms(-1)) from October 2002 (day similar to 5700 past explosion) of the shock interaction of SN 1987A and its circumstellar ring. A large number of narrow emission lines from the unshocked ring, with ion stages from neutral up to Ne V and Fe VII, have been identified. A nebular analysis of the narrow lines from the unshocked gas indicates gas densities of (similar to 1.5 - 5.0) x 10(3) cm(-3) and temperatures of similar to 6.5 x 10(3) - 2.4 x 104 K. This is consistent with the thermal widths of the lines. From the shocked component we observe a large range of ionization stages from neutral lines to [FeXIV]. From a nebular analysis we find that the density in the low ionization region is 4 x 10(6) - 10(7) cm-3. There is a clear difference in the high velocity extension of the low ionization lines and that of lines from [Fe X - XIV], with the latter extending up to similar to- 390 km s(-1) in the blue wing for [Fe XIV], while the low ionization lines extend to typically similar to- 260 km s(-1). For H alpha a faint extension up to similar to- 450 km s(-1) can be seen probably arising from a small fraction of shocked high density clumps. We discuss these observations in the context of radiative shock models, which are qualitatively consistent with the observations. A fraction of the high ionization lines may originate in gas which has yet not had time to cool, explaining the difference in width between the low and high ionization lines. The maximum shock velocities seen in the optical lines are similar to 510 km s(-1). We expect the maximum width of especially the low ionization lines to increase with time.
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| 3. |
- Gröningsson, Per, et al.
(författare)
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High resolution spectroscopy of the line emission from the inner circumstellar ring of SN 1987A and its hot spots
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We discuss high resolution VLT/UVES observations (FWHM ~ 6 km/s) from October 2002 (day ~5700 past explosion) of the shock interaction of SN 1987A and its circumstellar ring. A nebular analysis of the narrow lines from the unshocked gas indicates gas densities of (1.5-5.0)E3 cm-3 and temperatures of 6.5E3-2.4E4 K. This is consistent with the thermal widths of the lines. From the shocked component we observe a large range of ionization stages from neutral lines to [Fe XIV]. From a nebular analysis we find that the density in the low ionization region is 4E6-1E7 cm-3. There is a clear difference in the high velocity extension of the low ionization lines and that of lines from [Fe X-XIV], with the latter extending up to ~ -390 km/s in the blue wing for [Fe XIV], while the low ionization lines extend to typically ~ -260 km/s. For H-alpha a faint extension up to ~ -450 km/s can be seen probably arising from a small fraction of shocked high density clumps. We discuss these observations in the context of radiative shock models, which are qualitatively consistent with the observations. A fraction of the high ionization lines may originate in gas which has yet not had time to cool down, explaining the difference in width between the low and high ionization lines. The maximum shock velocities seen in the optical lines are ~ 510 km/s. We expect the maximum width of especially the low ionization lines to increase with time.
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| 4. |
- Kotak, Rubina, et al.
(författare)
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Spitzer Measurements of Atomic and Molecular Abundances in the Type IIP SN 2005af
- 2006
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 651:2, s. L117-L120
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Tidskriftsartikel (refereegranskat)abstract
- We present results based on mid-infrared (3.6-30 μm) observations with the Spitzer Space Telescope of the nearby Type IIP supernova 2005af. We report the first ever detection of the SiO molecule in a Type IIP supernova. Together with the detection of the CO fundamental, this is an exciting finding as it may signal the onset of dust condensation in the ejecta. From a wealth of fine-structure lines we provide abundance estimates for stable Ni, Ar, and Ne that, via spectral synthesis, may be used to constrain nucleosynthesis models.
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| 5. |
- 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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| 6. |
- Mattila, Seppo, et al.
(författare)
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Massive stars exploding in a He-rich circumstellar medium - III. SN 2006jc : infrared echoes from new and old dust in the progenitor CSM
- 2008
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 389:1, s. 141-155
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Tidskriftsartikel (refereegranskat)abstract
- We present near- (NIR) and mid-infrared (MIR) photometric data of the Type Ibn supernova (SN) 2006jc obtained with the United Kingdom Infrared Telescope (UKIRT), the Gemini North Telescope and the Spitzer Space Telescope between days 86 and 493 post-explosion. We find that the IR behaviour of SN 2006jc can be explained as a combination of IR echoes from two manifestations of circumstellar material. The bulk of the NIR emission arises from an IR echo from newly condensed dust in a cool dense shell (CDS) produced by the interaction of the ejecta outward shock with a dense shell of circumstellar material ejected by the progenitor in a luminous blue variable (LBV)-like outburst about two years prior to the SN explosion. The CDS dust mass reaches a modest 3.0 × 10-4Msolar by day 230. While dust condensation within a CDS formed behind the ejecta inward shock has been proposed before for one event (SN 1998S), SN 2006jc is the first one showing evidence for dust condensation in a CDS formed behind the ejecta outward shock in the circumstellar material. At later epochs, a substantial and growing contribution to the IR fluxes arises from an IR echo from pre-existing dust in the progenitor wind. The mass of the pre-existing circumstellar medium (CSM) dust is at least ~8 × 10-3Msolar. This paper therefore adds to the evidence that mass-loss from the progenitors of core-collapse SNe could be a major source of dust in the Universe. However, yet again, we see no direct evidence that the explosion of an SN produces anything other than a very modest amount of dust.
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| 7. |
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| 8. |
- Meikle, Peter, et al.
(författare)
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A Spitzer Space Telescope Study of SN 2003gd: Still No Direct Evidence that Core-Collapse Supernovae are Major Dust Factories
- 2007
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Ingår i: The Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 665:1, s. 608-617
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Tidskriftsartikel (refereegranskat)abstract
- We present a new, detailed analysis of late-time mid-infrared observations of the Type II-P supernova (SN) 2003gd. At about 16 months after the explosion, the mid-IR flux is consistent with emission from 4×10-5 Msolar of newly condensed dust in the ejecta. At 22 months emission from pointlike sources close to the SN position was detected at 8 and 24 μm. By 42 months the 24 μm flux had faded. Considerations of luminosity and source size rule out the ejecta of SN 2003gd as the main origin of the emission at 22 months. A possible alternative explanation for the emission at this later epoch is an IR echo from preexisting circumstellar or interstellar dust. We conclude that, contrary to the claim of Sugerman and coworkers, the mid-IR emission from SN 2003gd does not support the presence of 0.02 Msolar of newly formed dust in the ejecta. There is, as yet, no direct evidence that core-collapse supernovae are major dust factories.
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| 9. |
- Melinder, Jens, et al.
(författare)
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Detection efficiency and photometry in supernova surveys : The Stockholm VIMOS Supernova Survey I
- 2008
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 490:1, s. 419-434
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The aim of the work presented in this paper is to test and optimise supernova detection methods based on the optimal image subtraction technique. The main focus is on applying the detection methods to wide field supernova imaging surveys and in particular to the Stockholm VIMOS Supernova Survey (SVISS). Methods. We have constructed a supernova detection pipeline for imaging surveys. The core of the pipeline is image subtraction using the ISIS 2.2 package. Using real data from the SVISS we simulate supernovae in the images, both inside and outside galaxies. The detection pipeline is then run on the simulated frames and the effects of image quality and subtraction parameters on the detection efficiency and photometric accuracy are studied. Results. The pipeline allows efficient detection of faint supernovae in the deep imaging data. It also allows controlling and correcting for possible systematic effects in the SN detection and photometry. We find such a systematic effect in the form of a small systematic flux offset remaining at the positions of galaxies in the subtracted frames. This offset will not only affect the photometric accuracy of the survey, but also the detection efficiencies. Conclusions. Our study has shown that ISIS 2.2 works well for the SVISS data. We have found that the detection efficiency and photometric accuracy of the survey are affected by the stamp selection for the image subtraction and by host galaxy brightness. With our tools the subtraction results can be further optimised, any systematic effects can be controlled and photometric errors estimated, which is very important for the SVISS, as well as for future SN searches based on large imaging surveys such as Pan-STARRS and LSST.
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| 10. |
- Stanishev, Vallery, et al.
(författare)
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SN 2003du: 480 days in the life of a normal type Ia supernova
- 2007
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 469:2, s. 645-661
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Tidskriftsartikel (refereegranskat)abstract
- Aims.We present a study of the optical and near-infrared (NIR) properties of the Type Ia Supernova (SN Ia) 2003du.Methods: An extensive set of optical and NIR photometry and low-resolution long-slit spectra was obtained using a number of facilities. The observations started 13 days before B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique.Results: The {UBVRIJHK} light curves and the color indices of SN 2003du closely resemble those of normal SNe Ia. SN 2003du reached a B-band maximum of 13.49 ± 0.02 mag on JD2 452 766.38 ± 0.5. We derive a B-band stretch parameter of 0.988 ±0.003, which corresponds to Δ m15=1.02 ±0.05, indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. Using an updated calibration of the V and {JHK} absolute magnitudes of SNe Ia, we find a distance modulus μ=32.79±0.15 mag to the host galaxy, UGC 9391. We measure a peak {uvoir} bolometric luminosity of 1.35(±0.20)×1043 erg s-1 and Arnett's rule implies that M56Ni≃0.68 ±0.14 Mȯ of 56Ni was synthesized during the explosion. Modeling of the {uvoir} bolometric light curve also indicates M56Ni in the range 0.6-0.8 Mȯ. The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II) = 0.22 ±0.02 and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Ca II H&K doublet and infrared triplet, and possibly in Si II λ6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of Si II λ6355 line in many SNe Ia is due to the presence of two blended absorption components.
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| 11. |
- Vaisanen, Petri, et al.
(författare)
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Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These data are combined with archival HST imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components.One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disk and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7x10^10 M_solar for both. The third component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for AGN activity is found from optical or mid-infrared data. The star formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the Bird shows kinematic, dynamical, and emission line properties typical for cool ultra luminous IR galaxies. However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation does not come from the two major K-band nuclei, but from the third irregular component. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components.
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| 12. |
- Väisänen, P, et al.
(författare)
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Adaptive optics imaging and optical spectroscopy of a multiple merger in a luminous infrared galaxy
- 2008
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 384:3, s. 886-906
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Tidskriftsartikel (refereegranskat)abstract
- We present near-infrared (NIR) adaptive optics imaging obtained with VLT/NACO and optical spectroscopy from the Southern African Large Telescope of a luminous IR galaxy (LIRG) IRAS 19115-2124. These data are combined with archival Hubble Space Telescope imaging and Spitzer imaging and spectroscopy, allowing us to study this disturbed interacting/merging galaxy, dubbed the Bird, in extraordinary detail. In particular, the data reveal a triple system where the LIRG phenomenon is dominated by the smallest of the components. One nucleus is a regular barred spiral with significant rotation, while another is highly disturbed with a surface brightness distribution intermediate to that of disc and bulge systems, and hints of remaining arm/bar structure. We derive dynamical masses in the range 3-7 × 1010Msolarfor both. The third component appears to be a 1-2 × 1010Msolar mass irregular galaxy. The total system exhibits HII galaxy-like optical line ratios and strengths, and no evidence for active galactic nucleus (AGN) activity is found from optical or mid-IR data. The star formation rate is estimated to be ~190Msolaryr-1. We also report a search for supernovae from NIR images separated by five months and search for superstar cluster candidates. We detect outflowing gas from the Bird mostly in the range 100-300 km s-1 using NaI D absorption features. Overall, the Bird shows kinematic, dynamical and emission-line properties typical for cool ultraluminous IR galaxies (ULIRGs). However, the interesting features setting it apart for future studies are its triple merger nature, and the location of its star formation peak - the strongest star formation, as revealed by Spitzer imaging, does not come from the two major K-band nuclei, but from the third irregular component. This is in contrast to the conventional view that the (U)LIRG phases are powered by infalling gas to the major nuclei of the merging spiral galaxies. Aided by simulations, we discuss scenarios where the irregular component is on its first high-speed encounter with the more massive components. Based on observations made with ESO Telescopes at the Paranal Observatory under programme 073.D-0406A, and with the Southern African Large Telescope (SALT).
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| 13. |
- Östlin, Göran, et al.
(författare)
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Constraining the mass of the GRB 030329 progenitor
- 2008
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 387:3, s. 1227-1236
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Tidskriftsartikel (refereegranskat)abstract
- The long-duration gamma-ray burst (GRB) GRB 030329, associated with the supernova (SN) SN 2003dh, occurred inside a star-forming dwarf galaxy at redshift z = 0.1685. The low redshift, and a rich set of archival Hubble Space Telescope (HST ) images, makes this GRB well suited for a detailed study of the stellar population in the immediate vicinity of the explosion. Since the lifetime of a star is directly tied to its mass, the age of the stellar population can be used to put constraints on the GRB and SN progenitor mass. From the HST images, we extract the colours of the precise site from which the GRB originated, and find that the colours are significantly different from those of the overall host galaxy and the surrounding starburst environment. We have used spectral evolutionary models, including nebular emission, to carefully constrain the age of the stellar population, and hence the progenitor, at the very explosion site. For instantaneous burst models, we find that a population age of similar to 5 Myr best matches the data, suggesting a very massive (M(ZAMS) > 50 M(circle dot)) star as the progenitor, with an upper limit of 8 Myr (M(ZAMS) > 25 M(circle dot)). For more extended star formation scenarios, the inferred progenitor age is in most cases still very young (< 7 Myr, implying M(ZAMS) > 25 M(circle dot)), with an upper limit of 20 Myr (M(ZAMS) > 12 M(circle dot)). These age estimates are an order of magnitude lower than the ages inferred from the overall host galaxy colours, indicating that progenitor mass estimates based on data for spatially unresolved GRB host galaxies will in general be of limited use. Our results are consistent with the collapsar scenario.
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