| 1. |
- Bersten, Melina C., et al.
(författare)
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THE TYPE IIb SUPERNOVA 2011dh FROM A SUPERGIANT PROGENITOR
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 757:1
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Tidskriftsartikel (refereegranskat)abstract
- A set of hydrodynamical models based on stellar evolutionary progenitors is used to study the nature of SN 2011dh. Our modeling suggests that a large progenitor star-with R similar to 200 R-circle dot-is needed to reproduce the early light curve (LC) of SN 2011dh. This is consistent with the suggestion that the yellow super-giant star detected at the location of the supernova (SN) in deep pre-explosion images is the progenitor star. From the main peak of the bolometric LC and expansion velocities, we constrain the mass of the ejecta to be approximate to 2 M-circle dot, the explosion energy to be E = (6-10) x 10(50) erg, and the Ni-56 mass to be approximately 0.06 M-circle dot. The progenitor star was composed of a helium core of 3-4 M-circle dot and a thin hydrogen-rich envelope of approximate to 0.1M(circle dot) with a main-sequence mass estimated to be in the range of 12-15 M-circle dot. Our models rule out progenitors with helium-core masses larger than 8 M-circle dot, which correspond to M-ZAMS greater than or similar to 25M(circle dot). This suggests that a single star evolutionary scenario for SN 2011dh is unlikely.
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| 2. |
- Clark, Peter, et al.
(författare)
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LSQ13ddu : a rapidly evolving stripped-envelope supernova with early circumstellar interaction signatures
- 2020
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 492:2, s. 2208-2228
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the rapidly evolving and unusual supernova LSQ13ddu, discovered by the La Silla-QUEST survey. LSQ13ddu displayed a rapid rise of just 4.8 +/- 0.9 d to reach a peak brightness of -19.70 +/- 0.02 mag in the LSQgr band. Early spectra of LSQ13ddu showed the presence of weak and narrow He I features arising from interaction with circumstellar material (CSM). These interaction signatures weakened quickly, with broad features consistent with those seen in stripped-envelope SNe becoming dominant around two weeks after maximum. The narrow He I velocities are consistent with the wind velocities of luminous blue variables but its spectra lack the typically seen hydrogen features. The fast and bright early light curve is inconsistent with radioactive Ni-56 powering but can be explained through a combination of CSM interaction and an underlying Ni-56 decay component that dominates the later time behaviour of LSQ13ddu. Based on the strength of the underlying broad features, LSQ13ddu appears deficient in He compared to standard SNe Ib.
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| 3. |
- Elias-Rosa, Nancy, et al.
(författare)
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The Type IIn Supernova SN 2010bt : The Explosion of a Star in Outburst
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 860:1
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Tidskriftsartikel (refereegranskat)abstract
- It is well known that massive stars (M > 8M(circle dot)) evolve up to the collapse of the stellar core, resulting in most cases in a supernova (SN) explosion. Their heterogeneity is related mainly to different configurations of the progenitor star at the moment of the explosion and to their immediate environments. We present photometry and spectroscopy of SN. 2010bt, which was classified as a Type. IIn. SN from a spectrum obtained soon after discovery and was observed extensively for about 2 months. After the seasonal interruption owing to its proximity to the Sun, the SN was below the detection threshold, indicative of a rapid luminosity decline. We can identify the likely progenitor with a very luminous star (log L/L-circle dot approximate to 7) through comparison of Hubble Space Telescope images of the host galaxy prior to explosion with those of the SN obtained after maximum light. Such a luminosity is not expected for a quiescent star, but rather for a massive star in an active phase. This progenitor candidate was later confirmed via images taken in 2015 (similar to 5 yr post-discovery), in which no bright point source was detected at the SN position. Given these results and the SN behavior, we conclude that SN. 2010bt was likely a Type IIn SN and that its progenitor was a massive star that experienced an outburst shortly before the final explosion, leading to a dense H-rich circumstellar environment around the SN progenitor.
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| 4. |
- 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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| 5. |
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| 6. |
- Kotak, Rubina, et al.
(författare)
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A new look at the pulsating DB white dwarf GD 358: Line-of-sight velocity measurements and constraints on model atmospheres
- 2003
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 397, s. 1043-1055
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Tidskriftsartikel (refereegranskat)abstract
- We report on our findings of the bright, pulsating, helium atmospherewhite dwarf GD 358, based on time-resolved optical spectrophotometry. Weidentify 5 real pulsation modes and at least 6 combination modes atfrequencies consistent with those found in previous observations. Themeasured Doppler shifts from our spectra show variations with amplitudesof up to 5.5 km s-1 at the frequencies inferred from the fluxvariations. We conclude that these are variations in the line-of-sightvelocities associated with the pulsational motion. We use the observedflux and velocity amplitudes and phases to test theoretical predictionswithin the convective driving framework, and compare these with similarobservations of the hydrogen atmosphere white dwarf pulsators (DAVs).The wavelength dependence of the fractional pulsation amplitudes(chromatic amplitudes) allows us to conclude that all five real modesshare the same spherical degree, most likely, l=1. This is consistentwith previous identifications based solely on photometry. We find that ahigh signal-to-noise mean spectrum on its own is not enough to determinethe atmospheric parameters and that there are small but significantdiscrepancies between the observations and model atmospheres. The sourceof these remains to be identified. While we infer Teff =24 kKand log g ~ 8.0 from the mean spectrum, the chromatic amplitudes, whichare a measure of the derivative of the flux with respect to thetemperature, unambiguously favour a higher effective temperature, 27 kK,which is more in line with independent determinations from ultra-violetspectra.The data presented herein were obtained at the W.M. Keck Observatory,which is operated as a scientific partnership among the CaliforniaInstitute of Technology, the University of California and the NationalAeronautics and Space Administration. The Observatory was made possibleby the generous financial support of the W.M. Keck Foundation.
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| 7. |
- Kotak, Rubina, et al.
(författare)
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A puzzling periodicity in the pulsating DA white dwarf G 117-B15A
- 2004
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 413, s. 301-308
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Tidskriftsartikel (refereegranskat)abstract
- We present time-resolved optical spectrophotometry of the pulsatinghydrogen atmosphere (DA) white dwarf G 117-B15A. We find threeperiodicities in the pulsation spectrum (215 s, 272 s, and 304 s) all ofwhich have been found in earlier studies. By comparing the fractionalwavelength dependence of the pulsation amplitudes (chromatic amplitudes)with models, we confirm a previous report that the strongest mode, at215 s, has ℓ=1. The chromatic amplitude for the 272 s mode is verypuzzling, showing an increase in fractional amplitude with wavelengththat cannot be reproduced by the models for any ℓ at opticalwavelengths. Based on archival HST data, we show that while thebehaviour of the 215 s mode at ultra-violet wavelengths is as expectedfrom models, the weird behaviour of the 272 s periodicity is notrestricted to optical wavelengths in that it fails to show the expectedincrease in fractional amplitude towards shorter wavelengths. We discusspossible causes for the discrepancies found for the 272 s variation, butfind that all are lacking, and conclude that the nature of thisperiodicity remains unclear.Based in part on data obtained at the W.M. Keck Observatory, which isoperated as a scientific partnership among the California Institute ofTechnology, the University of California and the National Aeronauticsand Space Administration. The Observatory was made possible by thegenerous financial support of the W.M. Keck Foundation.
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| 8. |
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| 9. |
- Kotak, Rubina
(författare)
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Inside Pulsating White Dwarfs: Clues from time-resolved spectroscopy
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Several analyses using time-resolved optical spectrocopy of pulsating white dwarfs are presented. The data have been put to a number of uses. First, line-of-sight velocities associated with the pulsations have been measured in three hydrogen-atmosphere white dwarfs (DAVs), bringing the total number of such measurements up to five. They have also been measured for the first time in a pulsating helium-atmosphere white dwarf (DBV). The relative velocity to flux amplitude ratios are compared with theoretical expectations based on theories of mode driving via convection. Secondly, the fractional, wavelength-dependent pulsation amplitudes (``chromatic amplitudes'') have been used to identify the spherical degree of the pulsation modes. Consistent results are obtained for objects with mode identifications based solely on photometry. This shows that the technique works. The new mode identifications can be used in pulsation models to constrain the asteroseismological solution of the white dwarf in question. The chromatic amplitudes have also been used to understand the shortcomings of currently used model atmospheres. These are most likely due to the lack of a realistic treatement of convection. Combining all the available information from data such as ours is a first step towards constraining atmospheric properties in a convectionally unstable environment from an observational perspective. In the final chapter an attempt is made to explain the observed quasi-periodic variations in the rotationally split modes of certain pulsators.
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| 10. |
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| 11. |
- Kotak, Rubina, et al.
(författare)
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Pulsating or not? A search for hidden pulsations below the red edge of the ZZ Ceti instability strip
- 2002
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 391:3, s. 1005-1012
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Tidskriftsartikel (refereegranskat)abstract
- The location of the red edge of the ZZ Ceti instability strip is definedobservationally as being the lowest temperature for which a white dwarfwith a H-rich atmosphere (DA) is known to exhibit periodic brightnessvariations. Whether this cut-off in flux variations is actually due to acessation of pulsation or merely due to the attenuation of anyvariations by the convection zone, rendering them invisible, is notclear. The latter is a theoretical possibility because with decreasingeffective temperature, the emergent flux variations become an eversmaller fraction of the amplitude of the flux variations in theinterior. In contrast to the flux variations, the visibility of thevelocity variations associated with the pulsations is not thought to besimilarly affected. Thus, models imply that were it still pulsating, awhite dwarf just below the observed red edge should show velocityvariations. In order to test this possibility, we used time-resolvedspectra of three DA white dwarfs that do not show photometricvariability, but which have derived temperatures only slightly lowerthan the coolest ZZ Ceti variables. We find that none of our threetargets show significant periodic velocity variations, and set 95%confidence limits on amplitudes of 3.0, 5.2, and 8.8 km s-1.Thus, for two out of our three objects, we can rule out velocityvariations as large as 5.4 km s-1 observed for the strongestmode in the cool white dwarf pulsator ZZ Psc. Inorder to verify our procedures, we also examined similar data of a knownZZ Ceti, HL Tau 76. Applying external informationfrom the light curve, we detect significant velocity variations for thisobject with amplitudes of up to 4 km s-1. Our results suggestthat substantial numbers of pulsators having large velocity amplitudesdo not exist below the observed photometric red edge and that the latterprobably reflects a real termination of pulsations. The data presentedherein were obtained at the W. M. Keck Observatory, which is operated asa scientific partnership among the California Institute of Technology,the University of California and the National Aeronautics and SpaceAdministration. The Observatory was made possible by the generousfinancial support of the W. M. Keck Foundation.
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| 12. |
- 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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| 13. |
- Kotak, Rubina, et al.
(författare)
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Time-resolved optical spectroscopy of the pulsating DA white dwarf HS 0507+0434B : New constraints on mode identification and pulsation properties
- 2002
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Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 388:1, s. 219-234
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed analysis of time-resolved optical spectra of the ZZ Ceti white dwarf, HS 0507+0434B. Using the wavelength dependence of observed mode amplitudes, we deduce the spherical degree, , of the modes, most of which have . The presence of a large number of combination frequencies (linear sums or differences of the real modes) enabled us not only to test theoretical predictions but also to indirectly infer spherical and azimuthal degrees of real modes that had no observed splittings. In addition to the above, we measure line-of-sight velocities from our spectra. We find only marginal evidence for periodic modulation associated with the pulsation modes: at the frequency of the strongest mode in the lightcurve, we measure an amplitude of km s -1, which has a probability of 2% of being due to chance; for the other modes, we find lower values. Our velocity amplitudes and upper limits are smaller by a factor of two compared to the amplitudes found in ZZ Psc. We find that this is consistent with expectations based on the position of HS 0507+0434B in the instability strip. Combining all the available information from data such as ours is a first step towards constraining atmospheric properties in a convectionally unstable environment from an observational perspective.
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| 14. |
- 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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| 15. |
- Nagao, Takashi, et al.
(författare)
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Diversity of Dust Properties in External Galaxies Confirmed by Polarization Signals from Type II Supernovae
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 941:1
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Tidskriftsartikel (refereegranskat)abstract
- Investigating interstellar (IS) dust properties in external galaxies is important not only to infer the intrinsic properties of astronomical objects but also to understand the star/planet formation in the galaxies. From the non–Milky Way–like extinction and interstellar polarization (ISP) observed in reddened Type Ia supernovae (SNe), it has been suggested that their host galaxies contain dust grains whose properties are substantially different from the Milky Way (MW) dust. It is important to investigate the universality of such non-MW-like dust in the universe. Here we report spectropolarimetry of two highly extinguished Type II SNe (SN 2022aau and SN 2022ame). SN 2022aau shows a polarization maximum at a shorter wavelength than MW stars, which is also observed in some Type Ia SNe. This is clear evidence for the existence of non-MW-like dust in its host galaxy (i.e., NGC 1672). This fact implies that such non-MW-like dust might be more common in some environments than expected, and thus it might affect the picture of the star/planet formation. On the other hand, SN 2022ame shows MW-like ISP, implying the presence of MW-like dust in its host galaxy (i.e., NGC 1255). Our findings confirm that dust properties of galaxies are diverse, either locally or globally. The present work demonstrates that further investigation of IS dust properties in external galaxies using polarimetry of highly reddened SNe is promising, providing a great opportunity to study the universality of such non-MW-like dust grains in the universe.
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| 16. |
- Schulze, Steve, et al.
(författare)
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The Palomar Transient Factory Core-collapse Supernova Host-galaxy Sample. I. Host-galaxy Distribution Functions and Environment Dependence of Core-collapse Supernovae
- 2021
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 255:2
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Tidskriftsartikel (refereegranskat)abstract
- Several thousand core-collapse supernovae (CCSNe) of different flavors have been discovered so far. However, identifying their progenitors has remained an outstanding open question in astrophysics. Studies of SN host galaxies have proven to be powerful in providing constraints on the progenitor populations. In this paper, we present all CCSNe detected between 2009 and 2017 by the Palomar Transient Factory. This sample includes 888 SNe of 12 distinct classes out to redshift z approximate to 1. We present the photometric properties of their host galaxies from the far-ultraviolet to the mid-infrared and model the host-galaxy spectral energy distributions to derive physical properties. The galaxy mass function of Type Ic, Ib, IIb, II, and IIn SNe ranges from 10(5) to 10(11.5) M (circle dot), probing the entire mass range of star-forming galaxies down to the least-massive star-forming galaxies known. Moreover, the galaxy mass distributions are consistent with models of star-formation-weighted mass functions. Regular CCSNe are hence direct tracers of star formation. Small but notable differences exist between some of the SN classes. Type Ib/c SNe prefer galaxies with slightly higher masses (i.e., higher metallicities) and star formation rates than Type IIb and II SNe. These differences are less pronounced than previously thought. H-poor superluminous supernovae (SLSNe) and SNe Ic-BL are scarce in galaxies above 10(10) M (circle dot). Their progenitors require environments with metallicities of < 0.4 and < 1 solar, respectively. In addition, the hosts of H-poor SLSNe are dominated by a younger stellar population than all other classes of CCSNe. Our findings corroborate the notion that low metallicity and young age play an important role in the formation of SLSN progenitors.
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| 17. |
- 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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| 18. |
- Tanaka, Masaomi, et al.
(författare)
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The outermost ejecta of Type Ia supernovae
- 2008
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 677:1, s. 448-460
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Tidskriftsartikel (refereegranskat)
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| 19. |
- Valenti, Stefano, et al.
(författare)
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A SPECTROSCOPICALLY NORMAL TYPE Ic SUPERNOVA FROM A VERY MASSIVE PROGENITOR
- 2012
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Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 749:2, s. L28-
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Tidskriftsartikel (refereegranskat)abstract
- We present observations of the Type Ic supernova (SN Ic) 2011bm spanning a period of about one year. The data establish that SN 2011bm is a spectroscopically normal SN Ic with moderately low ejecta velocities and with a very slow spectroscopic and photometric evolution (more than twice as slow as SN 1998bw). The Pan-STARRS1 retrospective detection shows that the rise time from explosion to peak was similar to 40 days in the R band. Through an analysis of the light curve and the spectral sequence, we estimate a kinetic energy of similar to 7-17 foe and a total ejected mass of similar to 7-17 M-circle dot, 5-10 M-circle dot of which is oxygen and 0.6-0.7 M-circle dot is Ni-56. The physical parameters obtained for SN 2011bm suggest that its progenitor was a massive star of initial mass 30-50 M-circle dot. The profile of the forbidden oxygen lines in the nebular spectra shows no evidence of a bi-polar geometry in the ejected material.
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