| 1. |
- Yaron, O., et al.
(författare)
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Confined dense circumstellar material surrounding a regular type II supernova
- 2017
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Ingår i: Nature Physics. - 1745-2473 .- 1745-2481. ; 13:5, s. 510-517
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Tidskriftsartikel (refereegranskat)abstract
- With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, which sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF 13dqy = SN 2013fs a mere similar to 3 h after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at similar to 6 h post-explosion) spectra, map the distribution of material in the immediate environment (less than or similar to 1015 cm) of the exploding star and establish that it was surrounded by circumstellar material (CSM) that was ejected during the final similar to 1 yr prior to explosion at a high rate, around 10(-3) solar masses per year. The complete disappearance of flash-ionized emission lines within the first several days requires that the dense CSM be confined to within less than or similar to 10(15) cm, consistent with radio non-detections at 70-100 days. The observations indicate that iPTF 13dqy was a regular type II supernova; thus, the finding that the probable red supergiant progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars.
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| 2. |
- Khazov, D., et al.
(författare)
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FLASH SPECTROSCOPY : EMISSION LINES FROM THE IONIZED CIRCUMSTELLAR MATERIAL AROUND < 10-DAY-OLD TYPE II SUPERNOVAE
- 2016
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 818:1
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Tidskriftsartikel (refereegranskat)abstract
- Supernovae (SNe) embedded in dense circumstellar material (CSM) may show prominent emission lines in their early-time spectra (<= 10 days after the explosion), owing to recombination of the CSM ionized by the shock-breakout flash. From such spectra (flash spectroscopy), we can measure various physical properties of the CSM, as well as the mass-loss rate of the progenitor during the year prior to its explosion. Searching through the Palomar Transient Factory (PTF and iPTF) SN spectroscopy databases from 2009 through 2014, we found 12 SNe II showing flash-ionized (FI) signatures in their first spectra. All are younger than 10 days. These events constitute 14% of all 84 SNe in our sample having a spectrum within 10 days from explosion, and 18% of SNe. II observed at ages <5 days, thereby setting lower limits on the fraction of FI events. We classified as blue/featureless (BF) those events having a first spectrum that is similar to that of a blackbody, without any emission or absorption signatures. It is possible that some BF events had FI signatures at an earlier phase than observed, or that they lack dense CSM around the progenitor. Within 2 days after explosion, 8 out of 11 SNe in our sample are either BF events or show FI signatures. Interestingly, we found that 19 out of 21 SNe brighter than an absolute magnitude M-R = -18.2 belong to the FI or BF groups, and that all FI events peaked above M-R = -17.6 mag, significantly brighter than average SNe II.
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| 3. |
- Prentice, S. J., et al.
(författare)
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The bolometric light curves and physical parameters of stripped-envelope supernovae
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 458:3, s. 2973-3002
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Tidskriftsartikel (refereegranskat)abstract
- The optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (SNe) are constructed using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak luminosity L-p, enabling the construction of a luminosity function. Subsequently, the mass of Ni-56 synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNe Ic-BL) and gamma-ray burst SNe are the most luminous subtypes with a combined median L-p, in erg s(-1), of log(L-p)= 43.00 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesize approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median M-Ni = 0.34, 0.16, 0.14, and 0.11 M-circle dot, respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from L-p/2 to L-p more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.
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| 4. |
- Fremling, Christoffer, et al.
(författare)
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PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 5806
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593
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Tidskriftsartikel (refereegranskat)abstract
- Context. We investigate two stripped-envelope supernovae (SNe) discovered in the nearby galaxy NGC 5806 by the (intermediate) Palomar Transient Factory [(i)PTF]. These SNe, designated PTF12os/SN 2012P and iPTF13bvn, exploded within ~520 days of one another at a similar distance from the host-galaxy center. We classify PTF12os as a Type IIb SN based on our spectral sequence; iPTF13bvn has previously been classified as Type Ib having a likely progenitor with zero age main sequence (ZAMS) mass below ~17 M⊙. Because of the shared and nearby host, we are presented with a unique opportunity to compare these two SNe.Aims. Our main objective is to constrain the explosion parameters of iPTF12os and iPTF13bvn, and to put constraints on the SN progenitors. We also aim to spatially map the metallicity in the host galaxy, and to investigate the presence of hydrogen in early-time spectra of both SNe.Methods. We present comprehensive datasets collected on PTF12os and iPTF13bvn, and introduce a new automatic reference-subtraction photometry pipeline (FPipe) currently in use by the iPTF. We perform a detailed study of the light curves (LCs) and spectral evolution of the SNe. The bolometric LCs are modeled using the hydrodynamical code hyde. We analyze early spectra of both SNe to investigate the presence of hydrogen; for iPTF13bvn we also investigate the regions of the Paschen lines in infrared spectra. We perform spectral line analysis of helium and iron lines to map the ejecta structure of both SNe. We use nebular models and late-time spectroscopy to constrain the ZAMS mass of the progenitors. We also perform image registration of ground-based images of PTF12os to archival HST images of NGC 5806 to identify a potential progenitor candidate.Results. We find that our nebular spectroscopy of iPTF13bvn remains consistent with a low-mass progenitor, likely having a ZAMS mass of ~12M⊙. Our late-time spectroscopy of PTF12os is consistent with a ZAMS mass of ~15M⊙. We successfully identify a source in pre-explosion HST images coincident with PTF12os. The colors and absolute magnitude of this object are consistent between pre-explosion and late-time HST images, implying it is a cluster of massive stars. Our hydrodynamical modeling suggests that the progenitor of PTF12os had a compact He core with a mass of 3.25+ 0.77-0.56M⊙ at the time of the explosion, which had a total kinetic energy of 0.54+ 0.41-0.25 × 1051 erg and synthesized 0.063+ 0.020-0.011M⊙ of strongly mixed 56Ni. Spectral comparisons to the Type IIb SN 2011dh indicate that the progenitor of PTF12os was surrounded by a thin hydrogen envelope with a mass lower than 0.02M⊙. We also find tentative evidence that the progenitor of iPTF13bvn could have been surrounded by a small amount of hydrogen prior to the explosion. This result is supported by possible weak signals of hydrogen in both optical and infrared spectra.
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| 5. |
- Sollerman, Jesper, et al.
(författare)
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Late-time observations of the extraordinary Type II supernova iPTF14hls
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 621
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We study iPTF14hls, a luminous and extraordinary long-lived Type II supernova, which lately has attracted much attention and disparate interpretation.Methods. We have presented new optical photometry that extends the light curves up to more than three years past discovery. We also obtained optical spectroscopy over this period, and furthermore present additional space-based observations using Swift and HST.Results. After an almost constant luminosity for hundreds of days, the later light curve of iPTF14hls finally fades and then displays a dramatic drop after about 1000 d, but the supernova is still visible at the latest epochs presented. The spectra have finally turned nebular, and our very last optical spectrum likely displays signatures from the deep and dense interior of the explosion. A high-resolution HST image highlights the complex environment of the explosion in this low-luminosity galaxy.Conclusions. We provide a large number of additional late-time observations of iPTF14hls, which are (and will continue to be) used to assess the many different interpretations for this intriguing object. In particular, the very late (+1000 d) steep decline of the optical light curve is difficult to reconcile with the proposed central engine models. The lack of very strong X-ray emission, and the emergence of intermediate-width emission lines including [S II] that we propose originate from dense, processed material in the core of the supernova ejecta, are also key observational tests for both existing and future models.
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| 6. |
- Taddia, Francesco, et al.
(författare)
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Metallicity from Type II supernovae from the (i)PTF
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 587
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Tidskriftsartikel (refereegranskat)abstract
- Type IIP supernovae (SNe IIP) have recently been proposed as metallicity (Z) probes. The spectral models of Dessart et al. (2014, MNRAS, 440, 1856) showed that the pseudo-equivalent width of Fe lambda 5018 (pEW(5018)) during the plateau phase depends on the primordial Z, but there was a paucity of SNe IIP exhibiting pEW(5018) that were compatible with Z < 0.4 Z(circle dot). This lack might be due to some physical property of the SN II population or to the fact that those SNe have been discovered in luminous, metal-rich targeted galaxies. Here we use SN II observations from the untargeted (intermediate) Palomar Transient Factory [(i)PTF] survey, aiming to investigate the pEW5018 distribution of this SN population and, in particular, to look for the presence of SNe II at lower Z. We perform pEW(5018) measurements on the spectra of a sample of 39 (i) PTF SNe II, selected to have well-constrained explosion epochs and light-curve properties. Based on the comparison with the pEW(5018) spectral models, we subgrouped our SNe into four Z bins from Z approximate to 0.1 Z(circle dot) up to Z approximate to 2 Z(circle dot). We also independently investigated the Z of the hosts by using their absolute magnitudes and colors and, in a few cases, using strong-line diagnostics from spectra. We searched for possible correlations between SN observables, such as their peak magnitudes and the Z inferred from pEW(5018). We found 11 events with pEW(5018) that were small enough to indicate Z approximate to 0.1 Z(circle dot). The trend of pEW(5018) with Z matches the Z estimates obtained from the host-galaxy photometry, although the significance of the correlation is weak. We also found that SNe with brighter peak magnitudes have smaller pEW(5018) and occur at lower Z.
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| 7. |
- Blagorodnova, N., et al.
(författare)
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The Broad Absorption Line Tidal Disruption Event iPTF15af : Optical and Ultraviolet Evolution
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 873:1
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Tidskriftsartikel (refereegranskat)abstract
- We present multiwavelength observations of the tidal disruption event (TDE) iPTF15af, discovered by the intermediate Palomar Transient Factory survey at redshift z = 0.07897. The optical and ultraviolet (UV) light curves of the transient show a slow decay over 5 months, in agreement with previous optically discovered TDEs. It also has a comparable blackbody peak luminosity of L-peak approximate to 1.5 x 10(44) erg s(-1). The inferred temperature from the optical and UV data shows a value of (3-5) x 10(4) K. The transient is not detected in X-rays up to L-X < 3 x 10(42) erg s(-1) within the first 5 months after discovery. The optical spectra exhibit two distinct broad emission lines in the He II region, and at later times also H alpha emission. Additionally, emission from [N III] and [O III] is detected, likely produced by the Bowen fluorescence effect. UV spectra reveal broad emission and absorption lines associated with high-ionization states of N V, C IV, Si IV, and possibly P V. These features, analogous to those of broad absorption line quasars (BAL QSOs), require an absorber with column densities N-H > 10(23) cm(-2). This optically thick gas would also explain the nondetection in soft X-rays. The profile of the absorption lines with the highest column density material at the largest velocity is opposite that of BAL QSOs. We suggest that radiation pressure generated by the TDE flare at early times could have provided the initial acceleration mechanism for this gas. Spectral UV line monitoring of future TDEs could test this proposal.
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| 8. |
- Fremling, Christoffer, et al.
(författare)
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The rise and fall of the Type Ib supernova iPTF13bvn Not a massive Wolf-Rayet star
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 565
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Tidskriftsartikel (refereegranskat)abstract
- Context. We investigate iPTF13bvn, a core-collapse (CC) supernova (SN) in the nearby spiral galaxy NGC 5806. This object was discovered by the intermediate Palomar Transient Factory (iPTF) very close to the estimated explosion date and was classified as a stripped-envelope CC SN, likely of Type Ib. Furthermore, a possible progenitor detection in pre-explosion Hubble Space Telescope (HST) images was reported, making this the only SN Ib with such an identification. Based on the luminosity and color of the progenitor candidate, as well as on early-time spectra and photometry of the SN, it was argued that the progenitor candidate is consistent with a single, massive Wolf-Rayet (WR) star. Aims. We aim to confirm the progenitor detection, to robustly classify the SN using additional spectroscopy, and to investigate if our follow-up photometric and spectroscopic data on iPTF13bvn are consistent with a single-star WR progenitor scenario. Methods. We present a large set of observational data, consisting of multi-band light curves (UBVRI, g' r' i' z') and optical spectra. We perform standard spectral line analysis to track the evolution of the SN ejecta. We also construct a bolometric light curve and perform hydrodynamical calculations to model this light curve to constrain the synthesized radioactive nickel mass and the total ejecta mass of the SN. Late-time photometry is analyzed to constrain the amount of oxygen. Furthermore, image registration of pre- and post-explosion HST images is performed. Results. Our HST astrometry confirms the location of the progenitor candidate of iPTF13bvn, and follow-up spectra securely classify this as a SN Ib. We use our hydrodynamical model to fit the observed bolometric light curve, estimating the total ejecta mass to be 1.9 M-circle dot and the radioactive nickel mass to be 0.05 M-circle dot. The model fit requires the nickel synthesized in the explosion to be highly mixed out in the ejecta. We also find that the late-time nebular r'-band luminosity is not consistent with predictions based on the expected oxygen nucleosynthesis in very massive stars. Conclusions. We find that our bolometric light curve of iPTF13bvn is not consistent with the previously proposed single massive WR-star progenitor scenario. The total ejecta mass and, in particular, the late-time oxygen emission are both significantly lower than what would be expected from a single WR progenitor with a main-sequence mass of at least 30 M-circle dot.
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| 9. |
- Gal-Yam, Avishay, et al.
(författare)
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A Wolf-Rayet-like progenitor of SN 2013cu from spectral observations of a stellar wind
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 509:7501, s. 471-
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Tidskriftsartikel (refereegranskat)abstract
- The explosive fate of massive Wolf-Rayet stars(1) (WRSs) is a key open question in stellar physics. An appealing option is that hydrogen-deficient WRSs are the progenitors of some hydrogen-poor supernova explosions of types IIb, Ib and Ic (ref. 2). A blue object, having luminosity and colours consistent with those of some WRSs, has recently been identified in pre-explosion images at the location of a supernova of type Ib (ref. 3), but has not yet been conclusively determined to have been the progenitor. Similar work has so far only resulted in non-detections(4). Comparison of early photometric observations of type Ic supernovae with theoretical models suggests that the progenitor stars had radii of less than 1012 centimetres, as expected for some WRSs(5). The signature of WRSs, their emission line spectra, cannot be probed by such studies. Here we report the detection of strong emission lines in a spectrum of type IIb supernova 2013cu (iPTF13ast) obtained approximately 15.5 hours after explosion (by 'flash spectroscopy', which captures the effects of the supernova explosion shock breakout flash on material surrounding the progenitor star). We identify Wolf-Rayet-like wind signatures, suggesting a progenitor of the WN(h) subclass (those WRSs with winds dominated by helium and nitrogen, with traces of hydrogen). The extent of this dense wind may indicate increased mass loss from the progenitor shortly before its explosion, consistent with recent theoretical predictions(6).
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