| 1. |
- Pastorello, A., et al.
(author)
-
Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients : another piece of the puzzle
- 2018
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 474:1, s. 197-218
-
Journal article (peer-reviewed)abstract
- Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability that ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude M-r approximate to -15.3 mag, while the second one (Event B) occurred over one month later and reached M-r approximate to -18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of an SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. While the similarity with SN 2005gl supports a genuine SN explosion scenario for SN 2009ip-like events, the unequivocal detection of nucleosynthesized elements in their nebular spectra is still missing.
|
|
| 2. |
- Gal-Yam, A., et al.
(author)
-
A WC/WO star exploding within an expanding carbon-oxygen-neon nebula
- 2022
-
In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 601:7892, s. 201-204
-
Journal article (peer-reviewed)abstract
- The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their outer hydrogen envelopes as they evolve. Such Wolf-Rayet stars(1) emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars(2,3), leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion(4). Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients(5-8). Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf-Rayet stars may be the progenitors of some rapidly evolving transients.
|
|
| 3. |
- Yaron, O., et al.
(author)
-
Confined dense circumstellar material surrounding a regular type II supernova
- 2017
-
In: Nature Physics. - 1745-2473 .- 1745-2481. ; 13:5, s. 510-517
-
Journal article (peer-reviewed)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.
|
|
| 4. |
- Khazov, D., et al.
(author)
-
FLASH SPECTROSCOPY : EMISSION LINES FROM THE IONIZED CIRCUMSTELLAR MATERIAL AROUND < 10-DAY-OLD TYPE II SUPERNOVAE
- 2016
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 818:1
-
Journal article (peer-reviewed)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.
|
|
| 5. |
- Prentice, S. J., et al.
(author)
-
The bolometric light curves and physical parameters of stripped-envelope supernovae
- 2016
-
In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 458:3, s. 2973-3002
-
Journal article (peer-reviewed)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.
|
|
| 6. |
- Fremling, Christoffer, et al.
(author)
-
PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 5806
- 2016
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 593
-
Journal article (peer-reviewed)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.
|
|
| 7. |
- Lunnan, R., et al.
(author)
-
Two New Calcium-rich Gap Transients in Group and Cluster Environments
- 2017
-
In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 836:1
-
Journal article (peer-reviewed)abstract
- We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca II] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset similar to 150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out an underlying host system to a limit of M-R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. We show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. We also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.
|
|
| 8. |
- Ofek, E. O., et al.
(author)
-
PTF13efv-AN OUTBURST 500 DAYS PRIOR TO THE SNHUNT 275 EXPLOSION AND ITS RADIATIVE EFFICIENCY
- 2016
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 824:1
-
Journal article (peer-reviewed)abstract
- The progenitors of some supernovae (SNe) exhibit outbursts with super-Eddington luminosities prior to their final explosions. This behavior is common among SNe IIn, but the driving mechanisms of these precursors are not yet well-understood. SNHunt 275 was announced as a possible new SN during 2015 May. Here we report on pre-explosion observations of the location of this event by the Palomar Transient Factory (PTF) and report the detection of a precursor about 500 days prior to the 2015 May activity (PTF 13efv). The observed velocities in the 2015 transient and its 2013 precursor absorption spectra are low (1000-2000 km s(-1)), so it is not clear yet if the recent activity indeed marks the final disruption of the progenitor. Regardless of the nature of this event, we use the PTF photometric and spectral observations, as well as Swift-UVOT observations, to constrain the efficiency of the radiated energy relative to the total kinetic energy of the precursor. We find that, using an order-of-magnitude estimate and under the assumption of spherical symmetry, the ratio of the radiated energy to the kinetic energy is in the range of 4 x 10(-2) to 3.4 x 10(3).
|
|
| 9. |
- Pessi, Priscila Jael, et al.
(author)
-
Broad-emission-line dominated hydrogen-rich luminous supernovae
- 2023
-
In: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 523:4, s. 5315-5340
-
Journal article (peer-reviewed)abstract
- Hydrogen-rich Type II supernovae (SNe II) are the most frequently observed class of core-collapse SNe (CCSNe). However, most studies that analyse large samples of SNe II lack events with absolute peak magnitudes brighter than −18.5 mag at rest-frame optical wavelengths. Thanks to modern surveys, the detected number of such luminous SNe II (LSNe II) is growing. There exist several mechanisms that could produce luminous SNe II. The most popular propose either the presence of a central engine (a magnetar gradually spinning down or a black hole accreting fallback material) or the interaction of supernova ejecta with circumstellar material (CSM) that turns kinetic energy into radiation energy. In this work, we study the light curves and spectral series of a small sample of six LSNe II that show peculiarities in their H α profile, to attempt to understand the underlying powering mechanism. We favour an interaction scenario with CSM that is not dense enough to be optically thick to electron scattering on large scales – thus, no narrow emission lines are observed. This conclusion is based on the observed light curve (higher luminosity, fast decline, blue colours) and spectral features (lack of persistent narrow lines, broad H α emission, lack of H α absorption, weak, or non-existent metal lines) together with comparison to other luminous events available in the literature. We add to the growing evidence that transients powered by ejecta–CSM interaction do not necessarily display persistent narrow emission lines.
|
|
| 10. |
- Sollerman, Jesper, et al.
(author)
-
Late-time observations of the extraordinary Type II supernova iPTF14hls
- 2019
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 621
-
Journal article (peer-reviewed)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.
|
|
