Supernova 2002ap Research Articles

Connection of supernovae 2002ap, 2003gd, 2013ej, and 2019krl in M 74 with atomic gas accretion and spiral structure

Studying the nature of various types of supernovae (SNe) is important for our understanding of stellar evolution. Observations of atomic and molecular gas in the host galaxies of gamma-ray bursts (GRBs) and SNe have recently been used to learn about the nature of the explosions themselves and the star formation events during which their progenitors were born. Based on archival data for M 74, which previously has not been investigated in the context of SN positions, we report the gas properties in the environment of the broad-lined type Ic (Ic-BL) SN 2002ap and the type II SNe 2003gd, 2013ej, and 2019krl. The SN 2002ap is located at the end of an off-centre, asymmetric, 55 kpc-long HIextension containing 7.5% of the total atomic gas in M 74, interpreted as a signature of external gas accretion. It is the fourth known case of an explosion of a presumably massive star located close to a concentration of atomic gas (after GRBs 980425, 060505, and SN 2009bb). It is unlikely that all these associations are random (at a 3σsignificance), so the case of SN 2002ap adds to the evidence that the birth of the progenitors of type Ic-BL SNe and GRBs is connected with the accretion of atomic gas from the intergalactic medium. The HIextension could come from tidally disrupted companions of M 74, or be a remnant of a galaxy or a gas cloud that accreted entirely from the intragroup medium. The other (type II) SNe in M 74 are located at the outside edge of a spiral arm. This suggests that either their progenitors were born when gas was piling up there or that the SN progenitors moved away from the arm due to their orbital motions. These type II SNe do not seem to be related to gas accretion.

ASASSN-16fp (SN 2016coi): a transitional supernova between Type Ic and broad-lined Ic

We present results based on a well sampled optical ($UBVRI$) and ultraviolet ({\it Swift}/UVOT) imaging, and low-resolution optical spectroscopic follow-up observations of the nearby Type Ic supernova (SN) ASASSN-16fp (SN 2016coi). The SN was monitored during the photospheric phase ($-10$ to $+$33 days with respect to the $B$-band maximum light). The rise to maximum light and early post-maximum decline of the light curves are slow. The peak absolute magnitude ($M_{V}$ = $-17.7\pm0.2$ mag) of ASASSN-16fp is comparable with broad-lined Ic SN 2002ap, SN 2012ap and transitional Ic SN 2004aw but considerably fainter than the GRB/XRF associated supernovae (e.g. SN 1998bw, 2006aj). Similar to the light curve, the spectral evolution is also slow. ASASSN-16fp shows distinct photospheric phase spectral lines along with the C\,{\sc ii} features. The expansion velocity of the ejecta near maximum light reached $\sim$16000 km s$^{-1}$ and settled to $\sim$8000 km s$^{-1}$, $\sim$1 month post-maximum. Analytical modelling of the quasi-bolometric light curve of ASASSN-16fp suggests that $\sim$0.1 M$_{\odot}$ $^{56}$Ni mass was synthesized in the explosion, with a kinetic energy of 6.9$^{+1.5}_{-1.3}$ $\times$ 10$^{51}$ erg and total ejected mass of $\sim$4.5\,$\pm$\,0.3 M$_{\odot}$.

OPTICAL OBSERVATIONS OF THE TYPE Ic SUPERNOVA 2007gr IN NGC 1058

We present extensive optical observations of the normal Type Ic supernova (SN) 2007gr, spanning from about one week before maximum light to more than one year thereafter. The optical light and color curves of SN 2007gr are very similar to those of the broad-lined Type Ic SN 2002ap, but the spectra show remarkable differences. The optical spectra of SN 2007gr are characterized by unusually narrow lines, prominent carbon lines, and slow evolution of the line velocity after maximum light. The earliest spectrum (taken at t=-8 days) shows a possible signature of helium (He~I 5876 at a velocity of ~19,000 km s{-1}). Moreover, the larger intensity ratio of the [O I] 6300 and 6364 lines inferred from the early nebular spectra implies a lower opacity of the ejecta shortly after the explosion. These results indicate that SN 2007gr perhaps underwent a less energetic explosion of a smaller-mass Wolf-Rayet star (~ 8--9 Msun) in a binary system, as favored by an analysis of the progenitor environment through pre-explosion and post-explosion Hubble Space Telescope images. In the nebular spectra, asymmetric double-peaked profiles can be seen in the [O~I] 6300 and Mg~I] 4571 lines. We suggest that the two peaks are contributed by the blueshifted and rest-frame components. The similarity in velocity structure and the different evolution of the strength of the two components favor an aspherical explosion with the ejecta distributed in a torus or disk-like geometry, but inside the ejecta the O and Mg have different distributions.

A deeper search for the progenitor of the Type Ic supernova 2002ap

Images of the site of the Type Ic Supernova 2002ap taken before explosion were analysed previously by Smartt et al. (2002). We have uncovered new unpublished, archival pre-explosion images from the Canada-France-Hawaii Telescope (CFHT) that are vastly superior in depth and image quality. In this paper we present a further search for the progenitor star of this unusual Type Ic supernova. Aligning high-resolution Hubble Space Telescope (HST) observations of the supernova itself with the archival CFHT images allowed us to pinpoint the location of the progenitor site on the ground based observations. We find that a source visible in the B and R band pre-explosion images close to the position of the SN is (1) not coincident with the SN position within the uncertainties of our relative astrometry, and (2) is still visible �4.7 yrs post explosion in late-time observations taken with the William Herschel Telescope. We therefore conclude that it is not the progenitor of SN 2002ap. We derived absolute limiting magnitudes for the progenitor of MB > -4.2 ± 0.5 and MR > -5.1 ± 0.5. These are the deepest limits yet placed on a Type Ic supernova progenitor. We rule out all massive stars with initial masses greater than 7-8M⊙ (the lower mass limit for stars to undergo core collapse) that have not evolved to become Wolf-Rayet stars. This is consistent with the prediction that Type Ic supernovae should result from the explosions of Wolf-Rayet stars. Comparing our luminosity limits with stellar models of single stars at appropriate metallicity (Z=0.008) and with standard mass loss rates, we find no model that produces a Wolf-Rayet star of low enough mass and luminosity to be classed as a viable progenitor. Models with twice the standard mass loss rates provide possible single star progenitors but all are initially more massive than 30-40M⊙. We conclude that any single star progenitor must have experienced at least twice the standard mass loss rates, been initially more massive than 30 40M⊙ and exploded as a W-R star of final mass 10-12M⊙. Alternatively a progenitor star of lower initial mass may have evolved in an interacting binary system. Mazzali et al. (2002) propose such a binary scenario for the progenitor of SN 2002ap in which a star of initial mass 15-20M⊙ is stripped by its binary companion, becoming a 5M⊙ Wolf-Rayet star prior to explosion. We constrain any possible binary companion to a main sequence star of 6 20M⊙, a neutron star or a black hole. By combining the pre-explosion limits with the ejecta mass estimates and constraints from X-ray and radio observations we conclude that any binary interaction most likely occurred as Case B mass transfer, either with or without a subsequent common envelope evolution phase.

The Optical/Near‐Infrared Light Curves of SN 2002ap for the First 1.5 Years after Discovery

Supernova (SN) 2002ap in M74 was observed in the UBVRIJHK bands for the first 40 days following its discovery (2002 January 29) until it disappeared as a result of solar conjunction and then in June after it reappeared. The magnitudes and dates of peak brightness in each band were determined. While the rate of increase of the brightness before the peak is almost independent of wavelength, the subsequent rate of decrease becomes smaller with wavelength from the U to the R bands and is constant at wavelengths beyond the I band. The photometric evolution is faster than in the well-known hypernovae SNe 1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The bolometric light curve of SN 2002ap for the full period of observations was constructed. The absolute magnitude is found to be much fainter than that of SN 1998bw but is similar to that of SN 1997ef, which lies at the faint end of the hypernova population. The bolometric light curve at the early epochs was best reproduced with the explosion of a C + O star that ejects 2.5 M☉ with kinetic energy EK = 4 × 1051 ergs. A comparison of the predicted brightness of SN 2002ap with that observed after solar conjunction may imply that γ-ray deposition at the later epochs was more efficient than in the model. This may be due to an asymmetric explosion.

On the Light Curve and Spectrum of SN 2003dh Separated from the Optical Afterglow of GRB 030329

The net optical light curves and spectra of the supernova (SN) 2003dh are obtained from the published spectra of GRB 030329, covering about 6 days before SN maximum to about 60 days after. The bulk of the U-band flux is subtracted from the observed spectra using early-time afterglow templates, because strong line blanketing greatly depresses the UV and U-band SN flux in a metal-rich, fast-moving SN atmosphere. The blue-end spectra of the gamma-ray burst (GRB) connected hypernova SN 1998bw is used to determine the amount of subtraction. The subtraction of a host galaxy template affects the late-time results. The derived SN 2003dh light curves are narrower than those of SN 1998bw, rising as fast before maximum, reaching a possibly fainter maximum, and then declining ~ 1.2-1.4 times faster. We then build UVOIR bolometric SN light curve. Allowing for uncertainties, it can be reproduced with a spherical ejecta model of Mej ~ 7 ± 3 M☉, EK ~ 3.5 ± 1.5 × 1052 ergs, with EK/Mej ~ 5 following previous spectrum modeling, and M(56Ni) ~ 0.4 M☉. This suggests a progenitor main-sequence mass of ~25-40 M☉, lower than SN 1998bw but significantly higher than normal Type Ic SNe and the GRB-unrelated hypernova SN 2002ap.

The Early Spectroscopy of Supernovae

SummaryThe spectroscopy of a supernova (SN) just after its discovery is quite important not only for the spectral type classification but also for the planning further follow-up observations or the target-of-opportunity observations (ToOs). The early spectroscopy is needed also because the information from the outermost envelope of such exploding objects as SNe cannot be obtained in the later phase. In order to obtain the early spectrum, the quick circulation of the discovery information is important. We introduce our contributions with the public astronomical observatories in Japan, including the case of “hypernova” SN 2002ap discovered by a Japanese amateur astronomer. We summarize the time interval between the discoveries, the announcements, and the first spectral classifications of recent SNe, and discuss what would be required for the early spectroscopy.

Supernova Light-Curve Models for the Bump in the Optical Counterpart of X-Ray Flash 030723

XRF 030723 is the first X-ray flash (XRF) to show in its optical light curve (LC) a bump that has been interpreted as the signature of a supernova (SN). After subtracting the afterglow component from the observed optical LC of the XRF counterpart, the properties of the putative SN are constrained by means of synthetic LCs of core-collapse SNe. For the redshift range $z \sim 0.3$ -- 1, all possible models require a rather small mass of synthesized \Nifs, i.e. $M$(\Nifs) $\sim$ 0.01 -- 0.3 $\Msun$. The models used to describe the energetic SNe Ic associated with gamma-ray bursts (SNe 1998bw and 2003dh) are too massive for the observed LC. If the relation between ejected \Nifs mass and total ejecta mass established from models of various Type Ic SNe also holds for the putative SN in XRF 030723, the ejecta mass is constrained to be $\sim$ 1 -- 3 $\Msun$ and the kinetic energy $\lsim 1\times 10^{52}$ erg. This corresponds to a progenitor with $15\Msun \lesssim M_{\rm MS}\lesssim 25\Msun$. The SN therefore appears to have properties intermediate between a normal SN Ic like SN 1994I and a more energetic object like SN 2002ap.

A Failed Gamma‐Ray Burst with Dirty Energetic Jets Spirited Away? New Implications for the Gamma‐Ray Burst–Supernova Connection from SN 2002ap

The Type Ic supernova (SN) 2002ap is an interesting event with very broad spectral features like the famous energetic SN 1998bw associated with a gamma-ray burst (GRB) 980425. Here we examine the jet hypothesis from SN 2002ap recently proposed based on the redshifted polarized continuum found in a spectropolarimetric observation. We show that jets should be moving at about 0.23c to a direction roughly perpendicular to us, and the degree of polarization requires a jet kinetic energy of at least 5 × 1050 ergs, a similar energy scale to the GRB jets. The weak radio emission from SN 2002ap has been used to argue against the jet hypothesis, but we argue that this is not a problem because the jet is expected to be freely expanding and unshocked. However, the jet cannot be kept ionized because of adiabatic cooling without external photoionization or a heating source. We explored various ionization possibilities and found that only the radioactivity of 56Ni is a plausible source, indicating that the jet is formed and ejected from the central region of the core collapse, not from the outer envelope of the exploding star. Then we point out that, if the jet hypothesis is true, the jet will eventually sweep up enough interstellar medium and generate shocks in a few to 10 yr, producing strong radio emission that can be spatially resolved, giving us a clear test for the jet hypothesis. Discussions are also given on what the jet would imply for the GRB-SN connection, when it is confirmed. We suggest the existence of two distinct classes of GRBs from similar core-collapse events but by completely different mechanisms. Cosmologically distant GRBs having an energy scale of ~1050-1051 ergs are collimated jets generated by the central activity of core collapses, associated with 56Ni ejection along with the jets. SN 2002ap can be considered as a failed GRB of this type with large baryon contamination. On the other hand, much less energetic ones including GRB 980425 are rather isotropic, which may be produced by hydrodynamical shock acceleration at the outer envelope. We propose that the radioactive ionization for the SN 2002ap jet may give a new explanation also for the X-ray line features often observed in GRB afterglows.

The type Ic hypernova SN 2002ap

We investigate the properties of the Type Ic supernova (SN) 2002ap through models of its spectral evolution and light curve (LC). Its spectra are similar to those of the “hypernova” SN 1997ef, showing unusually broad O i, Ca ii, Si ii and Fe ii P Cygni lines. However, its kinetiv energy [∼ (4 – 10) × 10 51 ergs], and the mass ejected (2.5 – 5 M ⊙) are smaller, resulting in faster evolving LCs and spectra. About 0.07 M ⊙ 56Ni is required for its peak luminosity, some of which were mixed to the outer layer. We suggest that SN 2002ap, lying at the low-energy and low-mass end of the hypernova sequence, is likely the explosion of a 5 M ⊙ C+O star, corresponding to a main sequence mass 20 – 25 M ⊙.

The Optical/Near‐Infrared Light Curves of SN 2002ap for the First 140 Days after Discovery

Supernova (SN) 2002ap in M74 was observed in the $UBVRIJHK$ bands for the first 40 days following its discovery (2002 January 29) until it disappeared because of solar conjunction, and then in June after it reappeared. The magnitudes and dates of peak brightness in each band were determined. While the rate of increase of the brightness before the peak is almost independent of wavelength, the subsequent rate of decrease becomes smaller with wavelength from the $U$ to the $R$ band, and is constant at wavelengths beyond $I$. The photometric evolution is faster than in the well-known ``hypernovae'' SNe~1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The bolometric light curve of SN 2002ap for the full period of observations was constructed. The absolute magnitude is found to be much fainter than that of SN 1998bw, but is similar to that of SN 1997ef, which lies at the faint end of the hypernova population. The bolometric light curve at the early epochs was best reproduced with the explosion of a C+O star that ejects $2.5~M_\sun$ with kinetic energy $E_{\rm K}=4\times 10^{51}~{\rm ergs}$. A comparison of the predicted brightness of SN 2002ap with that observed after solar conjunction may imply that $\gamma$-ray deposition at the later epochs was more efficient than in the model. This may be due to an asymmetric explosion.

Aspherical supernova explosions

Core collapse supernovae (SN) are the final stages of stellar evolution in massive stars during which the central region collapses, forms a neutron star (NS), and the outer layers are ejected. Recent explosion scenarios assumed that the ejection is due to energy deposition by neutrinos into the envelope, but detailed models do not produce powerful explosions. There is new and mounting evidence for an asphericity and, in particular, for axial symmetry in several supernovae which may be hard to reconcile within the spherical picture. This evidence includes the observed high polarization and its variation with time, pulsar kicks, high velocity iron-group and intermediate-mass elements material observed in remnants, direct observations of the debris of SN 1987A, etc. Some of the new evidence is discussed in more detail. To be in agreement with the observations, any successful mechanism must invoke some sort of axial symmetry for the explosion. We consider jet-induced/dominated explosions of core collapse supernovae. Our study is based on detailed 3-d hydrodynamical and radiation transport models. We find that the observations can be explained by low velocity, massive jets which stall well within the SN envelope. Such outflows may be produced by MHD-mechanisms, convective dominated accretion disks on the central object or asymmetric neutrino emissions. Asymmetric density/chemical distributions and, for SN 2002ap, off-center energy depositions have been identified as crucial for the interpretation of the polarization.

Photospheric‐Phase Spectropolarimetry and Nebular‐Phase Spectroscopy of the Peculiar Type Ic Supernova 2002ap

ABSTRACTThe early‐time optical spectrum of the Type Ic supernova (SN) 2002ap was characterized by unusually broad features, leading some authors to designate it a “hypernova.” We present optical spectropolarimetry of this object 16 and 37 days after the estimated date of explosion. After correcting for interstellar polarization, we find evidence for a high level of intrinsic continuum polarization at both epochs: p≳1.3% on day 16 and p≳1.0% on day 37. Prominent line polarization is also seen, especially in the trough of the Ca ii near‐infrared triplet during the second epoch. When interpreted in terms of the oblate, electron‐scattering model atmospheres of Höflich, our results imply an asymmetry of at least 20% (day 16) and 17% (day 37). The data suggest a fair degree of axisymmetry, although the polarization angle of the dominant polarization axes are different by about 55° between the two epochs, implying a complex morphology for the thinning ejecta. In particular, there exists some spectropolarimetric evidence for a different distribution of Ca relative to iron‐group elements. We also present flux spectra of SN 2002ap taken 131 and 140 days after the explosion. The spectra are characterized by a very weak continuum and broad emission lines, indicating that SN 2002ap has entered the nebular phase. The spectral features are substantially similar to those of “normal” SNe Ic in the nebular phase, and the emission lines are not significantly broader. However, some of the broad lines are very sharply peaked and may possess a narrow component (probably unresolved by our spectra, FWHM≲400 km s-1) that is redshifted by ∼580 km s-1 with respect to the systemic velocity of the host galaxy.

Early-Phase Spectra of “Hypernova” SN 2002[CLC]ap[/CLC

The spectral evolution of the peculiar Type Ic supernova (SN) 2002ap during the first 40 days is presented. The spectra display very broad absorption features, which are typical of The maximum expansion velocity measured on the earliest spectra exceeds 3 × 104 km s-1. The spectrum of SN 2002ap at the epoch of maximum brightness resembles that of SN 1997ef more than that of SN 1998bw. The spectral evolution of SN 2002ap proceeds at about 1.5 times the rate of SN 1997ef. The parameterized supernova spectrum synthesis code SYNOW was used to perform line identification and deduce velocity information from the early-phase spectra, which are heavily affected by line blending. The photospheric velocity, as deduced from the fitting results and from the blueshift of the Si II λ6355 absorption minimum, is lower than in previously studied hypernovae. At advanced epochs, the Si II λ6355 absorption minimum becomes difficult to distinguish. This may be caused by the growth of [O I] λλ6300, 6364 emission. Together with the rapid spectral evolution, this suggests that SN 2002ap should enter the nebular phase sooner than previously studied hypernovae.

On the Progenitor of the Type I[CLC]c[/CLC] Supernova 2002[CLC]ap[/CLC

This Letter presents wide-field optical and near-IR (UBVRIHαK') images of the galaxy M74 that were taken between 0.6 and 8.3 yr before the discovery of the Type Ic supernova 2002ap. We have located the position of the supernova on these images with an accuracy of 03. We find no sign of a progenitor object on any of the images. The deepest of these images is the B-band exposure, which has a sensitivity limit corresponding to an absolute magnitude of MB ≤ -6.3. From our observed limits, we rule out as the progenitor all evolved states of single stars with initial masses greater than 20 M☉ unless the W-R phase has been entered. Two popular theories for the origin of Type Ic supernovae are the core collapse of massive stars when they are in the W-R phase or the core collapse of a massive star in an interacting binary that has had its envelope stripped through mass transfer. Our prediscovery images would be sensitive only to the most luminous ~30% of W-R stars, hence leaving a substantial fraction of typical W-R stars as viable progenitors. The energetics measured from modeling the initial light curve and spectral evolution of SN 2002ap suggest an explosion of a 5 M☉ C+O core. While W-R stars generally have measured final masses greater than this, the uncertainties associated with the explosion model, stellar evolutionary calculations, and mass measurements suggest we cannot definitively rule out a W-R star progenitor. The alternative scenario is that the progenitor was a star of initial mass ~20-25 M☉ that was part of an interacting binary and stripped of its hydrogen and helium envelope via mass transfer. We discuss future observations of the supernova environment that will provide further constraints on the nature of the progenitor star.

The Type I[CLC]c[/CLC] Hypernova SN 2002[CLC]ap[/CLC

Photometric and spectroscopic data of the energetic Type Ic supernova (SN) 2002ap are presented, and the properties of the SN are investigated through models of its spectral evolution and its light curve. The SN is spectroscopically similar to the hypernova SN 1997ef. However, its kinetic energy [~(4-10) ? 1051 ergs] and the mass ejected (2.5-5 M?) are smaller, resulting in a faster evolving light curve. The SN synthesized ~0.07 M? of 56Ni, and its peak luminosity was similar to that of normal SNe. Brightness alone should not be used to define a hypernova, whose defining character, namely very broad spectral features, is the result of high kinetic energy. The likely main-sequence mass of the progenitor star was 20-25 M?, which is also lower than that of both hypernovae SN 1997ef and SN 1998bw. SN 2002ap appears to lie at the low-energy and low-mass end of the hypernova sequence as it is known so far. Observations of the nebular spectrum, which is expected to dominate by the summer of 2002, are necessary to confirm these values.

Supernova 2002ap: the first month

Supernova (SN) 2002ap in M74 was discovered on January 29, 2002. Being one of the nearest (10 Mpc) SN events in the last decades, and spectroscopically similar to the so-called ``hypernovae'' 1997ef and 1998bw, both possibly associated with gamma-ray bursts (GRBs), it is of great interest. Shortly after its discovery, we launched an intensive photometric and spectroscopic monitoring campaign of this event, and here we report the results of the first month of observations. We use our UBVRI photometry to estimate the magnitudes at, and dates of, peak brightness. Our data suggest that this object reached its peak B-band luminosity on Feb. 7.1(-1.3)(+2) UT. Based on its similarity to SN 1998bw, we estimate the range of possible dates for a GRB that may have been associated with SN 2002ap. We find that it may include dates outside the time frame for which all available gamma-ray data have been intensively scanned, according to recent reports. The absolute magnitude at peak brightness of SN 2002ap (M_B = -16.9) shows that it was significantly fainter than SN 1998bw, or normal type-Ia SNe, but similar to SN 1997ef. Our spectroscopic observations confirm that SN 2002ap is strikingly similar to SNe 1998bw and 1997ef. We briefly describe the spectral evolution of this object. To assist other observers and to stimulate theoretical models, we make our entire data set publicly available in digital form.