Properties of Magnetars Mimicking 56 Ni-Powered Light Curves in Type IC Superluminous Supernovae

Cano

et al. 2017

ApJ

Broad-lined type Ic supernovae (SNe Ic-BL) are a subclass of rare core collapse SNe whose energy source is debated in the literature. Recently a series of investigations on SNe Ic-BL with the magnetar (plus 56 Ni) model were carried out. Evidence for magnetar formation was found for the well-observed SNe Ic-BL 1998bw and 2002ap. In this paper we systematically study a large sample of SNe Ic-BL not associated with gamma-ray bursts. We use photospheric velocity data determined in a homogeneous way. We find that the magnetar+ 56 Ni model provides a good description of the light curves and velocity evolution of our sample of SNe Ic-BL, although some SNe (not all) can also be described by the pure-magnetar model or by the two-component pure-56 Ni model (3 out of 12 are unlikely explained by two-component model). In the magnetar+ 56 Ni model, the amount of 56 Ni required to explain their luminosity is significantly reduced, and the derived initial explosion energy is, in general, in accordance with neutrino heating. Some correlations between different physical parameters are evaluated and their implications regarding magnetic field amplification and the total energy reservoir are discussed.

Section: Alternative Models?mentioning

confidence: 82%

A Monte Carlo Approach to Magnetar-powered Transients. II. Broad-lined Type Ic Supernovae Not Associated with GRBs

Cano

et al. 2017

ApJ

“…6 shows the magnetar model can mimic the 56 Ni-powered lightcurve very well. As discussed in Moriya et al (2017), they found that most 56 Ni-powered lightcurves can be reproduced by magnetars that require the magnetar spin-down to be by almost pure dipole radiation with the breaking index close to 3.…”

Section: Bolometric Lightcurve and Model Fitsmentioning

confidence: 98%

The evolution of superluminous supernova LSQ14mo and its interacting host galaxy system

Chen

Nicholl

Smartt

et al. 2017

A&A

We present and analyse an extensive dataset of the superluminous supernova (SLSN) LSQ14mo (z = 0.256), consisting of a multicolour lightcurve from −30 d to +70 d in the rest-frame (relative to maximum light) and a series of six spectra from PESSTO covering −7 d to +50 d. This is among the densest spectroscopic coverage, and best-constrained rising lightcurve, for a fast-declining hydrogenpoor SLSN. The bolometric lightcurve can be reproduced with a millisecond magnetar model with ∼ 4 M ejecta mass, and the temperature and velocity evolution is also suggestive of a magnetar as the power source. Spectral modelling indicates that the SN ejected ∼ 6 M of CO-rich material with a kinetic energy of ∼ 7 × 10 51 erg, and suggests a partially thermalised additional source of luminosity between −2 d and +22 d. This may be due to interaction with a shell of material originating from pre-explosion mass loss. We further present a detailed analysis of the host galaxy system of LSQ14mo. PESSTO and GROND imaging show three spatially resolved bright regions, and we used the VLT and FORS2 to obtain a deep (five-hour exposure) spectra of the SN position and the three star-forming regions, which are at a similar redshift. The FORS spectrum at +300 days shows no trace of SN emission lines and we place limits on the strength of [O i] from comparisons with other Ic supernovae. The deep spectra provides a unique chance to investigate spatial variations in the host star-formation activity and metallicity. The specific star-formation rate is similar in all three components, as is the presence of a young stellar population. However, the position of LSQ14mo exhibits a lower metallicity, with 12 + log(O/H) = 8.2 in both the R 23 and N2 scales (corresponding to ∼ 0.3 Z ). We propose that the three bright regions in the host system are interacting, which thus triggers star formation and forms young stellar populations.

“…However, the capability of a magnetar to mimic radioactive decay would require a pure dipole radiation and a narrow set of fine-tuned parameters, in particular for the magnetic field and Ni masses (Moriya et al 2017). In Figure 14, we display the space parameter where a magnetar (in the dipole case) can mimic the radioactive 56 Co decay from Moriya et al (2017), and compare it with the results from our magnetar fit on the SLSN light curves. The reference time intervals are derived from the observed times after peak where the SLSN decay follows the radioactive rate (Figure 10) and using the explosion times from the magnetar fits to the data (Figure 21).…”

Section: Magnetar Modelingmentioning

confidence: 99%

“…The late-time decays expected within the magnetar scenario can, under certain circumstances, mimic the radioactive 56 Co decay (e.g., Moriya et al 2017). We further discuss this in Section 5.8.…”

Section: Decay Ratesmentioning

confidence: 99%

“…At later times, e.g., 400 days postpeak, the magnetar model is expected to have a decay rate that is noticeably slower than 1 mag/100 days (e.g., Inserra et al 2013). However, the capability of a magnetar to mimic radioactive decay would require a pure dipole radiation and a narrow set of fine-tuned parameters, in particular for the magnetic field and Ni masses (Moriya et al 2017). In Figure 14, we display the space parameter where a magnetar (in the dipole case) can mimic the radioactive 56 Co decay from Moriya et al (2017), and compare it with the results from our magnetar fit on the SLSN light curves.…”

Section: Magnetar Modelingmentioning

confidence: 99%

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Light Curves of Hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

Gal‐Yam

Rubin

et al. 2018

ApJ

139

126

We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average, by about 4 and 2mag, respectively. The peak absolute magnitudes of SLSNe-I in rest-frame g band span −22M g −20 mag, and these peaks are not powered by radioactive 56 Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on photometric properties. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly declining and slowly declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times, the SLSN-I light curves slow down and cluster around the 56 Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 M e of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay of 56 Co, up to ∼400 days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.