Abstract
It has been widely argued that Type-I superluminous supernovae (SLSNe-I) are driven by powerful central engines with a long-lasting energy injection after the core-collapse of massive ...progenitors. One of the popular hypotheses is that the hidden engines are fast-rotating pulsars with a magnetic field of B ∼ 1013–1015 G. Murase, Kashiyama & Mészáros proposed that quasi-steady radio/submm emission from non-thermal electron–positron pairs in nascent pulsar wind nebulae can be used as a relevant counterpart of such pulsar-driven supernovae (SNe). In this work, focusing on the nascent SLSN-I remnants, we examine constraints that can be placed by radio emission. We show that the Atacama Large Millimeter/submillimetre Array can detect the radio nebula from SNe at DL ∼ 1 Gpc in a few years after the explosion, while the Jansky Very Large Array can also detect the counterpart in a few decades. The proposed radio follow-up observation could solve the parameter degeneracy in the pulsar-driven SN model for optical/UV light curves, and could also give us clues to young neutron star scenarios for SLSNe-I and fast radio bursts.
Using data from the Sloan Digital Sky Survey (SDSS)-DR7, including structural measurements from 2D surface brightness fits with gim2d, we show how the fraction of quiescent galaxies depends on galaxy ...stellar mass M
*, effective radius R
e, fraction of r-band light in the bulge, B/T, and their status as a central or satellite galaxy at 0.01 < z < 0.2. For central galaxies we confirm that the quiescent fraction depends not only on stellar mass, but also on R
e. The dependence is particularly strong as a function of
, with α ∼ 1.5. This appears to be driven by a simple dependence on B/T over the mass range 9 < log (M
*/M) < 11.5, and is qualitatively similar even if galaxies with B/T > 0.3 are excluded. For satellite galaxies, the quiescent fraction is always larger than that of central galaxies, for any combination of M
*, R
e and B/T. The quenching efficiency is not constant, but reaches a maximum of ∼0.7 for galaxies with 9 < log (M
*/M) < 9.5 and R
e < 1 kpc. This is the same region of parameter space in which the satellite fraction itself reaches its maximum value, suggesting that the transformation from an active central galaxy to a quiescent satellite is associated with a reduction in R
e due to an increase in dominance of a bulge component.
On the diversity of magnetar-driven kilonovae Sarin, Nikhil; Omand, Conor M B; Margalit, Ben ...
Monthly notices of the Royal Astronomical Society,
09/2022, Letnik:
516, Številka:
4
Journal Article
Recenzirano
ABSTRACT
A non-negligible fraction of binary neutron star mergers are expected to form long-lived neutron star remnants, dramatically altering the multimessenger signatures of a merger. Here, we ...extend existing models for magnetar-driven kilonovae and explore the diversity of kilonovae and kilonova afterglows. Focusing on the role of the (uncertain) magnetic field strength, we study the resulting electromagnetic signatures as a function of the external dipolar and internal toroidal fields. These two parameters govern, respectively, the competition between magnetic-dipole spin-down and gravitational-wave spin-down (due to magnetic-field deformation) of the rapidly rotating remnant. We find that even in the parameter space where gravitational-wave emission is dominant, a kilonova with a magnetar central engine will be significantly brighter than one without an engine, as this parameter space is where more of the spin-down luminosity is thermalized. In contrast, a system with minimal gravitational-wave emission will produce a kilonova that may be difficult to distinguish from ordinary kilonovae unless early epoch observations are available. However, as the bulk of the energy in this parameter space goes into accelerating the ejecta, such a system will produce a brighter kilonova afterglow that will peak in shorter times. To effectively hide the presence of the magnetar from the kilonova and kilonova afterglow, the rotational energy inputted into the ejecta must be ≲10−3to 10−2Erot. We discuss the different diagnostics available to identify magnetar-driven kilonovae in serendipitous observations and draw parallels to other potential magnetar-driven explosions, such as superluminous supernovae and broad-line supernovae Ic.
ABSTRACT
Several types of energetic supernovae, such as superluminous supernovae (SLSNe) and broad-line Ic supernovae (Ic-BL SNe), could be powered by the spin-down of a rapidly rotating magnetar. ...Currently, most models used to infer the parameters for potential magnetar-driven supernovae make several unsuitable assumptions that likely bias the estimated parameters. In this work, we present a new model for magnetar-driven supernovae that relaxes several of these assumptions and an inference workflow that enables accurate estimation of parameters from light curves of magnetar-driven supernovae. In particular, in this model, we include the dynamical evolution of the ejecta, coupling it to the energy injected by the magnetar itself while also allowing for non-dipole spin down. We show that the model can reproduce SLSN and Ic-BL SN light curves consistent with the parameter space from computationally expensive numerical simulations. We also show the results of parameter inference on four well-known example supernovae, demonstrating the model’s effectiveness at capturing the considerable diversity in magnetar-driven supernova light curves. The model fits each light curve well and recovers parameters broadly consistent with previous works. This model will allow us to explore the full diversity of magnetar-driven supernovae under one theoretical framework, more accurately characterize these supernovae from only photometric data, and make more accurate predictions of future multiwavelength emission to test the magnetar-driven scenario better.
Abstract
We investigate effects of energetic pulsar wind nebulae (PWNe) on dust formation and evolution. Dust emission has been observed in many supernova remnants that also have neutron stars as ...compact remnants. We study the dependence of dust formation time and size on properties of the ejecta and central pulsar. We find that a pulsar with an initial spin period $P \sim 1\hbox{-}10\, \rm ms$ and a dipole magnetic field $B \sim 10^{12\hbox{-}15}\, \rm G$ can either accelerate or delay dust formation, with a time-scale of several months to over 10 yr, and reduce the average size of dust by a factor of ∼10 or more compared to the non-pulsar case. We also find that infrared dust emission may be detectable in typical superluminous supernovae out to ∼100–1000 Mpc in 2–5 yr after the explosion, although this depends sensitively on the spectral index of non-thermal emission from the nebula. We discuss implications to previous supernova observations. Some discrepancies between dust formation models and observations, such as the formation time in SN1987A or the dust size in the Crab Nebula, could be explained by the influence of a pulsar, and knowledge of the dust emission will be important for future ALMA observations of superluminous supernovae.
Context.
Many energetic supernovae (SNe) are thought to be powered by the rotational energy of a highly magnetized, rapidly rotating neutron star. The emission from the associated luminous pulsar ...wind nebula (PWN) can photoionize the SN ejecta, leading to a nebular spectrum of the ejecta with signatures that might reveal the PWN. SN 2012au is hypothesized to be one such SN.
Aims.
We investigate the impact of different ejecta and PWN parameters on the SN nebular spectrum, and test whether any photoionization models are consistent with SN 2012au. We study how constraints from the nebular phase can be linked into modeling of the diffusion phase and the radio emission of the magnetar.
Methods.
We present a suite of late-time (1–6 yr) spectral simulations of SN ejecta powered by an inner PWN. Over a large grid of one-zone models, we study the behavior of the physical state and line emission of the SN as the PWN luminosity (
L
PWN
), the injected spectral energy distribution (SED) temperature (
T
PWN
), the ejecta mass (
M
ej
), and the composition (pure O or realistic) vary. We discuss the resulting emission in the context of the observed behavior of SN 2012au, a strong candidate for a PWN-powered SN. We used optical light-curve models and broadband PWN models to predict possible radio emission from SN 2012au.
Results.
The SN nebular spectrum varies as
T
PWN
varies because the ejecta become less ionized as
T
PWN
increases. Ejecta models with low mass and high PWN power obtain runaway ionization for O I, and in extreme cases, also O II, causing a sharp decrease in their ion fraction over a small change in the parameter space. Certain models can reproduce the oxygen line luminosities of SN 2012au reasonably well at individual epochs, but we find no model that fits over the whole time evolution. This is likely due to uncertainties and simplifications in the model setup. Using our derived constraints from the nebular phase, we predict that the magnetar powering SN 2012au had an initial rotation period ~15 ms, and it is expected to be a strong radio source (
F >
100 μJy) for decades.
ABSTRACT
Fast-rotating pulsars and magnetars have been suggested as the central engines of superluminous supernovae (SLSNe) and fast radio bursts, and this scenario naturally predicts non-thermal ...synchrotron emission from their nascent pulsar wind nebulae (PWNe). We report results of high-frequency radio observations with ALMA and NOEMA for three SLSNe (SN 2015bn, SN 2016ard, and SN 2017egm), and present a detailed theoretical model to calculate non-thermal emission from PWNe with an age of ∼1−3 yr. We find that the ALMA data disfavours a PWN model motivated by the Crab nebula for SN 2015bn and SN 2017egm, and argue that this tension can be resolved if the nebular magnetization is very high or very low. Such models can be tested by future MeV–GeV gamma-ray telescopes such as AMEGO.
ABSTRACT
We present a sample of 14 hydrogen-rich superluminous supernovae (SLSNe II) from the Zwicky Transient Facility (ZTF) between 2018 and 2020. We include all classified SLSNe with peaks Mg < ...−20 mag with observed broad but not narrow Balmer emission, corresponding to roughly 20 per cent of all hydrogen-rich SLSNe in ZTF phase I. We examine the light curves and spectra of SLSNe II and attempt to constrain their power source using light-curve models. The brightest events are photometrically and spectroscopically similar to the prototypical SN 2008es, while others are found spectroscopically more reminiscent of non-superluminous SNe II, especially SNe II-L. 56Ni decay as the primary power source is ruled out. Light-curve models generally cannot distinguish between circumstellar interaction (CSI) and a magnetar central engine, but an excess of ultraviolet (UV) emission signifying CSI is seen in most of the SNe with UV data, at a wide range of photometric properties. Simultaneously, the broad H α profiles of the brightest SLSNe II can be explained through electron scattering in a symmetric circumstellar medium (CSM). In other SLSNe II without narrow lines, the CSM may be confined and wholly overrun by the ejecta. CSI, possibly involving mass lost in recent eruptions, is implied to be the dominant power source in most SLSNe II, and the diversity in properties is likely the result of different mass loss histories. Based on their radiated energy, an additional power source may be required for the brightest SLSNe II, however – possibly a central engine combined with CSI.
Abstract
The dividing line between gamma-ray bursts (GRBs) and ordinary stripped-envelope core-collapse supernovae (SNe) is yet to be fully understood. Observationally mapping the variety of ejecta ...outcomes (ultrarelativistic, mildly relativistic, or nonrelativistic) in SNe of Type Ic with broad lines (Ic-BL) can provide a key test to stellar explosion models. However, this requires large samples of the rare SN Ic-BL events with follow-up observations in the radio, where fast ejecta can be probed largely free of geometry and viewing angle effects. Here, we present the results of a radio (and X-ray) follow-up campaign of 16 SNe Ic-BL detected by the Zwicky Transient Facility (ZTF). Our radio campaign resulted in four counterpart detections and 12 deep upper limits. None of the events in our sample is as relativistic as SN 1998bw and we constrain the fraction of SN 1998bw-like explosions to <19% (3
σ
Gaussian equivalent), a factor of ≈2 smaller than previously established. We exclude relativistic ejecta with radio luminosity densities in between ≈5 × 10
27
erg s
−1
Hz
−1
and ≈10
29
erg s
−1
Hz
−1
at
t
≳ 20 days since explosion for ≈60% of the events in our sample. This shows that SNe Ic-BL similar to the GRB-associated SNe 1998bw, 2003lw, and 2010bh, or to the relativistic SNe 2009bb and iPTF17cw, are rare. Our results also exclude an association of the SNe Ic-BL in our sample with largely off-axis GRBs with energies
E
≳ 10
50
erg. The parameter space of SN 2006aj-like events (faint and fast-peaking radio emission) is, on the other hand, left largely unconstrained, and systematically exploring it represents a promising line of future research.
ABSTRACT
Optical imaging polarimetry was conducted on the hydrogen poor superluminous supernova 2020znr during three phases after maximum light (≈ +34 d, +288 d, and +289 d). After instrumental and ...interstellar polarization correction, all measurements are consistent with null-polarization detection. Modelling the light curve with a magnetar spin-down model shows that SN2020znr has similar magnetar and ejecta parameters to other SLSNe. A comparison of the best-fitting values discussed in the literature on SN 2017egm and SN 2015bn, two hydrogen poor SLSNe showing an increase of polarization after maximum light, suggests that SN 2020znr has higher mass ejecta that may prevent access to the geometry of the inner ejecta with optical polarimetry. The combined information provided by spectroscopy and light-curve analysis of type I SLSNe may be an interesting avenue to categorize the polarization properties of this class of transients. This approach would require to expand the sample of SLSNe polarimetry data currently available with early and late time epochs new measurements.
PDF
