The X‐Ray and Radio Emission from SN 2002ap: The Importance of Compton Scattering

et al. 2017

ApJ

We present early-time Swift and Chandra X-ray data along with late-time optical and near-infrared observations of SN 2013by, a Type IIL supernova (SN) that occurred in the nearby spiral galaxy ESO 138−G10 (D ∼ 14.8 Mpc). Optical and NIR photometry and spectroscopy follow the late-time evolution of the supernova from days +89 to +457 post-maximum brightness. The optical spectra and X-ray light curves are consistent with the picture of a SN having prolonged interaction with circumstellar material (CSM) that accelerates the transition from supernova to supernova remnant (SNR). Specifically, we find SN 2013by's Hα profile exhibits significant broadening (∼ 10,000 km s −1 ) on day +457, the likely consequence of high-velocity, H-rich material being excited by a reverse shock. A relatively flat X-ray light curve is observed that cannot be modeled using inverse-Compton scattering processes alone but requires an additional energy source most likely originating from the SN-CSM interaction. In addition, we see the first overtone of CO emission near 2.3 µm on day +152, signaling the formation of molecules and dust in the SN ejecta and is the first time CO has been detected in a Type IIL supernova. We compare SN 2013by to Type IIP supernovae whose spectra show the rarely observed SN-to-SNR transition in varying degrees and conclude that Type IIL SNe may enter the remnant phase at earlier epochs than their Type IIP counterparts.

Section: Discussionmentioning

confidence: 99%

The Transition of a Type IIL Supernova into a Supernova Remnant: Late-time Observations of SN 2013by

Black

Milisavljević

et al. 2017

ApJ

“…At early epochs (t30 days), the X-ray emission from SNe originating from H-stripped progenitors is dominated by Inverse Compton processes (e.g., Björnsson & Fransson 2004). .…”

Section: Low-density Cavity At R2×10 16 CMmentioning

confidence: 99%

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

Kamble

Milisavljevic

et al. 2017

ApJ

171

269

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ∼40 keV. SN 2014C shows ordinary explosion parameters (E k ∼1.8×10 51 erg and M ej ∼1.7 M e ). However, over an ∼1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of ∼1 M e of hydrogen-rich material at ∼6×10 16 cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ∼10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 10 3 -10 4 years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.

“…Inverse Compton (IC) emission is a well-known source of X-rays in young stellar explosions (Björnsson & Fransson 2004;Chevalier & Fransson 2006). X-ray emission originates from the up-scattering of optical photons from the SN photosphere by a population of relativistic electrons accelerated at the shock front.…”

Section: Constraints On Slsne-i Environmentsmentioning

confidence: 99%

Results from a Systematic Survey of X-Ray Emission from Hydrogen-poor Superluminous SNe

Chornock

Metzger

et al. 2018

ApJ

We present the results from a sensitive X-ray survey of 26 nearby hydrogen-poor superluminous supernovae (SLSNe-I) with Swift, Chandra, and XMM. This data set constrains the SLSN evolution from a few days until ∼2000 days after explosion, reaching a luminosity limit L x ∼10 40 erg s −1 and revealing the presence of significant X-ray emission possibly associated with PTF 12dam. No SLSN-I is detected above L 10 erg s-, suggesting that the luminous X-ray emission L x ∼10 45 erg s −1 associated with SCP 60F6 is not common among SLSNe-I. We constrain the presence of off-axis gamma-ray burst (GRB) jets, ionization breakouts from magnetar engines and the density in the sub-parsec environments of SLSNe-I through inverse Compton emission. The deepest limits rule out the weakest uncollimated GRB outflows, suggesting that if the similarity of SLSNe-I with GRB/SNe extends to their fastest ejecta, then SLSNe-I are either powered by energetic jets pointed far away from our line of sight (θ>30°), or harbor failed jets that do not successfully break through the stellar envelope. Furthermore, if a magnetar central engine is responsible for the exceptional luminosity of SLSNe-I, our X-ray analysis favors large magnetic fields B 2 10 14 >´G and ejecta masses M M 3 ej > ☉ , in agreement with optical/UV studies. Finally, we constrain the pre-explosion mass-loss rate of stellar progenitors of SLSNe-I. For PTF 12dam we infer M M 2 10 yr 5 1 <´--☉, suggesting that the SN shock interaction with an extended circumstellar medium is unlikely to supply the main source of energy powering the optical transient and that some SLSN-I progenitors end their lives as compact stars surrounded by a low-density medium similar to long GRBs and type Ib/c SNe.