Atacama Compact Array observations of the pulsar-wind nebula of SNR 0540-69.3

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>We present observations of the pulsar-wind nebula (PWN) region of SNR 0540-69.3. The observations were made with the Atacama Compact Array (ACA) in Bands 4 and 6. We also add radio observations from the Australia Compact Array at 3 cm. For 1.449–233.50 GHz, we obtain a synchrotron spectrum $F_{\nu } \propto \nu ^{-\alpha _{\nu }}$, with the spectral index αν = 0.17 ± 0.02. To conclude how this joins the synchrotron spectrum at higher frequencies, we include hitherto unpublished AKARI mid-infrared data, and evaluate published data in the ultraviolet (UV), optical, and infrared (IR). In particular, some broad-band filter data in the optical must be discarded from our analysis due to contamination by spectral line emission. For the UV/IR part of the synchrotron spectrum, we arrive at $\alpha _{\nu } = 0.87^{+0.08}_{-0.10}$. There is room for 2.5 × 10−3 M⊙ of dust with a temperature of ∼55 K if there are dual breaks in the synchrotron spectrum, one around ∼9 × 1010 Hz and another at ∼2 × 1013 Hz. The spectral index then changes at ∼9 × 1010 Hz from αν = 0.14 ± 0.07 in the radio to $\alpha _{\nu } = 0.35^{-0.07}_{+0.05}$ in the millimetre-to-far-IR range. The ACA Band 6 data marginally resolve the PWN. In particular, the strong emission $\text{$\sim$} 1\hbox{$.\!\!^{\prime \prime }$}5$ south-west of the pulsar, seen at other wavelengths, and resolved in the 3 cm data with its 0.″8 spatial resolution, is also strong in the millimetre range. The ACA data clearly reveal the supernova remnant shell ∼20–35 arcsec west of the pulsar, and for the shell we derive αν = 0.64 ± 0.05 for the range 8.6–145 GHz.</jats:p>

Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

“…The [Ca ii] profile appears to show very little evolution in the FWHM until t ∼ 70 days, and this is a further argument in favour of the hypothesis that these lines form in the circumstellar environment. We also note that none of the typical nebular lines, such as [O iii] (λλ = 4959, 5007 Å) and [S ii] (λλ = 6716, 6731 Å) lines (Lundqvist & Fransson 1996;Lundqvist et al 2015Lundqvist et al , 2020, were detected in spectra. This implies that the wind density is high enough for those nebular lines to be collisionally deexcited, but that [Ca ii] can exist at much higher density (e.g., critical density: Li & McCray 1993).…”

Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

“…The [Ca ii] profile appears to show very little evolution in the FWHM until t ∼ 70 days, and this is a further argument in favour of the hypothesis that these lines form in the circumstellar environment. We also note that none of the typical nebular lines, such as [O iii] (λλ= 4959, 5007 Å) and [S ii] (λλ= 6716, 6731 Å) lines (Lundqvist & Fransson 1996;Lundqvist et al 2015Lundqvist et al , 2020, were detected in spectra. This implies that the wind density is high enough for those nebular lines to be collisionally de-excited, but that [Ca ii] can exist at much higher density (e.g.…”

Clumps and Rings of Ejecta in SNR 0540–69.3 as Seen in 3D

“…Most notably, SNR 0540 is O-rich, is thought to originate from a more massive progenitor (15 M e , Chevalier 2006; Williams et al 2008), and shows a shell of emission due to the interaction between the blast wave and surrounding medium. The shell has a radius of ∼30″ and emits in radio, millimeter waves, and X-rays (Manchester et al 1993;Hwang et al 2001;Brantseg et al 2014;Lundqvist et al 2020).…”