Probing the spectrum of the magnetar 4U 0142+61 with JWST
arxiv(2024)
摘要
JWST observed the magnetar 4U 0142+61 with the MIRI and NIRCam instruments
within a 77 min time interval on 2022 September 20-21. The low-resolution MIRI
spectrum and NIRCam photometry show that the spectrum in the wavelength range
1.4-11 μm range can be satisfactorily described by an absorbed power-law
model, f_ν∝ν^-α, with a spectral slope α
=0.96±0.02, interstellar extinction A_V= 3.9±0.2, and normalization f_0
= 59.4± 0.5 μJy at λ = 8 μm. These observations do not
support the passive disk model proposed by Wang et al. (2006), based on the
Spitzer photometry, which was interpreted as evidence for a fallback disk from
debris formed during the supernova explosion. We suggest a nonthermal origin
for this emission and source variability as the most likely cause of
discrepancies between the JWST data and other IR-optical observing campaigns.
However, we cannot firmly exclude the presence of a large disk with a different
dependence of the effective disk temperature on distance from the magnetar.
Comparison with the power-law fit to the hard X-ray spectrum above 10 keV,
measured by NuSTAR contemporaneously with JWST, shows that the X-ray spectrum
is significantly harder. This may imply that the X-ray and IR nonthermal
emission come from different sites in the magnetosphere of the magnetar.
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