Calvera: a low-mass strangeon star torqued by debris disk?
Abstract
Calvera is a 59 ms isolated pulsar, being unique due to its non-detection in radio, optical and gamma-rays but the purely thermal emission in soft X-rays. It is suggested that Calvera could be an ordinary middle-aged pulsar with significant magnetospheric activity at a large distance (Shibanov et al. 2016). Alternatively, it is proposed in this paper that Calvera is a low-mass strangeon star with inactive magnetosphere (dead). In this scenario, we jointly fit the spectra obtained by the XMM-Newton Observatory and the Chandra X-ray Observatory with the strangeon star atmosphere model. The spectral model is successful in explaining the radiation properties of Calvera and X-ray Dim Isolated Neutron Stars, both showing similar observation features. Within the dead pulsar picture, Calvera might be of high temperature at 0.67keV, possessing a small stellar radius R < 4km and a presumably small magnetic field B <1011 G and and is probably braked by the fall-back disk accretion. Future advanced facilities may provide unique opportunities to know the real nature of Calvera.
- Publication:
-
American Astronomical Society Meeting Abstracts #231
- Pub Date:
- January 2018
- Bibcode:
- 2018AAS...23124302L