{"title":"On the X-ray efficiency of the white dwarf pulsar candidate ZTF J190132.9+145808.7","authors":"Aya Bamba, Yukikatsu Terada, Kazumi Kashiyama, Shota Kisaka, Takahiro Minami, Tadayuki Takahashi","doi":"10.1093/pasj/psae041","DOIUrl":null,"url":null,"abstract":"Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this context, we studied the X-ray emissions from ZTF J190132.9+145808.7 (hereafter ZTF J1901+14), a notable massive isolated WD in the Galaxy, using the Chandra X-ray observatory. Our results showed 3.5σ level evidence of X-ray signals, although it is marginal. Under the assumption of a photon index of 2, we derived its intrinsic flux to be 2.3 (0.9–4.7) × 10−15 erg cm−2 s−1 and luminosity 4.6 (2.0–9.5) × 1026 erg s−1 for a 0.5–7 keV band in the $90\\%$ confidence range, given its distance of 41 pc. We derived the X-ray efficiency (η) concerning the spin-down luminosity to be 0.012 (0.0022–0.074), a value comparable to that of ordinary neutron star pulsars. The inferred X-ray luminosity may be compatible with curvature radiation from sub-TeV electrons accelerated within open magnetic fields in the magnetosphere of ZTF J1901+14. Conducting more extensive X-ray observations is crucial to confirm whether ZTF J1901+14-like isolated WDs are also significant sources of X-rays and sub-TeV electron cosmic rays, similar to other WD pulsars in accreting systems.","PeriodicalId":20733,"journal":{"name":"Publications of the Astronomical Society of Japan","volume":null,"pages":null},"PeriodicalIF":2.2000,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Publications of the Astronomical Society of Japan","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1093/pasj/psae041","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ASTRONOMY & ASTROPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Strongly magnetized, rapidly rotating massive white dwarfs (WDs) emerge as potential outcomes of double degenerate mergers. These WDs can act as sources of non-thermal emission and cosmic rays, gethering attention as WD pulsars. In this context, we studied the X-ray emissions from ZTF J190132.9+145808.7 (hereafter ZTF J1901+14), a notable massive isolated WD in the Galaxy, using the Chandra X-ray observatory. Our results showed 3.5σ level evidence of X-ray signals, although it is marginal. Under the assumption of a photon index of 2, we derived its intrinsic flux to be 2.3 (0.9–4.7) × 10−15 erg cm−2 s−1 and luminosity 4.6 (2.0–9.5) × 1026 erg s−1 for a 0.5–7 keV band in the $90\%$ confidence range, given its distance of 41 pc. We derived the X-ray efficiency (η) concerning the spin-down luminosity to be 0.012 (0.0022–0.074), a value comparable to that of ordinary neutron star pulsars. The inferred X-ray luminosity may be compatible with curvature radiation from sub-TeV electrons accelerated within open magnetic fields in the magnetosphere of ZTF J1901+14. Conducting more extensive X-ray observations is crucial to confirm whether ZTF J1901+14-like isolated WDs are also significant sources of X-rays and sub-TeV electron cosmic rays, similar to other WD pulsars in accreting systems.
期刊介绍:
Publications of the Astronomical Society of Japan (PASJ) publishes the results of original research in all aspects of astronomy, astrophysics, and fields closely related to them.