MEREGHETTI, SandroSandroMEREGHETTITaverna, RobertoRobertoTavernaBaldeschi, LucaLucaBaldeschiCRESTAN, SilviaSilviaCRESTANTurolla, RobertoRobertoTurollaZane, SilviaSilviaZaneRIGOSELLI, MichelaMichelaRIGOSELLI2025-02-212025-02-2120210004-637Xhttp://hdl.handle.net/20.500.12386/36133Calvera (1RXS J141256.0+792204) is an isolated neutron star detected only through its thermal X-ray emission. Its location at high Galactic latitude (b = +37 ) is unusual if Calvera is a relatively young pulsar, as suggested by its spin period (59 ms) and period derivative (3.2 10-15 s s-1). Using the Neutron Star Interior Composition Explorer, we obtained a phase-connected timing solution spanning four years, which allowed us to measure the second derivative of the frequency d? ? =-2.5× 10-23 Hz s-2 and to reveal timing noise consistent with that of normal radio pulsars. A magnetized hydrogen atmosphere model, covering the entire star surface, provides a good description of the phase-resolved spectra and energy-dependent pulsed fraction. However, we found that a temperature map more anisotropic than that produced by a dipole field is required, with a hotter zone concentrated toward the poles. By adding two small polar caps, we found that the surface effective temperature and that of the caps are ~0.1 and ~0.36 keV, respectively. The inferred distance is ~3.3 kpc. We confirmed the presence of an absorption line at 0.7 keV associated with the emission from the whole star surface, difficult to interpret as a cyclotron feature and more likely originating from atomic transitions. We searched for pulsed ?-ray emission by folding seven years of Fermi-LAT data using the X-ray ephemeris, but no evidence for pulsations was found. Our results favor the hypothesis that Calvera is a normal rotation-powered pulsar, with the only peculiarity of being born at a large height above the Galactic disk.STAMPAenArticle10.3847/1538-4357/ac34f22-s2.0-85121781429https://iopscience.iop.org/article/10.3847/1538-4357/ac34f2https://api.elsevier.com/content/abstract/scopus_id/85121781429FIS/05 - ASTRONOMIA E ASTROFISICA