HAWC J0630+186 Could Not Be Powered by PSR J0630+19

Abstract

3HWC J0630+186 is one of the very-high-energy gamma-ray sources in the third High-Altitude Water Cherenkov (HAWC) catalog, its origin and source are, however, not clearly identified. The only possible associated source is PSR J0630+19 depart from the center of 3HWC J0630+186. A few TeV halos of pulsars are currently believed the most dominant TeV-PeV gamma-ray sources, and PSR J0630+19 was firstly discovered by Arecibo survey with normal pulsar period, but its age and spin-down luminosity are not available. It is then difficult to determine if 3HWC J0630+186 and PSR J0630+19 are associated or not. With the awarded telescope time in five-hundred-meter aperture spherical radio telescope (FAST) observing cycle, we have obtained the follow-up timing observations of PSR J0630+19 with observed duration more than one year. From our pulsar data analysis, we determined a more precise position and derived parameters via pulsar timing. The parameters indicate that it is an old pulsar with energy loss too low to power the very-high-energy emissions from 3HWC J0630+186.

Figures (4)

• Figure 1: Radio pulses detected from PSR J0630+19 on September 4, 2024 is presented in the form of diagnostic plot generated using the prepfold routine in the PRESTO software package. The validity of derived parameters can be found in the top-right section of the plot, where the $\chi^{2}$ is a function of DM, $P$, and $\dot{P}$, respectively. The confidence contours for $P$ and $\dot{P}$ are displayed in the bottom-right section. In the central portion, the averaged pulse profile is shown as a function of observing frequency.
• Figure 2: SnapShotDec observation of PSR J0630+19. The colormap represents the likelihood. All the dots (including gray and purple dots) are the beam positions. Three purple dots correspond to the three beams that detected pulse signals while the blue pentagram indicates the newly calculated coordinates for PSR J0630+19, as R.A.=06:30:05.33, Dec.=+19:35:03.8.
• Figure 3: Left panel: The pulse profile with 1.6-hour integration time. Due to the very low duty cycle of the pulse signal, a zoom-in view of the phase range 0.05--0.15 is provided. Right panel: The timing residuals plotted against observational date for the four frequency channels.
• Figure 4: $P$-$\dot{P}$ diagram, with the position of PSR J0630+19 marked by a red star. Magnetars, normal pulsars, and binary pulsars are represented by black squares, black dots, and black circles, respectively. Several colored lines indicate the theoretical “death lines” below which pulsars are not expected to emit radio signals according to different models. The red solid line corresponds to the traditional death line 1975ApJ...196...51R1992AA...254..198B. The purple dashed line shows the death line from Equation (9) of 1993ApJ...402..264C. The blue dash-dotted line is the prediction from curvature radiation in the vacuum gap model 2000ApJ...531L.135Z. And the orange dash-dotted line represents the death line predicted by curvature radiation (CR) in the space-charge-limited flow (SCLF) model 2000ApJ...531L.135Z. Finally, the green dash-dotted line corresponds to the death line from inverse Compton scattering (ICS) in SCLF model.