FAST ultra-wideband observation of abnormal emission-shift events of PSR B0919+06

Abstract

PSR B0919+06 is known for its abnormal emission phenomenon, where the pulse emission window occasionally shifts progressively in longitude and returns afterwards. The physical mechanism behind this phenomenon is still under investigation. In this paper, we present our ultra-wideband observation of this pulsar using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), with simultaneous measurements in the frequency ranges 280-780 MHz and 1250-1550 MHz. We have identified three abnormal events, each of which becomes less apparent as the frequency decreases. At 1400 MHz, the averaged profile slightly shifted after the first and third abnormal events, implying a relationship between abnormal event and profile variation. We also found a linear trend in the left-edge position of the averaged profiles between the first and third event as well as after the third event, suggesting the existence of a slow-drifting mode between the two major events. The second event has a comparatively small shift in phase and is thus categorized as a "small flare state". During the third event, a sequence of approximately nine pulses was seen to significantly weaken in all frequency bands, likely associated with the pseudo-nulling observed at 150 MHz. A three-component de-composition analysis of the normal averaged profiles shows that the trailing component is dominant at our observing frequencies, while the centre component has a comparatively steeper spectrum. We found the overall flux density in an abnormal event to slightly differ from that in an ordinary state, and the difference shows a frequency dependence. A comparison of the normal, abnormal and dimmed averaged profile indicates that the leading component is likely to be stable in all states. Pulsar; B0919+06; Radio PACS number(s): 95.55.Jz, 95.85.Bh, 97.60.Gb Citation: Y.-Z. Yu, B. Peng, K. Liu, et al, FAST ultra-wideband observation of abnormal emission-shift events of PSR B0919+06, Sci. China-Phys. Mech. Astron. 62, 959504 (2019), doi: xxx

Multi-frequency study of the peculiar pulsars PSR B0919+06 and PSR B1859+07

“…They clearly show that if absorption is to explain the emission in PSR B0919+06, it has to be extremely complicated and variable in time and observing frequency and hence, unlikely to be the case here. Moreover, Yu et al (2019) found some peculiar emission properties of swooshes that were studied over a large (0.27-1.6 GHz) frequency range. In particular, they found that not all swooshes at higher frequencies are associated with pseudo-nulls and the folded profile during the swoosh showed evidence for a different spectral index.…”

“…On average, the best-fit value of 𝛼 for all swooshes ranged from 0.35-0.6 with a mean value of 0.51±0.3 suggesting that there is a consistent relationship between the emission mechanism causing the swoosh and the emitted frequency. Previously, Shaifullah et al (2018) and Yu et al (2019), have shown that pulses during a swoosh appear to null at lower frequencies. We note that in our dataset, while that behaviour is generally consistent with the conclusions by previous authors, we see a varied behaviour in radio emission at 220 MHz during a swoosh.…”

“…It is important to note that when these models were proposed, the observations mainly lacked simultaneous observations over a wide range of frequencies. Recently, multi-frequency studies were performed by Shaifullah et al (2018) and Yu et al (2019) where the chromatic behaviour of swooshes was seen for the first time. They clearly show that if absorption is to explain the emission in PSR B0919+06, it has to be extremely complicated and variable in time and observing frequency and hence, unlikely to be the case here.…”

“…Recently, interest in these two pulsars has renewed with new observations over a large radio frequency range. Using observations over multiple frequencies, Yu et al (2019) and Shaifullah et al (2018) showed that the swooshes of PSR B0919+06 were chromatic in nature whereby during a swoosh, the offset from the typical phase becomes smaller and emission itself becomes weaker at lower radio frequencies. All these observations pose important questions about how this behaviour can fit in the standard pulsar radio emission framework (Ruderman & Sutherland 1975), how these swooshing pulsars are related to other nulling and mode changing pulsars and how these different phenomena can be attributed to the same underlying emission mechanism.…”

The conceptual designs of radio telescopes in Guizhou karst region

“…FAST自2016年建成以来进行了密集的调试, 并 于2020年1月完成了国家验收. 在FAST调试期间, 通 过实测确定了FAST的基本性能 [9] , 并已经取得了一 系列成果 [10][11][12][13][14][15] . 这证明了FAST The Five-hundred-meter Aperture Spherical Radio Telescope (FAST)-a large-aperture radio telescope constructed in a karst depression-is completing its commissioning.…”