DSN Radio and NICER X-ray Observations of PSR J1846-0258 Following Its Recent Outburst

ATel #13988; Walid A. Majid (JPL, Caltech), Aaron B. Pearlman (Caltech), Thomas A. Prince (Caltech, JPL), Teruaki Enoto (RIKEN, Japan), Zaven Arzoumanian (NASA GSFC), Keith Gendreau (NASA GSFC), Charles J. Naudet (JPL), Jonathon Kocz (Caltech), Shinji Horiuchi (CSIRO, CDSCC), Alice K. Harding (NASA GSFC), Wynn C. G. Ho (Haverford College), Lucien Kuiper (SRON, The Netherlands)
on 3 Sep 2020; 21:03 UT
Credential Certification: Aaron B. Pearlman (aaron.b.pearlman@caltech.edu)

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PSR J1846-0258 is a rotation-powered pulsar in the supernova remnant Kes 75. The pulsar has a rotation period of 0.32 s. Recently, Swift (ATel #13913) and MAXI/GSC (ATel #13922) reported the detection of an X-ray flare from this source. While radio emission has not yet been reported from this source, other magnetar-like sources have exhibited transient radio emission following similar X-ray bursts. The recent X-ray activity from this pulsar prompted us to carry out contemporaneous observations at both radio and X-ray wavelengths soon after the reported burst. Radio follow-up observations at 1.5 GHz (ATel #13950), performed using the 32-m Mk2 telescope at Jodrell Bank Observatory between 2020 August 5 and 2020 August 15, yielded 1-sigma upper limits on the pulsar's radio flux density, which ranged from 86 uJy to 126 uJy (assuming a 50% duty cycle).

We carried out radio observations using the Deep Space Network (DSN) 34-m diameter radio telescope (DSS-35) in Canberra, Australia at center frequencies of 8.3 GHz (X-band) and 31.9 GHz (Ka-band). The DSN observations were performed simultaneously at the two frequency bands on 2020 August 3, starting at 14:41:07 UTC, for 5285 s. The data were recorded with bandwidths of 352 MHz at X-band and 353 MHz at Ka-band using the pulsar backend in filterbank search mode with a frequency and time resolution of roughly 1 MHz and 512 microseconds, respectively. We also carried out several snapshot observations of the source in the X-ray band with the Neutron Star Interior Composition Explorer Mission (NICER) instrument onboard the International Space Station (ISS). The NICER observations were conducted over a period starting from 2020 August 2, 16:07:04 UTC to 2020 August 8, 20:57:28 UTC for a total on-source observing time of ~30 ks.

We detected significant evidence of X-ray pulsations (see the folded X-ray pulse profile provided at the bottom of this ATel) after searching over the P-Pdot space around the nominal spin period of the pulsar. Our measurements yielded a value of 3.03792176(4) Hz for the spin frequency and -6.82(5) x 10^-11 Hz^-2 for the first time derivative of the spin frequency. We then used these spin period measurements, obtained from the NICER data, as the nominal spin frequency to search the radio data for pulsed radio emission. The radio data in both frequency bands were dedispersed at a range of DM values from 0 to 5000 pc cm^-3 using DM steps of 50 pc cm^-3. The time series from each DM trial was then folded with the newly derived spin period. We found no evidence of pulsed emission in the simultaneous X-band and Ka-band data. Assuming a 10% duty cycle, we place 7-sigma upper limits of 190 uJy and 385 uJy on the pulsar's flux density at X-band and Ka-band, respectively. We also carried out searches for single dispersed pulses in both frequency bands and found no evidence of bright individual pulses. Additional multi-frequency radio observations will be particularly informative given the enhanced X-ray activity of this source.

We thank the DSN and NICER scheduling and operation teams for their rapid response in scheduling the observations.

X-ray Pulse Profile of PSR J1846-0258 (NICER, 2020 August 2-2020 August 8)