Radio Detection of an Elusive Millisecond Pulsar in the Globular Cluster NGC 6397

Zhang, L.; Ridolfi, A.; Blumer, Harsha; Freire, P. C. C.; Manchester, R. N.; McLaughlin, M. A.; Kremer, Kyle; Cameron, Andrew D.; Zhang, Zhi-Yu; Behrend, J.; Burgay, M.; Buchner, S.; Champion, D. J.; Chen, Weiwei; Dai, Shi; Feng, Yi; Fu, X.; Meng, Guang; Hobbs, G.; Keane, E. F.; Krämer, M.; Levin, Lina; Li, Xiang-Dong; Ni, Mingkang; Pan, Jingshan; Padmanabh, P. V.; Possenti, A.; Ransom, S. M.; Tsai, Chao-Wei; Krishnan, V. Venkatraman; Wang, Pei; Zhang, Jie; Zhi, Qi‐Jun; Zhang, Yongkun; Li, Di

doi:10.3847/2041-8213/ac81c3

Cited by 11 publications

(11 citation statements)

References 29 publications

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“…The pilot surveys revealed BH candidates in M22 (Strader et al 2012a), M62 (Chomiuk et al 2013), and 47 Tucanae (Miller-Jones et al 2015), with the full survey detecting additional BH candidates in M10 (Shishkovsky et al 2018) and NGC 6397 (Zhao et al 2020) and transitional millisecond pulsar candidates in Terzan 5 (Bahramian et al 2018) and NGC 6652 (Paduano et al 2021). A new "hidden" MSP was also detected in NGC 6397 (Zhao et al 2020), which has recently been confirmed by MeerKAT and Parkes timing (Zhang et al 2022). As alluded to above, the full MAVERIC survey has been used to search for signatures of IMBH accretion in GCs (Strader et al 2012b;Tremou et al 2018).…”

Section: Multiwavelength Sources In Globular Clustersmentioning

confidence: 52%

Ultradeep ATCA Imaging of 47 Tucanae Reveals a Central Compact Radio Source

Paduano,

Bahramian,

Miller-Jones

et al. 2024

ApJ

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We present the results of an ultradeep radio continuum survey, containing ∼480 hr of observations, of the Galactic globular cluster 47 Tucanae with the Australia Telescope Compact Array. This comprehensive coverage of the cluster allows us to reach rms noise levels of 1.19 μJy beam−1 at 5.5 GHz, 940 nJy beam−1 at 9 GHz, and 790 nJy beam−1 in a stacked 7.25 GHz image. This is the deepest radio image of a globular cluster and the deepest image ever made with the Australia Telescope Compact Array. We identify ATCA J002405.702-720452.361, a faint (6.3 ± 1.2 μJy at 5.5 GHz, 5.4 ± 0.9 μJy at 9 GHz), flat-spectrum (α = −0.31 ± 0.54) radio source that is positionally coincident with the cluster center and potentially associated with a faint X-ray source. No convincing optical counterpart was identified. We use radio, X-ray, optical, and UV data to show that explanations involving a background active galactic nucleus, a chromospherically active binary, or a binary involving a white dwarf are unlikely. The most plausible explanations are that the source is an undiscovered millisecond pulsar or a weakly accreting black hole. If the X-ray source is associated with the radio source, the fundamental plane of black-hole activity suggests a black hole mass of ∼54–6000 M ⊙, indicating an intermediate-mass black hole or a heavy stellar-mass black hole.

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Section: Multiwavelength Sources In Globular Clustersmentioning

confidence: 52%

Ultradeep ATCA Imaging of 47 Tucanae Reveals a Central Compact Radio Source

Paduano,

Bahramian,

Miller-Jones

et al. 2024

ApJ

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“…Unlike the DM delays observed preceding black widow eclipses (PSR J1544+4937 (Bhattacharyya et al 2013 (1992) observed PSR B1744−24A in Terzan 5 at several frequencies and noted long-term disappearances at all frequencies, with evidence that they could be episodic in nature rather than random. PSR J1740−5340 in the globular cluster NGC 6397 exhibits eclipses around superior conjunction of the pulsar for 40% of its orbit, as well as random DM variations over a wide range of orbital phases (D'Amico et al 2001b), while the newly found PSR J1740−5340b exhibits eclipses for 50% of its orbit (Zhang et al 2022). PSR J2039−5617 (Corongiu et al 2021), PSR J1048+2339 (Deneva et al 2016), and J1417−4402 (Camilo et al 2016) also undergo eclipses for roughly half their orbit.…”

Section: Eclipses and Flux Variabilitymentioning

confidence: 91%

Green Bank Telescope Discovery of the Redback Binary Millisecond Pulsar PSR J0212+5321

Perez

Bogdanov

Halpern

et al. 2023

ApJ

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We report the discovery of a 2.11 ms binary millisecond pulsar during a targeted search of the redback optical candidate coincident with the γ-ray source 3FGL J0212.5+5320 using the Robert C. Byrd Green Bank Telescope (GBT) with the Breakthrough Listen backend at L band. Over a seven month period, five pointings were made near inferior conjunction of the pulsar in its 20.9 hr orbit, resulting in two detections, lasting 12 and 42 minutes. The pulsar dispersion measure (DM) of 25.7 pc cm−3 corresponds to a distance of 1.15 kpc in the NE2001 Galactic electron density model, consistent with the Gaia parallax distance of 1.16 ± 0.03 kpc for the companion star. We suspect the pulsar experiences wide orbital eclipses, similar to other redbacks, as well as scintillation and DM delays caused by its interaction with its companion and surroundings. Although the pulsar was only detected over ≈3.7% of the orbit, its measured acceleration is consistent with published binary parameters from optical radial velocity spectroscopy and light-curve modeling of the companion star, and it provides a more precise mass ratio and a projected semimajor axis for the pulsar orbit. We also obtained a refined optical photometric orbit ephemeris, and observed variability of the tidally distorted companion over 7 yr. A hard X-ray light curve from NuSTAR shows expected orbit-modulated emission from the intrabinary shock. The pulsar parameters and photometric ephemeris greatly restrict the parameter space required to search for a coherent timing solution including pulsar spin-down rate, either using Fermi γ-rays or further radio pulse detections.

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“…SSGs in GCs are typically binary stars and X-ray sources, suggesting an evolutionary path distinct from that for single stars (Geller et al 2017). So far, there are three cases of SSG-radio associations in GCs: two MSPs, PSR J1740-5340A and B, in NGC 6397 (Zhao et al 2020;Zhang et al 2022) match with steep radio sources, and an SSG matches a flat-to-inverted source in M10 (M10-VLA1) (Shishkovsky et al 2018) that is likely a BH binary or an unusual RS CVn-type AB. The Chandra ID can be best modelled by a power-law, with a photon index of 2.5 ± 0.4, consistent with typical accreting stellar-mass BHs in quiescence (e.g., Reynolds et al 2014).…”

Section: Exotica In M4 21mentioning

confidence: 99%

Exotica in the globular cluster M4, studied with Chandra, HST, and the VLA

Lugger

Cohn

Heinke

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Using the Hubble Ultraviolet Globular Cluster Survey (HUGS) and additional HST archival data, we have carried out a search for optical counterparts to the low-luminosity Chandra X-ray sources in the globular cluster M4 (NGC 6121). We have also searched for optical or X-ray counterparts to radio sources detected by the VLA. We find 24 new confident optical counterparts to Chandra sources for a total of 40, including the 16 previously identified. Of the 24 new identifications, 18 are stellar coronal X-ray sources (active binaries, ABs), the majority located along the binary sequence in a V606 − I814 colour-magnitude diagram and generally showing an Hα excess. In addition to confirming the previously detected cataclysmic variable (CV, CX4), we identify one confident new CV (CX76), and two candidates (CX81 and CX101). One MSP is known in M4 (CX12), and another strong candidate has been suggested (CX1); we identify some possible MSP candidates among optical and radio sources, such as VLA20, which appears to have a white dwarf counterpart. One X-ray source with a sub-subgiant optical counterpart and a flat radio spectrum (CX8, VLA31) is particularly mysterious. The radial distribution of X-ray sources suggests a relaxed population of average mass ∼1.2 − 1.5 M⊙. Comparing the numbers of ABs, MSPs, and CVs in M4 with other clusters indicates that AB numbers are proportional to cluster mass (primordial population), MSPs to stellar encounter rate (dynamically formed population), while CVs seem to be produced both primordially and dynamically.

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Radio Detection of an Elusive Millisecond Pulsar in the Globular Cluster NGC 6397

Cited by 11 publications

References 29 publications

Ultradeep ATCA Imaging of 47 Tucanae Reveals a Central Compact Radio Source

Ultradeep ATCA Imaging of 47 Tucanae Reveals a Central Compact Radio Source

Green Bank Telescope Discovery of the Redback Binary Millisecond Pulsar PSR J0212+5321

Exotica in the globular cluster M4, studied with Chandra, HST, and the VLA

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