A Repeating Fast Radio Burst
2016 · paper · Astronomy
Reports ten additional radio bursts from the direction of FRB 121102, seen with the Arecibo telescope. They show the source repeats, with varying spectra, supporting models involving a young, highly magnetised extragalactic neutron star.
Checked: PDF from arxiv.org, fetched 4 Oct 2026. Page numbers are those of that PDF.
3 findings
Reference or label "The ±1-σ range of DMs for the 10 new bursts is 558.1 ± 3.3 pc cm−3": only 9 of the 10 new bursts have a DM (Burst 7 has none; "We measured the DM for 10 of the 11 bursts"), and the quoted value is reproduced by the 10 Table 1 DMs that include the discovery burst (Burst 1), not by the 9 new ones.
- p. 17 Methods, Measurement of dispersion measure and index, last paragraph
The ±1-σ range of DMs for the 10 new bursts is 558.1 ± 3.3 pc cm−3
- p. 16 Methods, Measurement of dispersion measure and index, first paragraph
We measured the DM for 10 of the 11 bursts
- p. 9 Table 1, DM column and footnote e
Burst 7 was too weak and corrupted by RFI to include.
- p. 3 Main text, paragraph beginning 'The measured DMs'
The measured DMs of all 11 bursts are consistent to within the uncertainties
Only the authors can say what is right here.
Judge's note: Read the DM column of Table 1 from the page image: 553, 560, 566, 555, 558, 559, (blank), 556.5, 557.4, 558.7, 556.5. All ten values: mean 558.01, population variance 10.835 (s.d. 3.29), matching the printed 558.1 ± 3.3 to within the rounding of the table values. The nine new bursts alone: mean 558.57, s.d. about 3.0-3.2. So the set described as 'the 10 new bursts' appears to be the 10 bursts with a measured DM, including Burst 1, and the sentence then compares it with the Burst 1 discovery value. No text explains a tenth new-burst DM. The population label is wrong or loose; only the authors can confirm which set was used. The separate 'all 11 bursts' wording raised by some reviewers here is the subject of C002.
Second check: another model agreed
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Wording Main text says "The measured DMs of all 11 bursts are consistent to within the uncertainties", but the Methods say "We measured the DM for 10 of the 11 bursts" and Table 1 has no DM for Burst 7 ("Burst 7 was too weak and corrupted by RFI to include").
- p. 3 main text, paragraph beginning 'The measured DMs'
The measured DMs of all 11 bursts are consistent to within the uncertainties
- p. 16 Methods, Measurement of dispersion measure and index
We measured the DM for 10 of the 11 bursts
- p. 9 Table 1, row 7, DM column (blank)
Burst 7 was too weak and corrupted by RFI to include.
Judge's note: Checked p3, p16, p17 and Table 1 on p9 in the page images. Table 1 has 10 DM entries (Burst 7 blank) and the Methods state 10 of 11. The same sentence speaks of 'the dispersion indices' matching 2.0, while the Methods fitted an index only for Bursts 8 and 11. No statement elsewhere gives a measured DM for Burst 7 (it was only found in the search near DM 559). Wording overstates the data; the conclusion is not affected.
Second check: another model agreed
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Wording Methods state "In p2030/p2886 observations, the major axis of the ALFA receiver was rotated 19°/90° with respect to North", but the next paragraph says the 2013 follow-up gridding was "in that case rotated 19° with respect to North", and Extended Data Table 1 lists those 2013 observations under project p2886.
- p. 13 Methods, Positional gridding strategy, first paragraph
In p2030/p2886 observations, the major axis of the ALFA receiver was rotated 19◦/90◦
- p. 13 Methods, Positional gridding strategy, second paragraph
2013 follow-up gridding4 with ALFA (in that case rotated 19◦ with respect to North)
- p. 21 Extended Data Table 1, 2013-12-09 and 2013-12-10 rows
2013-12-09 p2886 FRBGRID1a
- p. 13 Methods, Positional gridding strategy, first paragraph
In p2030/p2886 observations, the major axis of the ALFA receiver was rotated 19◦/90◦with respect to North
Only the authors can say what is right here.
Judge's note: Checked p13 and Extended Data Table 1 (p21) in the page images. The 2013-12-09/10 rows (FRBGRID1a-3a, ALFA) carry project code p2886, and the first Methods sentence also places the 2013 follow-up under p2886. So p2886 ALFA observations used both 19° (2013) and 90° (2015, 'aligned East-West'), and the one-angle-per-project mapping is incorrect or incomplete as written. No statement elsewhere restricts the first sentence to the 2015 data. Only the authors can say whether the mapping sentence or the project code is what needs amending.
Second check: another model agreed
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11 minor (typos and the like; most checked by the judge only)
Wording Methods: "the expected pulse broadening is ∼20µs ν^−4.4 with ν in GHz, an order of magnitude smaller than the ∼2 ms pulse widths and ∼0.7 ms intra-channel dispersion smearing"; 20 µs is a factor of 100 below 2 ms (35 below 0.7 ms), and the main text and Table 1 give widths of "w50 = 2.8−8.7 ms", none near 2 ms.
- p. 18 Methods, The role of interstellar scattering, first lines
an order of magnitude smaller than the ∼2 ms pulse widths
- p. 4 Main text, second paragraph
w50 = 2.8−8.7 ms
- p. 17 Methods, The role of interstellar scattering (end of p17)
the expected pulse broadening is ∼20µs ν−4.4 with ν
- p. 18 first lines
an order of magnitude smaller than the ∼2 ms pulse widths and ∼0.7 ms intra-channel
Only the authors can say what is right here.
Judge's note: Read pages 17 and 18 (the sentence runs across the page break), page 4 and Table 1 on page 9. At 1 GHz the stated expression gives 20 µs, a factor of 100 below 2 ms, and less at the 1.4 GHz observing frequency, so "an order of magnitude" understates the gap by the paper's own numbers. Table 1 FWHM widths run from 2.8 to 8.7 ms, so "∼2 ms" matches no reported width; no intrinsic or deconvolved width is defined anywhere in the text. The conclusion that scattering is negligible is unaffected, so this is loose wording, not a wrong result. Only the authors can say whether the coefficient or the wording is intended.
Second check: another model agreed
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Wording "the observed intra-session separations of our bursts (23 to 572 s)" omits the roughly 3700 s gap between Bursts 5 and 6, both on 2 June 2015, which the Methods call one "observing session"; the range given is that within a single scan.
- p. 5 Main text, first paragraph
the observed intra-session separations of our bursts (23 to 572 s)
- p. 9 Table 1, barycentric peak times of Bursts 5 and 6
57175.699727826
- p. 15 Methods, Timing analysis of burst arrival times
the eight bursts detected in the 2015 June 2 observing session
Judge's note: Recomputed from the Table 1 arrival times on the page image: Burst 2 to 3 is 572 s, Burst 6 to 7 is 23 s, Burst 5 to 6 is 3702 s. Bursts 4-5 and 6-11 were in different pointings (FRBGRID2b and FRBGRID6b, Extended Data Table 1) and Figure 2 labels 2 June as 'two scans', so the authors evidently mean separations within one scan; but the Methods (p15) describe 'the eight bursts detected in the 2015 June 2 observing session'. A terminology inconsistency; the argument about orbital periods is unchanged.
Second check: another model agreed
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Wording Extended Data Table 2 caption: "The J2000 ALFA Beam 0 positions are listed." The FRBDISC entry (05h32m09s, +33d05m13s) is the centre of the discovery beam, which Extended Data Table 1 gives as "1 (Beam4)" for the 2012-11-02 FRBDISC pointing, not the Beam 0 position of that survey pointing.
- p. 22 Extended Data Table 2 caption and FRBDISC row
The J2000 ALFA Beam 0 positions are listed.
- p. 21 Extended Data Table 1, 2012-11-02 row
1 (Beam4)
- p. 10 Figure 1, black-outlined beams and label '1'
1
Judge's note: Read pages 21, 22 and Figure 1 on page 10. In Figure 1 the beam labelled 1 sits at about 05h32m09s, +33d05m and is one of the outer black-outlined beams of the discovery pointing, whose central beam is near +32d59m. The separation between the FRBDISC coordinates and the refined position (05h31m58s, +33d08m04s) is about 220 arcsec, or 3.7 arcmin, which is the distance the text gives "from the beam centre of the discovery burst". So FRBDISC is the Beam 4 centre for the two 2012 ALFA rows. For the later single-pixel follow-up rows FRBDISC is simply the pointing centre, and for all grid positions the caption is right, so the imprecision affects only the 2012 rows.
Second check: another model agreed
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Typo Affiliation 1 prints the postal code with a 'B-' prefix: "Auf dem Hügel 69, B-53121 Bonn, Germany"; the country prefix for a German address would be 'D-'.
- p. 1 Affiliation 1
Auf dem H¨ugel 69, B-53121 Bonn, Germany
- p. 1 Affiliation 1
Auf dem Hügel 69, B-53121 Bonn, Germany
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that the country prefix used with German postal codes is 'D-' (and that 'B-' denotes Belgium). The page image and crop clearly show 'B-53121 Bonn, Germany', so this is not an extraction artefact. Cosmetic.
Second check: none (judge only)
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Typo Reference 1 has an open page range: "Science 318, 777– (2007)."
- p. 6 Reference 1
Science 318, 777– (2007).
Judge's note: Visible on the p6 page image: a dash follows 777 with no end page, whereas other entries give either a full range or a single article number. Either the end page should be supplied or the dash removed.
Second check: none (judge only)
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Typo Reference 11 writes the arXiv identifier with a colon, "ArXiv:1501:00753 (2015)", and then correctly as "1501.00753" in the same entry.
- p. 6 Reference 11
ArXiv:1501:00753 (2015). 1501.00753.
- p. 6 Reference 11
ArXiv:1501:00753 (2015)
Judge's note: Seen on the p6 page image: italic 'ArXiv:1501:00753' followed by monospaced '1501.00753'. The entry contradicts itself; the other preprint entries (7, 15) use 'ArXiv e-prints' in this field.
Second check: none (judge only)
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Typo Author Contributions has a doubled full stop: "S.C. and J.M.C.. L.G.S., J.W.T.H.,"
- p. 8 Author Contributions
S.C. and J.M.C.. L.G.S., J.W.T.H.,
- p. 8 Author Contributions
S.C. and J.M.C..
Judge's note: Visible on the p8 page image: 'J.M.C..' with two periods before the next sentence.
Second check: none (judge only)
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Typo Acknowledgements read "a Canadian Research Chair in Observational Astrophysics"; the programme is named "Canada Research Chair".
- p. 8 Acknowledgements
a Canadian Research Chair in Observational
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: that the official name of the programme is 'Canada Research Chair'. The page image shows 'a Canadian Research Chair in Observational Astrophysics'. Cosmetic; meaning unchanged.
Second check: none (judge only)
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Typo Table 1 footnote a has "(i.e the time delay due to dispersion is removed)" without the second full stop of "i.e."
- p. 9 Table 1, footnote a
(i.e the time delay due to dispersion is
- p. 9 Table 1, footnote a
(i.e the time delay due to dispersion
Judge's note: Seen on the p9 page image: footnote a prints 'i.e the', while footnote b of the same table prints 'i.e. an assumed gain', as does the rest of the paper.
Second check: none (judge only)
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Typo The paragraph ends without a full stop: "These values are as expected for radio waves traveling through a cold, ionised medium"
- p. 17 Methods, Measurement of dispersion measure and index, paragraph beginning 'The DM value was fit'
traveling through a cold, ionised medium
Judge's note: Seen on the p17 page image: the paragraph ends at 'ionised medium' with no period before the next paragraph ('Frequency-dependent pulse profile evolution...').
Second check: none (judge only)
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Typo The RISS length scale is introduced as "l_RISS ∼ 2 kpc×6 mas = 12 AU" and written with a different subscript in the next sentence: "∆t_RISS = l_ISS/V_eff = 215 V_100^−1 ν_1GHz^−2.2 days"; l_ISS is not defined anywhere.
- p. 18 Methods, The role of interstellar scattering, second paragraph
lRISS ∼ 2 kpc×6 mas = 12 AU
- p. 18 Methods, The role of interstellar scattering, second paragraph
∆tRISS = lISS/Veff
- p. 18 Methods, interstellar scattering
lISS/Veff
- p. 18 Methods, RISS paragraph
lRISS ∼
Judge's note: Read on the page 18 image: the subscripts are RISS and then ISS as printed, so it is not an extraction artefact. 12 AU divided by 100 km/s is about 208 days, which matches the 215-day prefactor, so both symbols are the same quantity and the fix is l_RISS.
Second check: none (judge only)