A bright X-ray flaring event from the intermediate supergiant fast X-ray transient IGR J00370+6122 observed with NuSTAR

We present an analysis of a long NuSTAR observation of the intermediate supergiant fast X-ray transient (SFXT) IGR J00370+6122, obtained around the peak of its orbital modulation.

By Ducci, Serim, Romano +3Oct 20, 2026

Score████░░░░░░4.4

VerdictWorth a reader's time today.

Read the original PDF

Abstract

We present an analysis of a long NuSTAR observation of the intermediate supergiant fast X-ray transient (SFXT) IGR J00370+6122, obtained around the peak of its orbital modulation. The observation has a net exposure ~93 ks. During the observation, the source displayed a bright flaring event that was resolved into numerous short flares with durations of 10-1000 s. The 3-70 keV luminosity spanned a dynamic range of ~200, from ~1E34 to ~1.8E36 erg/s; the maximum was reached for only ~40 s in total. The spectrum is well described by an absorbed double-Comptonisation model, with parameters consistent with those found in other X-ray pulsars accreting at similarly low luminosities. This is the first detection of a double-hump continuum in IGR J00370+6122, which extends this spectral state to the class of intermediate SFXTs. We searched for the previously reported ~346 s and ~674 s periodicities and find no significant signal at either period, which makes their interpretation as the neutron star spin period less likely. Using ~21 yr of Swift/BAT monitoring, we refine the orbital period of the system to P_orb=15.6654 +/- 0.0008 d. Finally, we discuss the observed flaring activity in the framework of quasi-spherical settling accretion, which is expected at the observed luminosities.

L. Ducci, M. M. Serim, P. Romano, E. Bozzo, L. Ji, C. Malacaria

The editor's rubric

Heuristic review

Leverage3 / 5: A method or resource many groups across the field will adopt within a year.; 18% of this desk’s rubric
Magnitude3 / 5: Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.; 20% of this desk’s rubric
Evidence3 / 5: Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.; 22% of this desk’s rubric
Novelty3 / 5: A genuinely new approach to an open problem.; 22% of this desk’s rubric
Trajectory2 / 5: Some room to improve with obvious engineering.; 10% of this desk’s rubric
Stakes2 / 5: Benefits a professional community (practitioners, clinicians, engineers).; 8% of this desk’s rubric

Dimension	Level	Weight	What that level means
Leverage	███░░ 3	18%	A method or resource many groups across the field will adopt within a year.
Magnitude	███░░ 3	20%	Large gain: roughly 2x, or a clear new state of the art on a hard, unsaturated problem.
Evidence	███░░ 3	22%	Solid: multiple benchmarks or cohorts, ablations, fair baselines, released code or data.
Novelty	███░░ 3	22%	A genuinely new approach to an open problem.
Trajectory	██░░░ 2	10%	Some room to improve with obvious engineering.
Stakes	██░░░ 2	8%	Benefits a professional community (practitioners, clinicians, engineers).

Editor’s rationale

Heuristic triage from title and abstract text only, not a reading of the paper. Cues found: method (we propose); firsts (first); novelty (discovery); verification (error bars).

How the score was computed

rank-2026-10-18

Score████░░░░░░4.4

Score = 10 × (75% × adjusted merit / 10 + 15% × attention + 10% × freshness)

Desks place stronger verdicts first, then use this score to order work within the same verdict.

Merit: 5.6 / 10; Weighted rubric, evidence-gated.
Adjusted merit: 4.6 / 10; Shrunk toward the desk prior by editor confidence (38%).
Attention: 0%; Citations, upvotes, points, mentions.
Freshness: 91%; Half-life decay since publication.

No attention signals recorded yet.

The record

Reviewed by heuristic-v7 on Oct 21, 2026, 07:29 UTC. Paper type: method.
Categories: astro-ph.HE
TOP, No.4 in the Physics edition of October 21, 2026.