1E 1547.0–5408: A Galactic Magnetar

• 1E 1547.0–5408 is a Galactic magnetar—a young, high-field neutron star with a ~2.1 s spin period exhibiting both X-ray and radio emissions.
• The source displays recurring, large-amplitude X-ray outbursts and transient radio activity, serving as a benchmark for studies in magnetar phenomenology and neutron-star kinematics.
• Dust-scattering echoes from its intense burst events provide key insights into distance measurements and the interplay between interstellar dust and magnetar emissions.

1E 1547.0–5408 is a Galactic magnetar identified at different wavelengths as the Einstein X-ray source 1E 1547.0–5408, the radio pulsar PSR J1550–5418, and the burst-active source SGR J1550–5418. It is a young, highly magnetized neutron star with a spin period of about $2.1$ s, recurrent large-amplitude X-ray outbursts, transient radio activity, a prominent hard X-ray tail, and a line of sight strongly affected by interstellar dust. These properties have made it a benchmark system for studies of magnetar outbursts, dust-scattering echoes, radio-loud magnetospheres, neutron-star kinematics, and X-ray polarimetry (Tiengo et al., 2010, Lower et al., 2023, Taverna et al., 21 Jan 2026).

1. Identification and fundamental properties

1E 1547.0–5408 is classified as an anomalous X-ray pulsar and magnetar candidate, and later work established that it is also an intermittently radio-bright magnetar. Radio pulsations give a period near $2.07$ s, while X-ray timing has measured values such as $P = 2.072135 \pm 0.00005$ s and $P = 2.092684438 \pm 9.4\times 10^{-8}$ s at different epochs. Timing-based magnetic-field estimates place it firmly in the magnetar regime, with representative surface dipole values of order $10^{14}\,\mathrm{G}$; published examples include $B \approx 2.2\times 10^{14}\,\mathrm{G}$, $B \sim 3.2\times 10^{14}\,\mathrm{G}$, and $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$ (Teruaki et al., 2010, Yasuda et al., 2015, Taverna et al., 21 Jan 2026).

The source is also notable for its youth. Reported characteristic ages place it in the kyr range, including $\tau_c \sim 1.4$ kyr, $\tau_c \sim 0.69$ kyr, and a very young characteristic age $2.07$0 yr, while the spin-down luminosity is of order $2.07$1 (Teruaki et al., 2010, Yasuda et al., 2015, Deller et al., 2012). It has long been discussed in connection with the shell-like radio structure G327.24–0.13, proposed as a supernova remnant, consistent with a young neutron star origin (Tiengo et al., 2010, Olausen et al., 2011).

Distance estimates have differed by method. Dispersion-measure modeling suggested values near $2.07$2 kpc, whereas dust-scattering analyses favored $2.07$3–$2.07$4 kpc, with a best-fit geometric estimate $2.07$5 kpc for one dust model and a broader plausible range of about $2.07$6–$2.07$7 kpc across acceptable dust prescriptions (Tiengo et al., 2010, Deller et al., 2012). Later X-ray polarimetric work adopted $2.07$8 kpc, while radio timing and dispersion analyses in 2022 quoted model-dependent distances of $2.07$9 and $P = 2.072135 \pm 0.00005$0 kpc (Taverna et al., 21 Jan 2026, Lower et al., 2023). A conservative summary is that 1E 1547.0–5408 is a nearby Galactic-plane magnetar at a few kiloparsecs, behind a complex dust distribution.

2. Recurrent outbursts and broad-band radiative phenomenology

The long-term X-ray history of 1E 1547.0–5408 shows three flux levels: low, intermediate, and high. The low state was exemplified by the August 2006 XMM-Newton observation, the intermediate state by Einstein, ASCA, and 2007 XMM observations, and the high state by the 2008 and 2009 outbursts and their decays (Bernardini et al., 2011). This pattern already indicated that the source was not simply switching between a single quiescent level and rare flares, but sampling multiple radiative states over decades.

The 2008 October outburst began with Swift/BAT detection of short SGR-like bursts on 2008 October 3. Swift/XRT was on target in less than $P = 2.072135 \pm 0.00005$1 s, measuring a 2–10 keV flux of about $P = 2.072135 \pm 0.00005$2, more than $P = 2.072135 \pm 0.00005$3 times the quiescent level. Over the next day the spectrum softened rapidly: in single-component fits the photon index steepened from about $P = 2.072135 \pm 0.00005$4 to about $P = 2.072135 \pm 0.00005$5, or the blackbody temperature fell from about $P = 2.072135 \pm 0.00005$6 to about $P = 2.072135 \pm 0.00005$7 keV, while the pulsed fraction increased from about $P = 2.072135 \pm 0.00005$8 to $P = 2.072135 \pm 0.00005$9 during the Swift observing window (Israel et al., 2010). A phase-coherent timing solution over this interval required a positive $P = 2.092684438 \pm 9.4\times 10^{-8}$0, indicating increasing spin-down torque during the decay (Israel et al., 2010).

The January 2009 event was more extreme. Around 2009 January 22 the source reactivated at its historically highest X-ray flux level and emitted dozens of short bursts; Suzaku/WAM alone detected at least $P = 2.092684438 \pm 9.4\times 10^{-8}$1 bursts in the $P = 2.092684438 \pm 9.4\times 10^{-8}$2–$P = 2.092684438 \pm 9.4\times 10^{-8}$3 band between 00:57 and 17:02 UTC from the source direction (Tiengo et al., 2010, Yasuda et al., 2015). Follow-up broad-band spectroscopy with Suzaku on January 28–29 showed that the persistent $P = 2.092684438 \pm 9.4\times 10^{-8}$4–$P = 2.092684438 \pm 9.4\times 10^{-8}$5 keV emission was well described by an absorbed blackbody with $P = 2.092684438 \pm 9.4\times 10^{-8}$6 keV plus a hard power law with photon index $P = 2.092684438 \pm 9.4\times 10^{-8}$7. The absorption-uncorrected 2–10 keV flux was $P = 2.092684438 \pm 9.4\times 10^{-8}$8, while the 20–100 keV flux was $P = 2.092684438 \pm 9.4\times 10^{-8}$9, and pulsations were detected up to at least $10^{14}\,\mathrm{G}$0 keV (Teruaki et al., 2010). In this active state the hard component carried about three times as much radiative power as the soft thermal emission in the combined 2–100 keV band, and the hard X-ray tail had become more enhanced than the soft component relative to fainter states (Teruaki et al., 2010).

Broad-band monitoring through 2011 showed that the 2009 event also produced a transient hard pulsed component. In the $10^{14}\,\mathrm{G}$1–$10^{14}\,\mathrm{G}$2 keV band a new Gaussian-like pulse emerged at phase $10^{14}\,\mathrm{G}$3, offset from the soft broad pulse, reached maximum after a delay of $10^{14}\,\mathrm{G}$4 days, and faded below detectability within about $10^{14}\,\mathrm{G}$5 days. At its peak the pulsed 20–150 keV luminosity was $10^{14}\,\mathrm{G}$6, comparable to the spin-down luminosity (Kuiper et al., 2012). This established that in 1E 1547.0–5408 the hard, pulsed, and persistent components can evolve on different timescales.

Short-burst spectroscopy reinforced the connection between burst and persistent emission. A Suzaku reanalysis identified 18 short bursts on January 28–29 with 10–70 keV fluences from $10^{14}\,\mathrm{G}$7 to $10^{14}\,\mathrm{G}$8. The three brightest bursts were fit by two-blackbody models, while the stacked spectrum of 13 weaker bursts required two blackbodies plus a power law fixed at the persistent photon index $10^{14}\,\mathrm{G}$9. Above $B \approx 2.2\times 10^{14}\,\mathrm{G}$0 keV the ratio of stacked weak-burst spectrum to the persistent spectrum was approximately constant at $B \approx 2.2\times 10^{14}\,\mathrm{G}$1, supporting a close spectral kinship between persistent hard emission and unresolved weak bursts (Enoto et al., 2012).

A later high-energy episode occurred in 2022. After a Swift/BAT short burst on 2022 April 7, NICER observed a soft X-ray flux peak of $B \approx 2.2\times 10^{14}\,\mathrm{G}$2, declining back to the baseline $B \approx 2.2\times 10^{14}\,\mathrm{G}$3 over 17 days. Joint NICER and NuSTAR spectroscopy showed that the outburst primarily affected the thermal components, especially the hotter blackbody, while the 10–70 keV power-law flux remained consistent with pre-outburst values (Lower et al., 2023). This suggests that surface heating and hard-tail production can decouple in some radiative episodes.

3. Dust-scattering echoes, distance determination, and line-of-sight structure

The most distinctive environmental diagnostic associated with 1E 1547.0–5408 is the X-ray dust echo produced after the January 2009 burst storm. Swift/XRT and XMM-Newton images revealed three expanding rings around the source, produced by elastic scattering of a short burst by three thin dust layers along the line of sight. For a source at distance $B \approx 2.2\times 10^{14}\,\mathrm{G}$4, a dust layer at fractional distance $B \approx 2.2\times 10^{14}\,\mathrm{G}$5, and a burst at $B \approx 2.2\times 10^{14}\,\mathrm{G}$6, the ring radius obeys

$B \approx 2.2\times 10^{14}\,\mathrm{G}$7

so the ring expansion is a purely geometrical $B \approx 2.2\times 10^{14}\,\mathrm{G}$8 effect (Tiengo et al., 2010).

Fitting the ring radii showed that all three structures shared a common burst time consistent with the bright January 22 event at $B \approx 2.2\times 10^{14}\,\mathrm{G}$9 MJD. With $B \sim 3.2\times 10^{14}\,\mathrm{G}$0 fixed at that burst time, the expansion coefficients were $B \sim 3.2\times 10^{14}\,\mathrm{G}$1, $B \sim 3.2\times 10^{14}\,\mathrm{G}$2, and $B \sim 3.2\times 10^{14}\,\mathrm{G}$3 arcmin day$B \sim 3.2\times 10^{14}\,\mathrm{G}$4, implying three distinct dust layers (Tiengo et al., 2010). Under the best-fitting BARE-GR-B dust model, the source distance is $B \sim 3.2\times 10^{14}\,\mathrm{G}$5 kpc, and the dust layers lie at approximately 2.2, 2.6, and 3.4 kpc (Tiengo et al., 2010). These distances are consistent with structures inferred from CO line observations.

The ring brightness and spectral evolution also constrained the burst energetics. In the original analysis, assuming a hard bremsstrahlung-like spectrum with $B \sim 3.2\times 10^{14}\,\mathrm{G}$6 keV, the burst energy in the 1–100 keV band was estimated as $B \sim 3.2\times 10^{14}\,\mathrm{G}$7–$B \sim 3.2\times 10^{14}\,\mathrm{G}$8, placing it in the giant-flare regime but without a long-lived pulsating tail (Tiengo et al., 2010). Later work on a different burst observed on 2009 February 3 showed how sensitive such energetics are to the dust model. That event had a $B \sim 3.2\times 10^{14}\,\mathrm{G}$9–$B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$0 keV fluence of $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$1, followed by a $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$2 ks X-ray tail with fluence $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$3, but most of the tail beyond the first $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$4–$B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$5 s was shown to be dust-scattered burst emission rather than intrinsic magnetar afterglow (Pintore et al., 2017). Using the revised dust columns, the January 22 burst energy was re-estimated as $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$6 erg for a thermal bremsstrahlung spectrum with $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$7 keV, or $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$8 erg for $B_{\rm sd} \approx 2\times 10^{14}\,\mathrm{G}$9 keV (Pintore et al., 2017).

The broader implication is methodological. Because all known Galactic magnetars lie behind substantial dust columns, delayed scattered emission can contaminate apparent afterglows and long tails. In 1E 1547.0–5408 this effect is unambiguous: ring emission was brighter than the persistent source for part of the 2009 episode, and the later February 3 tail was dominated by scattering after the first tens of seconds (Tiengo et al., 2010, Pintore et al., 2017). The source is therefore a standard reference for dust-scattering systematics in magnetar burst studies.

4. Timing behavior, radio activity, and neutron-star kinematics

Timing campaigns around the 2008 and 2009 outbursts established 1E 1547.0–5408 as one of the noisiest and most torque-variable magnetars. RXTE and Swift monitoring after the 2008 October outburst yielded a phase-coherent solution for the first 29 days with

$\tau_c \sim 1.4$0

and the pulsed flux decay was interrupted by a spike about 9 days after the outburst. The post-outburst $\tau_c \sim 1.4$1 was about 60 times larger than the 2007 value inferred from radio timing, indicating a rapidly evolving torque (Dib et al., 2012). By contrast, the first 23 days after the 2009 January outburst gave

$\tau_c \sim 1.4$2

with $\tau_c \sim 1.4$3 consistent with zero, even though the persistent flux rose far more than in 2008 (Dib et al., 2012). This mismatch between radiative and torque changes is one of the clearest examples of partial decoupling between magnetar spin-down and X-ray output.

Independent Chandra and RXTE analyses reached a similar conclusion. During the Chandra monitoring windows after the 2008 and 2009 outbursts, the soft X-ray spectral shape remained comparatively stable, while in 2008 the spin-down rate increased by a factor of 2.2 over the same span. The lack of corresponding spectral evolution argued against a simple one-parameter relation between spin-down-inferred field strength and spectrally inferred magnetospheric state (Ng et al., 2010).

Radio behavior adds a further diagnostic. 1E 1547.0–5408 was among the first magnetars with coherent radio pulsations, and its radio flux density and pulse profile are highly variable on timescales from hours to months (Deller et al., 2012). The 2022 event was unprecedented among radio-loud magnetars: Parkes observations showed that the persistent radio emission disappeared at least 22 days before the Swift/BAT burst of April 7, remained undetected through April 9, and was re-detected on April 19 (Lower et al., 2023). Joint radio and X-ray timing showed that the outburst coincided with a spin-up glitch with $\tau_c \sim 1.4$4, $\tau_c \sim 1.4$5, and a subsequent linear increase in spin-down rate of $\tau_c \sim 1.4$6 over 147 days (Lower et al., 2023). A quasi-static magnetic-reconfiguration model interpreted the sequence as an initially mild perturbation near the polar caps, radio-gap pollution and shut-off, followed weeks later by a larger energy redistribution that powered the burst and altered the star’s quadrupole moment enough to issue the glitch (Collaboration et al., 2023).

The source is also one of the few magnetars with a direct proper-motion measurement. VLBI astrometry with the Australian Long Baseline Array yielded $\tau_c \sim 1.4$7 mas yr$\tau_c \sim 1.4$8, $\tau_c \sim 1.4$9 mas yr$\tau_c \sim 0.69$0, and a total proper motion $\tau_c \sim 0.69$1 mas yr$\tau_c \sim 0.69$2. Adopting $\tau_c \sim 0.69$3 kpc gives a Galactic-rotation-corrected transverse velocity of $\tau_c \sim 0.69$4, comparable to ordinary young pulsars and inconsistent with the idea that magnetars generically require natal kicks $\tau_c \sim 0.69$5 (Deller et al., 2012).

5. Extended emission, supernova-remnant environment, and nebular constraints

Extended X-ray emission around 1E 1547.0–5408 was initially discussed as a possible pulsar wind nebula, but multi-epoch XMM-Newton analysis showed that the extended component is dominated by dust scattering. Radial profiles in four epochs—quiescent, post-outburst, strong outburst, and decay—revealed significant soft excess below 6 keV out to $\tau_c \sim 0.69$6, while above 6 keV the profile was consistent with the instrumental point-spread function (Olausen et al., 2011). The extended flux tracked the point-source flux closely, with the 2009 outburst epoch showing the expected time-delay offset for a dust halo illuminated by a rapidly decaying source (Olausen et al., 2011).

This behavior is incompatible with a rotation-powered nebula dominating the emission. The 2–10 keV flux upper limit for any genuine PWN is $\tau_c \sim 0.69$7, three times lower than the previously claimed value, implying an efficiency $\tau_c \sim 0.69$8 for $\tau_c \sim 0.69$9 kpc (Olausen et al., 2011). The residual large-radius component is instead consistent with X-ray emission from the shell of G327.24–0.13, providing independent support for the magnetar–SNR association (Olausen et al., 2011).

The proper-motion result is also consistent with this environment. With $2.07$00 mas yr$2.07$01 and age $2.07$02 yr, the total angular displacement since birth is $2.07$03, much smaller than the $2.07$04 diameter of the proposed remnant shell, so the magnetar remains well within the remnant (Deller et al., 2012). The combined picture is therefore of a young magnetar embedded in, or at least projected against, a shell-type SNR, observed through a dust-rich Galactic-plane line of sight that dominates its extended X-ray appearance.

6. X-ray polarization, viewing geometry, and current interpretive issues

A 500 ks IXPE observation in March–April 2025 established 1E 1547.0–5408 as one of the most strongly polarized X-ray magnetars yet measured. In the 2–6 keV band the phase-averaged spectrum is well fit by a single absorbed blackbody with $2.07$05 keV and $2.07$06 km for $2.07$07 kpc. The same dataset yielded a linear polarization degree $2.07$08 and polarization angle $2.07$09, with no significant energy dependence of PA but some evidence, at the $2.07$10 level, for a minimum in PD between 3 and 4 keV (Taverna et al., 21 Jan 2026). Phase-resolved spectroscopy showed a nearly constant emitting radius of about 1.2 km and a temperature varying from about 0.61 to 0.71 keV over the spin cycle, implying a single fairly small hot spot with a non-uniform temperature distribution (Taverna et al., 21 Jan 2026).

Phase-resolved PA modulation was successfully fit with a rotating vector model,

$2.07$11

which tied the X-ray polarization swing to the projected magnetic axis (Taverna et al., 21 Jan 2026). The IXPE analysis found that both the dipole axis and line of sight are misaligned with respect to the spin axis, and argued that in this geometry the high polarization cannot be regarded as compelling evidence by itself for vacuum birefringence in the magnetosphere (Taverna et al., 21 Jan 2026). At the same time, the possible PD dip near 3–4 keV is compatible with partial mode conversion at the vacuum resonance in a magnetized atmosphere, so the data remain suggestive of QED effects without providing a unique “smoking gun” (Taverna et al., 21 Jan 2026).

A subsequent Bayesian comparative study of 1E 1547.0–5408 and 1E 2259+586 revisited the geometry using both a classical rotating vector model and a twisted-magnetosphere extension. For 1E 1547.0–5408 the observed PA curve was already well reproduced by the classical model, and the twisted-magnetosphere version showed no statistically significant advantage. When radio-informed priors were imposed, the posterior shifted toward a nearly aligned configuration consistent with radio constraints; in either case there was no evidence for a strong, static global twist in the current epoch (Li et al., 12 Apr 2026). A plausible implication is that the unusually high X-ray polarization of 1E 1547.0–5408 reflects a confluence of favorable viewing geometry, intrinsically polarized surface emission, and magnetospheric propagation effects, rather than a single dominant cause.

In that sense 1E 1547.0–5408 now occupies a central place in magnetar research for two distinct reasons. First, its 2009 echo turned it into an archetype for dust-scattering tomography and for the reassessment of magnetar afterglows. Second, its radio activity, timing irregularities, broad-band outbursts, and strong IXPE polarization make it one of the best laboratories for studying how crustal heating, magnetospheric twist, coherent radio emission, and polarized thermal X-rays are coupled in a high-field neutron star (Tiengo et al., 2010, Lower et al., 2023, Taverna et al., 21 Jan 2026).