Definition
SGR 0501+4516 is a soft gamma repeater (SGR), a subclass of magnetars—highly magnetized neutron stars—that intermittently emit short bursts of soft gamma‑ray and hard X‑ray radiation.
Overview
SGR 0501+4516 was first detected on 22 August 2008 by the Burst Alert Telescope (BAT) aboard the Swift satellite, which recorded a rapid rise in soft gamma‑ray activity from a previously uncatalogued source. Follow‑up observations with Swift, RXTE, Fermi, and ground‑based X‑ray telescopes confirmed the source as a new member of the SGR family. It is located in the direction of the constellation Taurus, with J2000 coordinates approximately RA 05h 01m , Dec +45° 16′. Subsequent timing analysis revealed a spin period of about 5.762 seconds and a period derivative indicating a surface magnetic field strength on the order of 10¹⁴ gauss, characteristic of magnetars. The source exhibited a cluster of burst activity lasting several weeks after discovery, after which it entered a quiescent state with only occasional low‑level X‑ray emission.
Etymology / Origin
The designation “SGR 0501+4516” follows the standard naming convention for soft gamma repeaters, where “SGR” identifies the object class. The numerical portion encodes the approximate right ascension (05 h 01 m) and declination (+45° 16′) of the source in the sky, using J2000 coordinates. The naming does not imply any historical or mythological origin beyond this systematic coordinate‑based convention.
Characteristics
| Property | Description |
|---|---|
| Object type | Soft gamma repeater (magnetar) |
| Discovery date | 22 August 2008 (Swift/BAT) |
| Coordinates (J2000) | RA 05 h 01 m , Dec +45° 16′ |
| Spin period | ≈ 5.762 s |
| Period derivative | ≈ 1 × 10⁻¹¹ s s⁻¹ (implying B ≈ 10¹⁴ G) |
| Burst activity | Initial outburst comprised dozens of short (< 1 s) soft gamma‑ray bursts; activity declined within weeks, with occasional weaker bursts detected thereafter. |
| X‑ray spectrum | Typically modeled with a combination of a blackbody (kT ≈ 0.5 keV) and a power‑law component (photon index ≈ 2–3). |
| Distance estimate | Uncertain; based on absorption and association with Galactic structure, an approximate distance of 5–10 kpc is inferred, but accurate measurement is not confirmed. |
| Association | No confirmed association with a supernova remnant or known stellar cluster. |
Related Topics
- Magnetars – Neutron stars powered by ultra‑strong magnetic fields rather than rotational energy.
- Soft Gamma Repeaters (SGRs) – A class of magnetars that episodically emit short, intense bursts of soft gamma‑rays.
- Anomalous X‑ray Pulsars (AXPs) – Another manifestation of magnetars, typically observed as persistent X‑ray sources.
- Swift Satellite – A multi‑wavelength space observatory that detected the initial burst from SGR 0501+4516.
- High‑energy astrophysics – The broader field studying energetic phenomena such as gamma‑ray bursts, pulsars, and magnetars.
- Neutron star timing – Techniques used to measure spin periods and period derivatives, crucial for estimating magnetic field strengths.
Note: While many observational parameters for SGR 0501+4516 have been reported in peer‑reviewed literature, certain values (e.g., precise distance) remain uncertain due to limitations in current measurements.
