First Very Low Frequency detection of short repeated bursts from magnetar SGR J1550-5418

Abstract

We report on the first detection of ionospheric disturbances caused by short repeated gamma-ray bursts from the magnetar SGR J1550-5418. Very low frequency (VLF) radio wave data obtained in South America clearly show sudden amplitude and phase changes at the corresponding times of eight SGR bursts. Maximum amplitude and phase changes of the VLF signals appear to be correlated with the gamma-ray fluence. On the other hand, VLF recovery timescales do not show any significant correlation with the fluence, possibly suggesting that the bursts' spectra are not similar to each other. In summary, the Earth's ionosphere can be used as a very large gamma-ray detector and the VLF observations provide us with a new method to monitor high energy astrophysical phenomena without interruption such as Earth Occultation.

14 pages, 4 figures, accepted by ApJL

References in corpus (3)

• Strong bursts from the anomalous X-ray pulsar 1E 1547.0-5408 observed with the INTEGRAL/SPI Anti-Coincidence Shield
• Giant Flare in SGR 1806-20 and Its Compton Reflection from the Moon
• Comparative study of the inial spikes of SGR giant flares in 1998 and 2004 observed with GEOTAIL: Do magnetospheric instabilities trigger large scale fracturing of magnetar's crust?

Cited by in corpus (4)

• Magnetars: the physics behind observations
• SGR J1550-5418 bursts detected with the Fermi Gamma-ray Burst Monitor during its most prolific activity
• Pulsars and magnetars
• Burst Tails from SGR J1550-5418 Observed with Rossi X-ray Timing Explorer