利用Fermi大面積望遠鏡觀測兩個磁星/超新星殘骸的區域：尋找源自磁星的伽瑪射線

Observing Two Magnetar/Supernova-Remnant Regions with Fermi Large Area Telescope: A Search for Gamma-ray Excess from Magnetars

楊健恒(Kin-Hang Yeung)

指導教授 ： 江國興

國立清華大學/理學院/天文研究所/碩士(2017年)

摘要

磁星是一種表面磁場特別強的中子星。他們表面頻繁的震動會造成其反複的X射線爆發。磁星的位置通常與超新星殘骸位置重疊。雖然超新星殘骸已被確認會發射很強的伽瑪射線，但在能量幾十萬電子伏特以上的範圍（>300 keV），我們目前尚未測到來自磁星的伽瑪射線。因此，雖然費米大面積望遠鏡（Fermi LAT）已經分別在兩個磁星（SGR 1806-20和1E 1841-045）的區域檢測到明顯的十億電子伏特（GeV）光源，但是這不代表我們已確定此伽瑪射線源自磁星。我們需要先確定在他們附近超新星殘骸的伽瑪射線的能量。此外，藉由回溯磁星的X射線爆發歷史與磁星附近的伽瑪射線通量之間的相關性，也可確認觀測到的伽瑪射線是否真的來自磁星。在SGR 1806-20的區域，我們推測其區域附近可能有一個由磁星的磁場衰變所造成的脈衝風星雲，它可能主導數個GeV以上的輻射。而在1E 1841-045的區域，我們所觀測到的低於10 GeV的伽瑪射線十分可能就是來自於磁星。

關鍵字

磁星 ； 超新星殘骸

並列摘要

Magnetars are a category of neutron stars with unusually high magnetic fields on their surface. Frequent starquakes on magnetars lead to their recurrent X-ray outbursts. The positions of magnetars are commonly coincident with supernova remnants (SNRs). While SNRs have been confirmed to be a kind of luminous gamma-ray sources, none of our known magnetars have been seen at energies above several hundred kiloelectronvolts (keV). Therefore, although Fermi Large Area Telescope (LAT) detected two bright gigaelectronvolt (GeV)-clumps respectively in the regions of magnetars SGR 1806-20 and 1E 1841-045, we need to constrain the gamma-ray contribution from their associated and/or adjacent SNRs before claiming discoveries of gamma-ray excess originated from magnetars. It is also important to search for correlation between the X-ray outburst history of a magnetar and the gamma-ray flux in its region. For the SGR 1806-20 region, we speculate the existence of a PWN powered by the magnetic-field decay of the magnetar and it may dominate the emission above several GeV. In the 1E 1841-045 region, the magnetar is seemingly a necessary and sufficient source for the gamma-ray emission below 10 GeV.

並列關鍵字

Magnetar ； Supernova Remnant

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