Revealing the nature of the population constituting the Galactic Ridge X-ray Emission using Near-Infrared

2022 Fiscal Year Final Research Report

• Project/Area Number: 17K18019
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics; Astronomy
• Research Institution: National Astronomical Observatory of Japan (2022); Nagoya University (2017-2021)
• Principal Investigator: MORIHANA Kumiko 国立天文台, ハワイ観測所, RCUH職員 (50640843)
• Project Period (FY): 2017-04-01 – 2023-03-31
• Keywords: 赤外線天文学 / X線天文学 / 白色矮星連星系 / 狭帯域フィルター

Outline of Final Research Achievements

We have studied the population constituting the Galactic Ridge X-ray Emission (GRXE), which is the apparently extended X-ray emission along the Galactic plane. One of the major population constituting the GRXE has been considered to be cataclysmic variables (CVs). However, it is difficult to search CVs only using X-ray due to poor statistics of photons. Then, we focused on that NIR spectra of CVs have Pa-beta emission lines, where interstellar absorption is small. We constructed a narrow-band on-filter that transmits only in the Pa-beta wavelength and a special off-filter that has transmission bands on both sides of Pa-beta to accurately subtract continuous emission. The filter set improved the detection and we detected emission-line sources through observations of the Galactic plane.
We further carried out deep NIR imaging observation at the Galactic bulge. We revealed that the GRXE at the bulge is contributed by non-magnetic CVs and white dwarf binaries in detached binary systems.

Free Research Field

光赤外天文学

Academic Significance and Societal Importance of the Research Achievements

広大な銀河面において輝線天体を全て分光観測により行うのは現実的ではない。輝線波長に透過幅を持つ狭帯域フィルターを用いれば、広い銀河面でも輝線天体を効率よく検出可能である。しかし、輝線成分は天体スペクトルの連続光成分の上にのっているため連続光成分を精度よく差し引くことが難しく、既存の狭帯域フィルターでは等価幅の大きい輝線天体の検出に限られてきた。本研究で開発した特殊狭帯域フィルターは輝線の両側で連続光成分を取得することで、傾きを持つスペクトルでも連続光成分を精度よく差し引くことができるため、弱い輝線天体まで検出を可能にした。