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arXiv 1201.6491astro-ph.HE
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用MAXI和RXTE观测LS V+44 17的爆发及在脉冲剖面中发现一个倾斜结构

Outburst of LS V+44 17 Observed by MAXI and RXTE, and Discovery of a Dip Structure in the Pulse Profile

Ryuichi Usui, Mikio Morii, Nobuyuki Kawai, Takayuki Yamamoto, Tatehiro Mihara, Mutsumi Sugizaki, Masaru Matsuoka, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Mas… 展开作者

Ryuichi Usui, Mikio Morii, Nobuyuki Kawai, Takayuki Yamamoto, Tatehiro Mihara, Mutsumi Sugizaki, Masaru Matsuoka, Kazuo Hiroi, Masaki Ishikawa, Naoki Isobe, Masashi Kimura, Hiroki Kitayama, Mitsuhiro Kohama, Takanori Matsumura, Satoshi Nakahira, Motoki Nakajima, Hitoshi Negoro, Motoko Serino, Megumi Shidatsu, Tetsuya Sootome, Kousuke Sugimori, Fumitoshi Suwa, Takahiro Toizumi, Hiroshi Tomida, Yoko Tsuboi, Hiroshi Tsunemi, Yoshihiro Ueda, Shiro Ueno, Kazutaka Yamaoka, Kyohei Yamazaki, Atsumasa Yoshida

摘要:

报道了首次观测到Be/X射线双星LS V +44 17/RX J0440.9+4431的X射线爆发,并在脉冲轮廓中发现了吸收凹陷结构。MAXI GSC在2010年4月发现了该源的爆发。这是自1997年LS V +44 17被确认为Be/X射线双星以来,首次探测到其瞬态活动。从后续的RXTE观测资料中,我们发现了一个狭窄的倾斜结构的脉冲轮廓,在较低的能量带更清晰。在3 $-$ 100 keV频带中的脉冲相位平均能谱可以用包含具有指数截止和黑体分量的幂律函数的连续模型拟合,所述幂律函数在低能量下由吸收分量修改。在光谱中还检测到弱铁K $α$发射线。从脉冲相位分辨光谱,我们发现,在浸渍阶段的吸收柱密度远高于在其他阶段。在随后的RXTE观测中,在较低的通量水平上没有看到这种下降。这些结果表明,脉冲轮廓的下降源于吸积柱对中子星辐射的遮蔽。

英文摘要:

We report on the first observation of an X-ray outburst of a Be/X-ray binary pulsar LS V +44 17/RX J0440.9+4431, and the discovery of an absorption dip structure in the pulse profile. An outburst of this source was discovered by MAXI GSC in 2010 April. It was the first detection of the transient activity of LS V +44 17 since the source was identified as a Be/X-ray binary in 1997. From the data of the follow-up RXTE observation near the peak of the outburst, we found a narrow dip structure in its pulse profile which was clearer in the lower energy bands. The pulse-phase-averaged energy spectra in the 3$-$100 keV band can be fitted with a continuum model containing a power-law function with an exponential cutoff and a blackbody component, which are modified at low energy by an absorption component. A weak iron K$α$ emission line is also detected in the spectra. From the pulse-phase-resolved spectroscopy we found that the absorption column density at the dip phase was much higher than those in the other phases. The dip was not seen in the subsequent RXTE observations at lower flux levels. These results suggest that the dip in the pulse profile originates from the eclipse of the radiation from the neutron star by the accretion column.

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