标题： M82中超亮X射线源的62天X射线周期性和X射线耀斑 显示英文标题

标题： A 62 Day X-Ray Periodicity and an X-Ray Flare from the Ultraluminous X-Ray Source in M82

摘要： 在对M82为期240天的X射线监测中，我们发现了一个周期为$62.0 \pm 2.5$天的X射线周期性现象，其峰峰值幅度对应于M82中的各向同性光度为$2.4 \times 10^{40} \rm erg s^{-1}$，并且出现了一次达到峰值光度$9.8 \times 10^{40} \rm erg s^{-1}$的X射线耀发。 这种周期性和耀发很可能起源于M82中的超亮X射线源（ULX），该源已被识别为可能的中等质量黑洞。 我们建议62天的调制是由一个罗氏瓣溢流伴星的X射线双星轨道运动引起的，这意味着伴星的平均密度接近$5 \times 10^{-5} \rm g cm^{-3}$，因此是一颗巨星或超巨星。 耀发后不久的Chandra观测显示能量谱与无热成分或线发射证据的幂律一致。 在耀发期间使用VLA进行的射电观测使我们能够排除该源为喷流源，并对X射线发射的相对论束模型施加了严格的限制。 Chandra观测还揭示了第二个X射线源，在0.3-7 keV能段达到了$4.4 \times 10^{-12} \rm erg cm^{-2} s^{-1}$的流量，这比该源之前观察到的任何流量都要高得多，对应的各向同性光度为$1.1 \times 10^{40} \rm erg s^{-1}$。 这个源是M82中的第二个超亮X射线源，可能引起从M82中心区域检测到的QPOs。 显示英文摘要

摘要： In 240 days of X-ray monitoring of M82, we have discovered an X-ray periodicity at $62.0 \pm 2.5$ days with a peak to peak amplitude corresponding to an isotropic luminosity of $2.4 \times 10^{40} \rm erg s^{-1}$ in M82 and an X-ray flare reaching a peak luminosity of $9.8 \times 10^{40} \rm erg s^{-1}$. The periodicity and flare likely originate from the ultraluminous X-ray source (ULX) in M82 which has been identified as a possible intermediate mass black hole. We suggest that the 62~day modulation is due to orbital motion within an X-ray binary with a Roche-lobe overflowing companion star which would imply that the average density of the companion star is near $5 \times 10^{-5} \rm g cm^{-3}$ and is therefore a giant or supergiant. Chandra observations just after the flare show an energy spectrum that is consistent with a power-law with no evidence of a thermal component or line emission. Radio observations made with the VLA during the flare allow us to rule out a blazar identification for the source and place strong constraints on relativistically beamed models of the X-ray emission. The Chandra observations reveal a second X-ray source reached a flux of $4.4 \times 10^{-12} \rm erg cm^{-2} s^{-1}$ in the 0.3-7 keV band which is dramatically higher than any flux previously seen from this source and corresponds to an isotropic luminosity of $1.1 \times 10^{40} \rm erg s^{-1}$. This source is a second ultraluminous X-ray source in M82 and may give rise to the QPOs detected from the central region of M82.