阿佩普 (恆星系統)

阿佩普 是位於矩尺座的一個三合星系統，包含沃夫–瑞葉星聯星和一顆熾熱的超巨星。以埃及神話中的蛇神命名，該恒星系統被恆星風和宇宙塵的巨大複合體包圍，這些複合體被聯星主星的高轉速拋入太空，並在次星的影響下形成「風車」形狀。2010年代對該系統的地面研究得出結論，該系統是銀河系中最著名的伽馬射線暴前身候選者。

阿佩普

甚大望遠鏡拍攝的紅外影像
（ ESO/Callingham等人。）[lower-alpha 1]。
觀測資料
曆元 J2000.0
星座 矩尺座
星官
赤經 16h 00m 50.5s
赤緯 -51° 42′ 45″
視星等（V） 17.5
特性
演化阶段WR 聯星
视星等 (J)10.2
视星等 (K)6.9
天体测定
距离2,000+400
−300[3] pc
绝对星等 (MV)-5.15 / -5.15 / -7.4[3]
其他命名
WR 70-16、2MASS J16005047-5142449[4]
參考資料庫
SIMBAD资料

命名法

阿佩普（英語：），發音為 /ˈɑːpɛp/，由荷蘭無線電天文研究所的Joseph Callingham領導的天文學家團隊命名，他在2016年至2018年間研究了該系統，並發表了一篇關於他們觀測結果的科學論文[5][6]。它是以埃及神話中太陽神拉的同名死敵命名的，他經常被描繪成一條巨蛇；他們的競爭被描述為「一個恰當的典故」，指的是該系統及其恆星風在紅外中的外觀是「一顆被龍卷包圍在內的恆星」[5][7]。在由XMM-牛頓衛星太空望遠鏡觀測到的天體物理X射線源偶然源的恆星目錄中，該系統被編目為2XMM J160050.7–514245[8]。它也被稱為WR 70-16。

特性

阿佩普是一個三合星系統[6][9]，包含一顆被描述為「中央發動機」，軌道週期為~100年的沃夫–瑞葉星聯星 沃夫–瑞葉星聯星[10]，和被描述為「北方伴星」，圍繞中心發動機運行，距離約1,700天文單位，週期>10,000年的第三顆熱的超巨星[11]。阿佩普中心的聯星由碳（WC8）和氮序（WN4-6b）亞型的兩顆經典沃夫-瑞葉星組成，使阿佩普成為銀河系中經典WR+WR聯星系統的最強案例[3]。碳序沃夫–瑞星通常是製造塵埃的工廠。一個巨大的恆星風和宇宙塵埃複合體圍繞著這個系統[7][9][12]，類似於另一個產生風車星雲的沃夫 – 瑞葉星系統WR 104[13]。恆星風的速度為12 × 106 km/h（7.5 × 106 mph）[6][12]，在系統的邊緣，塵埃速度為 2 × 106 km/h（1.2 × 106 mph），表明中央發動機至少有一個部件正在快速旋轉，其中其表面重力接近於由其向外的離心力平衡[9][14]。這個元件從兩極產生更快的恆星風，從赤道產生較慢的風，赤道風與其次級風的相互作用產生了系統的「風車」形狀[15][16]。快速旋轉的沃夫–瑞葉星理論上能够在超新星期間產生伽馬射線暴，該系統已被確定為伽馬射線暴的前身[17]。估計阿佩普距離地球約~2.4 千秒差距[18]，或~8,000 光年[10][19]，潛在差異為+0.2和-0.5千秒差距，估計視覺消光為11.4[18]。

觀察
Map of the constellation Norma
阿佩普在矩尺座中的位置（紅圈）

阿佩普位於星座矩尺座，在赤經16h 00m 50.5s和赤緯-51° 42′ 45″[1]。該系統可以解析為兩個組成部分：「中央發動機」沃夫-瑞葉聯星，和「北方伴星」超巨星[20]。系統的總視星等為17.5，分辨出的中央發動機和北方伴星的視星等分別為19.0和17.8[21]。它的紅外光譜能量分佈（SED）是獨一無二的，亮度範圍從2.2μm處的6.4等到22μm處的-2.4等[22]。使用歐洲南方天文台（ESO）的儀器SINFONI，在甚大望遠鏡上進行的調查量測到，中央發動機在紅外J波段中的視星等為10.2±0.2，北方伴星的視星級為9.6±0.2[23]。SINFONI 還量測了系統在K波段中的表觀星等，對於中央發動機為6.9±0.2，對C為8.1±0.2[24]， 在 L 波段，對於中央發動機為4.7±0.1，北方辦星為7.3±0.1[24]，和在M波段的中央發動機為4.4±0.3，北方伴星為7.0±0.2[24]。SINFONI的觀測進一步詳細說明，北方伴星可能是一顆傳統的B1Ia+高光度恆星[25]。A和B顯示了WC7恆星的典型光譜[26]，但具有額外的WN4或WN5恆星特徵，理論上來自中央發動機的恆星之一；如果得到證實，這將使阿佩普成為一個罕見的WR星的聯星系統[27]。另一種基於SINFONI數據的假設認為，光譜可能都來自一顆不尋常的過渡WN/WC星，而北方伴星則是一顆傳統的OB恆星[28]。將WR星大犬座EZ和WR 90的光譜結合起來，將產生與WR聯星觀測到的光譜幾乎相同的光譜。

該系統是在銀河系星系中發現的第一個伽馬射線爆發前身候選者[7]，儘管它在早期的觀測中並不為人所知，比如使用XMM-牛頓衛星和Chandra太空望遠鏡的觀測，早在2004年8月，它就被簡單地確定為天體物理X射線源[29]。天文學家喬·卡林厄姆（Callingham）在雪梨大學的大學生研究期間首次用莫隆格羅天文台合成望遠鏡觀測到阿佩普[12][30]，並被認為是一個潜在的碰撞風聯星，其射電源亮如海山二（船底座η）[31]。卡林厄姆和彼得·塔希爾 (天文學家)在1998年領導了WR104的發現[32]，並在觀察到阿佩普的極端紅外特性後，尋求對其感興趣[33][34]，2016年8月使用ESO的甚大望遠鏡進行觀測[1][35]。使用英澳望遠鏡和澳大利亞望遠鏡緻密陣列進行的進一步觀測[19]，以及各國際機構的貢獻 [lower-alpha 2]，導致2018年11月19日在《自然·天文學》上發表了科學論文[15]。它得出的結論是，該系統是沃夫–瑞葉聯星，是伽馬射線暴的前身[9][36]。以前人們認為，這種系統只在比銀河系年輕的星系中發現[16]。

相關條目
  • 伽馬射線暴清單

參考資料

註解

  1. 2016年8月13日，歐洲南方天文台的甚大望遠鏡拍攝的兩張紅外影像的合成圖：儀器NACO以2.24微米的波長拍攝系統中心的一顆恆星，儀器VISIR以8.9微米的波長拍攝這一顆恆星周圍的塵埃和氣體雲。影像的寬度為0.26×0.26弧分[1][2]
  2. Contributions from the University of Edinburgh, the University of New South Wales, New York University, and the University of Sheffield, and the University of Sydney.[16]

來源

  1. Callingham, Joseph. . Nature. 20 November 2018 [26 November 2018]. （原始内容存档于26 November 2018）.
  2. Callingham, J. R.; Tuthill, P. G.; Pope, B. J. S.; Williams, P. M.; Crowther, P. A.; Edwards, M.; Norris, B.; Kedziora-Chudczer, L. (PDF). University of Sydney School of Physics. 24 September 2018 [20 November 2018]. （原始内容存档 (PDF)于20 November 2018）.
  3. Plait, Phil. . Syfy Wire. 19 November 2018 [22 November 2018]. （原始内容存档于22 November 2018）.

引文

  1. Callingham et al. 2018，page 3, "Figure 1. VISIR 8.9 μm image of Apep taken on 2016 August 13, displaying the exotic dust pattern being sculpted by the system. The 2.24 μm NACO image of the region bounded by the blue box, of dimension 1.8" × 1.8", is shown in the upper right corner."
  2. ESO staff. . European Southern Observatory (ESO). 19 November 2018 [6 January 2019]. （原始内容存档于6 January 2019）. Field of view: 0.26 x 0.26 arcminutes
  3. Callingham, J. R.; Crowther, P. A.; Williams, P. M.; Tuthill, P. G.; Han, Y.; Pope, B. J. S.; Marcote, B. . Monthly Notices of the Royal Astronomical Society. 2020, 495 (3): 3323–3331. Bibcode:2020MNRAS.495.3323C. S2CID 218470247. arXiv:2005.00531 可免费查阅. doi:10.1093/mnras/staa1244.
  4. . SIMBAD. 斯特拉斯堡天文資料中心. [2021-12-24].
  5. Callingham et al. 2018，page 3, "we here adopt the moniker "Apep" after the sinuous form of this infrared plume [...] The serpent diety from Egyptian mythology; mortal enemy of sun god Ra. We think this is an apt allusion to the image which evokes a star embattled within a dragon’s coils."
  6. Dvorsky, George. . Gizmodo. 19 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. ...but to the researchers who recently investigated this enigmatic object, it’s simply "Apep" [...] The speed of gas within the nebula was clocked at 12 million kilometers per hour [...] featuring a massive triple star system at its core—a binary pair and a lone star...
  7. Letzter, Rafi. . Live Science. 19 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. For the first time, astronomers have found a star system in our galaxy that could produce a gamma-ray burst [...] the researchers nicknamed it "Apep" after the Egyptian snake-deity of chaos. [...] The name works nicely for the system, which is surrounded by long, fiery pinwheels of matter cast out into space...
  8. XMM-Newton Survey Science Centre. . University of Leicester Department of Physics and Astronomy. 20 August 2008 [20 November 2018]. （原始内容存档于20 November 2018）. 2XMM is a catalogue of serendipitous X-ray sources from the European Space Agency's (ESA) XMM-Newton observatory
  9. Carpineti, Alfredo. . IFL Science!. 19 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. Three stars are in this picture, although the two Wolf-Rayet stars look like a single one in the center [...] the winds are moving at 12 million kilometers (7.5 million miles) per hour. [...] The observations were possible thanks to the Very Large Telescope [...] the dust at the edge of the system is moving at the slower pace of 2 million kilometers (1.2 million miles) per hour.
  10. Griffin, Andrew. . The Independent. 19 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. The swirling cloud of dust is a mere 8,000 light years from Earth is a vast system made up of two shockingly bright stars. [...] The two bright stars orbit each other every hundred years or so, according to the researchers.
  11. Plait 2018，"At 250 billion kilometers out from the bright star (about ten times the distance of Neptune from the Sun), it would take more than 10,000 years to circle it once..."
  12. Strom, Marcus. . University of Sydney. 20 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. ...the astronomers have measured the velocity of the stellar winds as fast as 12 million kilometres an hour, about 1 percent the speed of light. [...] We discovered this star as an outlier in a survey with a radio telescope operated by the University of Sydney.
  13. Plait 2018，"Sometimes, if they are in a tight binary, you get a pinwheel. The most famous example of that is WR 104..."
  14. Plait 2018，"The astronomers who observed it think that the primary (brighter) one is spinning extremely rapidly, so fast it's nearly at the breakup rate — in other words, spinning so fast that the gravity of the star at the surface is nearly balanced by the centrifugal force outwards."
  15. Weule, Genelle. . ABC News Australia. 20 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. Writing in the journal Nature Astronomy [...] the most violent star is creating stellar winds at two speeds — fast at the poles, slow at the equator [...] the beautiful pinwheel of blazing dust is created not by the fast polar winds, but by the turbulence that arises when the second star in the central engine passes through that first star's slow-moving equatorial wind.
  16. Devitt, James. . New York University. 19 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. "It was not expected such a system would be found in our galaxy—only in younger galaxies much further away," [...] The discovery of the system [...] also included scientists from the Netherlands Institute for Radio Astronomy, the University of Sydney, the University of Edinburgh, the University of Sheffield, and the University of New South Wales. [...] is adorned with a dust "pinwheel"— whose strangely slow motion suggests current theories on star deaths may be incomplete.
  17. Clery, Daniel. . Science. 20 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. One of stars is an unusually massive sun known as a Wolf-Rayet star. When such stars run out of fuel, they collapse, causing a supernova explosion. Theorists believe that if the Wolf-Rayet star is also spinning fast, the explosion will produce intense jets of gamma rays out of either pole...
  18. Callingham et al. 2018，page 18–19, "If we use the visual extinction AV = 11.4 [...] we need a distance of d = 2.4+0.2
    −0.5     to get realistic absolute magnitudes for the components. [...] Despite these uncertainties, all lines of evidence suggest that Apep is located [less-than around] 4.5 kpc, and likely around d ≈ 2.4 kpc."
  19. Mannix, Liam. . The Sydney Morning Herald. 20 November 2018 [20 November 2018]. （原始内容存档于20 November 2018）. In a part of the Milky Way 8000-odd light-years away [...] The system was spotted by PhD student Dr Joe Callingham while he was sorting through data, and later confirmed using the Anglo-Australian Telescope at Coonabarabran in regional NSW.
  20. Callingham et al. 2018，page 2, "The 2.24μm NACO observation (Figure 1, inset) resolves Apep into a 0.739" ± 0.002" binary with a fainter companion to the North."
  21. Callingham et al. 2018，page 18, "...the known visual magnitude V = 17.5 for Apep (V = 17.8 for the OB supergiant that is the northern companion and V = 19.0 for the Central Engine)..."
  22. Callingham et al. 2018，page 18–19, "...was first noted as a high-luminosity outlier in our Galactic plane X-ray and radio survey, and revealed as an exceptional object on considering its infra-red spectral energy distribution (SED), where it brightens from an apparent magnitude of 6.4 at 2.2μm to −2.4 at 22μm, with both measurements on the Vega system."
  23. Callingham et al. 2018，page 14, "Apep was resolved by SINFONI [...] We summed the J-band data over the Central Engine and northern companion to derive the J-band magnitudes of 10.2±0.2 and 9.6±0.2, respectively."
  24. Callingham et al. 2018，page 22, "Supplementary Information Table 2. Summary of the NACO observations of Apep. Separation refers to the angular separation between the Central Engine and northern companion, identified in the inset of Figure 1. The uncertainties reported are for 90% confidence."
  25. Callingham et al. 2018，page 21, "Despite this, we favour the northern companion being an B1 Ia+ supergiant but further observations, particularly optical spectra, are necessary to confirm this spectral type."
  26. Callingham et al. 2018，page 20, "...the spectrum of Apep shows stronger He II and weaker C IV line emission than is stereotypical for a WC7 star."
  27. Callingham et al. 2018，page 20, "The weakness in the J-band, where dust emission is negligible [...] points to the additional continuum from a companion star. The abnormal strength of the He II lines for a WC7 star suggests an early WN sub-type companion. The absence of N V and relative weakness of He I, and with comparison to WN spectra, implies the presence of a subtype WN4 or WN5 star. Double WR binaries are, however, rare, with very few known."
  28. Callingham et al. 2018，page 21, "An alternative spectral subtype classification to the WC7+WN4-5 model, that equally well describes the spectra shown in Figure 2, is that of a WR star in the brief transitory phase between WN and WC (WN/WC) with an unseen OB-type companion."
  29. Callingham et al. 2018，page 25, "Supplementary Information Table 3. Summary of the 0.2 and 10.0 keV observations of Apep. ObsID corresponds to the unique identification number assigned to each observation by the respective X-ray observatory.
  30. Callingham 2018，"The path that led to the discovery of Apep started with a relatively simple crossmatch between X-ray and radio surveys in the last year of my undergraduate study at the University of Sydney..."
  31. Callingham 2018，"Momentum was behind the idea that Apep was a new colliding-wind binary but the radio emission would make it the brightest radio colliding-wind binary discovered outside of the unique object Eta Carinae..."
  32. Tuthill, Peter G.; Monnier, John D.; Danchi, William C. . Nature. 1 April 1999, 398 (6727): 487–489 [2023-07-30]. Bibcode:1999Natur.398..487T. ISSN 0028-0836. S2CID 4373103. arXiv:astro-ph/9904092 可免费查阅. doi:10.1038/19033. （原始内容存档于2023-02-22）.
  33. Tuthill, Peter. . University of Sydney School of Physics. 1999 [26 November 2018]. （原始内容存档于26 November 2018）. These results are further described in our letter in Nature "A dusty pinwheel nebula around the massive star wr 104" by Peter Tuthill, John Monnier and William Danchi Volume 398, pp. 487–489, April 8, 1999.
  34. Callingham 2018，"This is where the imaging guru Peter Tuthill (University of Sydney) comes into the story as the extreme infrared properties of Apep particularly caught his attention. [...] It immediately brought to mind the so-called "Pinwheel Nebulae" that Peter had discovered 20 years ago, but this was larger and with more complicated structure than the clean Archimedean spiral observed in those systems."
  35. Callingham 2018，"We wrote a proposal to use a mid-infrared camera on the European Southern Observatory’s Very Large Telescope (VLT) to image the source in the middle of my PhD..."
  36. Callingham et al. 2018，page 1, "Near-critical stellar rotation is known to drive such winds, suggesting this Wolf-Rayet system as a potential Galactic progenitor system to long-duration gamma-ray bursts."

外部連結
维基共享资源上的相关多媒体资源：阿佩普

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