ASCA Observation of NGC 1808

Publications of the Astronomical Society of Japan

Awaki, Hisamitsu²  Koyama, Katsuji²  Tsuru, Takeshi²  Iwasawa, Kazushi¹  Ueno, Shiro² 

[1] Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK;Department of Physics, Faculty of Science, Kyoto University, Sakyo-ku, Kyoto 606-01

关键词: Galaxies:active;    "Galaxies: individual (NGC 1808)";    "Galaxies: nuclei";    X-rays:spectra;   

DOI  :  10.1093/pasj/48.3.409

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

TheJapaneseX-raysatelliteASCAobservedNGC1808,whichisknowntoexhibitbothSeyfertandstarburstactivities.InthesoftX-rayband,ASCAdetectedemissionlinesfromhighlyionizedMgandSi,whichconfirmedthepresenceofathinthermalplasma,duepossiblytostarburstactivity.ThethinthermalplasmaconsistsoftwotemperaturecomponentsofkT∼0.78keVandkT∼0.35keV.Wefoundthattheintrinsicabsorptiontowardthe0.78keVplasmaisNH∼7×1021cm−2,whichisgreaterthanthegalacticforegroundvalueof2.8×1020cm−2(Dickey,Lockman1990,AAA53.155.163).ThisresultimpliesthatmostoftheX-rayemissionfromthisplasmacomesfromthecentralregion.Theabsorptiontowardthe0.35keVplasma,ontheotherhand,showsalowvaluecomparedtothegalacticabsorption.ThisindicatesthattheplasmaismoreextendedlikeanX-rayhalo.Themetalabundanceofabout1solarvaluefoundinthethinthermalplasmaislargerthanthatofthearchetypicalstarburstgalaxyM82.Inadditiontothethinhotplasma,ASCAdetectedahardX-raycomponentfromNGC1808,withaluminosityof2×1040ergs−1(0.5–10keVband),obscuredbyanabsorbingcolumnof1.0×1022cm−2.ThehardX-rayfluxandspectrummayalsobeattributabletostarburstactivity.However,thehardX-raysexhibitedalong-termvariabilityfromtheGingaandASCAobservations,suggestingthepresenceofalow-luminosityAGNinNGC1808.

【 授权许可】

Unknown