An [identifier](https://n2t.net/99152/h1031) whose string, possibly modified by adding a well-known prefix, may be acted upon by widely available software systems to gain access to the [identifier](ht
tps://n2t.net/99152/h1031)'s associated [thing](https://n2t.net/99152/h1191), or to a suitable surrogate.
A descriptive word specifically meaning (1) a probability of ~50% for an M- class x-ray flare (see x-ray flare class); (2) disturbed geomagnetic levels such that 16 < Ak index < 30.
Exerting an influence or producing a changeor effect. An active measurement is one which produces a transmission orexcitation as a part of the measurement cycle.
A central region of an active galaxy, which is a light-year or less in diameter and has an abnormally high luminosity. The nucleus emits high energy radiation (gamma rays, X-rays, ultraviolet) and sho
ws variability over various time-scales, sometimes very short (hours to weeks). Emission line spectra reveal high velocity motions up to 10^4 km s^-1. AGNs are divided into two main types. Type I refers to an AGN whose nucleus is visible (the spectra has both narrow and broad emission lines), while in type II AGN, the broad line region (BLR) is obscured and the lines are very narrow. This may be due either to the viewing angle or some intrinsic difference in structure.
A central region of an active galaxy, which is a light-year or less in diameter and has an abnormally high luminosity. The nucleus emits high energy radiation (gamma rays, X-rays, ultraviolet) and sho
ws variability over various time-scales, sometimes very short (hours to weeks). Emission line spectra reveal high velocity motions up to 10^4 km s^-1. AGNs are divided into two main types. Type I refers to an AGN whose nucleus is visible (the spectra has both narrow and broad emission lines), while in type II AGN, the broad line region (BLR) is obscured and the lines are very narrow. This may be due either to the viewing angle or some intrinsic difference in structure.
A central region of an active galaxy, which is a light-year or less in diameter and has an abnormally high luminosity. The nucleus emits high energy radiation (gamma rays, X-rays, ultraviolet) and sho
ws variability over various time-scales, sometimes very short (hours to weeks). Emission line spectra reveal high velocity motions up to 10^4 km s^-1. AGNs are divided into two main types. Type I refers to an AGN whose nucleus is visible (the spectra has both narrow and broad emission lines), while in type II AGN, the broad line region (BLR) is obscured and the lines are very narrow. This may be due either to the viewing angle or some intrinsic difference in structure.