orion.txt

Orion stare flares

Description:

Our Sun and ordinary stars we see at nighttime appear constant in
brightness to our naked eyes.  But at other wavelengths of light where
the stars are much fainter (such as radio, X-ray and gamma-rays), the
stars are violently variable on rapid timescales.  These emission
arises from explosive releases of energy at the stellar surface
associated with magnetic fields.  These solar or stellar flares occur
when magnetic fields generated in the stellar interior erupt on the
surface and, due to convective motions, are twisted until a sudden
reconfiguation occurs.  The process resembles the spark appearing when
two wires are crossed in an electric circuit.  The result is a sudden
acceleration of particles to extremely high energies, and the heating
of gas trapped in magnetic loops to X-ray emitting temperatures
(106-108 degrees Kelvin).

Ordinary stars exhibit their highest levels of magnetic activity, and
their strongest flares, during the youngest pre-main sequence phases
(Feigelson & Montmerle 1999).  X-ray telescopes such as the Chandra
X-ray Observatory provide an excellent view of these flares.  The most
extensive dataset obtained in this field was the Chandra Orion
Ultradeep Project (COUP), where Chandra observed the Orion Nebula
region of young stars for nearly two weeks continuously.  The X-ray
sources are sometimes very faint with only a handful of photons
arriving over the observation, and sometimes orders of magnitude
brighter.

The time between the arrival times of these photons can be viewed as
random observations from an Exponential distribution.



Usage:

df <- read.csv("https://raw.githubusercontent.com/roualdes/data/master/orion.csv")

Format:

     A data frame with 209 observations on the following 3 variables.

     'time' arrival time of flares (hours)

     'energy' energy of flares (Kelvin)

     'diff' time between arrival of flares

Source:

     Collected from the following page (and its linked pages) on
     March 6, 2020:

     <https://astrostatistics.psu.edu/datasets/Chandra_flares.html>