F3501--Scientific workflow in
astrophysics
Autumn – 2024
Prapti Mondal
Doc. Ernst Paunzen
Delta delphini star
• Introduction to Delta Delphini
• Overview: Delta Delphini (δ Delphini) is a binary star
system in the constellation Delphinus.
• Distance: Approximately 238 light-years from Earth.
• Brightness: Apparent magnitude of 4.43, visible to
the naked eye.
• Objective: To explore the characteristics,
classification, and scientific significance of Delta
Delphini.
Location in
the Sky
• Constellation: Delphinus (the
Dolphin).
• Coordinates: Right Ascension:
20h 39m 38.25s; Declination:
+15° 54′ 43.9″.
• Observation: Best viewed in
the Northern Hemisphere
during late summer.
Delta Delphini – A Binary Star
• Binary Nature: Spectroscopic binary
with two stars orbiting a common
center of mass.
• Orbital Period: Around 40.58 days.
• Components: Delta Delphini A
(primary, brighter) and Delta Delphini
B (secondary, fainter).
Spectral Classification of Delta Delphini
• Type: Classified as an A7III or A7IV star.
• A7: White star, hotter than the Sun with temperatures between
7,500K and 10,000K.
• III or IV: Suggests it’s in the giant or subgiant phase, having left the
main sequence.
• Significance: Understanding its stage in stellar evolution.
• Spectral class : kA7hF1VmF1pSrEuCr
Delta Delphini as a Chemically Peculiar (CP)
Star
• Am Star: Classified as an A-type metallic-line (Am) star.
• Chemical Peculiarities: Overabundance of certain elements like
zinc, strontium, zirconium; underabundance of calcium and
scandium.
• Cause: Likely caused by slow rotation and diffusion processes
that lead to uneven distribution of elements.
Chemically Peculiar Stars (CP Stars)
• Definition: Stars with abnormal abundances of specific chemical
elements.
• Types of CP Stars: Am, Ap (magnetic stars), Bp (peculiar B-type
stars), etc.
• Significance in Astronomy: Chemically peculiar stars help
astronomers understand how stellar rotation and magnetic fields
affect the distribution of elements.
Am Stars and Delta Delphini
• Characteristics of Am Stars:
• Strong metallic lines in the spectrum.
• Slow rotational velocity.
• Found predominantly in binary systems.
• Delta Delphini as an Example: Exhibits these features, making it
a key object for studying Am stars.
Walraven VBLUW photometric system
• This photometric system measured light
from the visible to the near ultraviolet,
with passbands at the effective
wavelengths of 542 nm (V), 427 nm (B),
385 nm (L), 362 nm (U) and 323 nm (W).
For this reason it is also known as the
Walraven VBLUW Photometer.
Table 2. The photometric parameters of delta delphini star in the VBLUW system (in
log intensity scale) and in the UBV system (in mag scale with subscript j)
PHOTOMETRY
• Two subgroups based on their apparent
visual magnitudes and the source of their
spectral-type classifications,
• 1. Bright δ Delphini stars with mv < 6.7
• 2. Faint δ Delphini stars with mv >6.7
• A Comparison of the ß
and b — y Temperature
Indices
• (b - y)0 = 2.943 - ß-
0.09δc1 - 0.2δc2
• ∆MV =8 δc1
lines are delineate the observed instability strip.
Variability
Variability
Rotation
Am stars slow
rotators
Normal stars
rotate fast
Am: and δ Del
rotate faster
than Am
Anomalousabundance
δ
Delphini
stars
anomalousabundance
S
Del stars and
the Ba || stars
DISCUSSION
• (i) anomalous-abundance 8 Delphini stars are evolved Am stars
may be incorrect
• (ii) each of the pulsating anomalous-abundance 8 Delphini stars
may be a binary consisting of an Am star and a 8 Scuti star
• (iii) diffusion and pulsation may be able to coexist in a single star
under some conditions
• (iv) the diffusion hypothesis may not be the correct explanation for
the abundance anomalies of the metallic-line stars