Absorption lines near compact objects.
Gravitationally distorted P-Cygni profiles.
Dorodnitsyn A.
NASA GSFC
Heδ
P-Cygni star
First noted in 1600
Heγ
HeI
First documented: Willem Janszoom Blaeuw
(Dutch astronomer and
mathematician 1571-1638) on
August 8, 1600.
Supergiant B2
P-Cygny profiles as an intrinsic signature of an outflow
Broad Absorption Lines
Narrow Absorption Lines
Narrow Absorption Lines
Cataclysmic Variables I
The maximum observed blueshifted absorption (vedge)
reaching 5000 km s-1,
indicating mass-loss rates up to dM/dt~10-9 M yr-1
Typical short-wavelength spectra of the
nova-like variables IX Vel and V3885 Sgr.
Cataclysmic Variables II
Theoretical PCygni profiles for a
specific mass-loss rate and velocity law for nine values of the
inclination (Mauche and
Raymond 1987).
Geometry for a disk wind.
From Shlosman and Vitello (1993).
Assumptions and geometry
GRAVITATIONALLY REDSHIFTED ABSORPTION
Yaqoob, Serlemitsos (2005)
quasar E 1821+643
If the absorption line (at 6.2 keV in
the quasar frame) is real, we argue that it
could be due to gravitationally redshifted
Fe xxv or Fe xxvi resonance absorption
within 10 − 20 gravitational radii of the
putative central black hole.
Nandra et al (1999)
Absorption feature in NGC 3516.
Interpretation: an absorption feature
at 5.9 keV, as being due to
resonance scattering by iron.
GRAVITATIONALLY REDSHIFTED ABSORPTION?
Narrow components within Fe Kα line
(results from overlapping observations from Chandra and XMM on NGC3516
Turner et al. ApJ 2002, 574, L123
Gravitationally red-shifted narrow lines
Schematic representation of the components of the Fe Ka
line in NGC 3516.
X-Ray P-Cygni from Galactic Microquasar
Time variability of a P-Cygni Line
(Brandt & Schultz, 2000)
Circinus X-1 (Циркуль X-1)
Gravitationally Redshifted Absorption Lines in the
Burst Spectra of the Neutron Star in EXO 0748-676
•Direct method of determining the composition of a
neutron star is to measure the gravitational redshift at the
surface.
•Extensive searches have been conducted for
gravitationally redshifted
absorption features in isolated neutron stars. Most
neutron stars show no discrete spectral structure. Only
1E1207.4-5209 shows absorption features, but these
have not been uniquely identified.
Evolution of the spectral features was established
– Early: Fe XXVI dominates ion balance.• Identifying 13.0
Å with transitions of
Fe XXVI n=2-3 at z=0.35
• Higher order n ∅ 2 transitions would
lie at λ<9.7 Å
– Late: Fe XXV dominates ion balance.
Bursting neutron stars are excellent targets for these
searches:
• Identifying 13.75 Å with transitions of
Fe XXV n=2-3 at z=0.35
– During the bursts, the neutron star outshines the
accretion-generated
light by an order of magnitude.
– Continuing accretion provides a constant source of
heavy elements at
the neutron star surface.
– Low magnetic fields in LMXBs vastly simplify the
spectral analysis.
- Early: 13.0 Å (25.3, 26.3, 26.9 Å)
Red line- continuum +
interstellar
-Late: 13.75 Å, 25.2 Å,
26.4 Å (17.8, 19.7 Å)
Cottam et al,
Nature, 2002
Gravitationally Redshifted Absorption Lines II
Photon’s frequency in the co-moving
frame:
Optical depth along the ray:
Dorodnitsyn, 2007 MNRAS, subm.
Dorodnitsyn, 2006 MNRAS, subm.
Equal Frequency Surfaces I
EFS is determined from the solution
of the following equation:
Velocity profiles:
“Hubble’s law”
Typical trans-sonic wind at NP
Equal Frequency Surfaces II
- maximum red-shift
- maximum blue-shift
Dorodnitsyn, 2006 MNRAS, subm.
Illustration to the geometry
of equal frequency surfaces
( not to scale )
- Intensity at infinity
- Source function
- Escape probabilities
R=25rg, Vinf=0.01c (upper left), Vinf=0.01c (upper right)
R=10rg, Vinf=0.1c (lower left),
Dorodnitsyn A. 2007, subm
Plasma acceleration by the radiation pressure on
spectral lines in strong gravitational field
Dorodnitsyn, A.V. 2003, MNRAS, 339,
“Gravitationaly exposed flow” (GEF)
569
frequency of a
photon emitted by an
accretion disk
•
In addition to Sobolev effect (due to velocity
gradient) gravitational red-shifting of the
photon’s frequency should be taken into account
•
The resultant frequency of a photon in a restframe of the absorbing gas
•
Modified Sobolev optical depth that takes into
account grav. red-shifting. A characteristic
length:
gives a thickness of a shell where the
absorption due to a single line take place
Modified Sobolev optical depth