Stellar spectroscopy methods for study of supernova remnants
We present the method for study of the characteristics of the supernova remnants using their absorption properties. The background radiation sources are several stars with wide range of distances. Main task is accurate extraction of stellar spectra from observations. For Vela Jr. supernova remnant w...
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Advances in astronomy and space physics
2011
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| Цитувати: | Stellar spectroscopy methods for study of supernova remnants / Yu.V. Pakhomov, N.N. Chugai, A.F. Iyudin // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 15-18. — Бібліогр.: 7 назв. — англ. |
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irk-123456789-1189432017-06-02T03:03:58Z Stellar spectroscopy methods for study of supernova remnants Pakhomov, Yu.V. Chugai, N.N. Iyudin, A.F. Physics of Stars and Galaxies We present the method for study of the characteristics of the supernova remnants using their absorption properties. The background radiation sources are several stars with wide range of distances. Main task is accurate extraction of stellar spectra from observations. For Vela Jr. supernova remnant we found the absence of typical broad absorption in the spectral lines of Ca ii doublet. Using modeles of supernovae remnants and data on radiation in ⁴⁴Ti γ-ray line we estimated the age and the distance to Vela Jr. We showed that a hypernova may be a probable candidate for Vela Jr. protogenitor. 2011 Article Stellar spectroscopy methods for study of supernova remnants / Yu.V. Pakhomov, N.N. Chugai, A.F. Iyudin // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 15-18. — Бібліогр.: 7 назв. — англ. 987-966-439-367-3 http://dspace.nbuv.gov.ua/handle/123456789/118943 en Advances in Astronomy and Space Physics Advances in astronomy and space physics |
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Physics of Stars and Galaxies Physics of Stars and Galaxies |
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Physics of Stars and Galaxies Physics of Stars and Galaxies Pakhomov, Yu.V. Chugai, N.N. Iyudin, A.F. Stellar spectroscopy methods for study of supernova remnants Advances in Astronomy and Space Physics |
| description |
We present the method for study of the characteristics of the supernova remnants using their absorption properties. The background radiation sources are several stars with wide range of distances. Main task is accurate extraction of stellar spectra from observations. For Vela Jr. supernova remnant we found the absence of typical broad absorption in the spectral lines of Ca ii doublet. Using modeles of supernovae remnants and data on radiation in ⁴⁴Ti γ-ray line we estimated the age and the distance to Vela Jr. We showed that a hypernova may be a probable candidate for Vela Jr. protogenitor. |
| format |
Article |
| author |
Pakhomov, Yu.V. Chugai, N.N. Iyudin, A.F. |
| author_facet |
Pakhomov, Yu.V. Chugai, N.N. Iyudin, A.F. |
| author_sort |
Pakhomov, Yu.V. |
| title |
Stellar spectroscopy methods for study of supernova remnants |
| title_short |
Stellar spectroscopy methods for study of supernova remnants |
| title_full |
Stellar spectroscopy methods for study of supernova remnants |
| title_fullStr |
Stellar spectroscopy methods for study of supernova remnants |
| title_full_unstemmed |
Stellar spectroscopy methods for study of supernova remnants |
| title_sort |
stellar spectroscopy methods for study of supernova remnants |
| publisher |
Advances in astronomy and space physics |
| publishDate |
2011 |
| topic_facet |
Physics of Stars and Galaxies |
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http://dspace.nbuv.gov.ua/handle/123456789/118943 |
| citation_txt |
Stellar spectroscopy methods for study of supernova remnants / Yu.V. Pakhomov, N.N. Chugai, A.F. Iyudin // Advances in Astronomy and Space Physics. — 2011. — Т. 1., вип. 1-2. — С. 15-18. — Бібліогр.: 7 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
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| first_indexed |
2025-07-08T14:56:48Z |
| last_indexed |
2025-07-08T14:56:48Z |
| _version_ |
1837091111591477248 |
| fulltext |
Stellar spectroscopy methods for study of supernova remnants
Yu. V. Pakhomov1, N. N. Chugai1, A. F. Iyudin2
1Institute of Astronomy of RAS, 119017 Pyatnitskaya st. 48, Moscow, Russia
2Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119991 Vorobevy gory, GSP-1, Moscow, Russia
pakhomov@inasan.ru
We present the method for study of the characteristics of the supernova remnants using their absorption
properties. The background radiation sources are several stars with wide range of distances. Main task
is accurate extraction of stellar spectra from observations. For Vela Jr. supernova remnant we found the
absence of typical broad absorption in the spectral lines of Ca ii doublet. Using modeles of supernovae
remnants and data on radiation in 44Ti γ-ray line we estimated the age and the distance to Vela Jr. We
showed that a hypernova may be a probable candidate for Vela Jr. protogenitor.
Introduction
Most of the information about supernovae remnants (SNR) comes from UV, X-ray and γ-ray radiation,
that is avalable for observations only from space. In optical light we can see the interaction of shock wave
with interstellar clouds, but the main part of SNR is invisible. However, physical conditions inside SNR
provide appearance of the absorption lines. These lines should be broadened due to high velocities of the
SNR expansion. Study of such lines give us an information about physical characteristics of SNR. And
presence or absence of these lines in stellar spectra can be used for estimation of the distance to SNR.
We used this method for study of the very young SNR � Vela Jr. This SNR is invisible in optical light
and was discovered in 1998 by Aschenbach [1] in hard X-ray and Iyudin [4] in 1.16 MeV γ-ray line 44Ti.
The method
The method consists of the following steps: selection of the stars with wide range of distances on the
background of SNR; spectral observations of these stars; processing of the spectra; determination of stellar
parameters (e�ective temperature Teff , gravity log g, rotation velocity v sin i); estimation of the interstellar
reddening and distances to the stars; extraction of the interstellar spectra; searching for the broad absorption
lines in interstellar spectra; estimation of the distances to SNR and its physical characteristics.
The spectra were obtained on the ESO 3.6-m telescope NTT (program 080.D-0012(A) PI: A. F. Iyudin)
using the spectrograph EMMI in blue middle dispersion mode. The dispersion is 0.15Å/pix, the resolving
power is λ/∆λ = 9000. The signal-to-noise ratio is between 90 and 350. For each star there are two
overlapped spectra in the range of 3740�4021 Å. This spectral region encompasses resonance spectral lines
of Fe i (3860 Å) and Ca ii (3933 Å, 3968 Å).
Preliminary processing of the spectral CCD images were made with EMMI original emmi_quickred script
for MIDAS software; the atmosphere and interstellar extinction were taken into account for each individual
star. The spectra are �ux calibrated with the help of spectra of the standard star HD 60753 obtained during
the same set of observations. The derived response function was used to produce �ux calibrated stellar
spectra.
Results and conclusions
The stellar parameters were estimated using the method of the stellar athmospheres moddeling and
found by �tting the synthesized pro�les to six Balmer lines (H7�H12). The spectra were synthesized applying
Kurucz ATLAS9 code [5] and SynthVb package [7]. Obtained parameters are presented in Table 1. Interstellar
15
Advances in Astronomy and Space Physics Yu. V. Pakhomov, N. N. Chugai, A. F. Iyudin
reddening was calculated using observed and normal color indexes (B − V )0 [3] which were estimated using
stellar parameters.
Table 1: Parameters of the stars and distances calculated by spectral method and from Hipparcos parallaxes
Star Teff log g V sin i (B − V )0 AV M dsp dHIP
(K) (km s−1) (mag) (mag) (M¯) (pc) (pc)
HD75309 26500±400 3.60±0.10 210 -0.25 0.8 16 1900±300
HD75820 11400±200 4.00±0.10 200 -0.10 0.2 3.2 470±100 505±184
HD75873 8900±200 2.50±0.05 15 0.01 1.2 6 1400±200
HD75955 10400±200 3.85±0.10 190 -0.07 0.2 3.0 320± 70 262± 35
HD75968 12250±150 3.86±0.05 80 -0.11 0.0 3.8 570±140 719±254
HD76060 13400±200 4.10±0.10 240 -0.13 0.1 3.6 390± 90 335± 63
HD76589 11800±200 4.10±0.10 95 -0.10 0.1 3.2 390± 90 240± 76
HD76649 13300±150 3.65±0.05 33 -0.13 0.8 4.5 640±110
HD76744 10500±200 4.20±0.10 150 -0.08 0.5 2.4 270± 50
CD-454590 22400±400 3.60±0.10 140 -0.22 1.3 11 2400±300
CD-454606 29500±500 3.80±0.10 240 -0.27 2.0 17 1670±160
CD-454645 8400±200 4.35±0.10 80 0.08 0.4 1.8 330± 70
CD-454676 29000±500 3.70±0.10 125 -0.27 3.2 18 1080±150
CD-464666 10500±200 2.05±0.05 30 -0.08 2.1 12 5700±500
To determine the distances we used a modi�ed method of spectral parallaxes in which the stellar lu-
minosity is derived from stellar evolutionary tracks as follows. Using stellar parameters (Teff and log g)
and evolutionary tracks [6] we estimate the stellar mass and thus derive the bolometric luminosity. The
absolute magnitude MV is then determined using the bolometric correction. The distance was determined
from formula:
log dsp = 0.2 [{4.69− 2.5 (−10.607 + log (M/M¯) + 4 log Teff − log g)−BCV } −mV − 5 + AV ] , (1)
where BCV is the bolometric correction, AV is the interstellar absorption in V Johnson band and mV is the
apparent magnitude in V Johnson band.
Excluding modelled stellar spectra from observation gives the residual spectrum:
r =
C(λ) · F obs
l − F syn
l
F syn
c
, (2)
where r is the relative residual spectrum, F syn
c and F syn
l are the �ux in continuum and in lines of the
synthetic spectrum, F obs
l is the �ux in lines of the observed spectrum, and C(λ) is the smooth �tting factor
which is de�ned as linear approximation of the ratio of synthetic to observed spectrum F syn
l /F obs
l .
The relative residual spectra for all the stars are shown in Fig. 1. Also 3σ levels (equals to 1.5�4 %) are
indicated for each star. The spectra do not reveal broad absorption resonance lines of Ca ii 3933 Å, 3968 Å or
Fe i 3860 Å. Speci�cally, the relative depth of the broad Ca ii absorption (if any) produced by Vela Jr. is less
than 0.04 at the level of 3σ. Note, that weak absorption features at 3819 Å and 4009 Å in the hottest stars
of our sample are related to helium which generally shows non-local thermodynamic equilibrium excitation
e�ects and cannot be modelled reliably within the LTE approximation.
With the exception of two stars (HD 75873 and CD-454645) all the spectra show narrow unresolved
interstellar Ca ii lines. The interstellar absorptions can be divided into two major groups: low-velocity
|V | <50 km s−1, and high-velocity |V | >100 km s−1. Most stars have one component with positive radial ve-
locity of ∼22-48 km s−1. Three stars show high-velocity components: HD 75309 (+153 km s−1, −92 km s−1),
HD 76060 (−92 km s−1), and CD-454676 (−150 km s−1). These velocities are typical for high-velocity in-
terstellar Ca ii absorptions found earlier in the direction of old Vela SNR [2]. At least one star, CD-454676,
shows conspicuous CN absorption of electronic transitions R(0), R(1), and P (1) with the wavelengths of
3873.994 Å, 3874.602 Å, and 3875.759 Å correspondingly. The heliocentric radial velocity of these lines is
+23 km s−1 (VLSR = +10 km s−1), that is consistent with the radial velocity of Ca ii interstellar lines of
the same star.
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Advances in Astronomy and Space Physics Yu. V. Pakhomov, N. N. Chugai, A. F. Iyudin
Figure 1: The relative residual spectra with 3σ error box. The distance to each star is also indicated.
Table 2: Adopted parameters of supernovae
Parameters SN Ia SN IIP SN Ibc SN Ic(h)
M (M¯) 1.4 10 3 4
E (1051erg) 1.4 1 1.5 20
The absence of Fe I and Ca ii broad absorption in stellar spectra towards Vela Jr. requires a con�rmation
with modeling the broad Ca ii absorptions expected at the given age for the di�erent SN types. The predicted
pro�les of the Ca ii doublet at the age of 700 yr for di�erent of SNe are shown in Fig. 2 assuming that all Ca
is in Ca ii state. We assume that in SN IIP and SN Ibc the Ca abundance is solar, while for SN Ia we adopt
that Ca/Fe mass ratio is solar, while the total mass of iron in the ejecta is 0.6 M¯. Ejecta parameters for
di�erent SNe are given in Table 2. The boundary velocity of the unshocked ejecta is taken to be 5000 km s−1in
accordance with the distance of 200 pc and the age of 700 yr. The density distributions ρ(v) in the unshocked
ejecta are assumed to be exponential for compact pre-SNe and plateau with the outer power law ρ ∝ v−9
for SN IIP. The shown pro�les are computed for three values of impact parameter in units of the angular
radius: 0, 0.5, and 0.8. The predicted absorption turns out to be deep for all the impact parameters in the
case of SN Ia, rather deep for SN IIP, very weak for SN Ibc, and negligible (relative depth < 0.006) in case
of SN Ic(h). If Vela Jr. age and distance are close to the values adopted above, the progenitor was unlikely
to be of type SN Ia or SN IIP; association of the SNR with a SN Ibc or SN Ic(h) is therefore preferred.
The age-distance relations for all the discussed cases are shown in Fig. 3. The SN Ia exploded in the hot
interstellar medium phase shows almost the same age-distance relation as SN Ibc and therefore is not shown
in this �gure. The minimal distance for a given age corresponds to a SN IIP expanding in the warm neutral
interstellar medium phase, while the maximal distance corresponds to SN Ic(h) with 60 M¯ progenitor. In
combination with the 44Ti curves for the two extreme values of ejected 44Ti mass results in allowed ranges
of 450-900 yr and 150-1000 pc for the age and distance of Vela Jr. The major result of this plot is that
the distance of Vela Jr. cannot exceed 1 kpc. We thus conclude that at least several stars in our sample
(Table 1) lie behind the SNR.
The absence of a broad Ca ii absorption features in the spectra of stars with distances > 1 kpc suggests
17
Advances in Astronomy and Space Physics Yu. V. Pakhomov, N. N. Chugai, A. F. Iyudin
Figure 2: Absorption pro�le of Ca ii doublet expected in
the stellar spectrum for di�erent progenitors of Vela Jr.
The cases of impact parameter equal to 0, 0.5, and
0.8 are shown. The strongest absorption always cor-
responds to zero impact parameter
Figure 3: Age-distance relations provided by 44Ti mass
(thick solid lines) and radius of the supernova remnant.
The radius is calculated for SN IIP (dotted line), SN Ia
(thin solid line), SN Ibc (short-dashed line), SN Ic(h)
with 35 M¯ progenitor (long-dash line) and 60 M¯ pro-
genitor (dashed-dotted line).
that the SNR progenitor was either SN Ibc or SN Ic(h) because only for these SNe the expected absorption
is weak and could remain undetected (Fig. 2). For the case of SN Ibc at the age of 650 yr the modeled width
of 44Ti γ-line is less than width of observed line. High velocities in pro�le of this line can be explained by
distribution of 44Ti in external parts of bi-polar jets in the case of SN Ic(h). Thus hypernova is the most
possible progenitor of the Vela Jr.
References
[1] Aschenbach B. Nature, V. 396, pp. 141-142 (1998)
[2] Cha A. N., Sembach K. R. Astrophys. J. Suppl. Ser., V. 126, pp. 399-426 (2000)
[3] Castelli F., Kurucz R. L. in `Modelling of Stellar Atmospheres', eds.: N. Piskunov, W. W. Weiss, & D. F. Gray, V. 210,
p. 20 (2003)
[4] Iyudin A. F., Schönfelder V., Bennett K. et al. Nature, V. 396, pp. 142-144 (1998)
[5] Kurucz R. `ATLAS9 Stellar Atmosphere Programs and 2 km/s grid' Cambridge, Mass.: Smithsonian Astrophysical Obser-
vatory, V. 13 (1993)
[6] Schaller G., Schaerer D., Meynet G., Maeder A. Astron. & Astrophys. Suppl. Ser., V. 96, pp. 269-331 (1992)
[7] Tsymbal V., Lyashko D., Weiss W. W. in `Modelling of Stellar Atmospheres', eds.: N. Piskunov, W. W. Weiss, D. F. Gray,
V. 210, p. 49 (2003)
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