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Does SS 433 have cousins?
Vistas in Astronomy, Voi.25, pp.137-139, 1981. Printed in Great Britain. All rights reserved.
OO83-6656/81/O20137-O3500.50 per page/O Copyright©1981 Pergamon Press Ltd.
DOES SS 433 HAVE COUSINS? L. Maraschil and A. Treves2 ILaboratorio di Fisica Cosmica del CNR, Milano, Italy 2Istituto di Fisica delrUniversit/t, Milano, Italy
SS 433 appears in the list of radio stars possibly associated with SN remnants compiled by Ryle et al. (1978) together with Cir X-I.
The similarity of the two sources also extends to
their optical spectra as stressed by Clark and Murdin (1978).
Another strongly variable radii
star GT O236+610 was discovered in 1977 by Gregory and Taylor (1978).
It was successively
identified with an early type star with unusually broad Ha and HB emission (Gregory et al.j 1979).
Within the class of "variable radio stars" this is the fourth in peak luminosity
(2xlO 31 erg/s), the first being Cyg X-3, the second Cir X-I, and third SS 433, as noted by Gregory et al. (1979).
The four objects (see Table I) are all close binaries and X-ray emitters, though widely different in X-ray luminosity (for GT 0236 see Taylor and Gregory, 1980; Bignami et al.~ 19801 and their radio properties are unique among X-ray sources.
We discuss here the possibility
that they represent different examples of the same evolutionary stage, irm~ediately following the SN explosion and neutron star formation in the binary system and preceding that of the well known X-ray pulsators.
If the newly-born neutron star is spinning rapidly (P~IO ms) with the standard parameters magnetic field B=IOI2G, and radius a=lO 6 cm, its rotational power output can be above 1038 erg/s for a time of ~104 y. Since the duration of the X-ray phase in accreting massive binaries, which number about 20 in the Galaxy, is estimated to be of the order of 104-105 y~ several systems are to be expected in which the rotational power should contribute to the observed emission (lllarionov and Sunyaev, 1975; Maraschi and Treves, 1979, 1980).
Pulsar models agree in predicting that the bulk of the rotational energy is lost via a relativistic wind (low-frequency electromagnetic radiation and relativistic particles).
For
an isolated pulsar this energy loss gives rise to little observable radiation and is disperseq in the interstellar medium.
If, however, the pulsar belongs to a binary and the companion ha
a mass loss large enough to balance and confine the relativistic output of the pulsar within a cavity, most of the pulsar output must be released as heating of the boundary of the cavity and as synchrotron and Compton radiation of relativistic particles.
The relative importance
of these mechanisms depends on the density of the surrounding plasma (the mass transfer), on the value of magnetic field (the radius of the cavity), on the photon energy density (the luminosity of the primary), and the separation of the system.
Models of this type have been proposed for Cyg X-3 by Bignami et al. (1977) and GT 0236 by Maraschi and Treves (1980).
In the former case the system and the cavity are small (r ~ 5xlO
138
L. Maraschi and A. Treves
so that synchrotron radiation is important from radio to y-ray
frequencies.
The surrounding
plasma is dense (~lOl4cm "3) and a significant X-ray thermal component is generated. GT 0236 the separation is wider
For
(rc~ 3xlO 12) and the plasma density at the boundary lower
(108 cm-3), but the luminosity of the primary is larger, so that thermal radiation is negligible and Compton scattering dominates in the X-ray and
y-ray bands.
Synchrotron
radiation is still responsible for the radio emission.
In line with this picture are models of SS 433 involving a large mass transfer through a thick disk to a rapidly rotating neutron star (for references see the review paper by Milgrom in this volume).
According to van den Heuvel (this conference) it is possible that the prima
is leaving the main sequence and the neutron star is still young.
The thick disk would scree
from our observation all the non-thermal activity going on at the pulsar cavity.
Along the
axis of least resistance however a nozzle could be generated allowing the formation of relativistic jets (Blandford and Rees, 1976) which may entrain the plasma responsible for the nLoving line emission.
For Cir X-I no models of this type have been considered yet.
However in order to explain the
asymmetric light curves in the radio and X-ray bands a high eccentricity (e~O.8) has been suggested (Murdin
et al., 1980) which directly implies a young age.
A similar argument has
been put forward with regard to the asy~mnetric X-ray light curve of Cyg X-3 (Molteni 1980; Eisner et
al., 1980).
et al.,
Since the radio light curve of Cir X-I is similar to that of
GT 0236 and the latter system is much closer, it is possible that a direct confirmation of the eccentric hypothesis comes from the observation of its optical counterpart.
This would
be a strong argument in favour of the young age of these systems and indicate the possibility of neutron star formation with very short-lived SN remnants (4104 y), a point which has also been raised on the basis of pulsar statistics.
In conclusion SS 433 is unique for the presence of the highly blue and red shifted satellite lines; however in other important respects it can be related to other systems.
If this
kinship is real, it may lead to a better understanding of SS 433 itself.
Table I.
Parameters of the possible family of young pulsars in binary systems Cyg X-3
Cir X-I
Binary period
4.8 h
16.6 d
Other periods
17-34 d
164 d
Separation
i0 II cm
1012 cm
Optical i.r.lum.
1035-1036 erg/s 1038 erg/s
X-ray lum. Radio emission X-ray
variable
possible emission at
SN
Eccentricity
35 MeV, lO--eV absent 0.6?
3xlO 37 erg/s 1038 erg/s variable periodic
(CG 321?)
SS 433 13.3 d
GT 0236 26 d
6xlO 12 cm
1038 erg/s
1038 erg/s
1034-1035 erg/s
1033-1034 erg/s
variable
-
present?
present?
0.8?
0.i?
variable periodic
P(1 MeV)~]~ erg/ LIO O MeVLU absent
erg/
Does SS 433 Have Cousins?
139
REFERENCES I.
M. Ryle, J.L. Coswell, G. Hine and J. Shakeshaft (1978) Nature, 276, 571.
2.
D.H. Clark and P. Murdin (1978) Nature, 276, 44.
3.
P.C. Gregory and A.R. Taylor (1978) Nature, 272, 704
4.
P.C. Gregory, A.R. Taylor, D. Crampton, J.B. Hutchings, R.M.H. Hjellming, D. Hogg, H. Huatum, E. Gottleb, P.A. Fedman and S. Kwok (1979) A8tr.J. 84, 1030.
5.
A.R. Taylor and P.G. Gregory (1980) IAU Circ. No. 3464.
6.
G.F. Bignami, P.A. Caraveo, R.C. Lamb and T~H. Markert (1980) IAU Circ. No. 3518.
7.
A.F. lllarionov and R.A. Sunyaev (1975) Astr. Astrophys.
8.
L. Maraschi and A. Treves (1979) Nature, 279, 401.
9.
L. Maraschi and A. Treves (1980) NATO Advanced Inst. on Galactic X-ray sources. Cape Sounion (in press, J. Wiley).
39, 185.
iO.
G.F. Bignami, L. Marasehi and A. Treves (1977) Astr. Astrophy8. 55, 155.
ii.
L. Maraschi and A. Treves (1980) M.N.R.A.S.
12.
R.D. Blanford and M.J. Rees (1976) M.N.R.A.S.
13.
P. Murdin, D.L. Jouncey, R.F. Haynes, I. Lerche, G.D. Nicolson, S.S. Holt and K.L.J. Kaluzienhski (1980) Astr.Astrophy8. 8_/7, 292.
14.
D. Molteni, M. Rapisarda, N.R. Robba and L. Scarsi (1980) Astr.Astrophys.
15.
R.F. Elsner, P. Ghosh, W. Durbrow, M.C. Weisskopf, P.G. Sutherland and J.E. Grindlay (1980) Astrophys.J. 239, 335.
(in press). 169, 395.
87, 88.
OO83-6656/81/O20137-O3500.50 per page/O Copyright©1981 Pergamon Press Ltd.
DOES SS 433 HAVE COUSINS? L. Maraschil and A. Treves2 ILaboratorio di Fisica Cosmica del CNR, Milano, Italy 2Istituto di Fisica delrUniversit/t, Milano, Italy
SS 433 appears in the list of radio stars possibly associated with SN remnants compiled by Ryle et al. (1978) together with Cir X-I.
The similarity of the two sources also extends to
their optical spectra as stressed by Clark and Murdin (1978).
Another strongly variable radii
star GT O236+610 was discovered in 1977 by Gregory and Taylor (1978).
It was successively
identified with an early type star with unusually broad Ha and HB emission (Gregory et al.j 1979).
Within the class of "variable radio stars" this is the fourth in peak luminosity
(2xlO 31 erg/s), the first being Cyg X-3, the second Cir X-I, and third SS 433, as noted by Gregory et al. (1979).
The four objects (see Table I) are all close binaries and X-ray emitters, though widely different in X-ray luminosity (for GT 0236 see Taylor and Gregory, 1980; Bignami et al.~ 19801 and their radio properties are unique among X-ray sources.
We discuss here the possibility
that they represent different examples of the same evolutionary stage, irm~ediately following the SN explosion and neutron star formation in the binary system and preceding that of the well known X-ray pulsators.
If the newly-born neutron star is spinning rapidly (P~IO ms) with the standard parameters magnetic field B=IOI2G, and radius a=lO 6 cm, its rotational power output can be above 1038 erg/s for a time of ~104 y. Since the duration of the X-ray phase in accreting massive binaries, which number about 20 in the Galaxy, is estimated to be of the order of 104-105 y~ several systems are to be expected in which the rotational power should contribute to the observed emission (lllarionov and Sunyaev, 1975; Maraschi and Treves, 1979, 1980).
Pulsar models agree in predicting that the bulk of the rotational energy is lost via a relativistic wind (low-frequency electromagnetic radiation and relativistic particles).
For
an isolated pulsar this energy loss gives rise to little observable radiation and is disperseq in the interstellar medium.
If, however, the pulsar belongs to a binary and the companion ha
a mass loss large enough to balance and confine the relativistic output of the pulsar within a cavity, most of the pulsar output must be released as heating of the boundary of the cavity and as synchrotron and Compton radiation of relativistic particles.
The relative importance
of these mechanisms depends on the density of the surrounding plasma (the mass transfer), on the value of magnetic field (the radius of the cavity), on the photon energy density (the luminosity of the primary), and the separation of the system.
Models of this type have been proposed for Cyg X-3 by Bignami et al. (1977) and GT 0236 by Maraschi and Treves (1980).
In the former case the system and the cavity are small (r ~ 5xlO
138
L. Maraschi and A. Treves
so that synchrotron radiation is important from radio to y-ray
frequencies.
The surrounding
plasma is dense (~lOl4cm "3) and a significant X-ray thermal component is generated. GT 0236 the separation is wider
For
(rc~ 3xlO 12) and the plasma density at the boundary lower
(108 cm-3), but the luminosity of the primary is larger, so that thermal radiation is negligible and Compton scattering dominates in the X-ray and
y-ray bands.
Synchrotron
radiation is still responsible for the radio emission.
In line with this picture are models of SS 433 involving a large mass transfer through a thick disk to a rapidly rotating neutron star (for references see the review paper by Milgrom in this volume).
According to van den Heuvel (this conference) it is possible that the prima
is leaving the main sequence and the neutron star is still young.
The thick disk would scree
from our observation all the non-thermal activity going on at the pulsar cavity.
Along the
axis of least resistance however a nozzle could be generated allowing the formation of relativistic jets (Blandford and Rees, 1976) which may entrain the plasma responsible for the nLoving line emission.
For Cir X-I no models of this type have been considered yet.
However in order to explain the
asymmetric light curves in the radio and X-ray bands a high eccentricity (e~O.8) has been suggested (Murdin
et al., 1980) which directly implies a young age.
A similar argument has
been put forward with regard to the asy~mnetric X-ray light curve of Cyg X-3 (Molteni 1980; Eisner et
al., 1980).
et al.,
Since the radio light curve of Cir X-I is similar to that of
GT 0236 and the latter system is much closer, it is possible that a direct confirmation of the eccentric hypothesis comes from the observation of its optical counterpart.
This would
be a strong argument in favour of the young age of these systems and indicate the possibility of neutron star formation with very short-lived SN remnants (4104 y), a point which has also been raised on the basis of pulsar statistics.
In conclusion SS 433 is unique for the presence of the highly blue and red shifted satellite lines; however in other important respects it can be related to other systems.
If this
kinship is real, it may lead to a better understanding of SS 433 itself.
Table I.
Parameters of the possible family of young pulsars in binary systems Cyg X-3
Cir X-I
Binary period
4.8 h
16.6 d
Other periods
17-34 d
164 d
Separation
i0 II cm
1012 cm
Optical i.r.lum.
1035-1036 erg/s 1038 erg/s
X-ray lum. Radio emission X-ray
variable
possible emission at
SN
Eccentricity
35 MeV, lO--eV absent 0.6?
3xlO 37 erg/s 1038 erg/s variable periodic
(CG 321?)
SS 433 13.3 d
GT 0236 26 d
6xlO 12 cm
1038 erg/s
1038 erg/s
1034-1035 erg/s
1033-1034 erg/s
variable
-
present?
present?
0.8?
0.i?
variable periodic
P(1 MeV)~]~ erg/ LIO O MeVLU absent
erg/
Does SS 433 Have Cousins?
139
REFERENCES I.
M. Ryle, J.L. Coswell, G. Hine and J. Shakeshaft (1978) Nature, 276, 571.
2.
D.H. Clark and P. Murdin (1978) Nature, 276, 44.
3.
P.C. Gregory and A.R. Taylor (1978) Nature, 272, 704
4.
P.C. Gregory, A.R. Taylor, D. Crampton, J.B. Hutchings, R.M.H. Hjellming, D. Hogg, H. Huatum, E. Gottleb, P.A. Fedman and S. Kwok (1979) A8tr.J. 84, 1030.
5.
A.R. Taylor and P.G. Gregory (1980) IAU Circ. No. 3464.
6.
G.F. Bignami, P.A. Caraveo, R.C. Lamb and T~H. Markert (1980) IAU Circ. No. 3518.
7.
A.F. lllarionov and R.A. Sunyaev (1975) Astr. Astrophys.
8.
L. Maraschi and A. Treves (1979) Nature, 279, 401.
9.
L. Maraschi and A. Treves (1980) NATO Advanced Inst. on Galactic X-ray sources. Cape Sounion (in press, J. Wiley).
39, 185.
iO.
G.F. Bignami, L. Marasehi and A. Treves (1977) Astr. Astrophy8. 55, 155.
ii.
L. Maraschi and A. Treves (1980) M.N.R.A.S.
12.
R.D. Blanford and M.J. Rees (1976) M.N.R.A.S.
13.
P. Murdin, D.L. Jouncey, R.F. Haynes, I. Lerche, G.D. Nicolson, S.S. Holt and K.L.J. Kaluzienhski (1980) Astr.Astrophy8. 8_/7, 292.
14.
D. Molteni, M. Rapisarda, N.R. Robba and L. Scarsi (1980) Astr.Astrophys.
15.
R.F. Elsner, P. Ghosh, W. Durbrow, M.C. Weisskopf, P.G. Sutherland and J.E. Grindlay (1980) Astrophys.J. 239, 335.
(in press). 169, 395.
87, 88.