MICRO-QUASAR WITHIN OUR GALAXY !
Strange, Powerful Object in Milky Way Galaxy Shoots Out Material at Super Speeds
Movie made from of a series of VLA radio images of the 'microquasar' GRS 1915+105
taken at wavelength of 3.5 cm, depicting the rapid ejection of jets over the span of a month
(march 27 to April 30, 1994). The shape, motion and spectra of the radio jets
from this star and other jet emitting stars such as
SS433, CH Cyg, Cyg X-3 and
are almost identical to the properties of quasars like
Researchers using the
Very Large Array (VLA)
have discovered that a small,
powerful object in our own cosmic neighborhood is shooting out material at
nearly the speed of light -- a feat previously known to be performed only by
the massive cores of entire galaxies. In fact, because of the direction in
which the material is moving, it appears to be traveling faster than the speed
of light -- a phenomenon called "superluminal motion." This is the first
superluminal motion ever detected within our Galaxy.
During March and April of this year, Dr. Felix Mirabel of the Astrophysics
Section of the Center for Studies at Saclay, France, and Dr. Luis Rodriguez of
the Institute of Astronomy at the National Autonomous University in Mexico City
observed "a remarkable ejection event" in which the object shot out
material in opposite directions at 92 percent of the speed of light, or more
than 171,000 miles per second. This event ejected a mass equal to one-third
that of the moon with the power of 100 million suns. Such powerful ejections
are well known in distant galaxies and quasars, millions and billions of
light-years away, but the object Mirabel and Rodriguez observed is within our
own Milky Way Galaxy, only 40,000 light-years away. The object also is much
smaller and less massive than the core of a galaxy, so the scientists were
quite surprised to find it capable of accelerating material to such speeds.
Mirabel and Rodriguez believe that the object is likely a double-star system,
with one of the stars either an extremely dense neutron star or a black hole.
The neutron star or black hole is the central object of the system, with great
mass and strong gravitational pull. It is surrounded by a disk of material
orbiting closely and being drawn into it. Such a disk is known as an accretion
disk. The central object's powerful gravity, they believe, is pulling material
from a more-normal companion star into the accretion disk. The central object
is emitting jets of subatomic particles from its poles, and it is in these jets
that the rapidly-moving material was tracked.
The object, known as GRS 1915+105, also is a strong emitter of X-Rays,
sometimes becoming the strongest source of X-Rays in the Milky Way. The X-rays,
they think, are emitted from the system's accretion disk. The VLA observations,
along with other evidence the researchers have uncovered, leads them to believe
that, despite being much less massive than galactic cores, other double-star
systems may be capable of ejecting material at speeds near that of light. The
researchers reported their discovery in the
September 1 issue of the journal Nature.
"This discovery is one of the most valuable results of more than a decade and a
half of observations at the VLA," said Dr. Miller Goss, assistant director of
operations. "We see these fast-moving jets of material
throughout the universe, and they represent an important physical process.
However, they're usually so far away that it is difficult to study them. This
object, relatively nearby, offers the best opportunity yet to build a good
understanding of how such jets actually work," Goss added.
GRS 1915+105 was discovered in 1992 by an orbiting French-Russian X-ray
It had not been found before because its
X-rays are highly-energetic "hard" X- rays not regularly observed by satellites
before then. Since its discovery, it has repeatedly been seen as a source of
"hard" X-rays. Despite searching, the scientists have been unable to observe
the object in visible light. Observations with the VLA in 1992 and 1993 showed
that the object changed both its radio "brightness" and its apparent position
in the sky, but it was then too faint at radio wavelengths for precise
measurements. In March of 1994, the object began an outburst of strong radio
emission just as the VLA had entered a configuration capable of its most
precise positional measurements. Through March and April of 1994, Mirabel and
Rodriguez were able to track the movement of the two condensations in the jets
of material moving away from the object's core.
They found that the core remained stationary, while the approaching
condensation was apparently moving at 125 percent of the speed of light. After
correcting for relativistic effects, they conclude that the ejected material
actually is moving at 92 percent of light speed. Their calculations indicate
that the pair of "blobs" they tracked were ejected from the core on March 19,
during a period when the object was emitting more X-rays than usual.
GRS 1915+105 somewhat resembles a famous astronomical object that was
intensively studied in the late 1970s and early 1980s, called
The VLA was used for many
observations of SS433,
which, astronomers believe, is also a
double-star system with a dense, massive star as its centerpiece. SS433 has
jets similar to those of GRS 1915+105, but the fastest motions detected in
SS433's jets are only 26 percent the speed of light. Comparing it to quasars,
which are believed to be phenomena associated with supermassive black holes at
the centers of galaxies -- objects much larger and more massive than stars --
astronomers have called SS433 a "stellar microquasar." With kinetic energies 40
times those of SS433, GRS 1915+105 "appears to be a scaled up version" of the
other object, Mirabel and Rodriguez say.
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Comment in Science News (1994) on the distance
of GRS 1915+105 :
- 'John A. Biretta of the Space Telescope Science Institute in Baltimore cautions
that the researchers haven't pinned down the distance to the object
ejecting the gas, thought to be a neutron star or black hole that steals
matter from a less-dense companion. If this binary star lies much closer to
the Earth than the 40,000 light years they estimate, the blobs would still
be cruising, but not at superluminal speeds', he says. (See also the June 1994
meeting of the AAS in Minneapolis on the jets in M87)
SIMBAD Data for Granat 1915+105 (X-ray source) :
J2000.0 coord RA= 19 17 37 DEC= +11 03.6
galactic coord l= 45.74 b= -0.69
(IAU Circulars from 3722 to 6172 are available
- Mirabel,I.F., Rodriguez,L.F.: 1994, Nature, 371, 46.
A superluminal Source in the Galaxy
Castro-Tirado,A.J.: Is SGR 1900+14 = GRS 1915+105 ?
- Castro-Tirado,A.J., Geballe,T.R., Lund,N.: 1996, ApJ.lett., 461, 99.
Infrared Spectroscopy of the Superluminal Galactic Source GRS 1915+105 During the September
AAS site has full paper
K-band spectra from UKIRT,
J-K HR Diagram,
- Levinson,A., Blandford,R.: 1996, ApJ., 456, L29.
On the Jets Associated with Galactic Superluminal Sources (see also
- Boeer,M., Greiner,J., Motch,C.: 1996, AA., 305, 835.
The optical content of the error box of GRS 1915+105.
(see also LANL site)
- Meyer,O.: 1995, Sterne und Weltraum, 34, 93.
Der galaktische "Mikroquasar" GRS 1915+105.
- Chaty,S.: 1995, J. Astronomes Francais, 49, 47.
Observations multi-longueur d'onde de la source superluminique GRS 1915+105, permettant de
determiner son absorption visuelle, sa distance et sa nature.
- Sazonov,S., Sunyaev,R.: 1995, IAU Circ., 6274, 1.
- Pooley,G.: 1995, IAU Circ., 6267, 1.
- Eikennberry,S.S., Fazio,G.G.: 1995, IAU Circ., 6267, 1.
- Harmon,B.A., Maciesas,W.S., Zhang,S.N., Deal,K.J., Waltman,E.B., Foster,R.S., Ghigo,F.D.,
1995, IAU Circ., 6266, 1.
- Sazonov,S., Sunyaev,R., Zhang,S.N., Harmon,B.A., Paciesas,W.S., Fishman,G.J.:
1995, IAU Circ., 6209, 1
- Harmon,B.A., Paciesas,W.S., Fishman,G.J., Ghigo,F.D., Waltman,E.B., Foster,R.S.:
1995, IAU Circ., 6204, 1.
- Sazonov,S., Sunyaev,R.: 1995, IAU Circ., 6201, 1.
X-ray Nova 1994 in Scorpius and GRS 1915+105.
- Sazonov,S., Sunyaev,R.:
1995, IAU Circ., 6196, 1.
- Ebisawa,K., White,N.E., Kotani,T., Harmon,A.:
1995, IAU Circ., 6171, 1.
- Foster,R.S., Waltman,E.B., Tavani,M.: 1995, Bull. American Astron. Soc., 27, 1350.
Green bank interferometer observations of the galactic superluminal source GRS 1915+105.
- Rodriguez,L.F., Gerard,E., Mirabel,I.F., Gomez,Y., Velazquez,A.: 1995, ApJS., 101, 173.
Radio Monitoring of GRS 1915+105
- Bodo,G., Ghisellini,G.: 1995, ApJ., 441, 69.
The velocity of the emitting plasma of the superluminal galactic source GRS 1915+105
(see also LANL site)
- Mirabel,I.F., Rodriguez,L.F.: 1995, Astrophys.Sp.Sci., 231, 65.
Soft gamma-ray bursts from the superluminal source GRS 1915+105 ?
- Brandt,S., Lund,N.: 1995, Advances in Space Research, 16, 37.
Monitoring the activity variations of galactic X-ray sources with watch on EURECA
- Priedhorsky,W.C., Brandt,S., Lund,N.: 1995, AA., 300, 415.
Time series analysis of bright galactic X-ray sources.
- Liang,E.P., Li,H.: 1995, AA., 298, 45.
On relativistic ejections from GRS 1915+105.
- Sazonov,S.Yu., Sunyaev,R.A., Lapshov,I.Y., Lund,N., Brandt,S., Castro-Tirado,A.:
1994, Pis'ma Astron. Zh., 20, 901.
Two years of observations of the transient X-ray sources GRS 1915+105 by WATCH device on
board Granat Observatory.
(see also ESA site)
- Nagase,F., Inoue,H., Kotani,T., Ueda,Y.: 1994, IAU Circ., 6094, 1
GRS 1915+105 and X-ray nova in Scorpius.
- Sazonov,S., Sunyaev,R.: 1994, IAU Circ., 6080, 1.
- Durouchoux,P., Corbel,S., Wallyn,P., Grindlay,J.: 1994, IAU Circ., 6000, 1
- Sazonov,S., Sunyaev,R., Lapshov,I.: 1994, IAU Circ., 5959, 1
- Gerard,E., Rodriguez,L.F., Mirabel,I.F.: 1994, IAU Circ., 5958, 1.
- Castro-Tirado, et al. : 1994, ApJS., 92, 469.
Discovery and observations by watch of the X-ray transient GRS 1915+105
- Finoguenov, et al. : 1994, ApJ., 424, 940.
Localization and spectrum of the X-ray transient source GRS 1915+105
- Finoguenov,A., Vikhinin,A., Gilfanov,M., Sunyaev,R.: 1993, Pis'ma Astron. Zu., 19, 1075.
Localization and spectrum of the X-ray transient source GRS 1915+105.
- Wenzel,W., Splittgerber,E., Greiner,J.: 1993, IAU Inform. Bull. Var. Stars, 3882, 1
Unsuccessful search for an optical counterpart of GRS 1915+105.
- Rodriguez,L.F., Mirabel,I.F.: 1993, IAU Circ., 5900, 1.
- Mirabel,I.F., Duc,P.A., Teyssier,R., Paul,J., Rodriguez,L.F., Marti,J.:
1993, IAU Circ., 5830, 1
- Greiner,J.: 1993, IAU Circ., 5786, 1.
- Brandt,S., Castro-Tirado,A.J., Lund,N.: 1993, IAU Circ., 5779, 1.
GRS 1915+105 and Hercules X-1.
- Mirabel,I.F.: 1993, IAU Circ., 5773, 1.
- Lochner,J., Whitlock,L.: 1992, IAU Circ., 5658, 1.
GRS 1915+105 and B 1900+14.
- Harmon,B.A., Paciesas,W.S., Fishman,G.J.: 1992, IAU Circ., 5619, 1.
- Castro-Tirado,A.J., Brandt,S., Lund,N.: 1992, IAU Circ., 5590, 1.
Recent ASCA IAU Circulars Part 1 and
X-ray Binaries at Jodrell Bank
Physics News Update, No.193, Sept 6, 1994. A QUASAR-LIKE OBJECT
NEXUS NEWS 10th October 1994 (Small paragraph on 'QUASAR-LIKE OBJECT')
Physics News Update January 19 1995, Superluminal Jets from and Object (Schewe,P.F.: 1995,
- 1994, Science News, 146, 150. (Sept 3)
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