PSR J1811-1925 in G11.2-0.3
K1 Chandra associates pulsar and historic supernova
PSR J1811-1925; (in G11.2-0.3 dist: ~ 5 kpc)
| PSR J1811-1925 in G11.2-0.3|
P = 64.7 ms; P' = 4.2×10-14 s s-1;
tc = P/2P' = 24 kyr;
B = 1.8·1012 G
E'rot = 6.4·1039 erg s-1
PSR J1811-1925 G11.2-0.3|
||Authors: Kaspi, V. M., Roberts, M. E., Vasisht, G., Gotthelf, E. V., Pivovaroff, M., & Kawai, N. |
||Journal-ref: ApJ 560 (2001) 371 [astro-ph/0107292 ]|
||Title: Chandra Observations of G11.2-0.3: Implications for Pulsar Ages|
We present Chandra X-ray Observatory imaging observations of the young Galactic supernova remnant G11.2-0.3.
The image shows that the previously known young 65-ms X-ray pulsar is at position (J2000) RA 18h 11m 29.22s,
DEC -19o 25'27.''6, with 1 sigma error radius 0.''6. This is within 8'' of the geometric center of the shell.
This provides strong confirming evidence that the system is younger, by a factor of ~12, than the
characteristic age of the pulsar.
The age discrepancy suggests that pulsar characteristic ages can be poor age
estimators for young pulsars. Assuming conventional spin down with constant
magnetic field and braking index, the most likely explanation for the age
discrepancy in G11.2-0.3 is that the pulsar was born with a spin period of ~62 ms.
The Chandra image also reveals, for the first time, the morphology of the
pulsar wind nebula. The elongated hard-X-ray structure can be interpreted as
either a jet or a Crab-like torus seen edge on. This adds to the growing list
of highly aspherical pulsar wind nebulae and argues that such structures are common around young pulsars.
[January 11, 2001] Scientists using NASA's
Chandra X-ray Observatory have found new evidence that a pulsar in the constellation of Sagittarius was
created when a massive star exploded, witnessed by Chinese astronomers in the year 386 AD. If confirmed, this
will be only the second pulsar to be clearly associated with a historic event.
The scientists used Chandra to locate the pulsar exactly at the
geometric center of the supernova remnant known as G11.2-0.3. This
location provides very strong evidence that the pulsar, a neutron star
that is rotating 14 times a second, was formed in the supernova of 386 AD,
and therefore has an age of 1615 years.
Chandra / Roberts
Fig. Comparison of X-ray PWN emission and radio emission:
red represents photons of energies 0.6--1.65~keV, green is 3.5~cm radio, and blue is 4-9 keV photons.
"Determining the true ages of astronomical objects is notoriously
difficult, and for this reason, historical records of supernovae are of great importance," said Kaspi.
In roughly the past 2,000 years, fewer than 10 reports of probable supernovae have been archived mostly by Asian
astronomers. Of those handful, the remnant of 1054 AD, the Crab Nebula,
was until now the only pulsar whose birth could be associated with a
historic event and, hence, the only neutron star that has a firm age.
Between mid-April and mid-May in the year 386 AD, a young "guest star,"
presumably a supernova, was recorded by Chinese observers in the direction
of the sky now known as the constellation of Sagittarius. In the 1970s,
radio astronomers discovered an expanding nebula of gas and high-energy
particles, called G11.2-0.3, that is believed to be the remnant of that
explosion. In 1997, a team of X-ray astronomers used Japan’s ASCA
satellite to discover a pulsar in the same area of the sky. Past attempts
to identify the pulsar with G11.2-0.3, and hence the ancient Chinese observations, have been controversial.
The location of the pulsar at the center of the remnant provides new
evidence that it is associated with the remnant. Since pulsars are known
to move rapidly away from where they are formed, a pulsar near the center
of the remnant implies the system must be very young, since not enough
time has elapsed for the pulsar to travel far from its birthplace.
"We believe that the pulsar and the supernova remnant G11.2-0.3 are
both likely to be left over from the explosion seen by the Chinese
observers over 1600 years ago," said Roberts. "While this is exciting by
itself, it also raises new questions about what we know about pulsars especially during their infancies."
These questions follow from a discrepancy that arose when the ASCA team
applied the present spin rate to current models to determine the pulsar's
estimated lifetime and compare it to the age of G11.2-0.3. The result was
an age of roughly 24,000 years far predating the birth year of 386 AD.
To explain this contradiction, the Chandra team argues that this pulsar
may have had approximately the same spin rate today as it did at its
birth, as had been suggested by the ASCA data. If this is true, then it
could have important implications for the conventional wisdom regarding
pulsars, which, may be born spinning more slowly than has been thought.
"We now have strong evidence that the standard age estimate for this
pulsar is probably wrong, and it is much younger than previously
believed," said Kaspi. "This, in turn, suggests that other standard pulsar
age estimates may be wrong as well, and this has important implications for the population as a whole."
In addition to these results, the Chandra observations of G11.2-0.3
have, for the first time, revealed the bizarre appearance of the pulsar
wind nebula (also known as "plerions") at the center of the supernova
remnant. Its rough cigar-like shape is in contrast to the graceful arcs
observed around the Crab and Vela pulsars. However, together with those
pulsars, G11.2-0.3 demonstrates that such complicated structures are
ubiquitous around young pulsars. This has left astronomers confounded.
Chandra observed G11.2-0.3 with the Advanced CCD Imaging Spectrograph
at two epochs: August 6, 2000, and October 15, 2000, for approximately 20,000 and 15,000 seconds respectively.
The Pulsar Wind Nebula in G11.2-0.3
E' = 6.4·1039 erg s-1|
||Authors: Roberts, M.S.E., Tam, C.R., Kaspi, V.M.,
Maxim Lyutikov, Gautam Vasisht, Michael Pivovaroff, E.V. Gotthelf, Nobuyuki Kawai |
||Journal-ref: ApJ 588 (2003) 992 [astro-ph/0206450 ]|
||Title: The Pulsar Wind Nebula in G11.2-0.3|
We present an X-ray and radio study of the wind nebula surrounding the central pulsar
PSR J1811-1925 in the supernova remnant G11.2-0.3.
Using high resolution data obtained with the Chandra X-ray observatory and with
the VLA radio telescope we show the X-ray and radio emission is asymmetric around the pulsar,
despite the latter's central position in the very circular shell.
The new X-ray data allow us to separate the synchrotron emission of the pulsar
wind nebula from the surrounding thermal emission and that from the pulsar itself.
Based on X-ray data from two epochs, we observe temporal variation of the location of
X-ray hot spots near the pulsar, indicating relativistic motion.
We compare thermal emission observed within the shell, which may be associated with
the forward shock of the pulsar wind nebula, to thermal emission from a nearby
portion of the remnant shell, the temperature of which implies an expansion velocity
consistent with the identification of the remnant with the historical event of 386 A.D.
The measured X-ray and radio spectral indices of the nebula synchrotron emission
are found to be consistent with a single synchrotron cooling break.
The magnetic field implied by the break frequency is anomalously large given the
apparent size and age of the nebula if a spherical morphology is assumed,
but is consistent with a bipolar morphology.
Image credit: Chandra / VLA / Roberts
Fig. G11.2-0.3: A Textbook Supernova
In Chandra's X-ray image, the pulsar and a cigar-shaped cloud of energetic particles, known as a pulsar
wind nebula, are predominantly seen as high-energy X-rays (blue). A shell of heated gas from the outer
layers of the exploded star surrounds the pulsar and the pulsar wind nebula and emits lower-energy X-rays
(represented in green and red).
 Pulsar J1811-1925 and supernova in the year 386 AD
A 65 ms pulsar with spin-down energy E' = 6.4·1039 erg s-1 was discovered in
X-rays by ASCA. The characteristic spin-down age is much greater than the apparent age of
the SNR and that inferred from its remarkably central position within the
remnant given any reasonable transverse velocity (Kaspi et al. 2001, hereafter Paper I).
The simplest explanation for this apparent age discrepancy is that the initial spin period of the pulsar is very
near the current spin period, which in turn suggests that E' has remained
nearly constant since the supernova explosion.
G11.2-0.3 is a remarkably spherical young SNR plausibly associated with the historical event of 386 A.D.
recorded by Chinese astrologers.
The distance to G11.2-0.3 has been reasonably well determined to be d ~ 5~kpc from HI measurements.
We therefore have a system where the assumptions of spherical symmetry, at least in regards to
the shell around the pulsar, and constant known energy input
are observationally supported, and reasonable estimates of the physical
size of various components can be made.
The bright spherical radio shell, reminiscent of the remnants of Tycho's and Kepler's supernovae, and the
lack of an obvious hard central component in the ROSAT PSPC image,
initially led some authors to conclude that G11.2-0.3 was the remnant of a Type Ia supernova.
Chandra / Roberts
Fig. ACIS observing epochs 1 (top) and
2 (bottom), smoothed with a 3'' Gaussian, and
3.5 cm (bottom) VLA X-band image with a 3.1'' ×
2.8'' restoring beam. The line in the images shows
the 1-D slice for the profiles shown in Figure 5.
The first hints of a central plerionic component came from high
frequency single dish radio measurements which suggested a central flattening
of the radio spectrum.
ASCA observations first clearly demonstrated that there was a central, non-thermal X-ray source.
This component was resolved by Chandra, the image of which has been presented in Paper I.
Further single dish radio observations have clearly demonstrated
the existence of a flat central radio component.
Archival VLA observations separate the central plerion from the shell and measure
the spectral index to be a_r ~ 0.25,
a fairly typical value (Tam, Roberts, & Kaspi 2002, hereafter Paper II).
In this paper we combine the radio data with the Chandra data to make spectral measurements
of the pulsar itself, the hard pulsar wind nebula, and soft thermal
emission possibly related to the PWN which we compare to a portion of the shell.
We also present evidence for apparent temporal variation in the positions of emission features in
the central portion of the X-ray PWN, and make a detailed comparison of the X-ray morphology with a
new 3.5~cm VLA image.
Tam, C., Roberts, M. S. E., & Kaspi, V. M. 2002, ApJ, 572, 202 (Paper II)
Kaspi, V. M. & Helfand, D. J. 2002, To appear in Neutron Stars in Supernova Remnants (ASP
Conference Proceedings), eds P. O. Slane and B. M. Gaensler
Phase Coherent Timing of PSR J18111925: The Pulsar at the Heart of G11.20.3
PSR J1811-1736 (highly eccentric binary system)
Discovery of PSR J1811-1736
|n'||-1.01×10-11 Hz s-1|
|n''||1.4×10-20 Hz s-2|
| n =
|P ||64.677 ms|
|P' ||4.2×10-14 s s-1|
Comparing the efficiencies calculated by Possenti et al. (2002) for the 41
known rotation-powered X-ray pulsars,
PSR J18111925 is the third most efficient, with
PSR J18460258 (Gotthelf et al., 2000) being the first, and
PSR B150958 (Cusumano et al., 2001) the second.
Cusumano et al., A&A, 375 (2001) 397404
Crab: Correlated radio and X-ray Structures in Pulsar Wind Nebulae
Crab nebula - PWN - Pulsar Wind Nebulae|
||Authors: Mallory S.E. Roberts, Maxim Lyutikov, Bryan M. Gaensler, Crystal Brogan,
Cindy R. Tam, Roger W. Romani|
||ref: "X-Ray and Radio Connections" (2004) [astro-ph/0406592
||Title: Ain't No Crab, PWN Got A Brand New Bag:
Correlated radio and X-ray Structures in Pulsar Wind Nebulae|
|Abstract: The traditional view of radio pulsar wind nebulae (PWN),
encouraged by the Crab nebula's X-ray and radio morphologies, is that they are a result of the
integrated history of their pulsars' wind. The radio emission should therefore be largely
unaffected by recent pulsar activity, and hence minimally correlated with structures
in the X-ray nebulae. Observations of several PWN, both stationary (sPWN) and rapidly moving
(rPWN), now show clear morphological relationships between structures in the radio and X-ray
with radio intensity variations on the order of unity. We present high-resolution X-ray and
radio images of several PWN of both types and discuss the morphological relationships between the two wavebands.
||Authors: Bryan M. Gaensler|
||Ref: IAU Symposium, Vol. 218, (2004) [astro-ph/0405290 ]|
||Title: Shocks and Wind Bubbles Around Energetic Pulsars|
The Crab Nebula demonstrates that neutron stars can interact with
their environments in spectacular fashion, their relativistic winds generating
nebulae observable across the electromagnetic spectrum. At many previous
conferences, astronomers have discussed, debated and puzzled over the
complicated structures seen in the Crab, but have been limited to treating
most other pulsar wind nebulae (PWNe) as simple calorimeters for a pulsar's
spin-down energy. However, with the wealth of high-quality data which have now
become available, this situation has changed dramatically. I here review some
of the main observational themes which have emerged from these new
measurements. Highlights include the ubiquity of pulsar termination shocks,
the unambiguous presence of relativistic jets in PWNe, complicated time
variability seen in PWN structures, and the use of bow shocks to probe the
interaction of pulsar winds with the ambient medium.
Image credit: Chandra / ATCA / AAO / Gaensler
Examples of the three broad phases in PWN evolution.
(a) Chandra X-ray image of the Crab Nebula;
(b) ATCA radio image of SNR B0453685 in the LMC;
(c) AAO Ha (greyscale) and Chandra
X-ray (contours) images of the bow shock powered by PSR B1957+20.
PSR J1509-5850 and PSR J1740+1000 Parsec-Scale Tails
PSR J1509-5850 d = 4 kpc P = 89 ms NH = 2.1 × 1022 cm-2
LX(0.5-8 keV) ~ 1 × 1033 erg s-1
PSR J1740+1000 d = 1.4 kpc P = 154 ms NH = 1 × 1022 cm-2
LX(0.5-8 keV) ~ 2 × 1033 erg s-1
||Authors: O. Kargaltsev, Z. Misanovic, G. G. Pavlov, J. A. Wong, G. P. Garmire|
||Journal-ref: (2008) [0802.2963 ]|
||Title: X-ray Observations of Parsec-Scale Tails behind Two Middle-Aged Pulsars|
Chandra and XMM-Newton resolved extremely long tails behind two middle-aged pulsars, J1509-5850 and J1740+1000.
The tail of PSR J1509-5850 is discernible up to
5.6' from the pulsar (6.5 pc at a distance of 4 kpc), with a flux of
fX(0.5-8 keV) = 2 × 10-13 erg cm-2 s-1.
The tail spectrum fits an absorbed power-law (PL) model with the photon index of
G = 2.3 ± 0.2, corresponding to the luminosity of
LX(0.5-8 keV) ~ 1 × 1033 erg s-1, for
NH = 2.1 × 1022 cm-2.
The tail of PSR J1740+1000 is firmly detected up to 5' (2 pc at a 1.4 kpc
distance), with a flux of
fX(0.4-10 keV) = 4.2 × 10-12 erg cm-2 s-1.
The PL fit yields photon index of G = 1.45 ± 0.05 and
NH = 1 × 1021 cm-2.
The large extent of the tails suggests that the bulk flow in the tails starts as mildly
relativistic downstream of the termination shock, and then gradually decelerates.
Within the observed extent of the J1509-5850 tail, the average
flow speed exceeds 5,000 km s-1, and the equipartition magnetic field is a
few times 10-5 G.
For the J1740+1000 tail, the equipartition field is a
factor of a few lower. The harder spectrum of the J1740+1000 tail implies
either less efficient cooling or a harder spectrum of injected electrons. For
the high-latitude PSR J1740+1000, the orientation of the tail on the sky shows
that the pulsar is moving toward the Galactic plane, which means that it was
born from a halo-star progenitor.
The comparison between the J1509 and J1740
tails and the X-ray tails of other pulsars shows that the X-ray radiation
efficiency correlates poorly with the pulsar spin-down luminosity or age. The
X-ray efficiencies of the ram-pressure confined pulsar wind nebulae (PWNe) are
systematically higher than those of PWNe around slowly moving pulsars with
similar spin-down parameters.
Thanks to the high sensitivity and angular resolution of the Chandra and XMM-Newton observatories, about
50 PWNe have been detected in X-rays (Kaspi et al. 2006; Gaensler & Slane 2006; Kargaltsev
& Pavlov 2008, hereafter KP08). The X-ray observations have shown that PWNe have complex morphologies,
including toroidal structures around the pulsar, jets along the pulsars spin axis, and cometary tails
(see KP08 for Chandra images).
The well-known example of such a bowshock-tail PWN is the Mouse PWN produced
by the young, energetic pulsar J1747-2958 (tc = 26 kyr,
E'rot = 2.5 × 1036 erg s-1), which shows an X-ray tail
of the projected length lortogonal ~ 1 pc (Gaensler et al. 2004).
In addition to the Mouse, about a dozen X-ray PWNe with bowshock-tail morphologies have been discovered
recently (KP08). Interestingly, one of the longest tails, lortogonal ~ 1.5 pc, was found
behind the 3 Myr old pulsar B1929+10, with a relatively low spin-down power,
E'rot = 3.8 × 1033 erg s-1 (Wang et al. 1993; Becker et al. 2006;
Misanovic et al. 2007).
Although most of the known PWNe are powered by much younger and more powerful pulsars, it has been noticed
(Kargaltsev et al. 2007) that bowshock PWNe with extended tails are generally brighter than PWNe around slowly
PSR J15095850 (hereafter J1509) was discovered in the Parkes Multibeam Pulsar Survey (Kramer et al.
2003). The pulsar is located in the Galactic plane at the dispersion measure (DM) distance of about 4 kpc.
To study the X-ray properties of the pulsar and look for its PWN, we observed this field with Chandra.
In addition to detecting the pulsar, the observation revealed a spectacular long tail, first reported by
Kargaltsev et al. (2006). It was briefly described by Hui & Becker (2007; hereafter HB07), who also reported
the discovery of diffuse radio emission, possibly associated with the tail.
Becker, W., et al. 2006, ApJ, 645, 1421
Gaensler, B.M., & Slane, P.O. 2006, ARA&A 44, 17
Hui, C.Y., Becker, W. 2007, A&A, 470, 965 [0704.1265 ]
Radio and X-ray nebulae associated with PSR J1509-5850 (HB07)
Kargaltsev, O., & Pavlov, G. G. 2008, in 40 Years of Pulsars (KP08)
Kargaltsev, O., Pavlov, G.G., Sanwal, D., Wong, J., & Garmire, G.P. 2006, BAAS 38, 359
Kaspi, V.M., Roberts, M.S.E., & Harding, A.K. 2006, CUP
Kramer, M., et al. 2003, MNRAS 342, 1299
Misanovic, Z., Pavlov, G. G., & Garmire, G. P. 2007, ApJ,
Wang, Q.D., Li, Z.-Y., & Begelman, M.C. 1993, Nature 364, 127
The X-ray-emitting trail of the nearby pulsar PSR1929 + 10
K5 PSR J1811-1925 and its PWN (INTEGRAL)
PSR J1811-1925 d ~ 5 kpc |
||Authors: A.J. Dean, A. De Rosa, V.A. McBride, R. Landi, A.B. Hill, L. Bassani, A. Bazzano,
A.J. Bird, P. Ubertini|
||Journal-ref: MNRAS 384 (2008) L29 [0711.0648 ]|
||Title: INTEGRAL observations of PSR J1811-1925 and its associated Pulsar Wind Nebula|
We present spectral measurements made in the soft (20-100 keV) gamma-ray band of the
region containing the composite supernova remnant G11.2-0.3 and its associated
pulsar PSR J1811-1925.
Analysis of INTEGRAL/IBIS data allows characterisation
of the system above 10 keV. The IBIS spectrum is best fitted by a power law
having photon index of G = 1.8 ± 0.3 and a flux of
fX(20-100 keV) = 1.5 × 10-11 erg cm-2 s-1.
Analysis of archival Chandra data over different energy bands
rules out the supernova shell as the site of the soft gamma-ray emission while
broad band (1-200 keV) spectral analysis strongly indicates that the
INTEGRAL/IBIS photons originate in the central zone of the system which
contains both the pulsar and its nebula.
The composite X-ray and soft gamma-ray spectrum indicates that the pulsar provides around half of the
emission seen in the soft gamma-ray domain; its spectrum is hard with no sign of a cut off up to at least 80 keV.
The other half of the emission above 10 keV comes from the PWN; with a power law slope of 1.7 its spectrum
is softer than that of the pulsar.
From the IBIS/ISGRI mosaics we are able to derive 2
sigma upper limits for the flux from the location of the nearby TeV source HESS J1809-193 to be
fX(20-100 keV) = 4.8 × 10-12 erg cm-2 s-1.
Image credit: INTEGRAL / A.J. Dean et al
Fig. 1. INTEGRAL IBIS/ISGRI 1860 keV image of the region around PSR J1811-1925. Note that the image structure around the position of
PSR J1809-1917 is well below the detection threshold as determined by Bird et al. (2007) for the 3rd IBIS/ISGRI
catalogue. The fit ellipse (Aharonian et al. 2007) of the extended HESS source is reported with a magenta
ellipse. In the inset we show the Chandra images (~ 5' × 5') in 0.22 keV (left) and 48 keV (right).
We have also examined the likelihood of an association between PSR J1811-1925 and HESS J1809-193.
Although PSR J1811-1925 is the most energetic pulsar in the region, the only
one detected above 10 keV and thus a possible source of energy to fuel the TeV
fluxes, there is no morphological evidence to support this pairing, making it an unlikely counterpart.
2 PSR J1811-1925
An interesting case to investigate is the 65ms pulsar
PSR J1811-1925, discovered in X-rays by ASCA in the supernova remnant (SNR) G11.2-0.3 (Torii et al. 1997).
It is a composite SNR showing both an extended shell component and a compact plerionic component. This
discovery strongly suggests a direct association of the pulsar with the SNR and with a guest
star witnessed by Chinese astronomers in A.D. 386 as proposed by Clark & Stephenson (1977).
The distance of the system is ~ 5 kpc as inferred from H I measurements.
Thanks to X-ray observations performed by Chandra (Kaspi et al. 2001) it was possible to
localise the pulsar to within a few arc seconds from the geometric
centre of the shell of the SNR (Tam & Roberts 2003), thus
providing an indication that the system may be young.
The system PSR J1811-1925/G11.2-0.3 is located near the TeV source HESS J1809-193, recently discovered by
the HESS telescope array (Aharonian et al. 2007). Although the pulsar is energetic enough to power the high
energy gamma-rays, the association with the TeV source is not likely since the pulsar is clearly the companion
of G11.2-0.3 and HESS J1809-193 is offset from the supernova remnant, implying that PSR J1811-1925
could not have produced the TeV source due to its motion.
The likelihood of an association is further questioned by the presence of
a second pulsar/PWN system, J1809-1917 (Kargaltsev & Pavlov 2007), which is closer to the centroid of the
HESS source and also capable of supplying sufficient energy from the pulsar to power HESS J1809-193.
Aharonian, F., Akhperjanian, A.G., Bazar-Bachi, A.R. et al, 2007, A&A
Kargaltsev, O. & Pavlov, G.G., 2007,
Kaspi, V.M., Roberts, M.E., Vasisht, et al., 2001, ApJ 560, 371
Roberts, M.S.E., Tam, C.R., Kaspi, V.M. et al., 2003, ApJ 588, 992
Tam, C. & Roberts, M.S.E., 2003, ApJ 598, 30
Torii, K., Tsunemi, H., Dotani, T., & Mitsuda, K. 1997, ApJ 489, 145 (PSR J1811-1925)
Torii, K., et al. 1998, ApJ 494, L207 (PSR J1617-5055 in RCW 103)
|Literatur zu ""|
|Kaspi, V.M., Roberts, M.E., Vasisht, G., Gotthelf, E.V., |
Pivovaroff, M., & Kawai, N.
|2001||ApJ 560, 371||
"Chandra Observations of G11.2-0.3: Implications for Pulsar Ages"
|Roberts, M.S.E., Tam, C.R., Kaspi, V.M., et al.||2003||ApJ 588, 992||
"The Pulsar Wind Nebula in G11.2-0.3"
|Dean, A. J.; de Rosa, A.; McBride, V. A.; et al.||2008||MNRAS 384, L29||
"INTEGRAL observations of PSR J1811-1925 and its associated Pulsar Wind Nebula"
|H. Heintzmann||( Eintrag vom 17.4.2008) ||