695 research outputs found
The first deep X-ray and optical observations of the closest isolated radio pulsar
With a distance of 170 pc, PSR J2144-3933 is the closest isolated radio
pulsar currently known. It is also the slowest and least energetic radio
pulsar; indeed, its radio emission is difficult to account for with standard
pulsar models, since its position in the P-Pdot diagram is far beyond typical
"death lines". Here we present the first deep X-ray and optical observations of
PSR J2144-3933, performed in 2009 with XMM-Newton and the VLT, from which we
can set one of the most robust upper limits on the surface temperature of a
neutron star. We have also explored the possibility of measuring the neutron
star mass from the gravitational lensing effect on a background optical source.Comment: 4 pages, 3 figures; to appear in the Proceedings of the Pulsar
Conference 2010, Chia, Sardinia (Italy), 10-15 October 201
Constraining the optical emission from the double pulsar system J0737-3039
We present the first optical observations of the unique system J0737-3039
(composed of two pulsars, hereafter PSR-A and PSR-B). Ultra-deep optical
observations, performed with the High Resolution Camera of the Advanced Camera
for Surveys on board the Hubble Space Telescope could not detect any optical
emission from the system down to m_F435W=27.0 and m_F606W=28.3. The estimated
optical flux limits are used to constrain the three-component (two thermal and
one non-thermal) model recently proposed to reproduce the XMM-Newton X-ray
spectrum. They suggest the presence of a break at low energies in the
non-thermal power law component of PSR-A and are compatible with the expected
black-body emission from the PSR-B surface. The corresponding efficiency of the
optical emission from PSR-A's magnetosphere would be comparable to that of
other Myr-old pulsars, thus suggesting that this parameter may not dramatically
evolve over a time-scale of a few Myr.Comment: 16 pages, 3 figures, ApJ accepte
Detection of continuum radio emission associated with Geminga
A deep Very Large Array observation of the Geminga pulsar field led to the
discovery, at a higher than 10 sigma significance level, of radio emission
trailing the neutron star proper motion. This 10-arcsec-long radio feature,
detected with a flux of 0.4 mJy at 4.8 GHz, is marginally displaced (2.7\pm1.8
arcsec) from the pulsar (which, at any rate, is unlikely to contribute with
magnetospheric pulsed emission more than 15% to the total observed radio
luminosity, about 1E26 erg/s) and positionally coincident with the X-ray axial
tail recently discovered by Chandra and ascribed to the pulsar wind nebula
(PWN). Overall, the Geminga radio tail is compatible with the scenario of a
synchrotron-emitting PWN, but the present data do not allow us to discriminate
between different (and not always necessarily mutually exclusive) possible
processes for producing that. If this radio feature does not result from
intrinsic peculiarities of Geminga, but its proximity and radio-quiet nature
(both helping in not hindering the faint diffuse radio emission), other
relatively near and energetic radio-quiet pulsars could show similar structures
in dedicated interferometric observations.Comment: Version accepted by MNRAS Letters (new title and substantial changes
in response to referees reports); 5 pages, 2 colour figure
Long Term Study of the Double Pulsar J0737-3039 with XMM-Newton: pulsar timing
The relativistic double neutron star binary PSR J0737-3039 shows clear
evidence of orbital phase-dependent wind-companion interaction, both in radio
and X-rays. In this paper we present the results of timing analysis of PSR
J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that
collected ~20,000 X-ray counts from the system. We detected pulsations from PSR
J0737-3039A (PSR A) through the most accurate timing measurement obtained by
XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR A's pulse
profile in X-rays is very stable despite significant relativistic spin
precession that occurred within the time span of observations. This yields a
constraint on the misalignment between the spin axis and the orbital momentum
axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio
data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even
after its disappearance in radio. The unusual phenomenology of PSR B's X-ray
emission includes orbital pulsed flux and profile variations as well as a loss
of pulsar phase coherence on time scales of years. We hypothesize that this is
due to the interaction of PSR A's wind with PSR B's magnetosphere and
orbital-dependent penetration of the wind plasma onto PSR B closed field lines.
Finally, the analysis of the full XMM-Newton dataset provided evidences of
orbital flux variability (~7%) for the first time, involving a bow-shock
scenario between PSR A's wind and PSR B's magnetosphere.Comment: Comments: 16 Pages, 6 Figures. Accepted for publication in
Astrophysical Journal (Draft Version
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