64 research outputs found
Multiwavelength properties of a new Geminga-like pulsar: PSR J2021+4026
In this paper, we report a detailed investigation of the multiwavelength
properties of a newly detected gamma-ray pulsar, PSR J2021+4026, in both
observational and theoretical aspects. We firstly identify an X-ray source in
the XMM-Newton serendipitous source catalogue, 2XMM J202131.0+402645, located
within the 95% confidence circle of PSR J2021+4026. With an archival Chandra
observation, this identification provides an X-ray position with arcsecond
accuracy which is helpful in facilitating further investigations. Searching for
the pulsed radio emission at the position of 2XMM J202131.0+402645 with a 25-m
telescope at Urumqi Astronomical Observatory resulted in null detection and
places an upper-limit of 0.1~mJy for any pulsed signal at 18~cm. Together with
the emission properties in X-ray and gamma-ray, the radio quietness suggests
PSR J2021+4026 to be another member of Geminga-like pulsars. In the radio sky
survey data, extended emission features have been identified in the gamma-ray
error circle of PSR J2021+4026. We have also re-analyzed the gamma-ray data
collected by FERMI's Large Area Telescope. We found that the X-ray position of
2XMM J202131.0+402645 is consistent with that of the optimal gamma-ray timing
solution. We have further modeled the results in the context of outer gap model
which provides us with constraints for the pulsar emission geometry such as
magnetic inclination angle and the viewing angle. We have also discussed the
possibility of whether PSR J2021+4026 has any physical association with the
supernova remnant G78.2+2.1 (gamma-Cygni).Comment: 11 pages, 14 figure
XMM-Newton observation of PSRB2224+65 and its jet
We have investigated the pulsar PSRB2224+65 and its X-ray jet with XMM-Newton. Apart from the long X-ray jet which is almost perpendicular to the direction of proper motion, a putative extended feature at the pulsar position, which is oriented in the opposite direction to the proper motion, is also suggested by this deep X-ray imaging. Non-detection of any coherent X-ray pulsation disfavors the magnetospheric origin of the X-rays observed from the position of PSRB2224+65 and hence suggests that the interpretation of pulsar wind nebula is more viable. We have also probed the origin of PSRB2224+65 and identified a runaway star, which possibly originated from the Cygnus OB9 association, as a candidate for the former binary companion of the neutron star's progenitor. © 2012. The American Astronomical Society. All rights reserved.postprin
WASP-14 b: Transit Timing analysis of 19 light curves
Although WASP-14 b is one of the most massive and densest exoplanets on a
tight and eccentric orbit, it has never been a target of photometric follow-up
monitoring or dedicated observing campaigns. We report on new photometric
transit observations of WASP-14 b obtained within the framework of "Transit
Timing Variations @ Young Exoplanet Transit Initiative" (TTV@YETI). We
collected 19 light-curves of 13 individual transit events using six telescopes
located in five observatories distributed in Europe and Asia. From light curve
modelling, we determined the planetary, stellar, and geometrical properties of
the system and found them in agreement with the values from the discovery
paper. A test of the robustness of the transit times revealed that in case of a
non-reproducible transit shape the uncertainties may be underestimated even
with a wavelet-based error estimation methods. For the timing analysis we
included two publicly available transit times from 2007 and 2009. The long
observation period of seven years (2007-2013) allowed us to refine the transit
ephemeris. We derived an orbital period 1.2 s longer and 10 times more precise
than the one given in the discovery paper. We found no significant periodic
signal in the timing-residuals and, hence, no evidence for TTV in the system.Comment: 12 pages, 10 figures, 7 table
Discovery of X-ray Pulsation from the Geminga-like Pulsar PSR J 2021+4026
published_or_final_versio
Identification campaign of supernova remnant candidates in the Milky Way - I: Chandra observation of G308.3-1.4
ROSAT all-sky survey (RASS) data have provided another window to search for
supernova remnants (SNRs). In reexamining this data archive, a list of
unidentified extended X-ray objects have been suggested as promising SNR
candidate. However, most of these targets have not yet been fully explored by
the state-of-art X-ray observatories. For selecting a pilot target for a
long-term identification campaign, we have observed the brightest candidate,
G308.3-1.4, with Chandra X-ray observatory. An incomplete shell-like X-ray
structure which well-correlated with the radio shell emission at 843 MHz has
been revealed. The X-ray spectrum suggests the presence of a shock-heated
plasma. All these evidences confirm G308.3-1.4 as a SNR. The brightest X-ray
point source detected in this field-of-view is also the one locates closest to
the geometrical center of G308.3-1.4, which has a soft spectrum. The intriguing
temporal variability and the identification of optical/infrared counterpart
rule out the possibility of an isolated neutron star. On the other hand, the
spectral energy distribution from Ks band to R band suggests a late-type star.
Together with a putative periodicity of \sim1.4 hrs, the interesting excesses
in V, B bands and H-alpha suggest this source as a promising candidate of a
compact binary survived in a supernova explosion (SN).Comment: 19 pages, 10 figures, 2 tables, accepted for publication in Ap
Towards the Rosetta Stone of planet formation
Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of
their host systems may serve as the Rosetta Stone for planet formation
theories. They would give strong constraints on several aspects of planet
formation, e.g. time-scales (planet formation would then be possible within 10
Myrs), the radius of the planet could indicate whether planets form by
gravitational collapse (being larger when young) or accretion growth (being
smaller when young). We present a survey, the main goal of which is to find and
then characterise TEPs in very young open clusters.Comment: Poster contribution to Detection and Dynamics of Transiting
Exoplanets (Haute Provence Observatory Colloquium, 23-27 August 2010
A Detailed X-Ray Investigation of PSR J2021+4026 and the γ-Cygni Supernova Remnant
published_or_final_versio
Is there a compact companion orbiting the late O-type binary star HD 164816?
We present a multi-wavelength (X-ray, -ray, optical and radio) study
of HD 194816, a late O-type X-ray detected spectroscopic binary. X-ray spectra
are analyzed and the X-ray photon arrival times are checked for pulsation. In
addition, newly obtained optical spectroscopic monitoring data on HD 164816 are
presented. They are complemented by available radio data from several large
scale surveys as well as the \emph{FERMI} -ray data from its
\emph{Large Area Telescope}. We report the detection of a low energy excess in
the X-ray spectrum that can be described by a simple absorbed blackbody model
with a temperature of 50 eV as well as a 9.78 s pulsation of the X-ray
source. The soft X-ray excess, the X-ray pulsation, and the kinematical age
would all be consistent with a compact object like a neutron star as companion
to HD 164816. The size of the soft X-ray excess emitting area is consistent
with a circular region with a radius of about 7 km, typical for neutron stars,
while the emission measure of the remaining harder emission is typical for late
O-type single or binary stars. If HD 164816 includes a neutron star born in a
supernova, this supernova should have been very recent and should have given
the system a kick, which is consistent with the observation that the star HD
164816 has a significantly different radial velocity than the cluster mean. In
addition we confirm the binarity of HD 164816 itself by obtaining an orbital
period of 3.82 d, projected masses = 2.355(69) M,
= 2.103(62) M apparently seen at low inclination
angle, determined from high-resolution optical spectra.Comment: Accepted for publication by MNRAS, 11 pages, 6 figures, 4 table
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