204 research outputs found
A supernova remnant coincident with the slow X-ray pulsar AX J1845-0258
We report on Very Large Array observations in the direction of the
recently-discovered slow X-ray pulsar AX J1845-0258. In the resulting images,
we find a 5-arcmin shell of radio emission; the shell is linearly polarized
with a non-thermal spectral index. We class this source as a previously
unidentified, young (< 8000 yr), supernova remnant (SNR), G29.6+0.1, which we
propose is physically associated with AX J1845-0258. The young age of G29.6+0.1
is then consistent with the interpretation that anomalous X-ray pulsars (AXPs)
are isolated, highly magnetized neutron stars ("magnetars"). Three of the six
known AXPs can now be associated with SNRs; we conclude that AXPs are young
(~<10 000 yr) objects, and that they are produced in at least 5% of
core-collapse supernovae.Comment: 4 pages, 1 embedded EPS file, uses emulateapj.sty. Accepted to ApJ
Letter
Preparation & Characterization of Dimethylformamidyl Substituted Titanium( IV) Compounds
456-45
Precision Near Infrared Photometry For Exoplanet Transit Observations - I : Ensemble Spot Photometry for An All-Sky Survey
Near-IR observations are important for the detection and characterization of
exoplanets using the transit technique, either in surveys of large numbers of
stars or for follow-up spectroscopic observations of individual planets. In a
controlled laboratory experiment, we imaged critically sampled
spots onto an Teledyne Hawaii-2RG (H2RG) detector to emulate an idealized
star-field. We obtained time-series photometry of up to hr duration
for ensembles of pseudo-stars. After rejecting correlated temporal
noise caused by various disturbances, we measured a photometric performance of
50 ppm-hr limited only by the incident photon rate. After several
hours we achieve a photon-noise limited precision level of ppm after
averaging many independent measurements. We conclude that IR detectors such as
the H2RG can make the precision measurements needed to detect the transits of
terrestrial planets or detect faint atomic or molecular spectral features in
the atmospheres of transiting extrasolar planets.Comment: 15 pages, 15 figures. Accepted to PASP. For a brief video explaining
the key result of this paper, see http://www.youtube.com/user/OSUAstronom
Detection of a Compact X-ray Source in the Supernova Remnant G29.6+0.1: A Variable Anomalous X-ray Pulsar?
We present follow-up observations of the serendipitously discovered 7-s X-ray
pulsar AX J1845-0258, which displays characteristics similar to those observed
in the anomalous X-ray pulsars (AXPs). We find a dramatic reduction in its 3-10
keV flux in both new ASCA and RXTE datasets. Within the pulsar's position-error
locus, we detect a faint point source, AX J184453-025640, surrounded by an arc
of diffuse X-ray emission. This arc is coincident with the South-East quadrant
of the radio shell of the newly discovered supernova remnant G29.6+0.1,
reported in our companion paper (Gaensler et al. 1999). Lack of sufficient flux
from the source prevents us from confirming the 7-s pulsed emission observed in
the bright state; hence, at present we cannot definitively resolve whether AX
J1845-0258 and AX J184453-025640 are one and the same. If they are the same,
then the peak-to-peak luminosity changes recorded for AX J1845-0258 may be
larger than seen in other AXPs; closer monitoring of this pulsar might lead to
a resolution on the mechanism that drives AXPs.Comment: 5 pages with 2 figures, LaTex, emulateapj.sty. To appear in the
Astrophysical Journal Letter
A third red supergiant rich cluster in the Scutum-Crux arm
Aims. We aim to characterise the properties of a third massive, red supergiant dominated galactic cluster.
Methods. To accomplish this we utilised a combination of near/mid-IR photometry and spectroscopy to identify and classify the properties of cluster members, and statistical arguments to determine the mass of the cluster.
Results. We found a total of 16 strong candidates for cluster membership, for which formal classification of a subset yields spectral types from K3-M4 Ia and luminosities between log(L/L-circle dot) similar to 4.5-4.8 for an adopted distance of 6 +/- 1 kpc. For an age in the range of 16-20 Myr, the implied mass is 2-4 x 10(4) M-circle dot, making it one of the most massive young clusters in the Galaxy. This discovery supports the hypothesis that a significant burst of star formation occurred at the base of Scutum-Crux arm between 10-20 Myr ago, yielding a stellar complex comprising at least similar to 10(5) M-circle dot of stars (noting that since the cluster identification criteria rely on the presence of RSGs, we suspect that the true stellar yield will be significantly higher). We highlight the apparent absence of X-ray binaries within the star formation complex and finally, given the physical association of at least two pulsars with this region, discuss the implications of this finding for stellar evolution and the production and properties of neutron stars
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.Comment: 16 pages, 3 figures, Accepted for publication in ApJ. For a full
resolution version of Fig 1, see
http://www.physics.mcgill.ca/~vkaspi/G11.2-0.3/f1.ep
Palomar Testbed Interferometer
The Palomar Testbed Interferometer (PTI) is an infrared, phase-tracking interferometer in operation at Palomar Mountain since July 1995. It was funded by NASA for the purpose of developing techniques and methodologies for doing narrowangle astrometry for the purpose of detecting extrasolar planets. The instrument employs active fringe trackingin the infrared (2.0-2.4 ÎŒm) to monitor fringe phase. It is a dual-star interferometer; it is able to measure fringes on two separate stars simultaneously. An end-to-end heterodyne laser metrology system is used to monitor the optical path length of the starlight. Recently completed engineering upgrades have improved the initial instrument performance. These upgrades are:extended wavelength coverage, a single mode fiber for spatial filtering, vacuum pipes to relay the beams, accelerometers on the siderostat mirrors and a new baseline. Results of recent astrometry data indicate the instrument is approaching the astrometric limit as set by the atmosphere
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