<i>Chandra</i>ACIS Subpixel Event Repositioning: Further Refinements and Comparison between Backside‐ and Frontside‐illuminated X‐Ray CCDs

Li, Jingqiang; Kastner, Joel H.; Prigozhin, G.; Schulz, Norbert S.; Feigelson, E. D.; Getman, Konstantin V.

doi:10.1086/421866

Cited by 117 publications

(111 citation statements)

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“…All the observations were reprocessed from the original level 2 event files following the default ACIS reprocessing steps. The reprocessing applies the sub-pixel event-repositioning algorithm EDSER 4 (Li et al 2004), which improves on-axis image resolution, thereby improving the resolution for the crowded centre of 47 Tuc. The intrinsic on-axis PSF of the Chandra mirrors for a typical spectrum is reasonably represented by a Gaussian with FWHM of 0.4 (Chandra POG 5 , chapter 7).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Bhattacharya

Heinke

Chugunov

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We combined Chandra ACIS observations of the globular cluster 47 Tucanae (hereafter, 47 Tuc) from 2000, 2002, and 2014-15 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2 .79) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chromospherically active BY Dra or W UMa variables identified by Albrow et al. (2001). We present alternative positions derived from two methods, centroiding and image reconstruction, for faint, crowded sources. We are able to extract X-ray spectra of the recently discovered MSPs 47 Tuc aa, 47 Tuc ab, the newly timed MSP 47 Tuc Z, and the newly resolved MSPs 47 Tuc S and 47 Tuc F. Generally, they are well fit by black body or neutron star atmosphere models, with temperatures, luminosities and emitting radii similar to those of other known MSPs in 47 Tuc, though 47 Tuc aa and 47 Tuc ab reach lower X-ray luminosities. We limit X-ray emission from the full surface of the rapidly spinning (542 Hz) MSP 47 Tuc aa, and use this limit to put an upper bound for amplitude of r-mode oscillations in this pulsar as α < 2.5 × 10 −9 and constrain the shape of the r-mode instability window.

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Section: Observations and Data Reductionmentioning

confidence: 99%

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Bhattacharya

Heinke

Chugunov

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…To better isolate the point-like sources we employed the sub-pixel repositioning (SER) algorithm (Li et al 2003). By employing this algorithm, we decrease the FWHM of the point spread function (PSF) by 40%-70% (Li et al 2003(Li et al , 2004Anderson et al 2011), thereby allowing us to use the smallest source extraction region possible. Nevertheless, diffuse X-ray emission may still contaminate the point source spectra, as we further discuss in Section 2.5.…”

Section: Data Preparationmentioning

confidence: 99%

THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

Montez

Kastner

Balick

et al. 2015

ApJ

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We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-rayemitting sources at PN cores display relatively "hard" ( 0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-ray emission: (1) high-temperature plasmas with X-ray luminosities, L X , that appear uncorrelated with the CSPN bolometric luminosity, L bol and (2) lower-temperature plasmas with L X /L bol ∼ 10 −7 . We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.

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“…Two techniques can be used to avoid aliasing on the pixel grid. Either the photon positions are randomized with offsets up to half a pixel or their positions are corrected with an energy-dependent subpixel event repositioning (EDSER, Li et al 2004). The first method leads to a well-characterized, but artificially broadened PSF; the second method is characterized less well and has been implemented in CIAO only recently, but it increases the resolution of the resulting images directly.…”

Section: Chandramentioning

confidence: 99%

The evolution of the jet from Herbig Ae star HD 163296 from 1999 to 2011

Günther

Schneider

2013

A&A

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Young A and B stars, the so-called Herbig Ae/Be stars (HAeBe), are surrounded by an active accretion disk and drive outflows. We study the jet HH 409, which is launched from the HAeBe star HD 163296, using new and archival observations from Chandra and HST/STIS. In X-rays we can show that the central source is not significantly extended. The approaching jet, but not the counter-jet, is detected in Lyα. In addition, there is red-shifted Lyα emission extended in the same direction as the jet, that is also absent in the counter-jet. We can rule out an accretion or disk-wind origin for this feature. In the optical we find the knots B and B2 in the counter-jet. Knot B has been observed previously, so we can derive its proper motion of (0.37 ± 0.01) yr −1 . Its electron density is 3000 cm −3 , thus the cooling time scale is a few months only, so the knot needs to be reheated continuously. The shock speed derived from models of Hα and forbidden emission lines (FELs) decreased from 50 km s −1 in 1999 to 30 km s −1 in 2011 because the shock front loses energy as it travels along the jet. Knot B2 is observed at a similar position in 2011 as knot B was in 1999, but shows a lower ionization fraction and higher mass loss rate, proving variations in the jet launching conditions.

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ChandraACIS Subpixel Event Repositioning: Further Refinements and Comparison between Backside‐ and Frontside‐illuminated X‐Ray CCDs

Cited by 117 publications

References 9 publications

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

The evolution of the jet from Herbig Ae star HD 163296 from 1999 to 2011

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