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    The Center of Expansion and Age of the Oxygen-rich Supernova Remnant 1E 0102.2-7219
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    Abstract:
    We present new proper motion measurements of optically emitting oxygen-rich knots of supernova remnant 1E 0102.2-7219 (E0102), which are used to estimate the remnant's center of expansion and age. Four epochs of high resolution Hubble Space Telescope images spanning 19 yr were retrieved and analyzed. We found a robust center of expansion of alpha=1:04:02.48 and delta=-72:01:53.92 (J2000) with 1-sigma uncertainty of 1.77 arcseconds using 45 knots from images obtained with the Advanced Camera for Surveys using the F475W filter in 2003 and 2013 having the highest signal-to-noise ratio. We also estimate an upper limit explosion age of 1738 +/- 175 yr by selecting knots with the highest proper motions, that are assumed to be the least decelerated. We find evidence of an asymmetry in the proper motions of the knots as a function of position angle. We conclude that these asymmetries were most likely caused by interaction between E0102's original supernova blast wave and an inhomogeneous surrounding environment, as opposed to intrinsic explosion asymmetry. The observed non-homologous expansion suggests that the use of a free expansion model inaccurately offsets the center of expansion and leads to an overestimated explosion age. We discuss our findings as they compare to previous age and center of expansion estimates of E0102 and their relevance to a recently identified candidate central compact object.
    Keywords:
    Proper motion
    Center (category theory)
    Position (finance)
    We have made the first direct interferometric proper-motion measurements of the radio pulsar PSR B1757-24, which sits at the tip of the "beak" of the putative "Duck" supernova remnant. The peculiar morphology of this radio complex has been used to argue alternately that the pulsar's space motion was either surprisingly high or surprisingly low. In fact, we show that the pulsar's motion is so small that it and its associated nonthermal nebula G5.27-0.9 (the "head") are almost certainly unrelated to the much larger G5.4-1.2 (the "wings").
    Proper motion
    Crab Nebula
    Citations (32)
    Abstract The bright radio pulsar B1727−47, with a characteristic age of 80 kyr, was among the first pulsars discovered 50 yr ago. Using regular timing observations and its interferometric positions at three epochs, we measured, for the first time, the pulsar proper motion of 151 ± 19 mas yr −1 . At the dispersion measure distance of ≳2.7 kpc, this would suggest a record transverse velocity of the pulsar of ≳1900 km s −1 . However, a backward extrapolation of the pulsar track to its birth epoch points remarkably close to the center of the evolved nearby supernova remnant RCW 114, which suggests genuine association of the two objects. In this case, the pulsar is substantially closer (∼0.6 kpc) and younger (∼50 kyr), and its velocity (∼400 km s −1 ) is compatible with the observed pulsar velocity distribution. We also identified two new glitches of the pulsar. We discuss implications of our results for the properties of the pulsar and the remnant.
    Proper motion
    Citations (11)
    We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tycho's supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the remnant (i.e., the forward shock and protruding ejecta knots) varies from 0".20 yr^{-1} (expansion index m=0.33, where R = t^m) to 0".40 yr^{-1} (m=0.65) with azimuthal angle in 2000-2007 measurements, and 0".14 yr^{-1} (m=0.26) to 0".40 yr^{-1} (m=0.65) in 2003-2007 measurements. The azimuthal variation of the proper motion and the average expansion index of ~0.5 are consistent with those derived from radio observations. We also find proper motion and expansion index of the reverse-shocked ejecta to be 0".21-0".31 yr^{-1} and 0.43-0.64, respectively. From a comparison of the measured m-value with Type Ia supernova evolutionary models, we find a pre-shock ambient density around the remnant of <~0.2 cm^{-3}.
    Proper motion
    "The Duck" is a complicated non-thermal radio system, consisting of the energetic radio pulsar B1757-24, its surrounding pulsar wind nebula G5.27-0.90 and the adjacent supernova remnant (SNR) G5.4-1.2. PSR B1757-24 was originally claimed to be a young (~15 000 yr) and extreme velocity (>~1500 km/s) pulsar which had penetrated and emerged from the shell of the associated SNR G5.4-1.2, but recent upper limits on the pulsar's motion have raised serious difficulties with this interpretation. We here present 8.5 GHz interferometric observations of the nebula G5.27-0.90 over a 12-year baseline, doubling the time-span of previous measurements. These data correspondingly allow us to halve the previous upper limit on the nebula's westward motion to 14 milliarcseconds/yr (5-sigma), allowing a substantive reevaluation of this puzzling object. We rule out the possibility that the pulsar and SNR were formed from a common supernova explosion ~15 000 yrs ago as implied by the pulsar's characteristic age, but conclude that an old (>~70 000 yr) pulsar / SNR association, or a situation in which the pulsar and SNR are physically unrelated, are both still viable explanations.
    Pulsar wind nebula
    Proper motion
    Pulsar planet
    Citations (14)
    Abstract We present a third epoch of Chandra observations of the Type Ia Large Magellanic Cloud Supernova remnant 0509-67.5. With these new observations from 2020, the baseline for proper-motion measurements of the expansion has grown to 20 yr (from the earliest Chandra observations in 2000). We report here the results of these new expansion measurements. The lack of nearby bright point sources renders absolute image alignment difficult. However, we are able to measure the average expansion of the diameter of the remnant along several projection directions. We find that the remnant is expanding with an average velocity of 6120 (4900–7360) km s −1 . This high shock velocity is consistent with previous works, and also consistent with the inference that 0509-67.5 is expanding into a very low density surrounding medium. At the distance of the LMC, this velocity corresponds to an undecelerated age of 600 yr, with the real age somewhat smaller.
    Proper motion
    Large Magellanic Cloud
    Epoch (astronomy)
    Small Magellanic Cloud
    Point source
    Citations (2)
    In this paper, we present updated estimates of the velocity of the neutron star (NS) in the supernova remnant (SNR) Cassiopeia A using over two decades of Chandra observations. We use two methods: 1.) recording NS positions from dozens of Chandra observations, including the astrometric uncertainty estimates on the data points but not correcting the astrometry of the observations, and 2.) correcting the astrometry of the 13 Chandra observations that have a sufficient number of point sources with identified Gaia counterparts. For method #1, we find velocity of 280 $\pm$ 123 km s$^{-1}$, with an angle of 87 $\pm$ 22 degrees south of east. For method #2, we find a velocity of 445 $\pm$ 90 km s$^{-1}$ at an angle of 68 $\pm$ 12 degrees south of east. Both of these results match with the explosion-center-estimated velocity of $\sim$350 km s$^{-1}$ and the previous 10 year baseline proper motion measurement of 570 $\pm$ 260 km s$^{-1}$, but our use of additional data over a longer baseline has led to a smaller uncertainty by a factor of 2$\unicode{x2013}$3. Our estimates rule out velocities $\gtrsim$600 km s$^{-1}$ and better match with simulations of Cassiopeia A that include NS kick mechanisms.
    Cassiopeia A
    Astrometry
    Proper motion
    Radial velocity
    Star (game theory)
    Citations (2)
    C 400.2 is a galactic supernova remnant with a complex morphology consist- ing of two overlapping shells of dieren t diameters: a large shell to the southeastern side and a small shell to the northwestern side. In order to decide whether this morphology is due to two supernova explosions or to the blow-out of one supernova explosion in a medium with a density gradient, we study the kinematics of both shells. H Fabry-Perot data are more in agreement with the scenario of only one supernova explosion undergoing a blow-out due to a density gradient in clumpy media.
    Near-Earth supernova
    Citations (2)
    We analyze data from the Hubble Space Telescope's (HST) Advanced Camera for Surveys of the globular cluster (GC) Omega Cen. We construct a photometric catalog of 1.2 × 106 stars over a 10' × 10' central field down to below BF435W = 25 (M ∼ 0.35 M☉). The 2.5 to 4 year baseline between observations yields a catalog of some 105 proper motions over a smaller area, with 53,382 "high-quality" measurements in a central R ≲ 2' field. Artificial-star tests characterize the photometric incompleteness. We determine the cluster center to ∼1'' accuracy from star counts using two different methods, one based on isodensity contours and the other on "pie slices." We independently confirm the result by determining also the kinematical center of the HST proper motions, as well as the center of unresolved light seen in Two Micron All Sky Survey data. All results agree to within their 1''–2'' levels of uncertainty. The proper-motion dispersion of the cluster increases gradually inward, but there is no variation in kinematics with position within the central ∼15'': there is no dispersion cusp and no stars with unusually high velocities. We measure for the first time in any GC the variation in internal kinematics along the main sequence. The variation of proper-motion dispersion with mass shows that the cluster is not yet in equipartition. There are no differences in proper-motion kinematics between the different stellar populations of Omega Cen. Our results do not confirm the arguments put forward by Noyola, Gebhardt, and Bergmann to suspect an intermediate-mass black hole (IMBH) in Omega Cen. They determined line-of-sight velocity dispersions in two 5'' × 5'' fields, and reported higher motions in their central field. We find the proper-motion kinematics to be the same in both fields. Also, we find that they (as well as other previous studies) did not accurately identify the cluster center, so that both of their fields are in fact 12'' from the true center. We also do not confirm the central density cusp they reported (in part due to the different center, and in part due to biases induced by their use of unresolved light). The surface number-density distribution near the center does not differ strongly from a single-mass King model, although a shallow cusp may not be ruled out. In the companion paper, which is Paper II in this series, we present new dynamical models for the high-quality data presented here, with the aim of putting quantitative constraints on the mass of any possible IMBH.
    Proper motion
    Mass segregation
    Citations (211)
    We present the results of a high-resolution imaging survey for brown dwarf binaries in the Pleiades open cluster. The observations were carried out with the Advance Camera for Surveys onboard the Hubble Space Telescope. Our sample consists of 15 bona-fide brown dwarfs. We confirm 2 binaries and detect their orbital motion, but we did not resolve any new binary candidates in the separation range between 5.4AU and 1700AU and masses in the range 0.035--0.065~Msun. Together with the results of our previous study (Martin et al., 2003), we can derive a visual binary frequency of 13.3$^{+13.7}_{-4.3}$\% for separations greater than 7~AU masses between 0.055--0.065~M$_{\sun}$ and mass ratios between 0.45--0.9$
    Pleiades
    Proper motion
    Visual binary
    Citations (34)
    ABSTRACT A recent measurement of the proper motion of PSR J0908–4913 shows that it is a fast-moving object at a distance of some 3 kpc. Here, we present evidence that the pulsar is located at the edge of a previously unknown, filled-centre supernova remnant (SNR), G270.4–1.0. The velocity vector of the pulsar points directly away from the centre of the remnant. The putative association of the pulsar with SNR G270.4–1.0 implies the pulsar is ∼12 kyr old, significantly less than its characteristic age of 110 kyr. We show that the rotation axis of the pulsar points in the direction of the proper motion. Rotation measure and dispersion measure variations are seen over time, likely indicating the pulsar is passing behind a filament of the remnant.
    Proper motion
    X-ray pulsar
    Crab Pulsar
    Citations (8)