The enigma source, RX J1856.5-3754, is one of the so-called dim thermal neutron stars. Two puzzles of RXJ1856.5-3754 exist: (1) the observational X-ray spectrum is completely featureless; (2) the UV-optical intensity is about seven times larger than that given by the continuation of the blackbody model yielded by the X-ray data. Both the puzzles would not exist anymore if RX J1856.5-3754 is a l...

RX J1856.5−3754, a bright soft X-ray source believed to be the nearest thermally emitting neutron star, has commanded and continues to command intense interest from X-ray missions. One of the main goals is to determine the radius of this neutron star. An integral part of the determination is an accurate parallax. Walter (2001) analyzed Hubble Space Telescope (HST ) data and derived a parallax, ...

1. Multifunctional Initiators. 3749 2. Multifunctional Linking Agents 3751 3. Use of Difunctional Monomers 3754 B. Star−Block Copolymers 3754 C. Functionalized Stars 3755 1. Functionalized Initiators 3755 2. Functionalized Terminating Agents 3756 D. Asymmetric Stars 3757 1. Molecular Weight Asymmetry 3757 2. Functional Group Asymmetry 3760 3. Topological Asymmetry 3761 E. Miktoarm Star Polymers...

The isolated neutron star RX J185635-3754 is the closest known neutron star to the Sun. Based on HST WFPC2 obervations over a 3 year baseline, I report its proper motion (332±1 mas yr at a position angle of 100.3±0.1) and parallax (16.5±2.3 mas; 61 pc). This proper motion brings the neutron star from the general vicinity of the Sco-Cen OB association. For an assumed neutron star radial velocity...

Thanks to the high counting statistics provided by a recent XMM-Newton observation of RX J1856.5–3754 we have discovered that this isolated neutron star pulsates at a period of 7.055 s. This confirms that RX J1856.5–3754 is similar in nature to the the other six thermally emitting, nearby neutron stars discovered in soft X–rays with ROSAT. The pulsations are detected at consistent periods in se...

The isolated neutron star RX J185635-3754 is the closest known neutron star to the Sun. Based on HST WFPC2 obervations over a 3 year baseline, I report its proper motion (332±1 mas yr at a position angle of 100.3±0.1) and parallax (16.5±2.3 mas; 61 pc). This proper motion brings the neutron star from the general vicinity of the Sco-Cen OB association. For an assumed neutron star radial velocity...

RX J1856.5−3754 is one of the brightest, nearby isolated neutron stars, and considerable observational resources have been devoted to its study. In previous work, we found that our latest models of a magnetic, hydrogen atmosphere matches well the entire spectrum, from X-rays to optical (with best-fitting neutron star radius R ≈ 14 km, gravitational redshift zg ∼ 0.2, and magnetic field B ≈ 4 × ...

When an isolated magnetar with magnetic dipole field B ∼ 10 G moves at high velocity (v > 10 cm s) through the ISM, its transition into propeller effect driven spin-down may occur in less than 10 years. We propose that the nearby neutron star RXJ1856.5-3754 is such a magnetar, and has spun down by the propeller effect to a period greater than 10 sec within ∼ 5 × 10 years. This magnetar scenario...

We present the results of a deep search for pulsations from the nearby isolated neutron star RX J1856.5−3754 using the 450 ks Director’s Discretionary Time (DDT) Chandra LETG/HRC-S observation completed on 2001 Oct 15. No pulsations were detected. We find a 99% confidence upper limit on the pulsed fraction of ∼ 4.4% for worst-case sinusoidal pulsations with frequency . 50Hz and frequency deriva...

We present a new grid of LTE model atmospheres for weakly magnetic (B <∼ 10 10 G) neutron stars, using opacity and equation of state data from the OPAL project and employing a fully frequency and angle dependent radiation transfer. We discuss the differences to earlier models, including a comparison with a detailed NLTE calculation. As a first application of the new synthetic spectra, we re-ana...