|Paerels||The Mass and Radius of a Neutron Star: Chandra LETGS Observations of RX J1856.5-3754|
|Romani||Neutron Star Atmospherics: Towards the Mass and Radius of the Nearest Isolated Neutron Star|
|Walter||The Atomosphere and Interior of the Isolated Neutron Star RX J185635-3754|
PI: Frederik Paerels Proposal Title: The Mass and Radius of a Neutron Star: Chandra LETGS Observations of RX J1856.5-3754 Abstract: We propose to make a comprehensive analysis of the full Chandra dataset of observations of the isolated neutron star RX J1856.5-3754. Our preliminary analysis of the first 50 ks of data indicates the presence of absorption features in the LETG spectrum; with 500 ks of data we will characterize these features precisely, search for related features to confirm atomic identifications, and, potentially, measure both the mass and radius of this neutron star to ~10 % precision. Such a measurement would have immediate implications for the equation of state of bulk matter at greater than nuclear densities -- a regime where no other experimental constraints on --> -- theory exist or can be expected. =====================================================================================
PI: Roger Romani Proposal Title: Neutron Star Atmospherics: Towards the Mass and Radius of the Nearest Isolated Neutron Star Abstract: Identification of neutron star surface spectral features would strongly impact compact object physics and determine the high density EOS. RXJ185635-3754 provides the best hope of such measurement, as colors indicate strong opacity. However, existing data limits line EWs to values well below those of simple models. After pioneering the basic models, we have recently modeled rotational effects, surface re-heating and magnetic line shifts. These will be treated in the proposed work; they can account for the EW decrease, aid in line identification and are likely crucial to interpretation of the LETG spectrum. With our sophisticated atmosphere models and codes for (phase-resolved) spectral fitting, we will extract the best possible M and R constraints, whether or not lines are detected. =====================================================================================
PI: Frederick Walter Proposal Title: The Atmosphere and Interior of the Isolated Neutron Star RX J185635-3754 Abstract: We request funding to analyze the spectrum of the isolated neutron star RX J185635-3754. Our analysis of the multiwavelength spectral energy distribution indicates that the surface composition is heavy elements, and not Hydrogen. We find a tight contraint on the gravitational redshift, suggesting that the star is more compact than most realistic equations of state allow. The short CHANDRA LETG GTO spectrum has marginal S/N for detecting the expected absorption lines; the deep DDT exposure will permit us to determine the surface composition, gravitational redshift, and possibly the surface magnetic field strength. We will use the X-ray spectrum in concert with the full multi-wavelength spectral energy distribution to assess the surface temperature structure.
Last modified: 12/02/10