F. A. Cordova

The XMM-Newton optical/UV monitor telescope

The XMM-OM instrument extends the spec- tral coverage of the XMM-Newton observatory into the ul- traviolet and optical range. It provides imaging and time- resolved data on targets simultaneously with observations in the EPIC and RGS. It also has the ability to track stars in its field of view, thus providing an improved post- facto aspect solution for the spacecraft. An overview of the XMM-OM and its operation is given, together with cur- rent information on the performance of the instrument.

Relativistic O VIII Emission and Ionized Outflow in NGC 4051 Measured with XMM-Newton

We present XMM-Newton Reflection Grating Spectrometer observations of the soft X-ray spectrum of NGC 4051 and explore their implications for the inner accretion disk and ionized outflow in the active galactic nucleus. We fit the soft X-ray excess with a relativistically broadened O VIII recombination spectrum, including the entire line series and recombination continuum. This plus an underlying power-law continuum provides a much better fit to the soft X-ray spectrum than a single temperature or disk blackbody plus power law. The emission-line profiles, computed for a Kerr metric around a maximally rotating black hole, reveal a sharply peaked disk emissivity law and inner radius smaller than 1.7RG. The spectrum also includes narrow absorption and emission lines from C, N, O, Ne, and Fe in an ionized outflow. Outflow column densities are relatively low and do not create significant edges in the spectrum. The small amount of absorption bolsters confidence in the detection of relativistic emission-line features. The narrow-line emitter has a large (76%) global covering fraction, leading to strong forbidden lines and filling in of the resonance absorption lines. We also find broad C VI Lyα and very broad O VII emission from the broad-line region. The narrow- and broad-line regions span large ranges in ionization parameter and may arise in a disk outflow. The ionized absorber has a large ionization range, which is inconsistent with pressure equilibrium in a multiphase medium. The mass outflow rate exceeds the accretion rate by a factor of 1000.

The XMM-Newton view of stellar coronae: Coronal structure in the Castor X-ray triplet

We present results of a comprehensive X-ray investigation of the multiple stellar system Castor AB + YY Gem. The observations were obtained with the XMM - Newton observatory. We report the first spatially separated detection and identification of both Castor A and B as frequently flaring X-ray sources. Spectral modeling of the YY Gem and Castor coronal sources indicates a broad plasma distribution between 2-15 MK. Elemental abundances are found to be below solar photospheric values, with the abundance of Ne being highest (~0.7 times solar photospheric). The abundances increase during a large flare, most notably for Fe. The Ovii He-like line triplet indicates average coronal densities of the cooler plasma of a few times 10 10 cm -3 for YY Gem and Castor. The YY Gem light curve shows three deep eclipses, indicating that the coronae of both binary components are similarly active and are relatively compact. A 3-D light curve inversion shows that coronal active regions follow density scale heights compatible with spectroscopically measured temperatures. The dominant densities also agree with spectroscopic values. Most active regions are located between

The X-ray spectrum of the Seyfert I galaxy Markarian 766: Dusty warm absorber or relativistic emission lines?

\pm 50

High-velocity winds from a dwarf nova during outburst

degrees latitude, in agreement with findings from previous Doppler imaging. We also report the tentative detection of line broadening due to orbital motion.

XMM-Newton observations of polars in low accretion states

Competing models for broad spectral features in the soft X-ray spectrum of the Seyfert I galaxy Mrk766 are tested against data from a 130 ks XMM-Newton observation. A model including relativistically broadened Ly-alpha emission lines of OVIII, NVII and CVI is a better fit to 0.3-2 keV XMM RGS data than a dusty warm absorber. Moreover, the measured depth of neutral iron absorption lines in the spectrum is inconsistent with the magnitude of the iron edge required to produce the continuum break at 17-18Angstroms in the dusty warm absorber model. The relativistic emission line model can reproduce the broad-band (0.1-12 keV) XMM-EPIC data with the addition of a fourth line to represent emission from ionized iron at 6.7 keV and an excess due to reflection at energies above the iron line. The profile of the 6.7 keV iron line is consistent with that measured for the low energy lines. There is evidence in the RGS data at the 3sigma level for spectral features that vary with source flux. The covering fraction of warm absorber gas is estimated to be ~12%. Iron in the warm absorber is found to be overabundant with respect to CNO compared to solar values.

Hubble Space Telescope Observations of the Middle-aged Pulsar 0656+14

An ultraviolet spectrum of the dwarf nova TW Vir during an optical outburst shows shortward-shifted absorption features with edge velocities as high as 4800 km s/sup -1/, about the escape velocity of a white dwarf. A comparison of this spectrum with the UV spectra of other cataclysmic variables suggests that mass loss is evident only for systems with relatively high luminosities (> or approx. =10 L/sub sun/) and low inclination angles with respect to the observers line of sight. The mass loss rate for cataclysmic variables is of order 10/sup -11/ M/sub sun/ yr/sup -1/; this is from approx.10/sup -2/ to approx.10/sup -3/ of the mass accretion rate onto the compact star in the binary. The mass loss may occur by a mechanism similar to that invoked for early-type stars, i.e., radiation absorbed in the lines accelerates the accreting gas to the high velocities observed.

Soft X-ray emission from the radio pulsar PSR 0656 + 14

We have made a series of snap-shot observations of 37 polars using XMM-Newton. We found that 16 of these systems were in a low, or much reduced, accretion state. Of those, six were not detected in X-rays. This suggests that in any survey of polars, around half will be in a low accretion state. We tested if there was a bias towards certain orbital periods: this is not the case. Of the 10 systems that were detected at low but significant rates in X-rays, eight showed significant variability in their X-ray light curves. This implies that non-uniform accretion still takes place during low accretion epochs. The bolometric luminosity of these systems is similar to10(30) erg s(-1), two orders of magnitude less than for systems in a high accretion state. The X-ray spectra show no evidence of a distinct soft X-ray component. However, the X-ray and UV data imply that such a low-temperature component exists: its temperature is low enough for its flux distribution to move outside the bandpass of the X-ray instruments.

XMM-NEWTON OBSERVATIONS OF PSR B1706-44

Multiwavelength spectral observations of middle-aged (τ~104-106 yr) isolated pulsars enable one in principle to separate thermal radiation emitted from the neutron star surface and nonthermal radiation from its magnetosphere. We have previously detected the middle-aged radio and soft X-ray pulsar 0656+14 with the Hubble Space Telescope Faint Object Camera (FOC) long-pass filter F130LP. In the present Letter we report new FOC observations of this pulsar with three broadband filters: F430W, F342W, and F195W. The optical-UV spectral flux can be fitted with a two-component spectral model that combines a power-law spectrum with a Rayleigh-Jeans spectrum. The nonthermal component with the power-law index α=1.4−0.7+ 0.6 dominates at λ3000 A. The thermal component is characterized by the Rayleigh-Jeans parameter, G ≡ T6(R10/d500)2, where T=106T6 K is the brightness temperature, R=10R10 km is the neutron star radius as seen by a distant observer, and d=500d500 pc is the distance. For a plausible extinction, E(B-V)=0.03, we obtained G=3.6+ 1.6−2.0. The observed shape of the optical-UV spectrum of PSR 0656+14 differs drastically from those of both younger pulsars (Crab, 0540-69, Vela) and the older pulsar Geminga.

XMM–Newton observations of three short‐period polars: V347 Pav, GG Leo and EU UMa

A radio source with a flux density of a few mJy was found in the error region of the soft X-ray source E0656 + 14, and identified as the radio pulsar PSR 0656 + 14. The radio source has a steep, nonthermal spectrum and a high degree of linear (62 percent) and circular (19 percent) polarization. The X-ray spectrum of the pulsar is among the softest sources observed with the Einstein Observatory. The X-ray data taken with the Einstein imaging proportional counter (IPC) permit a range of blackbody temperatures of 3-6 x 10 to the 5th K, and an equivalent column density of hydrogen smaller than 4 x 10 to the 20th/sq cm. If the assumption is made that the X-ray flux is thermal radiation from surface of the neutron star, then the pulsar must be at a distance smaller than 550 pc, consistent with the low dispersion measure of PSR 0656 + 14. The X-ray timing data suggest that the X-ray emission is modulated at the pulsars 0.385-s spin period with an amplitude of 18 percent + or - 6 percent, and that there is a 0.0002 probability that this is spurious. It was noted that PSR 0656 + 14 is close to the geometric center of a 20-deg diameter soft X-ray emitting ring called the Gemini-Monoceros enhancement. The close distance of the pulsar, together with its relatively young age of 1.1 x 10 to the 5th yr, makes it possible that the ring is a supernova remnant from the explosion of the pulsars progenitor. A radio source extending over a region 1.2 to 3.3 arcmin south of the pulsar is a candidate for association with the pulsar.