Rodolfo Montez Jr. — Page 2

arXiv2009

Serendipitous XMM-Newton Detection of X-ray Emission from the Bipolar Planetary Nebula Hb 5

We report the serendipitous detection by the XMM-Newton X-ray Observatory of an X-ray source at the position of the Type I (He- and N-rich) bipolar planetary nebula Hb 5. The Hb 5 X-ray source appears marginally resolved. While the small number of total counts (~170) and significant off-axis angle of the X-ray source (~7.8') precludes a definitive spatial analysis, the morphology of the X-ray emission appears to trace the brightest features seen in optical images of Hb 5. The X-ray spectrum is indicative of a thermal plasma at a temperature between 2.4 and 3.7 MK and appears to display strong Neon emission. The inferred X-ray luminosity is L_X = 1.5 x 10^32 ergs/s. These results suggest that the detected X-ray emission is dominated by shock-heated gas in the bipolar nebula, although we cannot rule out the presence of a point-like component at the position of the central star. The implications for and correspondence with current models of shock-heated gas in planetary nebulae is discussed.

astro-ph.SR↗

arXiv2005

X-ray Imaging of Planetary Nebulae with Wolf-Rayet-type Central Stars: Detection of the Hot Bubble in NGC 40

We present the results of Chandra X-ray Observatory (CXO) observations of the planetary nebulae (PNs) NGC 40 and Hen 2-99. Both PNs feature late-type Wolf-Rayet central stars that are presently driving fast ~1000 km/s, massive winds into denser, slow-moving (~10 km/s) material ejected during recently terminated asymptotic giant branch (AGB) evolutionary phases. Hence, these observations provide key tests of models of wind-wind interactions in PNs. In NGC 40, we detect faint, diffuse X-ray emission distributed within a partial annulus that lies nested within a ~40'' diameter ring of nebulosity observed in optical and near-infrared images. Hen 2-99 is undetected. The inferred X-ray temperature (T_X ~10^6 K) and luminosity (L_X ~ 2 X 10^30 ergs/s) of NGC 40 are the lowest measured thus far for any PN displaying diffuse X-ray emission. These results, combined with the ring-like morphology of the X-ray emission from NGC 40, suggest that its X-ray emission arises from a ``hot bubble'' that is highly evolved and is generated by a shocked, quasi-spherical fast wind from the central star, as opposed to AGB or post-AGB jet activity. In constrast, the lack of detectable X-ray emission from Hen 2-99 suggests that this PN has yet to enter a phase of strong wind-wind shocks.

astro-ph↗