Bradley D. Spitzbart

A Combined Spitzer and Chandra Survey of Young Stellar Objects in the Serpens Cloud Core

We present Spitzer and Chandra observations of the nearby (~260 pc) embedded stellar cluster in the Serpens cloud core. We observed, using Spitzers IRAC and MIPS instruments, in six wavelength bands from 3 to 70 ?m, to detect thermal emission from circumstellar disks and protostellar envelopes and to classify stars using color-color diagrams and SEDs. These data are combined with Chandra observations to examine the effects of circumstellar disks on stellar X-ray properties. Young diskless stars were also identified from their increased X-ray emission. We have identified 138 YSOs in Serpens: 22 Class 0/I, 16 flat-spectrum, 62 Class II, 17 transition disk, and 21 Class III stars; 60 of these exhibit X-ray emission. Our primary results are the following: (1) 10 protostars detected previously in the submillimeter are detected at ? 1. This may be the result of grain growth through coagulation and/or the accretion of volatiles in the Serpens cloud core.

VARIABILITY IN PROTO-PLANETARY NEBULAE. I. LIGHT CURVE STUDIES OF 12 CARBON-RICH OBJECTS

We have carried out long-term (14 years) V and R photometric monitoring of 12 carbon-rich proto-planetary nebulae. The light and color curves display variability in all of them. The light curves are complex and suggest multiple periods, changing periods, and/or changing amplitudes, which are attributed to pulsation. A dominant period has been determined for each and found to be in the range of ~150 days for the coolest (G8) to 35-40 days for the warmest (F3). A clear, linear inverse relationship has been found in the sample between the pulsation period and the effective temperature and also an inverse relationship between the amplitude of light variation and the effective temperature. These are consistent with the expectation for a pulsating post-asymptotic giant branch (post-AGB) star evolving toward higher temperature at constant luminosity. The published spectral energy distributions and mid-infrared images show these objects to have cool (200 K), detached dust shells and published models imply that intensive mass loss ended 400-2000 years ago. The detection of periods as long as 150 days in these requires a revision in the published post-AGB evolution models that couple the pulsation period to the mass loss rate and that assume that intensive mass loss ended when the pulsation period had decreased to 100 days. This revision will have the effect of extending the timescale for the early phases of post-AGB evolution. It appears that real time evolution in the pulsation periods of individual objects may be detectable on the timescale of two or three decades.

Discovery of Nonthermal X-Ray Emission from the Embedded Massive Star-forming Region RCW 38

RCW~38 is a uniquely young (

THE STRUCTURE OF THE STAR-FORMING CLUSTER RCW 38

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X-Atlas: An Online Archive of Chandra's Stellar High-Energy Transmission Grating Observations

1 Myr), embedded (

Clusters Within Clusters: Star Formation in RCW 38

A_V \sim 10

IRAS 20050+2720: Clustering of Low Mass Stars

) stellar cluster surrounding a pair of early O stars (

Chandra and Spitzer observations of young clusters

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Chandra monitoring and trends analysis: status and lessons learned

O5.5) and is one of the few regions within 2 kpc other than Orion to contain over 1000 members. X-ray and deep near-infrared observations reveal a dense cluster with over 200 X-ray sources and 400 infrared sources embedded in a diffuse hot plasma within a 1 pc diameter. The central O star has evacuated its immediate surroundings of dust, creating a wind bubble

Chandra automated point source processing

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