SPI Measurements of the Diffuse Galactic Hard X-ray Continuum

INTEGRAL Spectrometer SPI data from the first year of the Galactic Centre Deep Exposure has been analysed for the diffuse continuum from the Galactic ridge. A new catalogue of sources from the INTEGRAL Imager IBIS has been used to account for their contribution to the celestial signal. Apparently diffuse emission is detected at a level ~10% of the total source flux. A comparison of the spectrum of diffuse emission with that from an analysis of IBIS data alone shows that they are consistent. The question of the contribution of unresolved sources to this ridge emission is still open.Comment: Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004. ESA SP-552. Reference to Terrier et al. (2004) updated to include astro-ph versio

The Spectral Variability of Cygnus X-1 at MeV Energies

In previous work, we have used data from the first three years of the CGRO mission to assemble a broad-band $\gamma$-ray spectrum of the galactic black hole candidate Cygnus X-1. Contemporaneous data from the COMPTEL, OSSE and BATSE experiments on CGRO were selected on the basis of the hard X-ray flux (45--140 keV) as measured by BATSE. This provided a spectrum of Cygnus X-1 in its canonical low X-ray state (as measured at energies below 10 keV), covering the energy range from 50 keV to 5 MeV. Here we report on a comparison of this spectrum to a COMPTEL-OSSE spectrum collected during a high X-ray state of Cygnus X-1 (May, 1996). These data provide evidence for significant spectral variability at energies above 1 MeV. In particular, whereas the hard X-ray flux {\it decreases} during the high X-ray state, the flux at energies above 1 MeV {\it increases}, resulting in a significantly harder high energy spectrum. This behavior is consistent with the general picture of galactic black hole candidates having two distinct spectral forms at soft $\gamma$-ray energies. These data extend this picture, for the first time, to energies above 1 MeV.Comment: 5 pages, 4 figures, to be published in AIP Conf. Proc., "The Fifth Compton Symposium

INTEGRAL-RXTE observations of Cygnus X-1

We present first results from contemporaneous observations of Cygnus X-1 with INTEGRAL and RXTE, made during INTEGRAL's performance verification phase in 2002 November and December. Consistent with earlier results, the 3-250 keV data are well described by Comptonization spectra from a Compton corona with a temperature of kT~50-90 keV and an optical depth of tau~1.0-1.3 plus reflection from a cold or mildly ionized slab with a covering factor of Omega/2pi~0.2-0.3. A soft excess below 10 keV, interpreted as emission from the accretion disk, is seen to decrease during the 1.5 months spanned by our observations. Our results indicate a remarkable consistency among the independently calibrated detectors, with the remaining issues being mainly related to the flux calibration of INTEGRAL.Comment: 6 pages, 3 figures. Figs. 2 and 3 are best viewed in color. Accepted for publication in the INTEGRAL special edition of A&A

COMPTEL detection of pulsed gamma-ray emission from B1509-58 up to at least 10 MeV

We report on the first firm detection of pulsed gamma-ray emission from PSR B1509-58 in the 0.75-30 MeV energy range in CGRO COMPTEL data collected over more than 6 years. The modulation significance in the 0.75-30 MeV pulse-phase distribution is 5.4 sigma and the lightcurve is similar to the lightcurves found earlier between 0.7 and 700 keV: a single broad asymmetric pulse reaching its maximum 0.38 +/- 0.03 in phase after the radio peak, compared to the offset of 0.30 found in the CGRO BATSE soft gamma-ray data, and 0.27 +/- 0.01 for RXTE (2-16 keV), compatible with ASCA (0.7-2.2 keV). Spectral analysis based on the excess counts in the broad pulse of the lightcurve shows that extrapolation of the OSSE power-law spectral fit with index -1.68 describes our data well up to 10 MeV. Above 10 MeV the spectrum breaks abruptly. The precise location of the break/bend between 10 and 30 MeV depends on the interpretation of the structure in the lightcurve measured by COMPTEL and EGRET above 10 MeV.Comment: 15 pages, 10 figures, accepted for publication in Astronomy and Astrophysic

Defining and Developing Curricula in the Context of Cooperative Extension

Effective curricula are considered to be the cornerstone of successful programming in Extension. However, there is no universal operationalized definition of the term curriculum as it applies to Extension. Additionally, the development of curricula requires a systematic process that takes into account numerous factors. We provide an operational definition of curriculum by describing the parts of a curriculum, discussing the organization of those elements, and recommending theoretical frameworks that complement the learn-by-doing approach used in Extension. We also describe strategies to guide curriculum development, adaptation, and evaluation that will help advance the potential of Extension curricula to achieve their intended outcomes

Prevalent Approaches to Professional Development in State 4-H Programs

High-quality 4-H programming requires effective professional development of educators. Through a mixed-methods study, we explored professional development offered through state 4-H programs. Survey results revealed that both in-person and online delivery modes were used commonly for 4-H staff and adult volunteers; for teen volunteers, in-person delivery was most common. Additionally, most professional development efforts were characterized as episodic, expert-led, and group-based (traditional approaches); the least common approaches were described as ongoing, learner-centered, and group-based (reform-based approaches). Interview data supported survey findings. Traditional approaches to professional development are considered ineffective; thus, the implementation of more reform-based professional development opportunities is recommended

INTEGRAL and XMM-Newton observations of the weak GRB 030227

We present INTEGRAL and XMM-Newton observations of the prompt gamma-ray emission and the X-ray afterglow of GRB030227, the first GRB for which the quick localization obtained with the INTEGRAL Burst Alert System (IBAS) has led to the discovery of X-ray and optical afterglows. GRB030227 had a duration of about 20 s and a peak flux of 1.1 photons cm^-2 s^-1 in the 20-200 keV energy range. The time averaged spectrum can be fit by a single power law with photon index about 2 and we find some evidence for a hard to soft spectral evolution. The X-ray afterglow has been detected starting only 8 hours after the prompt emission, with a 0.2-10 keV flux decreasing as t^-1 from 1.3x10e-12 to 5x10e-13 erg cm^-2 s^-1. The afterglow spectrum is well described by a power law with photon index 1.94+/-0.05 modified by a redshifted neutral absorber with column density of several 10e22 cm^-2. A possible emission line at 1.67 keV could be due to Fe for a redshift z=3, consistent with the value inferred from the absorption.Comment: 16 pages, 5 figures, latex, Accepted for publication in The Astrophysical Journal Letter

A High Sensitivity Measurement of the MeV Gamma-Ray Spectrum of Cygnus X-1

The Compton Gamma-Ray Observatory (CGRO) has observed the Cygnus region on several occasions since its launch in 1991. The data collected by the COMPTEL experiment on CGRO represent the most sensitive observations to date of Cygnus X-1 in the 0.75-30 MeV range. A spectrum accumulated by COMPTEL over 10 weeks of observation time shows significant evidence for emission extending out to several MeV. We have combined these data with contemporaneous data from both BATSE and OSSE to produce a broad-band gamma-ray spectrum, corresponding to the low X-ray state of Cygnus X-1, extending from 50 keV up to approximately 5 MeV. Although there is no evidence for any broad line-like emissions in the MeV region, these data further confirm the presence of a hard tail at energies above several hundred keV. In particular, the spectrum at MeV energies can be described as a power-law with a photon spectral index of $\alpha$ = -3.2, with no evidence for a cutoff at high energies. For the 200 keV to 5 MeV spectrum, we provide a quantitative description of the underlying electron spectrum, in the context of a hybrid thermal/non-thermal model for the emission. The electron spectrum can be described by a thermal Maxwellian with a temperature of $kT_e$ = 86 keV and a non-thermal power-law component with a spectral index of $p_e$ = 4.5. The spectral data presented here should provide a useful basis for further theoretical modeling.Comment: 28 pages, 6 figures, accepted for publication in ApJ. Considerably revised from original submissio