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We present new results of the HESS J1731-347/SNR G353.6-0.7 system from XMM-Newton and Suzaku X-ray observations and Delinha CO observations. We discover extended hard X-rays coincident with the bright, extended TeV source HESS J1731-347 and the shell of the radio supernova remnant (SNR). We find that spatially resolved X-ray spectra can generally be characterized by an absorbed power-law model, with a photon index of ∼2, typical of non-thermal emission. A bright X-ray compact source, XMMS J173203-344518, is also detected near the center of the SNR. We find no evidence of a radio counterpart or an extended X-ray morphology for this source, making it unlikely to be a pulsar wind nebular (PWN). The spectrum of the source can be well fitted by an absorbed blackbody with a temperature of ∼0.5 keV plus a power-law tail with a photon index of ∼5, reminiscent of the X-ray emission of a magnetar. CO observations toward the inner part of the High Energy Stereoscopic System (HESS) source reveal a bright cloud component at −20 ± 4 km s −1 , which is likely located at the same distance of ∼3.2 kpc as the SNR. Based on the probable association between the X-ray and γ -ray emissions and likely association between the CO cloud and the SNR, we argue that the extended TeV emission originates from the interaction between the SNR shock and the adjacent CO clouds rather than from a PWN.

Using the data acquired in the time-to-spill (TTS) mode for long gamma-ray bursts (GRBs) by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory (CGRO), we have carefully measured spectral lags in time between the low (25-55 keV ) and high (110-320 keV ) energy bands of individual pulses contained in 64 multipeak GRBs. We find that a temporal lead by higher energy -ray photons (i.e., positive lags) is the norm in this selected sample set of long GRBs. While relatively few in number, some pulses of several long GRBs do show negative lags. This distribution of spectral lags in long GRBs is in contrast to that in short GRBs. This apparent difference poses challenges to and places constraints on the physical mechanism(s) for producing long and short GRBs. The relation between the pulse peak count rates and the spectral lags is also examined. Observationally, there seems to be no clear evidence for a systematic spectral lag-luminosity connection for pulses within a given long GRB.

The so-called unidentified infrared emission (UIE) features at 3. 3, 6.2, 7.7, 8.6, and 11.3 µm ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs may have an aliphatic component as revealed by the detection in many UIE sources of the aliphatic C-H stretching feature at 3.4 µm. The ratio of the observed intensity of the 3.4 µm feature to that of the 3.3 µm aromatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers. This requires the knowledge of the intrinsic oscillator strengths of the 3.3 µm aromatic C-H stretch (A 3.3 ) and the 3.4 µm aliphatic C-H stretch (A 3.4 ). Lacking experimental data on A 3.3 and A 3.4 for the UIE candidate materials, one often has to rely on quantum-chemical computations. Although the second-order Møller-Plesset (MP2) perturbation theory with a large basis set is more accurate than the B3LYP density functional theory, MP2 is computationally very demanding and impractical for large molecules. Based on methylated PAHs, we show here that, by scaling the band strengths computed at an inexpensive level (e.g., B3LYP/6-31G * ) we are able to obtain band strengths as accurate as that computed at far more expensive levels (e.g., MP2/6-311+G(3df,3pd)). We calculate the model spectra of methylated PAHs and their cations excited by starlight of different spectral shapes and intensities. We find (I 3.4 /I 3.3 ) mod , the ratio of the model intensity of the 3.4 µm feature to that of the 3.3 µm feature, is insensitive to the spectral shape and intensity of the exciting starlight. We derive a straightforward relation for determining the aliphatic fraction of the UIE carriers (i.e., the ratio of the number of C atoms in aliphatic units N C,ali to that in aromatic rings N C,aro ) from the observed band ratios (I 3.4 /I 3.3 ) obs : N C,ali /N C,aro ≈ 0.57 × (I 3.4 /I 3.3 ) obs for neutrals and N C,ali /N C,aro ≈ 0.26 × (I 3.4 /I 3.3 ) obs for cations.