Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery of Extended X-Ray emission from the unidentified TeV source HESS J1614-518 using the Suzaku Satellite
200
0
0.0
(
0
)
Authors
Hironori Matsumoto
Ask ChatGPT about the research
No Arabic abstract
We report the Suzaku results of HESS J1614-518, which is the brightest extended TeV gamma-ray source discovered in the Galactic plane survey conducted using the H.E.S.S. telescope. We discovered three X-ray objects in the field of view of the X-ray Imaging Spectrometer (XIS), which were designated as Suzaku J1614-5141 (src A), Suzaku J1614-5152 (src B), and Suzaku J1614-5148 (src C). Src A is an extended source located at the peak position of HESS J1614-518, and therefore it is a plausible counterpart to HESS J1614-518. The X-ray flux in the 2-10 keV band is 5e-13 erg/s/cm^2, which is an order of magnitude smaller than the TeV flux. The photon index is 1.7, which is smaller than the canonical value of synchrotron emissions from high-energy electrons found in some supernova remnants. These findings present a challenge to models in which the origin of the TeV emission is the inverse Compton scattering of the cosmic microwave background by accelerated electrons that emit X-rays via synchrotron emission. Src B is located at a relatively dim region in the TeV band image; however, its hydrogen column density is the same as that of src A. Therefore, src B may also be physically related to HESS J1614-518. Src C is a foreground late-type B star. We also discovered a soft extended X-ray emission near HESS J1614-518.
rate research
Read More
We report the detection, with the CANGAROO-III imaging atmospheric Cherenkov telescope array, of a very high energy gamma-ray signal from the unidentified gamma-ray source HESS J1614-518, which was discovered in the H.E.S.S. Galactic plane survey. Diffuse gamma-ray emission was detected above 760 GeV at the 8.9 sigma level during an effective exposure of 54 hr from 2008 May to August. The spectrum can be represented by a power-law: 8.2+-2.2_{stat}+-2.5_{sys}x10^{-12}x (E/1TeV)^{-Gamma} cm^{-2} s^{-1} TeV^{-1} with a photon index Gamma of 2.4+-0.3_{stat}+-0.2_{sys}, which is compatible with that of the H.E.S.S. observations. By combining our result with multi-wavelength data, we discuss the possible counterparts for HESS J1614-518 and consider radiation mechanisms based on hadronic and leptonic processes for a supernova remnant, stellar winds from massive stars, and a pulsar wind nebula. Although a leptonic origin from a pulsar wind nebula driven by an unknown pulsar remains possible, hadronic-origin emission from an unknown supernova remnant is preferred.
HESS J1614$-$518 and HESS J1616$-$508 are two tera-electron volt (TeV) $gamma$-ray sources that are not firmly associated with any known counterparts at other wavelengths. We investigate the distribution of interstellar medium towards the TeV $gamma$-ray sources using results from a 7 mm-wavelength Mopra study, the Mopra Southern Galactic Plane CO Survey, the Millimetre Astronomers Legacy Team - 45 GHz survey and [CI] data from the HEAT telescope. Data in the CO(1$-$0) transition lines reveal diffuse gas overlapping the two TeV sources at several velocities along the line of sight, while observations in the CS(1$-$0) transition line reveal several interesting dense gas features. To account for the diffuse atomic gas, archival HI data was taken from the Southern Galactic Plane Survey. The observations reveal gas components with masses $sim10^3$ to $10^5$ M$_odot$ and with densities $sim10^2$ to $10^3$ cm$^{-3}$ overlapping the two TeV sources. Several origin scenarios potentially associated with the TeV $gamma$-ray sources are discussed in light of the distribution of the local interstellar medium. We find no strong convincing evidence linking any counterpart with HESS J1614$-$518 or HESS J1616$-$508.
HESS J0632+057 is one of only two unidentified very-high-energy gamma-ray sources which appear to be point-like within experimental resolution. It is possibly associated with the massive Be star MWC 148 and has been suggested to resemble known TeV binary systems like LS I +61 303 or LS 5039. HESS J0632+057 was observed by VERITAS for 31 hours in 2006, 2008 and 2009. During these observations, no significant signal in gamma rays with energies above 1 TeV was detected from the direction of HESS J0632+057. A flux upper limit corresponding to 1.1% of the flux of the Crab Nebula has been derived from the VERITAS data. The non-detection by VERITAS excludes with a probability of 99.993% that HESS J0632+057 is a steady gamma-ray emitter. Contemporaneous X-ray observations with Swift XRT reveal a factor of 1.8+-0.4 higher flux in the 1-10 keV range than earlier X-ray observations of HESS J0632+057. The variability in the gamma-ray and X-ray fluxes supports interpretation of the ob ject as a gamma-ray emitting binary.
New generation TeV gamma-ray telescopes have discovered many new sources, including several enigmatic unidentified TeV objects. HESS J0632+057 is a particularly interesting unidentified TeV source since: it is a point source, it has a possible hard-spectrum X-ray counterpart and a positionally consistent Be star, it has evidence of long-term VHE flux variability, and it is postulated to be a newly detected TeV/X-ray binary. We have obtained Swift X-ray telescope observations of this source from MJD 54857 to 54965, in an attempt to ascertain its nature and to investigate the hypothesis that its a previously unknown X-ray/TeV binary. Variability and spectral properties similar to those of the other 3 known X-ray/TeV binaries have been observed, with measured flux increases by factors of approximately 3. X-ray variability is present on multiple timescales including days to months; however, no clear signature of periodicity is present on the timescales probed by these data. If binary modulation is present and dominating the measured variability, then the period of the orbit is likely to be more than 54 days (half of this campaign), or it has a shorter period with a variable degree of flux modulation on successive high states. If the two high states measured to date are due to binary modulation, then the favored period is approximately 35-40 days. More observations are required to determine if this object is truly a binary system and to determine the extent that the measured variability is due to inter-orbit flaring effects or periodic binary modulation.
The imaging atmospheric Cherenkov array H.E.S.S. recently discovered an extended source in the 0.4$-$10 TeV energy range, HESS J1303-631. We obtained a 5 ks observation with the ACIS-I array on the Chandra X-ray observatory that does not reveal an obvious compact or diffuse X-ray counterpart. Archival ROSAT images are also blank in this region. Although there are several radio pulsars within the field of HESS J1303-631, none is detected in X-rays to a flux limit of $<5 times 10^{-14}$ ergs cm$^{-2}$ s$^{-1}$, and none is a likely counterpart on energetic grounds. Over the entire $17^{prime} times 17^{prime}$ ACIS-I field, we place an upper limit of $<5.4 times 10^{-12}$ ergs cm$^{-2}$ s$^{-1}$ on the excess diffuse flux in the 2-10 keV band. One hard point-source with flux $approx 4 times 10^{-14}$ ergs cm$^{-2}$ s$^{-1}$ lies within $0.^{prime}5$ of the centroid of the TeV emission. These exploratory observations suggest that deeper pointings with Chandra and XMM are needed before we can learn more about the nature of HESS J1303-631. Its similarity to the unidentified source TeV J2032+4130 indicates the probable existence of a new class of high-energy source in the Galactic plane that originates from young, massive stars or their supernova remnants.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
