107 research outputs found
Finding Rare AGN: X-ray Number Counts of Chandra Sources in Stripe 82
We present the first results of a wide area X-ray survey within the Sloan
Digital Sky Survey (SDSS) Stripe 82, a 300 deg region of the sky with a
substantial investment in multi-wavelength coverage. We analyzed archival {\it
Chandra} observations that cover 7.5 deg within Stripe 82 ("Stripe 82
ACX"), reaching 4.5 flux limits of 7.9,
3.4 and 1.8 erg s cm in the soft
(0.5-2 keV), hard (2-7 keV) and full (0.5-7 keV) bands, to find 774, 239 and
1118 X-ray sources, respectively. Three hundred twenty-one sources are detected
only in the full band and 9 sources are detected solely in the soft band.
Utilizing data products from the {\it Chandra} Source Catalog, we construct
independent Log-Log relationships, detailing the number density of X-ray
sources as a function of flux, which show general agreement with previous {\it
Chandra} surveys. We compare the luminosity distribution of Stripe 82 ACX with
the smaller, deeper CDF-S + E-CDFS surveys and with {\it Chandra}-COSMOS,
illustrating the benefit of wide-area surveys in locating high luminosity AGN.
We also investigate the differences and similarities of X-ray and optical
selection to uncover obscured AGN in the local Universe. Finally, we estimate
the population of AGN we expect to find with increased coverage of 100 deg
or 300 deg, which will provide unprecedented insight into the high
redshift, high luminosity regime of black hole growth currently
under-represented in X-ray surveys.Comment: Accepted for publication in MNRAS, 15 pages, 6 Figures, 2 Table
Opportunistic routing in wireless mesh networks
Opportunistic Routing (OR) has been proposed as a way to increase the performance of wireless networks by exploiting its broadcast nature. In OR, instead of pre-selecting a single specific node to be the next-hop as a forwarder for a packet, multiple nodes can potentially be selected as the next-hop forwarder. Thus the source can use multiple potential paths to deliver the packets to the destination. More specially, when the current node transmits a packet, all the candidates that receive the packet successfully will coordinate with each other to determine which one would actually forward the packet according to some criteria, while the other nodes will simply discard the packet. In this chapter, we survey the state of the art in OR, then focus on the candidates selection algorithms and carry out a comparative performance evaluation of the most relevant proposals appeared in the literature.Peer ReviewedPostprint (authorβs final draft
Evidence for Extended Hydrogen-Poor CSM in the Three-Peaked Light Curve of Stripped Envelope Ib Supernova
We present multi-band ATLAS photometry for SN 2019tsf, a stripped-envelope
Type Ib supernova (SESN). The SN shows a triple-peaked light curve and a late
(re-)brightening, making it unique among stripped-envelope systems. The
re-brightening observations represent the latest photometric measurements of a
multi-peaked Type Ib SN to date. As late-time photometry and spectroscopy
suggest no hydrogen, the potential circumstellar material (CSM) must be H-poor.
Moreover, late (>150 days) spectra show no signs of narrow emission lines,
further disfavouring CSM interaction. On the contrary, an extended CSM
structure is seen through a follow-up radio campaign with Karl G. Jansky Very
Large Array (VLA), indicating a source of bright optically thick radio emission
at late times, which is highly unusual among H-poor SESNe. We attribute this
phenomenology to an interaction of the supernova ejecta with
spherically-asymmetric CSM, potentially disk-like, and we present several
models that can potentially explain the origin of this rare Type Ib supernova.
The warped disc model paints a novel picture, where the tertiary companion
perturbs the progenitors CSM, that can explain the multi-peaked light curves of
SNe, and here we apply it to SN 2019tsf. This SN 2019tsf is likely a member of
a new sub-class of Type Ib SNe and among the recently discovered class of SNe
that undergo mass transfer at the moment of explosionComment: 23 pages, Comments are welcome, Submitted to Ap
Single frequency intake of Ξ±-linolenic acid rich phytosterol esters attenuates atherosclerosis risk factors in hamsters fed a high fat diet
Characterization of Nonionic Microemulsions by EPR. Part II. The Effect of Competitive Solubilization of Cholesterol and Phytosterols on the Nanostructure
Characterization of the Nonionic Microemulsions by EPR. I. Effect of Solubilized Drug on Nanostructure
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