Alak Ray — Page 3 | Searcharxiv

arXiv1998

Deep optical observations at the position of PSR1706-44 with the VLT-UT1

We present optical data gathered by the VLT Test Camera in the V-band at the radio (interferometric) position of PSR1706-44. We find no optical counterpart to the pulsar in the VLT image. At a distance of 2.7 arcsec from a nearby bright star, the 3-sigma upper limit to the pulsar magnitude above the background is V = 25.5. Within an error circle of 1.0 arcsec the upper limit is degraded in the direction towards the star. At a distance < 2 arcsec from the star we can with confidence only claim an upper limit of V = 24.5. This is still several magnitudes fainter than previous estimates. The implications of the optical upper limit taken together with the high energy pulsed gamma-ray radiation for theoretical models of pulsar emission are discussed.

astro-ph↗

arXiv1998

Oscillation Effects On Neutrinos From The Early Phase Of a Nearby Supernova

Neutrinos emitted during stellar core collapse leading to a supernova are primarily of the electron neutrino type at source which may undergo oscillation between flavor eigenstates during propagation to an earth-bound detector. Although the number of neutrinos emitted during the pre-bounce collapse phase is much smaller than that emitted in the post-bounce phase (in which all flavors of neutrinos are emitted), a nearby supernova event may nevertheless register a substantial number of detections from the pre-bounce phase at SuperKamiokande (SK) and the Sudbury Neutrino Observatory (SNO). The calorimetric measurement of the supernova neutrino fluence from this stage via the charge current and neutral current detection channels in SNO and the corresponding distortion of detected spectrum in SK over the no-oscillation spectrum, can probe information about neutrino mass difference and mixing which are illustrated here in terms of two- and three-flavor oscillation models.

astro-ph↗