arXiv subjects

C. S. J. Pun

Publications and source records attributed to C. S. J. Pun.

21 records · Page 2Linked to original sources

arXiv2000

HST Spectroscopy of Spot 1 on the Circumstellar Ring of SN 1987A

We present ultraviolet and optical spectra of the first bright spot (PA = 29 degrees) on Supernova 1987A's equatorial circumstellar ring taken with the Space Telescope Imaging Spectrograph. We interpret this spot as the emission produced by radiative shocks that occur where the supernova blast wave strikes an inward protrusion of the ring. The observed line widths and intensity ratios indicate the presence of radiative shocks with velocities ranging from 100 to 250 km s^-1 entering dense (> 10^4 cm^-3) gas. These observations, and future observations of the development of the spectra and line profiles, provide a unique opportunity to study the hydrodynamics of radiative shocks.

astro-ph↗

arXiv1998

New HST Observations of High Velocity Lyman Alpha and Balmer Alpha in SNR 1987A

We describe and model high velocity (~15,000 km/s) Lyman alpha and Balmer alpha emission from supernova remnant 1987A seen in September and October 1997 with the Space Telescope Imaging Spectrograph. Part of this emission comes from a reverse shock located at ~75% of the radius of the inner boundary of the inner circumstellar ring and confined within 30 degrees of the equatorial plane. Departure from axisymmetry in the Lyman alpha and Balmer alpha emission correlates with that seen in nonthermal radio emission and reveals an asymmetry in the circumstellar gas distribution. We also see diffuse high velocity Lyman alpha emission from supernova debris inside the reverse shock that may be due to excitation by nonthermal particles accelerated by the shock.

astro-ph↗

arXiv1997

Spatially Resolved STIS Spectroscopy of SN 1987A: Evidence for Shock Interaction with Circumstellar Gas

Visual and ultraviolet spatially resolved (~ 0."1) spectra of SN 1987A obtained on days 3715 and 3743 with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope show that the high-velocity SN debris is colliding with circumstellar gas. Very broad Ly-alpha emission with velocities extending to ~ +/- 20,000 km/s originates inside the inner circumstellar ring and appears to fill most of the surface area within 0."67 +/- 0."03 (0.14 pc at a distance of 50 kpc) of the ring's center. The observed Ly-alpha flux from the shocked ejecta is (1.85 +/- 0.53) 10^{-13} erg/cm2/s and (1.25 +/- 0.51) 10^{-12} erg/cm2/s after correcting for extinction. A spatially unresolved blue-shifted emission feature was discovered in H-alpha (and other lines) on the inner ring at p.a. 31 +/- 8 degree. The H-alpha emission extends to -250 km/s with no corresponding red-shifted emission. This highly localized interaction appears to be the initial contact of the supernova blast wave with an inward protrusion of the inner ring. The broad Ly-alpha emission and the `hot spot' are separate interaction phemonena associated with the reverse and forward shocks, respectively. We also find that the size of the inner ring in forbidden lines of oxygen has a dependence on ionization potential, in agreement with photoionization models of the ring.

astro-ph↗