VLBI Observations of SN 2008D

Abstract

We report on two epochs of very-long-baseline interferometry (VLBI) observations of the Type Ib/c supernova SN 2008D, which was associated with the X-ray outburst XRF 080109. At our first epoch, at t = 30 days after the explosion, we observed at 22 and 8.4 GHz, and at our second, at t = 133 days, at 8.4 and 5.0 GHz. The VLBI observations allow us to accurately measure the source's size and position at each epoch, and thus constrain its expansion velocity and proper motion. We find the source at best marginally resolved at both epochs, allowing us to place a 3sigma upper limit of ~0.75c on the expansion velocity of a circular source. For an elongated source, our measurements are compatible with mildly relativistic expansion. However, our 3sigma upper limit on the proper motion is 4 micro-arcsec/day, corresponding to an apparent velocity of <0.6c, and is consistent with a stationary flux centroid. This limit rules out a relativistic jet such as an gamma-ray burst jet away from the line of sight, which would be expected to show apparent proper motion of >c. Taken together, our measurements argue against the presence of any long-lived relativistic outflow in SN 2008D. On the other hand, our measurements are consistent with the nonrelativistic expansion velocities of <30,000 km/s and small proper motions (<500 km/s) seen in typical supernovae.

Accepted for publication in the Astrophysical Journal Letters

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Cited by in corpus (11)

• From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109
• Supernova Shock Breakout Through a Wind
• The Radio Luminosity-Risetime Function of Core-Collapse Supernovae
• Aspherical Supernova Shock Breakout and the Observations of Supernova 2008D
• Early UV/Optical Emission of The Type Ib SN 2008D
• AT 2018cow VLBI: No Long-Lived Relativistic Outflow
• Simultaneous polarization monitoring of supernovae SN2008D/XT080109 and SN2007uy: isolating geometry from dust
• Detailed Radio View on Two Stellar Explosions and Their Host Galaxy: XRF080109/SN2008D and SN2007uy in NGC2770
• Non-thermal photon production via bulk comptonization at supernova shock breakout
• NGC 2770: high supernova rate due to interaction
• VLBI Constraints on Type I b/c Supernovae