SN 2001em: No Jet-Driven Gamma Ray Burst Event

Abstract

We report on our second-epoch VLBI and VLA observations of the Type Ib/c supernova 2001em, five years after the explosion. It was suggested that SN 2001em might be a jet-driven gamma ray burst (GRB), with the jet oriented near the plane of the sky, which would entail relativistic expansion or motion. Our VLBI image shows that SN 2001em is still unresolved five years after the explosion. For a distance of 83 Mpc (H_0 = 70 km/s/Mpc), the nominal expansion velocity is 5800 +/- 10,000 km/s, and the proper motion is 33,000 +/- 34,000 km/s. Our values are inconsistent with either relativistic expansion or motion, but are consistent with the non-relativistic expansion speeds and small proper motions seen in other supernovae. In particular these values are consistent with radio emission from SN 2001em being due to normal, non-relativistic supernova ejecta interacting with the circumstellar medium. Our VLA observations show a power-law decay in flux density since the time of the peak in the 8.4 GHz radio lightcurve in ~2003.

5 pages, 2 figs, accepted for publication in ApJ Letters; added references

References in corpus (9)

• Off-Axis Afterglow Emission from Jetted Gamma-Ray Bursts
• Astrometric accuracy of phase-referenced observations with the VLBA and EVN
• Late Emission from the Type Ib/c SN 2001em: Overtaking the Hydrogen Envelope
• The Radio and X-ray Luminous Type Ibc Supernova 2003L
• SN 1993J VLBI (III): The Evolution of the Radio Shell
• The Location of the Core in M81
• The Case for a Misaligned Relativistic Jet from SN 2001em
• SN1993J VLBI (I): The Center of the Explosion and a Limit on Anisotropic Expansion
• An Upper Limit on the Expansion Velocity of GRB Candidate SN 2001em

Cited by in corpus (14)

• Metamorphosis of SN 2014C: Delayed Interaction Between a Hydrogen Poor Core-collapse Supernova and a Nearby Circumstellar Shell
• The Radio Luminosity-Risetime Function of Core-Collapse Supernovae
• Supernova 1996cr: SN 1987A's Wild Cousin?
• Radio limits on off-axis GRB afterglows and VLBI observations of SN 2003gk
• Supernova Interaction with a Dense Detached Shell in SN 2001em
• The double-peaked radio light curve of PTF11qcj
• SN 2001em: Not so Fast
• VLBI Observations of SN 2008D
• SN 1986J VLBI. IV. The Nature of the Central Component
• Late-Time Evolution and Modeling of the Off-Axis Gamma-ray Burst Candidate FIRST J141918.9+394036
• Survival of the Fittest: Numerical Modeling of Supernova 2014C
• VLBI Constraints on Type I b/c Supernovae
• Spitzer's Last Look at Extragalactic Explosions: Long-Term Evolution of Interacting Supernovae
• VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion