Multi-Epoch Observations of Extremely High-Velocity Emergent Broad Absorption

TL;DR

This study reports the discovery of the highest velocity broad absorption lines in a quasar, revealing rapid variability and proposing models involving bulk motion and ionization changes to explain the outflows.

Contribution

It presents the first detection of extremely high-velocity broad absorption lines with multi-epoch observations, and introduces models for their rapid variability.

Findings

Discovered broad absorption troughs at ~60,000 km/s and ~40,000 km/s.

Observed rapid variability over ~10 days in the rest frame.

Proposed models involving crossing disk and flow-tube scenarios for the outflows.

Abstract

We present the discovery of the highest velocity CIV broad absorption line to date in the z=2.47 quasar SDSS J023011.28+005913.6, hereafter J0230. In comparing the public DR7 and DR9 spectra of J0230, we discovered an emerging broad absorption trough outflowing at ~60,000 km/s, which we refer to as trough A. In pursuing follow up observations of trough A, we discovered a second emergent CIV broad absorption trough outflowing at ~40,000 km/s, namely trough B. In total, we collected seven spectral epochs of J0230 that demonstrate emergent and rapidly (~10 days in the rest-frame) varying broad absorption. We investigate two possible scenarios that could cause these rapid changes: bulk motion and ionization variability. Given our multi-epoch data, we were able to rule out some simple models of bulk motion, but have proposed two more realistic models to explain the variability of both troughs. Trough A is likely an augmented `crossing disk' scenario with the absorber moving at 10,000 < v (km/s) < 18,000. Trough B can be explained by a flow-tube feature travelling across the emitting region at 8,000 < v (km/s) < 56,000. If ionization variability is the cause for the changes observed, trough A's absorber has n_e >= 724 cm^-3 and is at r_{equal} >=2.00 kpc, or is at r < 2.00 kpc with no constraint on the density; trough B's absorber either has n_e >= 1540 cm^-3 and is at r_{equal} >= 1.37 kpc, or is at r < 1.37 kpc with no constraint on the density.