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TESS Detects Bright, Long-Lasting Gamma-Ray Burst

Astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) exoplanet-hunting mission have detected the rising and decaying optical afterglow of the gamma-ray burst event GRB 191016A. An artist’s impression of a blazar. Image credit: DESY / Science Communication Lab. GRB 191016A occurred on October 16, 2019, in a previously uncataloged galaxy in the northern constellation of…

Astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) exoplanet-hunting assignment have discovered the rising and decaying optical afterglow of this gamma-ray burst event GRB 191016A.

An artist’s impression of a blazar. Image credit: DESY / Science Communication Lab.

An artist’s impression of a blazar. Image credit: DESY / Science Communication Lab.

GRB 191016A occurred on October 16, 2019, in a previously uncataloged galaxy at the northern constellation of Aries.

The gamma-ray burst was initially detected by the Burst Alert Telescope (BAT) onboard NASA’s Neil Gehrels Swift Observatory.

The burst occurred too close to the Moon for Swift to safely slew to its own position, preventing follow-up observations.

TESS clearly discovered the rising pre-peak light curve of GRB 191016A.

“Our findings prove this TESS telescope is useful not just for finding new planets, but also for high-energy astrophysics,” explained Dr. Krista Lynne Smith, an astrophysicist in the Department of Physics at Southern Methodist University and Stanford University.

TESS full-frame image in the cadence just before the BAT trigger (left) and at the peak flux of the GRB 191016A burst (center); the emergence of the afterglow is apparent in the center of the image, indicated by the white arrow; the right panel shows the same region of the sky, with a slightly different orientation, in the Digitized Sky Survey (DSS); a small inset of TESS image is provided in the bottom left corner to demonstrate the change in orientation. Image credit: Smith et al., doi: 10.3847/1538-4357/abe6a2.

TESS full-frame picture in the cadence before the BAT trigger (left) and at the peak level of the GRB 191016A burst (center); the development of this afterglow is evident at the middle of the image, indicated by the arrow; the right panel shows the same area of the skies, with a slightly different orientation, in the Digitized Sky Survey (DSS); a small inset of TESS picture is provided in the bottom left corner to show the change in orientation. Picture credit: Smith et al. , doi: 10. 3847/1538-4357/abe6a2.

Dr. Smith and colleagues calculated that GRB 191016A had a peak magnitude of 15.1, which means that it was 10,000 times fainter than the faintest stars we could see with the naked eyes.

Most gamma ray bursts are dimmer — nearer to 160,000 times fainter than the faintest stars.

It is estimated that light in the burst’s host galaxy had been traveling 11.7 billion years prior to becoming visible by TESS.

GRB 191016A attained its peak brightness sometime between 1,000 and 2,600 minutes, then faded slowly until it dropped beneath the ability of TESS to detect it some 7,000 minutes after it first went off.

“Because the burst reached its peak brightness later and had a peak brightness that was higher than most bursts, it allowed the TESS telescope to make multiple observations before the burst faded below the telescope’s detection limit,” Dr. Smith said.

“We’ve provided the only space-based optical follow-up on this exceptional burst.”

The outcomes were published in the Astrophysical Journal.

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Krista Lynne Smith et al. 2021. GRB 191016A: A Long Gamma-Ray Burst Detected by TESS. ApJ 911, 43; doi: 10. 3847/1538-4357/ / abe6a2

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