ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

Anna Y.Q. Ho; Daniel A. Perley; Paz Beniamini; S. Bradley Cenko; S. R. Kulkarni; Igor Andreoni; Leo P. Singer; Kishalay De; Mansi M. Kasliwal; Christoffer Fremling; Eric C. Bellm; Richard Dekany; Alexandre Delacroix; Dmitry A. Duev; Daniel A. Goldstein; V. Zach Golkhou; Ariel Goobar; Matthew J. Graham; David Hale; Thomas Kupfer; Russ R. Laher; Frank J. Masci; Adam A. Miller; James D. Neill; Reed Riddle; Ben Rusholme; David L. Shupe; Roger Smith; Jesper Sollerman; Jan Van Roestel

doi:10.3847/1538-4357/abc34d

ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

Anna Y.Q. Ho, Daniel A. Perley, Paz Beniamini, S. Bradley Cenko, S. R. Kulkarni, Igor Andreoni, Leo P. Singer, Kishalay De, Mansi M. Kasliwal, Christoffer Fremling, Eric C. Bellm, Richard Dekany, Alexandre Delacroix, Dmitry A. Duev, Daniel A. Goldstein, V. Zach Golkhou, Ariel Goobar, Matthew J. Graham, David Hale, Thomas KupferRuss R. Laher, Frank J. Masci, Adam A. Miller, James D. Neill, Reed Riddle, Ben Rusholme, David L. Shupe, Roger Smith, Jesper Sollerman, Jan Van Roestel

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

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Abstract

We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g-r ≈ 0.6 mag) and luminous (M 1626 Å =-25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t j = 1 d (observer frame); (2) a luminous (L 0.3-10 KeV = 1046 erg s-1) X-ray counterpart; and (3) luminous (L 10 GHz = 4 × 1031 erg s-1 Hz-1) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E γ,iso < 7 × 1052 erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ0 ⪆ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.

Original language	English (US)
Article number	98
Journal	Astrophysical Journal
Volume	905
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/abc34d
State	Published - Dec 20 2020

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.3847/1538-4357/abc34d

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Ho, A. Y. Q., Perley, D. A., Beniamini, P., Cenko, S. B., Kulkarni, S. R., Andreoni, I., Singer, L. P., De, K., Kasliwal, M. M., Fremling, C., Bellm, E. C., Dekany, R., Delacroix, A., Duev, D. A., Goldstein, D. A., Golkhou, V. Z., Goobar, A., Graham, M. J., Hale, D., ... Van Roestel, J. (2020). ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart. Astrophysical Journal, 905(2), Article 98. https://doi.org/10.3847/1538-4357/abc34d

@article{630883fec4014a6aa6a1f6bf21f9f9a6,

title = "ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart",

abstract = "We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g-r ≈ 0.6 mag) and luminous (M 1626 {\AA} =-25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t j = 1 d (observer frame); (2) a luminous (L 0.3-10 KeV = 1046 erg s-1) X-ray counterpart; and (3) luminous (L 10 GHz = 4 × 1031 erg s-1 Hz-1) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E γ,iso < 7 × 1052 erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ0 ⪆ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.",

author = "Ho, {Anna Y.Q.} and Perley, {Daniel A.} and Paz Beniamini and Cenko, {S. Bradley} and Kulkarni, {S. R.} and Igor Andreoni and Singer, {Leo P.} and Kishalay De and Kasliwal, {Mansi M.} and Christoffer Fremling and Bellm, {Eric C.} and Richard Dekany and Alexandre Delacroix and Duev, {Dmitry A.} and Goldstein, {Daniel A.} and Golkhou, {V. Zach} and Ariel Goobar and Graham, {Matthew J.} and David Hale and Thomas Kupfer and Laher, {Russ R.} and Masci, {Frank J.} and Miller, {Adam A.} and Neill, {James D.} and Reed Riddle and Ben Rusholme and Shupe, {David L.} and Roger Smith and Jesper Sollerman and {Van Roestel}, Jan",

year = "2020",

month = dec,

day = "20",

doi = "10.3847/1538-4357/abc34d",

language = "English (US)",

volume = "905",

journal = "Astrophysical Journal",

issn = "0004-637X",

number = "2",

}

Ho, AYQ, Perley, DA, Beniamini, P, Cenko, SB, Kulkarni, SR, Andreoni, I, Singer, LP, De, K, Kasliwal, MM, Fremling, C, Bellm, EC, Dekany, R, Delacroix, A, Duev, DA, Goldstein, DA, Golkhou, VZ, Goobar, A, Graham, MJ, Hale, D, Kupfer, T, Laher, RR, Masci, FJ, Miller, AA, Neill, JD, Riddle, R, Rusholme, B, Shupe, DL, Smith, R, Sollerman, J & Van Roestel, J 2020, 'ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart', Astrophysical Journal, vol. 905, no. 2, 98. https://doi.org/10.3847/1538-4357/abc34d

TY - JOUR

T1 - ZTF20aajnksq (AT 2020blt)

T2 - A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

AU - Ho, Anna Y.Q.

AU - Perley, Daniel A.

AU - Beniamini, Paz

AU - Cenko, S. Bradley

AU - Kulkarni, S. R.

AU - Andreoni, Igor

AU - Singer, Leo P.

AU - De, Kishalay

AU - Kasliwal, Mansi M.

AU - Fremling, Christoffer

AU - Bellm, Eric C.

AU - Dekany, Richard

AU - Delacroix, Alexandre

AU - Duev, Dmitry A.

AU - Goldstein, Daniel A.

AU - Golkhou, V. Zach

AU - Goobar, Ariel

AU - Graham, Matthew J.

AU - Hale, David

AU - Kupfer, Thomas

AU - Laher, Russ R.

AU - Masci, Frank J.

AU - Miller, Adam A.

AU - Neill, James D.

AU - Riddle, Reed

AU - Rusholme, Ben

AU - Shupe, David L.

AU - Smith, Roger

AU - Sollerman, Jesper

AU - Van Roestel, Jan

PY - 2020/12/20

Y1 - 2020/12/20

N2 - We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g-r ≈ 0.6 mag) and luminous (M 1626 Å =-25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t j = 1 d (observer frame); (2) a luminous (L 0.3-10 KeV = 1046 erg s-1) X-ray counterpart; and (3) luminous (L 10 GHz = 4 × 1031 erg s-1 Hz-1) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E γ,iso < 7 × 1052 erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ0 ⪆ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.

AB - We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g-r ≈ 0.6 mag) and luminous (M 1626 Å =-25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t j = 1 d (observer frame); (2) a luminous (L 0.3-10 KeV = 1046 erg s-1) X-ray counterpart; and (3) luminous (L 10 GHz = 4 × 1031 erg s-1 Hz-1) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E γ,iso < 7 × 1052 erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ0 ⪆ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.

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ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

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Keck/LRIS optical spectrum of ZTF20aajnksq

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ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart

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Keck/LRIS optical spectrum of ZTF20aajnksq

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