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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

5386 results found.

  1. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  2. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  3. The EP-WXT trigger 01709259173 is likely a flaring star
  4. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  5. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  6. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  7. EP260321a: JinShan near-infrared observations
  8. EP260321a: Upper limits from a neutrino search with IceCube
  9. GRID detection of GRB 260320A
  10. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  11. GRB 260310A: LBT optical observations
  12. EP260321A: Mondy optical observations
  13. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  14. The EP-WXT trigger 01709259112 is likely a flaring star
  15. Fermi GRB 260323A: Global MASTER-Net observations report
  16. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  17. GRB 260320A: Glowbug gamma-ray detection
  18. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  19. EP260321a: COLIBRÍ further optical observations and brightening
  20. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  21. GRB 260321A: EP-FXT follow-up observation
  22. The EP-WXT trigger 01709259045 is likely a flaring star
  23. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  24. EP260321a: GOTO detection of blue variable source
  25. GRB 260321A: SVOM/VT optical upper limits
  26. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 260320A: Insight-HXMT/HE detection
  28. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  29. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  30. EP260321a: SVOM/VT optical upper limit
  31. GRB 260310A: continued optical observation at Mondy
  32. Fermi GBM Sub-Threshold Detection of GRB 260321A
  33. GRB 260321A: SVOM detection of a burst
  34. EP260321a: Global MASTER-Net observations report
  35. EP260321a: Einstein Probe detection of an X-ray transient
  36. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  37. GRB 260318A: Glowbug gamma-ray detection
  38. GRB 260320A: NuSTAR detection of prompt emission
  39. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  40. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  41. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  42. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  43. GRB 260310A/AT2026fgk: LBT near-infrared observations
  44. GRB 260318A: SVOM/GRM observation
  45. The EP-WXT trigger 01709258989 is likely a flaring star
  46. GRB 260318A: GECAM-B observation
  47. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  48. Fermi GRB 260318A: Global MASTER-Net observations report
  49. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  50. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  51. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  52. GRB 260310A / AT2026fgk: LCO optical observations
  53. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  54. GRB 260316B: GECAM-B observation
  55. GRB 260316B: SVOM/GRM observation
  56. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  57. EP260316a: COLIBRÍ faint optical counterpart candidate
  58. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  59. GRB 260316B: AstroSat CZTI detection
  60. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  61. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  62. EP260316a: Xinglong optical upper limit
  63. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  64. GRB 260314A: Glowbug gamma-ray detection
  65. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  66. IceCube-260315A: COLIBRÍ optical observations
  67. EP260314a: Xinglong optical upper limit
  68. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  69. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  70. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  71. GRB 260310A / AT 2026fgk: iTelescope optical observations
  72. EP260314a: COLIBRÍ optical upper limit
  73. GRID detection of GRB 260312B
  74. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  75. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  76. EP260314a: BOOTES-6/DPR optical upper limits at early times
  77. EP260314a: Global MASTER-Net observations report
  78. EP260314a: SVOM/VT optical candidate
  79. Fermi trigger No 795185313: Global MASTER-Net observations report
  80. IceCube Alert 260315A: Global MASTER-Net observations report
  81. EP260314a: Einstein Probe detection of an X-ray transient
  82. GRB 260314A: GECAM-B observation of a burst
  83. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  84. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  85. Fermi GRB 260314A: Global MASTER-Net observations report
  86. Fermi GRB 260313A: Global MASTER-Net observations report
  87. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  88. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  89. GRB 260310B: Insight-HXMT/HE detection
  90. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  91. GRB 260312B: AstroSat CZTI detection
  92. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  93. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  94. GRB 260308A: Insight-HXMT/HE detection
  95. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  96. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  97. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  98. GRB260310A / AT2026fgk: P200 Spectroscopy
  99. GRB 260312B: Glowbug gamma-ray detection
  100. GRB 260310A: potential optical counterpart

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