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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

22196 results found.

  1. EP260327a: Gemini-North optical upper limits
  2. EP260324a: GROWTH-India Telescope optical observation
  3. EP260327a: Global MASTER-Net observations report
  4. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  5. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  6. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  7. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  8. EP260321a: JinShan near-infrared observations
  9. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  10. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  11. EP260321a: Gemini-South confirmation of a supernova
  12. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  13. GRB 260310A: LBT optical observations
  14. EP260321A: Mondy optical observations
  15. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  16. Fermi GRB 260323A: Global MASTER-Net observations report
  17. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  18. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  19. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  20. EP260321a: COLIBRÍ further optical observations and brightening
  21. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  22. EP260214b: ATCA 6 GHz detection
  23. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  24. EP260321a: GOTO detection of blue variable source
  25. EP260321a: further Kinder optical observations
  26. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  28. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  29. EP260321a: SVOM/VT optical upper limit
  30. GRB 260310A: continued optical observation at Mondy
  31. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  32. EP260321a: Global MASTER-Net observations report
  33. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  34. GRB 260310A / AT 2026fgk: KAIT optical observations
  35. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  36. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  37. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  38. GRB 260310A/AT2026fgk: LBT near-infrared observations
  39. NOEMA Detection of GRB 260310A / AT 2026fgk
  40. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  41. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  42. Fermi GRB 260318A: Global MASTER-Net observations report
  43. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  44. GRB 260310A / AT 2026fgk: radio detection with the VLA
  45. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  46. GRB 260310A / AT2026fgk: LCO optical observations
  47. EP260316a: COLIBRÍ faint optical counterpart candidate
  48. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  49. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP260316a: optical upper limit with Kinder observations
  51. IceCube-260315A: COLIBRÍ optical observations
  52. EP260314a: optical upper limit with Kinder observations
  53. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  54. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  55. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  56. GRB 260310A / AT 2026fgk: iTelescope optical observations
  57. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260314a: Global MASTER-Net observations report
  59. Fermi trigger No 795185313: Global MASTER-Net observations report
  60. IceCube Alert 260315A: Global MASTER-Net observations report
  61. GRB 260310A / AT2026fgk: SAO RAS optical observations
  62. GRB 260310A/AT2026fgk: radio detection at 15GHz
  63. GRB 260310A / AT2026fgk: TNG NIR detection
  64. GRB 260310A / AT2026fgk: OASDG optical observations
  65. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  66. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  67. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  68. Fermi GRB 260314A: Global MASTER-Net observations report
  69. Fermi GRB 260313A: Global MASTER-Net observations report
  70. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  71. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  72. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  73. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  74. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  75. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  76. GRB260310A / AT2026fgk: P200 Spectroscopy
  77. GRB 260310A: potential optical counterpart
  78. Fermi GRB 260312B: Global MASTER-Net observations report
  79. Fermi GRB 260311B: Global MASTER-Net observations report
  80. GRB 260131A/B: radio detection with the VLA
  81. EP260302a: MeerKAT radio counterpart
  82. Fermi GRB 260310B: Global MASTER-Net observations report
  83. Fermi GRB 260310A: Global MASTER-Net observations report
  84. GRB 260307B: SVOM/ECLAIRs refined analysis
  85. GRB 260208A: radio detection with the VLA
  86. GRB 260307B: possible NOT optical counterpart
  87. GRB 260307B: SVOM/VT upper limit with X band data analysis
  88. Fermi GRB 260307A: Global MASTER-Net observations report
  89. GRB260307B: GROWTH-India Telescope optical upper limit
  90. GRB 260307B: SVOM/C-GFT upper limit
  91. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  92. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 260207A: TESS Detection and Possible VLA Counterpart
  94. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  95. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  96. GRB 260303A: 1.3m DFOT optical upper limit
  97. EP260214b: ATCA 6 GHz observations
  98. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  99. GRB 260303A: SVOM/ECLAIRs refined analysis
  100. Fermi GRB 260305A: Global MASTER-Net observations report

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