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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"

32541 results found.

  1. EP260213a: NUTTelA-TAO Early Optical Limits
  2. EP260213a: SVOM/C-GFT upper limit
  3. EP260213a: refined analysis of the EP-FXT observation
  4. GRB 260212A: SVOM/GRM observation of a long burst
  5. GRB 260211A - SVOM/ECLAIRs refined analysis
  6. GRB 260204A: SVOM/ECLAIRs refined analysis
  7. GRB 260211A: EP-FXT follow-up observation
  8. GRB 260211A: SVOM/VT optical observation
  9. GRB 260212A: Glowbug gamma-ray detection
  10. GRB 260211A: GOTO optical upper limit
  11. Fermi GRB 260212A: Global MASTER-Net observations report
  12. GRB 260211A: LAST optical upper limit
  13. GRB 260210A: SVOM/GRM observation
  14. Fermi GBM Sub-Threshold Detection of GRB 260211A
  15. Konus-Wind detection of GRB 260207B
  16. GRB 260128B: SVOM/ECLAIRs refined analysis
  17. GRID detection of GRB 260207B
  18. GRB 260211A: LCO optical upper limits
  19. GRB260131A/B: 3.6m DOT Optical Observations
  20. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  21. GRB 260208A: Swift UVOT detection
  22. Konus-Wind detection of GRB 260127B
  23. EP260209a: COLIBRÍ optical upper limit
  24. Fermi GRB 260210C: Global MASTER-Net observations report
  25. EP260209a: LCO optical upper limits
  26. EP260210a: Global MASTER-Net observations report
  27. EP260210a: refined analysis of the EP-FXT observation
  28. EP260209a: Global MASTER-Net observations report
  29. GRB 260208A: LCO detection of the optical counterpart
  30. EP260210a: Optical upper limits with Kinder observations
  31. IPN triangulation of GRB 260207B (short/hard with EE)
  32. GRB 260210A: Glowbug gamma-ray detection
  33. EP260210a: SVOM/VT optical upper limit
  34. GRB 260210A: AstroSat CZTI detection
  35. GRB 260208C: AstroSat CZTI detection
  36. EP260210a: COLIBRÍ optical upper limit
  37. EP260210a: SVOM/C-GFT upper limit
  38. GRB 260208B: refined analysis of the EP-FXT observation
  39. GRB 260207B: AstroSat CZTI detection
  40. GRB 260208C: SVOM/GRM observation
  41. GRB 260204A: Swift-XRT afterglow detection
  42. GRB 260208B: AstroSat CZTI detection of a bright long burst
  43. GRB260208A: Liverpool Telescope optical follow-up observations
  44. GRB 260208A: Glowbug gamma-ray detection
  45. GRB 260208A: NuSTAR detection of prompt emission
  46. GRB 260208A: Fermi GBM Observation
  47. Fermi GRB 260209A: Global MASTER-Net observations report
  48. GRB 260208B: Swift-XRT observations
  49. GRB 260131A/B: continued Mondy optical observations
  50. GRB 260204A: Swift/UVOT Upper Limits
  51. GRB 260208B: COLIBRÍ optical observations
  52. GRB 260208A: Mondy optical observations (duplicate submission)
  53. GRB 260208A: Mondy optical observations
  54. GRB 260208A: 1.3m DFOT optical detection
  55. GRB 260208A: COLIBRÍ optical observations
  56. GRB 260208B: EP-FXT observation
  57. GRB 260208A: NOT spectroscopic redshift z = 2.36
  58. GRB 260208A: Liverpool Telescope optical detection
  59. Fermi GRB 260208C: Global MASTER-Net observations report
  60. GRB 260208B: SVOM/VT optical candidate
  61. GRB 260208A: GECAM-B observation of a bright burst
  62. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  63. GRB 260208A: SVOM/VT optical observation
  64. Fermi GRB 260208D: Global MASTER-Net observations report
  65. GRB 260208A: Swift-XRT observations
  66. GRB 260208B: Swift ToO observations
  67. GRB 260208B: SVOM/GRM observation of a bright burst
  68. GRB 260208B: Fermi GBM Detection
  69. GRB 260208B: Fermi-LAT detection
  70. GRB 260208A: Fermi-LAT detection
  71. GRB 260207B: GECAM-B observation
  72. GRB 260208A: Swift ToO observations
  73. GRB 260208A: Fermi GBM Classification Correction
  74. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  75. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  76. Fermi GRB 260208A: Global MASTER-Net observations report
  77. GRB 260207A : MASTER optical counterpart discovery
  78. GRB 260131A/B: Mondy and Terskol optical observations
  79. Fermi GRB 260207B: Global MASTER-Net observations report
  80. GRB 260206A: Swift-XRT observations
  81. EP260131a: VLA detection
  82. GRB 260206A: Tiled Swift observations
  83. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  84. GRB 260204A: Swift-XRT observations
  85. GRB 260204A: LCO optical afterglow detection
  86. GRB 260204A: SVOM/VT optical candidate
  87. GRB 260204A : MASTER Global robotic net optical observations
  88. Fermi GBM Sub-Threshold Detection of GRB 260204A
  89. GRB 260204A: GOTO optical upper limit
  90. GRB 260204A: LCO optical upper limits
  91. EP260110a: Late GTC/EMIR near-infrared observations
  92. GRB 260121A: 239Alferov CubeSat detection
  93. Konus-Wind detection of GRB 260121A
  94. GRB 260131A/B: OHP/T193 optical observations
  95. GRB 260131A: KAIT optical observations
  96. GRB 251230A: MeerLICHT afterglow detection
  97. GRB 260131A: FTW optical and NIR observations
  98. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  99. GRID detection of GRB 260131A/B
  100. GRB 260131A/B: GTC/OSIRIS+ redshift confimation

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