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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"

32508 results found.

  1. EP260210a: SVOM/VT optical upper limit
  2. GRB 260210A: AstroSat CZTI detection
  3. GRB 260208C: AstroSat CZTI detection
  4. EP260210a: COLIBRÍ optical upper limit
  5. EP260210a: SVOM/C-GFT upper limit
  6. GRB 260208B: refined analysis of the EP-FXT observation
  7. GRB 260207B: AstroSat CZTI detection
  8. GRB 260208C: SVOM/GRM observation
  9. GRB 260204A: Swift-XRT afterglow detection
  10. GRB 260208B: AstroSat CZTI detection of a bright long burst
  11. GRB260208A: Liverpool Telescope optical follow-up observations
  12. GRB 260208A: Glowbug gamma-ray detection
  13. GRB 260208A: NuSTAR detection of prompt emission
  14. GRB 260208A: Fermi GBM Observation
  15. Fermi GRB 260209A: Global MASTER-Net observations report
  16. GRB 260208B: Swift-XRT observations
  17. GRB 260131A/B: continued Mondy optical observations
  18. GRB 260204A: Swift/UVOT Upper Limits
  19. GRB 260208B: COLIBRÍ optical observations
  20. GRB 260208A: Mondy optical observations (duplicate submission)
  21. GRB 260208A: Mondy optical observations
  22. GRB 260208A: 1.3m DFOT optical detection
  23. GRB 260208A: COLIBRÍ optical observations
  24. GRB 260208B: EP-FXT observation
  25. GRB 260208A: NOT spectroscopic redshift z = 2.36
  26. GRB 260208A: Liverpool Telescope optical detection
  27. Fermi GRB 260208C: Global MASTER-Net observations report
  28. GRB 260208B: SVOM/VT optical candidate
  29. GRB 260208A: GECAM-B observation of a bright burst
  30. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  31. GRB 260208A: SVOM/VT optical observation
  32. Fermi GRB 260208D: Global MASTER-Net observations report
  33. GRB 260208A: Swift-XRT observations
  34. GRB 260208B: Swift ToO observations
  35. GRB 260208B: SVOM/GRM observation of a bright burst
  36. GRB 260208B: Fermi GBM Detection
  37. GRB 260208B: Fermi-LAT detection
  38. GRB 260208A: Fermi-LAT detection
  39. GRB 260207B: GECAM-B observation
  40. GRB 260208A: Swift ToO observations
  41. GRB 260208A: Fermi GBM Classification Correction
  42. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  43. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  44. Fermi GRB 260208A: Global MASTER-Net observations report
  45. GRB 260207A : MASTER optical counterpart discovery
  46. GRB 260131A/B: Mondy and Terskol optical observations
  47. Fermi GRB 260207B: Global MASTER-Net observations report
  48. GRB 260206A: Swift-XRT observations
  49. EP260131a: VLA detection
  50. GRB 260206A: Tiled Swift observations
  51. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  52. GRB 260204A: Swift-XRT observations
  53. GRB 260204A: LCO optical afterglow detection
  54. GRB 260204A: SVOM/VT optical candidate
  55. GRB 260204A : MASTER Global robotic net optical observations
  56. Fermi GBM Sub-Threshold Detection of GRB 260204A
  57. GRB 260204A: GOTO optical upper limit
  58. GRB 260204A: LCO optical upper limits
  59. EP260110a: Late GTC/EMIR near-infrared observations
  60. GRB 260121A: 239Alferov CubeSat detection
  61. Konus-Wind detection of GRB 260121A
  62. GRB 260131A/B: OHP/T193 optical observations
  63. GRB 260131A: KAIT optical observations
  64. GRB 251230A: MeerLICHT afterglow detection
  65. GRB 260131A: FTW optical and NIR observations
  66. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  67. GRID detection of GRB 260131A/B
  68. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  69. GRB 260130A: Insight-HXMT/HE detection
  70. GRB 260130A: GECAM-B observation of a short burst
  71. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  72. GRB 260131A/B: EP/FXT X-ray afterglow detection
  73. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  74. GRB 260127B: Insight-HXMT/HE detection
  75. GRB 260127B: GECAM-B observation of a short burst
  76. GRB 260127A: GECAM-B observation
  77. GRB 260131A: NOT spectroscopic redshift z = 1.434
  78. EP260131a: Liverpool Telescope optical upper limits
  79. EP260131a: COLIBRÍ further observations
  80. Konus-Wind detection of GRB 260128A / EP260128a
  81. GRB 260131A: Insight-HXMT/HE detection
  82. Konus-Wind detection of GRB 260131A/B
  83. EP260131a: SVOM/VT optical observation
  84. EP260131a: Xinglong optical upper limit
  85. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  86. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  87. GRB 260131A/B: Fermi GBM Observation
  88. EP260131a: COLIBRÍ observations of slow optical fading
  89. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  91. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  92. EP260131a: COLIBRÍ optical observations of the counterpart
  93. GRB 260127B: AstroSat CZTI detection
  94. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  95. Fermi GRB 260130A: Global MASTER-Net observations report
  96. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  97. Fermi GRB 260129A: Global MASTER-Net observations report
  98. GRB 260128B: LCO optical upper limits
  99. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  100. EP260128a: J band upper limit by SYSU 80cm infrared telescope

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