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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"

15986 results found.

  1. GRB 260511A: EP-FXT follow-up observation
  2. GRB 260511B: EP-FXT follow-up observation
  3. GRB 260511B: LCO optical counterpart detection
  4. GRB260511B: MAO/AZT-22 optical observations
  5. GRB 260511A: SVOM/VT optical observations
  6. GRB 260511B: LCO optical observations
  7. GRB 260511B: OHP/T193 spectroscopic observations
  8. GRB 260511B: GOTO optical counterpart detection
  9. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  10. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  11. GRB 260511B: SVOM/VT optical observations
  12. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  14. GRB 260509A: SAO RAS optical observations
  15. GRB 260511A: REM near-infrared detection
  16. GRB 260511B: GROWTH-India Telescope optical observations
  17. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  18. GRB 260511B: NuSTAR detection of prompt emission
  19. GRB 260511A: NuSTAR detection of prompt emission
  20. GRB 260511B: Fermi GBM Detection
  21. GRB 260511B: SVOM/VT optical observation with VHF data
  22. GRB 260511B: TRT optical observation
  23. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  24. GRB 260511A: Fermi GBM Detection
  25. GRB 260511B SVOM/C-GFT optical counterpart detection
  26. EP260509a: LCO optical upper limits
  27. GRB 260511A: UTGO H50 optical afterglow observation
  28. GRB 260510C: EP-FXT follow-up observation
  29. GRB 260510C: SVOM/VT optical counterpart confirmation
  30. GRB 260511A: SVOM/VT optical observation with VHF data
  31. GRB 260511A: KAIT optical afterglow observations
  32. GRB 260511A: LCO optical afterglow detection
  33. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  34. GRB 260511A: TRT optical counterpart detection
  35. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  36. GRB 260510B: SVOM/VT optical upper limits
  37. GRB 260510C: SVOM/VT optical upper limits
  38. GRB 260510B: GOTO early upper limit
  39. GRB 260510B: LCO optical upper limits
  40. GRB 260509A: Liverpool Telescope optical observations
  41. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  42. GRB 260509A: LCO optical observations
  43. SVOM GRB 260509A: MASTER-OAFA optical observation
  44. GRB 260509A: KAIT optical observations
  45. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  46. GRB 260509A: SVOM/VT optical candidate with VHF data
  47. GRB 260509A: LCO optical counterpart detection
  48. GRB 260509A: GOTO optical counterpart candidate
  49. EP260507a: REM optical/NIR observations
  50. EP260507a: COLIBRÍ optical observations
  51. EP260507a: SVOM/VT optical observations
  52. EP260507a: NOT optical observations
  53. EP260507a: further Liverpool Telescope observations
  54. EP260507a: Liverpool Telescope optical upper limits
  55. EP260507a: GOTO optical counterpart detection
  56. EP260507a: TRT optical counterpart detection
  57. EP260507a: Kinder optical counterpart candidate
  58. EP260507a: LCO optical counterpart
  59. EP260502a is likely a flaring star
  60. GRB 260504B: SVOM/VT optical upper limits
  61. GRB 260502A: SVOM/GRM observation of a short GRB
  62. GRB 260503A: SVOM/GRM observation of a GRB
  63. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  64. GRB 260504B: REM optical/NIR observations
  65. GRB 260504B: AST3-2 i-band upper limit
  66. SVOM GRB 260504B: MASTER-OAFA optical observations
  67. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  68. GRB 260429B / EP260429a: EP-FXT follow-up observation
  69. EP260502a: BOOTES-7: early optical upper limit
  70. EP260502a: Las Cumbres upper limit
  71. GRB 260429A: SVOM/GRM observation of a short burst
  72. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  73. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  74. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  75. EP260429a: LCO optical upper limits
  76. EP260430a: LCO optical upper limits
  77. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  78. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  79. EP260416a: Mondy and Terskol optical upper limits
  80. GRB 260424B: COLIBRÍ optical upper limit
  81. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  82. EP260321a: Upper limits from ATCA radio observations
  83. GRB 260421B: Kilonova-Catcher optical afterglow detection
  84. The EP-WXT trigger 01709258652: Mondy optical observations
  85. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  86. EP260416a: Mondy optical observations
  87. GRB 260421B: 3.6m DOT optical observation
  88. EP260416a: ZTSh R band observations
  89. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  90. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  91. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  92. GRB 260421B: SVOM/GRM observation
  93. GRB 260421B: EP-FXT follow-up observation
  94. GRB 260421B: J-band upper limit with WINTER
  95. GRB 260421B: LCO optical counterpart detection
  96. GRB 260421B: SVOM/VT optical observations
  97. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  98. GRB 260310A: Late-time Chandra X-ray Detection
  99. EP260416a: 1.3m DFOT optical observation
  100. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115

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