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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"

15985 results found.

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

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