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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"

16152 results found.

  1. GRB 260511B: Fermi GBM Detection
  2. GRB 260511B: SVOM/VT optical observation with VHF data
  3. GRB 260511B: TRT optical observation
  4. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  5. GRB 260511A: Fermi GBM Detection
  6. GRB 260511B SVOM/C-GFT optical counterpart detection
  7. EP260509a: LCO optical upper limits
  8. GRB 260511A: UTGO H50 optical afterglow observation
  9. GRB 260510C: EP-FXT follow-up observation
  10. GRB 260510C: SVOM/VT optical counterpart confirmation
  11. GRB 260511A: SVOM/VT optical observation with VHF data
  12. GRB 260511A: KAIT optical afterglow observations
  13. GRB 260511A: LCO optical afterglow detection
  14. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  15. GRB 260511A: TRT optical counterpart detection
  16. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  17. GRB 260510B: SVOM/VT optical upper limits
  18. GRB 260510C: SVOM/VT optical upper limits
  19. GRB 260510B: GOTO early upper limit
  20. GRB 260510B: LCO optical upper limits
  21. GRB 260509A: Liverpool Telescope optical observations
  22. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  23. GRB 260509A: LCO optical observations
  24. SVOM GRB 260509A: MASTER-OAFA optical observation
  25. GRB 260509A: KAIT optical observations
  26. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  27. GRB 260509A: SVOM/VT optical candidate with VHF data
  28. GRB 260509A: LCO optical counterpart detection
  29. GRB 260509A: GOTO optical counterpart candidate
  30. EP260507a: REM optical/NIR observations
  31. EP260507a: COLIBRÍ optical observations
  32. EP260507a: SVOM/VT optical observations
  33. EP260507a: NOT optical observations
  34. EP260507a: further Liverpool Telescope observations
  35. EP260507a: Liverpool Telescope optical upper limits
  36. EP260507a: GOTO optical counterpart detection
  37. EP260507a: TRT optical counterpart detection
  38. EP260507a: Kinder optical counterpart candidate
  39. EP260507a: LCO optical counterpart
  40. EP260502a is likely a flaring star
  41. GRB 260504B: SVOM/VT optical upper limits
  42. GRB 260502A: SVOM/GRM observation of a short GRB
  43. GRB 260503A: SVOM/GRM observation of a GRB
  44. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  45. GRB 260504B: REM optical/NIR observations
  46. GRB 260504B: AST3-2 i-band upper limit
  47. SVOM GRB 260504B: MASTER-OAFA optical observations
  48. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  49. GRB 260429B / EP260429a: EP-FXT follow-up observation
  50. EP260502a: BOOTES-7: early optical upper limit
  51. EP260502a: Las Cumbres upper limit
  52. GRB 260429A: SVOM/GRM observation of a short burst
  53. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  54. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  55. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  56. EP260429a: LCO optical upper limits
  57. EP260430a: LCO optical upper limits
  58. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  59. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  60. EP260416a: Mondy and Terskol optical upper limits
  61. GRB 260424B: COLIBRÍ optical upper limit
  62. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  63. EP260321a: Upper limits from ATCA radio observations
  64. GRB 260421B: Kilonova-Catcher optical afterglow detection
  65. The EP-WXT trigger 01709258652: Mondy optical observations
  66. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  67. EP260416a: Mondy optical observations
  68. GRB 260421B: 3.6m DOT optical observation
  69. EP260416a: ZTSh R band observations
  70. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  71. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  72. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  73. GRB 260421B: SVOM/GRM observation
  74. GRB 260421B: EP-FXT follow-up observation
  75. GRB 260421B: J-band upper limit with WINTER
  76. GRB 260421B: LCO optical counterpart detection
  77. GRB 260421B: SVOM/VT optical observations
  78. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  79. GRB 260310A: Late-time Chandra X-ray Detection
  80. EP260416a: 1.3m DFOT optical observation
  81. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  82. GRB 260421B: BOOTES-7 early optical afterglow detection
  83. GRB 260421B: LCO optical afterglow confirmation
  84. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  85. GRB 260421B: TRT optical counterpart detection
  86. GRB 260412A: LCOGT Optical Upper Limits
  87. EP260416a: Optical follow-up observations with Kinder
  88. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  89. EP-WXT trigger 01709260303: KAIT optical observations
  90. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  91. GRB 260417A: SVOM/GRM observation
  92. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  93. EP260417a: GROWTH-India Telescope optical upper limit
  94. EP260417b: GROWTH-India Telescope optical upper limit
  95. EP260416a: Ondrejov D50 optical detection
  96. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  97. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  98. EP260416a: GMG Optical Observation
  99. EP260416a: LCO observations confirm end of flaring phase
  100. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope

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