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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"

22062 results found.

  1. GRB 260509A: SVOM/VT optical candidate with VHF data
  2. GRB 260509A: GOTO optical counterpart candidate
  3. EP260507a: REM optical/NIR observations
  4. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  5. EP260507a: COLIBRÍ optical observations
  6. EP260507a: SVOM/VT optical observations
  7. EP260507a: NOT optical observations
  8. EP260507a: further Liverpool Telescope observations
  9. EP260507a: Liverpool Telescope optical upper limits
  10. EP260507a: GOTO optical counterpart detection
  11. EP260507a: Kinder optical counterpart candidate
  12. GRB 260504B: SVOM/ECLAIRs refined analysis
  13. EP260502a is likely a flaring star
  14. Fermi GRB 260506A: Global MASTER-Net observations report
  15. IceCube Alert 260505A: Global MASTER-Net observations report
  16. GRB 260504B: SVOM/VT optical upper limits
  17. GRB 260421B: radio observation with the VLA
  18. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  19. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  20. GRB 260504B: REM optical/NIR observations
  21. GRB 260504B: AST3-2 i-band upper limit
  22. SVOM GRB 260504B: MASTER-OAFA optical observations
  23. Fermi GRB 260504A: Global MASTER-Net observations report
  24. GRB 260429B / EP260429a: EP-FXT follow-up observation
  25. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  26. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  27. EP260429a: Global MASTER-Net observations report
  28. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  29. Fermi GRB 260429A: Global MASTER-Net observations report
  30. EP260430a: Global MASTER-Net observations report
  31. Fermi GRB 260428A: Global MASTER-Net observations report
  32. GRB 260424B: COLIBRÍ optical upper limit
  33. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  34. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  35. IceCube Alert 260425A: Global MASTER-Net observations report
  36. Fermi trigger No 798737427: Global MASTER-Net observations report
  37. EP260321a: Upper limits from ATCA radio observations
  38. GRB 260421B: Kilonova-Catcher optical afterglow detection
  39. The EP-WXT trigger 01709258652: Mondy optical observations
  40. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  41. EP260416a: Mondy optical observations
  42. GRB 260421B: SVOM/ECLAIRs refined analysis
  43. GRB 260421B: 3.6m DOT optical observation
  44. EP260416a: ZTSh R band observations
  45. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  46. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  47. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  48. GOTO26djh/AT2026jpw: ATCA radio detection
  49. GRB 260421B: J-band upper limit with WINTER
  50. GRB 260421B: LCO optical counterpart detection
  51. GOTO26djh/AT2026jpw: radio detection at 15GHz
  52. GRB 260412A: SVOM/ECLAIRs refined analysis
  53. GRB 260421B: SVOM/VT optical observations
  54. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  55. GRB 260310A: Late-time Chandra X-ray Detection
  56. EP260416a: 1.3m DFOT optical observation
  57. Fermi GRB 260421C: Global MASTER-Net observations report
  58. Fermi GRB 260421B: Global MASTER-Net observations report
  59. GRB 260421B: LCO optical afterglow confirmation
  60. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  61. Fermi GRB 260421A: Global MASTER-Net observations report
  62. EP260321a: VLA radio follow-up
  63. EP260416a: Optical follow-up observations with Kinder
  64. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  65. EP-WXT trigger 01709260303: KAIT optical observations
  66. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  67. Fermi trigger No 798275385: Global MASTER-Net observations report
  68. Fermi GRB 260417B: Global MASTER-Net observations report
  69. EP260416a: Ondrejov D50 optical detection
  70. EP260417a: Global MASTER-Net observations report
  71. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  72. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  73. Fermi GRB 260417A: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 260411B
  75. EP260416a: LCO observations confirm end of flaring phase
  76. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  77. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  78. EP-WXT trigger 01709259586: KAIT optical observations
  79. EP260416a: WFST optical observations and rebrightening
  80. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  81. GRB 260411B: Glowbug gamma-ray detection
  82. EP260416a: COLIBRÍ optical counterpart candidate
  83. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  84. EP260416a: Global MASTER-Net observations report
  85. GOTO26djh/AT2026jpw : MASTER OT observation
  86. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  87. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  88. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  89. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  90. Fermi trigger No 797912738: Global MASTER-Net observations report
  91. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  92. EP260321a: CMO SAI J,K observations
  93. Fermi GRB 260413A: Global MASTER-Net observations report
  94. EP260321a: SVOM/VT optical observations and color changes around peak
  95. Fermi GRB 260412A: Global MASTER-Net observations report
  96. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  97. GRB 260411B: COLIBRÍ optical observations
  98. GRB 260411B: Ondrejov D50 optical afterglow detection
  99. GRB260411B: 3.6m DOT optical observation
  100. GRB 260411B: GOTO optical counterpart candidate

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