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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"

21572 results found.

  1. GRB 260510B: SVOM/VT optical upper limits
  2. GRB 260510C: SVOM/VT optical upper limits
  3. EP260509a: Global MASTER-Net observations report
  4. GRB 260510B: GOTO early upper limit
  5. GRB 260509A: Liverpool Telescope optical observations
  6. GRB 260509A: LCO optical observations
  7. SVOM GRB 260509A: MASTER-OAFA optical observation
  8. Fermi GRB 260510A: Global MASTER-Net observations report
  9. GRB 260509A: KAIT optical observations
  10. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  11. GRB 260509A: SVOM/VT optical candidate with VHF data
  12. GRB 260509A: GOTO optical counterpart candidate
  13. EP260507a: REM optical/NIR observations
  14. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP260507a: COLIBRÍ optical observations
  16. EP260507a: SVOM/VT optical observations
  17. EP260507a: NOT optical observations
  18. EP260507a: further Liverpool Telescope observations
  19. EP260507a: Liverpool Telescope optical upper limits
  20. EP260507a: GOTO optical counterpart detection
  21. EP260507a: Kinder optical counterpart candidate
  22. GRB 260504B: SVOM/ECLAIRs refined analysis
  23. EP260502a is likely a flaring star
  24. Fermi GRB 260506A: Global MASTER-Net observations report
  25. IceCube Alert 260505A: Global MASTER-Net observations report
  26. GRB 260504B: SVOM/VT optical upper limits
  27. GRB 260421B: radio observation with the VLA
  28. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  29. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  30. GRB 260504B: REM optical/NIR observations
  31. GRB 260504B: AST3-2 i-band upper limit
  32. SVOM GRB 260504B: MASTER-OAFA optical observations
  33. Fermi GRB 260504A: Global MASTER-Net observations report
  34. GRB 260429B / EP260429a: EP-FXT follow-up observation
  35. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  36. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  37. EP260429a: Global MASTER-Net observations report
  38. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  39. Fermi GRB 260429A: Global MASTER-Net observations report
  40. EP260430a: Global MASTER-Net observations report
  41. Fermi GRB 260428A: Global MASTER-Net observations report
  42. GRB 260424B: COLIBRÍ optical upper limit
  43. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  44. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  45. IceCube Alert 260425A: Global MASTER-Net observations report
  46. Fermi trigger No 798737427: Global MASTER-Net observations report
  47. EP260321a: Upper limits from ATCA radio observations
  48. GRB 260421B: Kilonova-Catcher optical afterglow detection
  49. The EP-WXT trigger 01709258652: Mondy optical observations
  50. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  51. EP260416a: Mondy optical observations
  52. GRB 260421B: SVOM/ECLAIRs refined analysis
  53. GRB 260421B: 3.6m DOT optical observation
  54. EP260416a: ZTSh R band observations
  55. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  56. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  57. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  58. GOTO26djh/AT2026jpw: ATCA radio detection
  59. GRB 260421B: J-band upper limit with WINTER
  60. GRB 260421B: LCO optical counterpart detection
  61. GOTO26djh/AT2026jpw: radio detection at 15GHz
  62. GRB 260412A: SVOM/ECLAIRs refined analysis
  63. GRB 260421B: SVOM/VT optical observations
  64. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  65. GRB 260310A: Late-time Chandra X-ray Detection
  66. EP260416a: 1.3m DFOT optical observation
  67. Fermi GRB 260421C: Global MASTER-Net observations report
  68. Fermi GRB 260421B: Global MASTER-Net observations report
  69. GRB 260421B: LCO optical afterglow confirmation
  70. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  71. Fermi GRB 260421A: Global MASTER-Net observations report
  72. EP260321a: VLA radio follow-up
  73. EP260416a: Optical follow-up observations with Kinder
  74. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  75. EP-WXT trigger 01709260303: KAIT optical observations
  76. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  77. Fermi trigger No 798275385: Global MASTER-Net observations report
  78. Fermi GRB 260417B: Global MASTER-Net observations report
  79. EP260416a: Ondrejov D50 optical detection
  80. EP260417a: Global MASTER-Net observations report
  81. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  82. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  83. Fermi GRB 260417A: Global MASTER-Net observations report
  84. Konus-Wind detection of GRB 260411B
  85. EP260416a: LCO observations confirm end of flaring phase
  86. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  87. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP-WXT trigger 01709259586: KAIT optical observations
  89. EP260416a: WFST optical observations and rebrightening
  90. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  91. GRB 260411B: Glowbug gamma-ray detection
  92. EP260416a: COLIBRÍ optical counterpart candidate
  93. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  94. EP260416a: Global MASTER-Net observations report
  95. GOTO26djh/AT2026jpw : MASTER OT observation
  96. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  97. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  98. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  99. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  100. Fermi trigger No 797912738: Global MASTER-Net observations report

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