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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"

21781 results found.

  1. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  2. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  3. GRB 260604C: 6 GHz VLA observations
  4. GRB 260604C: SAO RAS optical observations
  5. GRB 260604C: GRANDMA observations
  6. GRB260603A: SVOM/ECLAIRs refined analysis
  7. GRB 260604C: Liverpool Telescope optical detection
  8. EP260602d: EP-FXT follow-up observation
  9. GRB 260527A/EP260527a: 6 GHz VLA observations
  10. GRB 260604C: GOTO detections of the optical afterglow
  11. GRB 260604C: Kilonova-Catcher optical afterglow detection
  12. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. GRB 260604C: Jinshan optical observations
  14. EP260602d: J-band upper limit with WINTER
  15. EP260602b: J-band upper limit with WINTER
  16. GRB 260604C: LAST detection of optical counterpart candidate
  17. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  18. Fermi GRB 260604C: Global MASTER-Net observations report
  19. Fermi GRB 260604C: Global MASTER-Net observations report
  20. SVOM GRB260604.85: Global MASTER-Net observations report
  21. GRB 260604C: SVOM detection of a long burst
  22. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  23. GRB 260603A: NOT optical observations
  24. EP260603a: Global MASTER-Net observations report
  25. EP260603a: Einstein Probe detection of a fast X-ray transient
  26. EP260602d: Optical Upper limits with kinder observations
  27. EP260602b: Liverpool Telescope observations
  28. EP260602a: Liverpool Telescope optical upper limits
  29. EP260602b: Liverpool Telescope and LCO observations
  30. EP260602a: GTC and Liverpool Telescope optical observations
  31. GRB 260603A: Kilonova-Catcher optical upper limit
  32. GRB 260603A: SVOM/VT optical observations
  33. EP260602a: NOT NIR J-band observations
  34. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  35. Fermi trigger No 802141998: Global MASTER-Net observations report
  36. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  37. EP260602a: COLIBRÍ optical observations
  38. GRB260601B/EP260601a: NOT near-infrared observations
  39. SVOM GRB260603.23: Global MASTER-Net observations report
  40. Fermi GRB 260602B: Global MASTER-Net observations report
  41. Fermi GRB 260602B: Global MASTER-Net observations report
  42. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  43. EP260602a: SVOM/VT optical candidate
  44. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  45. GRB 260601B/EP260601a: J-band upper limit with WINTER
  46. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  47. EP260530a/AT 2026nwl: KAIT optical observations
  48. EP260602a: Optical upper limits with Kinder observations
  49. GRB 260601B/EP260601a: SVOM/VT optical observations
  50. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  51. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  52. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  53. GRB 260516D: VLA radio detection
  54. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  55. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  56. Fermi GRB 260601A: Global MASTER-Net observations report
  57. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  58. AT2026nik: EP-FXT X-ray counterpart
  59. Fermi trigger No 801900520: Global MASTER-Net observations report
  60. GRB 260531A: MAXI/GSC detection
  61. AT 2026nuz: COLIBRÍ optical observations
  62. EP260527a/GRB 260527A: further FTW optical and NIR observations
  63. GRB 260527A / EP260527a: VLA radio detection
  64. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  65. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  66. GRB 260529A: GOTO tentative optical afterglow candidate
  67. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  68. Fermi GRB 260529A: Global MASTER-Net observations report
  69. EP260526a: SVOM/VT optical upper limits
  70. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  71. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  72. EP260527a / GRB 260527A: NOT optical observations
  73. GRB 260527A/EP260527a: FTW optical and NIR observations
  74. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  75. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  76. EP260527a: SVOM/VT optical observation
  77. EP260527a: COLIBRÍ optical detection
  78. Fermi trigger No 801580882: Global MASTER-Net observations report
  79. EP260526a: Einstein Probe detection of a fast X-ray transient
  80. Fermi GRB 260526A: Global MASTER-Net observations report
  81. EP-WXT 01709266106: NOT optical upper limits
  82. Fermi GRB 260525A: Global MASTER-Net observations report
  83. Fermi GRB 260523A: Global MASTER-Net observations report
  84. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  85. GRB 260522A: GOTO optical upper limit
  86. Fermi trigger No 801135305: Global MASTER-Net observations report
  87. Fermi GRB 260522A: Global MASTER-Net observations report
  88. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  89. GRB 260509A: SVOM/ECLAIRs refined analysis
  90. GRB 260516D: SVOM/ECLAIRs refined analysis
  91. GRB 260515A: SVOM/ECLAIRs refined analysis
  92. GRB 260421B: radio detection with the VLA
  93. GRB 260516D: GOTO optical counterpart detection
  94. GRB 260516D: LCO optical observations
  95. GRB 260515A: further Liverpool Telescope observations
  96. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  97. GRB 260516D: GROWTH-India Telescope optical detection
  98. GRB 260515A: CrAO ZTSh BVRI optical observations
  99. Fermi GRB 260516C: Global MASTER-Net observations report
  100. SVOM GRB260516D: Global MASTER-Net observations report

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