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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"

27393 results found.

  1. GRB 260531A: MAXI/GSC detection
  2. AT 2026nuz: COLIBRÍ optical observations
  3. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  4. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  5. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  6. Fermi GRB 260529A: Global MASTER-Net observations report
  7. EP250526a: SVOM/VT optical upper limits
  8. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  9. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  10. EP260527a/GRB 260527A: EP-FXT follow-up observation
  11. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  12. EP260527a: SVOM/VT optical observation
  13. EP260527a: COLIBRÍ optical detection
  14. EP260527a: Einstein Probe detection of a fast X-ray transient
  15. Fermi trigger No 801580882: Global MASTER-Net observations report
  16. EP260526a: LCO optical upper limits
  17. EP260526a: Einstein Probe detection of a fast X-ray transient
  18. EP260526.405: COLIBRÍ optical upper limits
  19. The EP-WXT trigger 01709266106 is not a real source
  20. Fermi GRB 260526A: Global MASTER-Net observations report
  21. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  22. EP-WXT 01709266106: NOT optical upper limits
  23. Fermi GRB 260525A: Global MASTER-Net observations report
  24. GRB 260523B: AstroSat CZTI detection
  25. Fermi GRB 260523A: Global MASTER-Net observations report
  26. GRB 260522A: Fermi GBM Observation
  27. GRB 260522B: NuSTAR detection of prompt emission
  28. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  29. Fermi trigger No 801135305: Global MASTER-Net observations report
  30. Fermi GRB 260522A: Global MASTER-Net observations report
  31. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  32. GRB 260511A: iTelescope T-75 optical detection
  33. GRB 260520B: SVOM/GRM observation
  34. GRB 260411B: TERI Gamma-ray detection
  35. GRB 260407A: TERI Gamma-ray detection
  36. GRB 260307A: TERI Gamma-ray detection
  37. GRB 260225D: TERI Gamma-ray detection
  38. GRB 251118A: TERI Gamma-ray detection
  39. GRB 251113A: TERI Gamma-ray detection
  40. GRB 260428A: TERI Gamma-ray detection
  41. GRB 260519C: NuSTAR detection of prompt emission
  42. Konus-Wind detection of GRB 260518A
  43. GRB 260516D: SVOM/ECLAIRs refined analysis
  44. GRB 260421B: radio detection with the VLA
  45. GRB 260509A: CrAO ZTSh optical upper limit
  46. GRB 260516D: GOTO optical counterpart detection
  47. GRB 260516D: LCO optical observations
  48. GRB 260515A: further Liverpool Telescope observations
  49. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  50. GRB 260516D: GROWTH-India Telescope optical detection
  51. GRB 260516D: SVOM/VT optical bright candidate
  52. GRB 260515A: CrAO ZTSh BVRI optical observations
  53. Fermi GRB 260516C: Global MASTER-Net observations report
  54. SVOM GRB260516D: Global MASTER-Net observations report
  55. GRB 260516D: SVOM possible detection of a burst
  56. GRB 260515A: LCO optical counterpart detection
  57. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  59. EP260514a: NOT optical counterpart confirmation
  60. EP260514a: TRT optical counterpart candidate
  61. EP260514a: SVOM/VT optical candidate
  62. Fermi GRB 260516B: Global MASTER-Net observations report
  63. GRB 260515A: OHP/T193 optical observations
  64. EP260514a: COLIBRÍ optical upper limits
  65. GRB 260515A: LCO optical observations
  66. SVOM GRB 260515A: Global MASTER-Net observations report
  67. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  68. GRB 260515A: SVOM/VT optical candidate from VHF data
  69. GRB 260515A: JinShan optical counterpart candidate
  70. GRB 260515A: SVOM detection of a burst
  71. GRB 260510C: Glowbug gamma-ray detection
  72. EP260514a: GROWTH-India Telescope optical upper limit
  73. GRB 260511B: GMG Optical Upper Limit
  74. EP260514a: Global MASTER-Net observations report
  75. EP260514a: Einstein Probe detection of a fast X-ray transient
  76. EP260512a: LCO optical upper limits
  77. GRB 260511B: Mephisto multi-band optical followup
  78. Fermi GRB 260514A: Global MASTER-Net observations report
  79. GRB 260512A: AstroSat CZTI detection
  80. EP260512a: EP-FXT follow-up observation
  81. EP260507a: Xinglong Schmidt optical counterpart detection
  82. EP260512a: Global MASTER-Net observations report
  83. Fermi GRB 260513A: Global MASTER-Net observations report
  84. Fermi GRB 260512A: Global MASTER-Net observations report
  85. GRB 260511B: further SAO RAS optical observations
  86. GRB 260509A: SVOM/VT optical observations
  87. The EP-WXT trigger 01709262036 is likely a flaring star
  88. EP260512a: COLIBRÍ optical upper limits
  89. EP260512a: Einstein Probe detection of an X-ray transient
  90. GRB 260511B: further J-band observations by the SYSU 80 cm infrared telescope
  91. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  92. GRB 260512A: NuSTAR detection of prompt emission
  93. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  94. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  95. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  96. GRB 260511A: Glowbug gamma-ray detection
  97. GRB 260511B: SAO RAS optical observations
  98. GRB 260510D: Glowbug gamma-ray detection of a likely short burst
  99. GRB 260511B: FRAM-ORM optical detection
  100. GRB 260511A: EP-FXT follow-up observation

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