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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"

23574 results found.

  1. EP260602a: COLIBRÍ optical observations
  2. GRB260601B/EP260601a: NOT near-infrared observations
  3. SVOM GRB260603.23: Global MASTER-Net observations report
  4. Fermi GRB 260602B: Global MASTER-Net observations report
  5. Fermi GRB 260602B: Global MASTER-Net observations report
  6. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  7. GRB 260601B/EP260601a: J-band upper limit with WINTER
  8. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  9. EP260530a/AT 2026nwl: KAIT optical observations
  10. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  11. EP260602a: Optical upper limits with Kinder observations
  12. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  13. GRB 260601A: Glowbug gamma-ray detection of a short burst
  14. GRB 260531B: Glowbug gamma-ray detection
  15. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  16. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  17. Fermi GRB 260601A: Global MASTER-Net observations report
  18. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  19. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  20. Fermi trigger No 801900520: Global MASTER-Net observations report
  21. GRB 260531A: MAXI/GSC detection
  22. AT 2026nuz: COLIBRÍ optical observations
  23. IPN triangulation of GRB 260527A / EP260527a
  24. GRB 260527A / EP260527a: VLA radio detection
  25. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  26. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  27. GRB 260529A: GOTO tentative optical afterglow candidate
  28. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  29. Fermi GRB 260529A: Global MASTER-Net observations report
  30. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  31. EP260527a / GRB 260527A: NOT optical observations
  32. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  33. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  34. GRB 260526A: GECAM-B observation
  35. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  36. EP260526a: EP-FXT follow-up observation
  37. EP260527a: COLIBRÍ optical detection
  38. The EP-WXT trigger 01709266172 is likely a flaring star
  39. The EP-WXT trigger 01709266147 is likely a flaring star
  40. Fermi trigger No 801580882: Global MASTER-Net observations report
  41. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  42. GRB 260525A: AstroSat CZTI detection
  43. EP260526.405: COLIBRÍ optical upper limits
  44. GRB 260523B: AstroSat CZTI detection
  45. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  46. GRB 260522A: GOTO optical upper limit
  47. GRB 260519C: SVOM/GRM observation
  48. GRB 260511A: iTelescope T-75 optical detection
  49. GRB 260411B: TERI Gamma-ray detection
  50. GRB 260407A: TERI Gamma-ray detection
  51. GRB 260307A: TERI Gamma-ray detection
  52. GRB 260225D: TERI Gamma-ray detection
  53. GRB 251118A: TERI Gamma-ray detection
  54. GRB 251113A: TERI Gamma-ray detection
  55. GRB 260428A: TERI Gamma-ray detection
  56. Konus-Wind detection of GRB 260519C
  57. GRB 260509A: SVOM/ECLAIRs refined analysis
  58. Konus-Wind detection of GRB 260518A
  59. GRB 260518A: AstroSat CZTI detection of a long burst
  60. GRB 260516D: SVOM/ECLAIRs refined analysis
  61. GRB 260515A: SVOM/ECLAIRs refined analysis
  62. GRB 260421B: radio detection with the VLA
  63. GRB 260516D: GOTO optical counterpart detection
  64. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  66. GRB 260516D: SVOM/VT optical bright candidate
  67. GRB 260515A: CrAO ZTSh BVRI optical observations
  68. GRB 260516D: SVOM possible detection of a burst
  69. Konus-Wind detection of GRB 260515A
  70. GRB 260515A: LCO optical counterpart detection
  71. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  72. EP260514a: TRT optical counterpart candidate
  73. GRB 260515A: SVOM/VT optical observations
  74. GRB 260515A: OHP/T193 optical observations
  75. EP260514a: COLIBRÍ optical upper limits
  76. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  77. GRB 260515A: SVOM detection of a burst
  78. GRB 260510C: Glowbug gamma-ray detection
  79. GRB 260511B: NOT optical observations
  80. Konus-Wind detection of GRB 260512A
  81. GRB 260510C: CALET Gamma-Ray Burst Monitor detection
  82. EP260512a: LCO optical upper limits
  83. IPN triangulation of GRB 260512A
  84. GRB 260511B: Mephisto multi-band optical followup
  85. GRB 260512A: AstroSat CZTI detection
  86. EP260512a: EP-FXT follow-up observation
  87. GRB 260509A: SVOM/VT optical observations
  88. Konus-Wind detection of GRB 260511B
  89. The EP-WXT trigger 01709262036 is likely a flaring star
  90. EP260512a: COLIBRÍ optical upper limits
  91. EP260512a: Einstein Probe detection of an X-ray transient
  92. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  93. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  94. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  95. GRB 260511A: Glowbug gamma-ray detection
  96. Konus-Wind detection of GRB 260511A
  97. GRB 260510D: Glowbug gamma-ray detection of a likely short burst
  98. GRB 260511B: LCO optical counterpart detection
  99. GRB 260511B: GOTO optical counterpart detection
  100. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations

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