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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"

15984 results found.

  1. EP260602a: GTC and Liverpool Telescope optical observations
  2. GRB 260603A: EP-FXT follow-up observation
  3. GRB 260601B / EP260601a: Mondy optical upper limit
  4. EP260602b: EP-FXT follow-up observation
  5. GRB 260603A: Kilonova-Catcher optical upper limit
  6. GRB 260603A: SVOM/VT optical observations
  7. EP260602a: NOT NIR J-band observations
  8. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  9. EP260602a: SVOM/VT optical magnitudes correction
  10. GRB 260601A: SVOM/GRM observation of a short burst
  11. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  12. EP260602a: COLIBRÍ optical observations
  13. GRB260601B/EP260601a: NOT near-infrared observations
  14. EP260602b: Einstein Probe detection of a fast X-ray transient
  15. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  16. EP260602a: SVOM/VT optical candidate
  17. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  18. GRB 260601B/EP260601a: J-band upper limit with WINTER
  19. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  20. EP260530a/AT 2026nwl: KAIT optical observations
  21. EP260602a: Optical upper limits with Kinder observations
  22. GRB 260601B/EP260601a: SVOM/VT optical observations
  23. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  24. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  25. GRB 260516D: VLA radio detection
  26. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  27. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  28. AT2026nik: EP-FXT X-ray counterpart
  29. AT 2026nuz: COLIBRÍ optical observations
  30. EP260527a/GRB 260527A: further FTW optical and NIR observations
  31. GRB 260527A / EP260527a: VLA radio detection
  32. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  33. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  34. GRB 260529A: GOTO tentative optical afterglow candidate
  35. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  36. EP260526a: SVOM/VT optical upper limits
  37. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  38. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  39. EP260527a / GRB 260527A: NOT optical observations
  40. GRB 260527A/EP260527a: FTW optical and NIR observations
  41. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  42. EP260527a/GRB 260527A: EP-FXT follow-up observation
  43. EP260527a: SVOM/VT optical observation
  44. EP260527a: COLIBRÍ optical detection
  45. EP260526a: LCO optical upper limits
  46. EP260526.405: COLIBRÍ optical upper limits
  47. EP-WXT 01709266106: NOT optical upper limits
  48. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  49. GRB 260522A: GOTO optical upper limit
  50. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  51. GRB 260511A: iTelescope T-75 optical detection
  52. GRB 260520B: SVOM/GRM observation
  53. GRB 260421B: radio detection with the VLA
  54. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  55. GRB 260509A: CrAO ZTSh optical upper limit
  56. GRB 260516D: EP-FXT follow-up observation
  57. GRB 260516D: GOTO optical counterpart detection
  58. GRB 260516D: LCO optical observations
  59. GRB 260515A: further Liverpool Telescope observations
  60. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  62. GRB 260516D: GROWTH-India Telescope optical detection
  63. GRB 260516D: SVOM/VT optical bright candidate
  64. GRB 260516D: FRAM-ORM optical limit
  65. GRB 260515A: CrAO ZTSh BVRI optical observations
  66. GRB 260515A: Liverpool Telescope optical detection
  67. GRB 260515A: LCO optical counterpart detection
  68. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  69. GRB 260515A: EP-FXT follow-up observation
  70. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  71. EP260514a: NOT optical counterpart confirmation
  72. EP260514a: TRT optical counterpart candidate
  73. EP260514a: SVOM/VT optical candidate
  74. GRB 260515A: SVOM/VT optical observations
  75. GRB 260515A: OHP/T193 optical observations
  76. EP260514a: COLIBRÍ optical upper limits
  77. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  78. GRB 260515A: LCO optical observations
  79. GRB 260515A: NOT optical observations.
  80. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  81. GRB 260515A: SVOM/VT optical candidate from VHF data
  82. GRB 260515A: JinShan optical counterpart candidate
  83. EP260514a: GROWTH-India Telescope optical upper limit
  84. GRB 260511B: NOT optical observations
  85. GRB 260511B: GMG Optical Upper Limit
  86. EP260512a: LCO optical upper limits
  87. GRB 260511B: Mephisto multi-band optical followup
  88. EP260507a: Xinglong Schmidt optical counterpart detection
  89. GRB 260511B: further SAO RAS optical observations
  90. GRB 260509A: SVOM/VT optical observations
  91. EP260512a: COLIBRÍ optical upper limits
  92. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  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. MASS-Cube (GRID 2.0) detection of GRB 260511A
  97. GRB 260511B: SAO RAS optical observations
  98. GRB 260511B: FRAM-ORM optical detection
  99. GRB 260511A: EP-FXT follow-up observation
  100. GRB 260511B: EP-FXT follow-up observation

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