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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"

15985 results found.

  1. EP260602b: Liverpool Telescope and LCO observations
  2. EP260602a: GTC and Liverpool Telescope optical observations
  3. GRB 260603A: EP-FXT follow-up observation
  4. GRB 260601B / EP260601a: Mondy optical upper limit
  5. EP260602b: EP-FXT follow-up observation
  6. GRB 260603A: Kilonova-Catcher optical upper limit
  7. GRB 260603A: SVOM/VT optical observations
  8. EP260602a: NOT NIR J-band observations
  9. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  10. EP260602a: SVOM/VT optical magnitudes correction
  11. GRB 260601A: SVOM/GRM observation of a short burst
  12. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  13. EP260602a: COLIBRÍ optical observations
  14. GRB260601B/EP260601a: NOT near-infrared observations
  15. EP260602b: Einstein Probe detection of a fast X-ray transient
  16. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  17. EP260602a: SVOM/VT optical candidate
  18. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  19. GRB 260601B/EP260601a: J-band upper limit with WINTER
  20. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  21. EP260530a/AT 2026nwl: KAIT optical observations
  22. EP260602a: Optical upper limits with Kinder observations
  23. GRB 260601B/EP260601a: SVOM/VT optical observations
  24. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  25. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  26. GRB 260516D: VLA radio detection
  27. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  28. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  29. AT2026nik: EP-FXT X-ray counterpart
  30. AT 2026nuz: COLIBRÍ optical observations
  31. EP260527a/GRB 260527A: further FTW optical and NIR observations
  32. GRB 260527A / EP260527a: VLA radio detection
  33. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  34. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  35. GRB 260529A: GOTO tentative optical afterglow candidate
  36. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  37. EP260526a: SVOM/VT optical upper limits
  38. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  39. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  40. EP260527a / GRB 260527A: NOT optical observations
  41. GRB 260527A/EP260527a: FTW optical and NIR observations
  42. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  43. EP260527a/GRB 260527A: EP-FXT follow-up observation
  44. EP260527a: SVOM/VT optical observation
  45. EP260527a: COLIBRÍ optical detection
  46. EP260526a: LCO optical upper limits
  47. EP260526.405: COLIBRÍ optical upper limits
  48. EP-WXT 01709266106: NOT optical upper limits
  49. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  50. GRB 260522A: GOTO optical upper limit
  51. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  52. GRB 260511A: iTelescope T-75 optical detection
  53. GRB 260520B: SVOM/GRM observation
  54. GRB 260421B: radio detection with the VLA
  55. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  56. GRB 260509A: CrAO ZTSh optical upper limit
  57. GRB 260516D: EP-FXT follow-up observation
  58. GRB 260516D: GOTO optical counterpart detection
  59. GRB 260516D: LCO optical observations
  60. GRB 260515A: further Liverpool Telescope observations
  61. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  63. GRB 260516D: GROWTH-India Telescope optical detection
  64. GRB 260516D: SVOM/VT optical bright candidate
  65. GRB 260516D: FRAM-ORM optical limit
  66. GRB 260515A: CrAO ZTSh BVRI optical observations
  67. GRB 260515A: Liverpool Telescope optical detection
  68. GRB 260515A: LCO optical counterpart detection
  69. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  70. GRB 260515A: EP-FXT follow-up observation
  71. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  72. EP260514a: NOT optical counterpart confirmation
  73. EP260514a: TRT optical counterpart candidate
  74. EP260514a: SVOM/VT optical candidate
  75. GRB 260515A: SVOM/VT optical observations
  76. GRB 260515A: OHP/T193 optical observations
  77. EP260514a: COLIBRÍ optical upper limits
  78. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  79. GRB 260515A: LCO optical observations
  80. GRB 260515A: NOT optical observations.
  81. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  82. GRB 260515A: SVOM/VT optical candidate from VHF data
  83. GRB 260515A: JinShan optical counterpart candidate
  84. EP260514a: GROWTH-India Telescope optical upper limit
  85. GRB 260511B: NOT optical observations
  86. GRB 260511B: GMG Optical Upper Limit
  87. EP260512a: LCO optical upper limits
  88. GRB 260511B: Mephisto multi-band optical followup
  89. EP260507a: Xinglong Schmidt optical counterpart detection
  90. GRB 260511B: further SAO RAS optical observations
  91. GRB 260509A: SVOM/VT optical observations
  92. EP260512a: COLIBRÍ optical upper limits
  93. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  94. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  95. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  96. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  97. MASS-Cube (GRID 2.0) detection of GRB 260511A
  98. GRB 260511B: SAO RAS optical observations
  99. GRB 260511B: FRAM-ORM optical detection
  100. GRB 260511A: EP-FXT follow-up observation

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