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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"

16153 results found.

  1. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  2. GRB 260601B/EP260601a: J-band upper limit with WINTER
  3. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  4. EP260530a/AT 2026nwl: KAIT optical observations
  5. EP260602a: Optical upper limits with Kinder observations
  6. GRB 260601B/EP260601a: SVOM/VT optical observations
  7. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  8. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  9. GRB 260516D: VLA radio detection
  10. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  11. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  12. AT2026nik: EP-FXT X-ray counterpart
  13. AT 2026nuz: COLIBRÍ optical observations
  14. EP260527a/GRB 260527A: further FTW optical and NIR observations
  15. GRB 260527A / EP260527a: VLA radio detection
  16. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  17. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  18. GRB 260529A: GOTO tentative optical afterglow candidate
  19. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  20. EP260526a: SVOM/VT optical upper limits
  21. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  22. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  23. EP260527a / GRB 260527A: NOT optical observations
  24. GRB 260527A/EP260527a: FTW optical and NIR observations
  25. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  26. EP260527a/GRB 260527A: EP-FXT follow-up observation
  27. EP260527a: SVOM/VT optical observation
  28. EP260527a: COLIBRÍ optical detection
  29. EP260526a: LCO optical upper limits
  30. EP260526.405: COLIBRÍ optical upper limits
  31. EP-WXT 01709266106: NOT optical upper limits
  32. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  33. GRB 260522A: GOTO optical upper limit
  34. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  35. GRB 260511A: iTelescope T-75 optical detection
  36. GRB 260520B: SVOM/GRM observation
  37. GRB 260421B: radio detection with the VLA
  38. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  39. GRB 260509A: CrAO ZTSh optical upper limit
  40. GRB 260516D: EP-FXT follow-up observation
  41. GRB 260516D: GOTO optical counterpart detection
  42. GRB 260516D: LCO optical observations
  43. GRB 260515A: further Liverpool Telescope observations
  44. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  46. GRB 260516D: GROWTH-India Telescope optical detection
  47. GRB 260516D: SVOM/VT optical bright candidate
  48. GRB 260516D: FRAM-ORM optical limit
  49. GRB 260515A: CrAO ZTSh BVRI optical observations
  50. GRB 260515A: Liverpool Telescope optical detection
  51. GRB 260515A: LCO optical counterpart detection
  52. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. GRB 260515A: EP-FXT follow-up observation
  54. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  55. EP260514a: NOT optical counterpart confirmation
  56. EP260514a: TRT optical counterpart candidate
  57. EP260514a: SVOM/VT optical candidate
  58. GRB 260515A: SVOM/VT optical observations
  59. GRB 260515A: OHP/T193 optical observations
  60. EP260514a: COLIBRÍ optical upper limits
  61. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  62. GRB 260515A: LCO optical observations
  63. GRB 260515A: NOT optical observations.
  64. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  65. GRB 260515A: SVOM/VT optical candidate from VHF data
  66. GRB 260515A: JinShan optical counterpart candidate
  67. EP260514a: GROWTH-India Telescope optical upper limit
  68. GRB 260511B: NOT optical observations
  69. GRB 260511B: GMG Optical Upper Limit
  70. EP260512a: LCO optical upper limits
  71. GRB 260511B: Mephisto multi-band optical followup
  72. EP260507a: Xinglong Schmidt optical counterpart detection
  73. GRB 260511B: further SAO RAS optical observations
  74. GRB 260509A: SVOM/VT optical observations
  75. EP260512a: COLIBRÍ optical upper limits
  76. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  77. GRB 260509A: Infrared J and Hs observations with MDM/MIRAGE
  78. GRB 260510C: Infrared J and Hs detections with MDM/MIRAGE
  79. EP260507a: Infrared J and Hs upper limits with MDM/MIRAGE
  80. MASS-Cube (GRID 2.0) detection of GRB 260511A
  81. GRB 260511B: SAO RAS optical observations
  82. GRB 260511B: FRAM-ORM optical detection
  83. GRB 260511A: EP-FXT follow-up observation
  84. GRB 260511B: EP-FXT follow-up observation
  85. GRB 260511B: LCO optical counterpart detection
  86. GRB260511B: MAO/AZT-22 optical observations
  87. GRB 260511A: SVOM/VT optical observations
  88. GRB 260511B: LCO optical observations
  89. GRB 260511B: OHP/T193 spectroscopic observations
  90. GRB 260511B: GOTO optical counterpart detection
  91. GRB 260511B: Xinglong 2.16m/BEFOSC redshift confirmation
  92. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  93. GRB 260511B: SVOM/VT optical observations
  94. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  95. GRB 260511B: OSIRIS+/GTC redshift z=2.006
  96. GRB 260509A: SAO RAS optical observations
  97. GRB 260511A: REM near-infrared detection
  98. GRB 260511B: GROWTH-India Telescope optical observations
  99. GRB 260511B: J-band observations by the SYSU 80 cm infrared telescope
  100. GRB 260511B: NuSTAR detection of prompt emission

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