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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"

32494 results found.

  1. GRB 260527A/EP260527a: 6 GHz VLA observations
  2. GRB 260604C: GOTO detections of the optical afterglow
  3. GRB 260604C: Correction to GCN 44828
  4. GRB 260604C: Kilonova-Catcher optical afterglow detection
  5. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. GRB 260604C: Jinshan optical observations
  7. GRB 260604C: Fermi GBM Observation
  8. EP260602d: J-band upper limit with WINTER
  9. EP260602b: J-band upper limit with WINTER
  10. GRB 260604C: LAST detection of optical counterpart candidate
  11. Fermi GRB 260604C: Global MASTER-Net observations report
  12. Fermi GRB 260604C: Global MASTER-Net observations report
  13. GRB 260604C: SVOM detection of a long burst
  14. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  15. GRB 260603A: NOT optical observations
  16. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  17. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  18. EP260602a: EP-FXT follow-up observation
  19. EP260603a: Global MASTER-Net observations report
  20. EP260602d: Optical Upper limits with kinder observations
  21. EP260602b: Liverpool Telescope observations
  22. EP260602a: Liverpool Telescope optical upper limits
  23. EP260602b: Liverpool Telescope and LCO observations
  24. EP260602a: GTC and Liverpool Telescope optical observations
  25. Konus-Wind detection of GRB 260601B/EP260601a
  26. GRB 260603A: EP-FXT follow-up observation
  27. EP260601a/GRB 260601B: EP-FXT follow-up observation
  28. GRB 260601B / EP260601a: Mondy optical upper limit
  29. EP260602b: EP-FXT follow-up observation
  30. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  31. GRB 260603A: Kilonova-Catcher optical upper limit
  32. GRB 260603A: SVOM/VT optical observations
  33. EP260602a: NOT NIR J-band observations
  34. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  35. EP260602d: Einstein Probe detection of a fast X-ray transient
  36. EP260602a: SVOM/VT optical magnitudes correction
  37. GRB 260601A: SVOM/GRM observation of a short burst
  38. EP260602c: Einstein Probe detection of a fast X-ray transient
  39. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  40. EP260602a: COLIBRÍ optical observations
  41. GRB260601B/EP260601a: NOT near-infrared observations
  42. EP260602b: Einstein Probe detection of a fast X-ray transient
  43. GRB 260601B/EP260601a: Insight-HXMT detection
  44. Fermi GRB 260602B: Global MASTER-Net observations report
  45. Fermi GRB 260602B: Global MASTER-Net observations report
  46. EP260602a: SVOM/VT optical candidate
  47. GRB 260601A: GECAM-B observation of a short burst
  48. GRB 260601B/EP260601a: J-band upper limit with WINTER
  49. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  50. EP260530a/AT 2026nwl: KAIT optical observations
  51. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  52. EP260602a: Optical upper limits with Kinder observations
  53. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  54. GRB 260601B/EP260601a: SVOM/VT optical observations
  55. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  56. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  57. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  58. GRB 260601A: Glowbug gamma-ray detection of a short burst
  59. GRB 260531B: Glowbug gamma-ray detection
  60. GRB 260516D: VLA radio detection
  61. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  62. Fermi GRB 260601A: Global MASTER-Net observations report
  63. GRB 260531B: GECAM-B observation
  64. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  65. AT 2026nuz: COLIBRÍ optical observations
  66. IPN triangulation of GRB 260527A / EP260527a
  67. EP260527a/GRB 260527A: further FTW optical and NIR observations
  68. GRB 260527A / EP260527a: VLA radio detection
  69. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  70. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  71. GRB 260529A: GOTO tentative optical afterglow candidate
  72. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  73. GRB 260527A/EP260527a: Insight-HXMT detection
  74. Fermi GRB 260529A: Global MASTER-Net observations report
  75. EP260526a: SVOM/VT optical upper limits
  76. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  77. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  78. EP260527a / GRB 260527A: NOT optical observations
  79. GRB 260527A/EP260527a: FTW optical and NIR observations
  80. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  81. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  82. EP260527a/GRB 260527A: EP-FXT follow-up observation
  83. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  84. GRB 260526A: GECAM-B observation
  85. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  86. EP260526a: EP-FXT follow-up observation
  87. EP260527a: SVOM/VT optical observation
  88. EP260527a: COLIBRÍ optical detection
  89. EP260526a: LCO optical upper limits
  90. EP260526a: Einstein Probe detection of a fast X-ray transient
  91. GRB 260525A: AstroSat CZTI detection
  92. The EP-WXT trigger 01709266106 is not a real source
  93. Fermi GRB 260526A: Global MASTER-Net observations report
  94. Fermi GRB 260525A: Global MASTER-Net observations report
  95. GRB 260523B: AstroSat CZTI detection
  96. GRB 260523B: GECAM-B observation
  97. Fermi GRB 260523A: Global MASTER-Net observations report
  98. GRB 260522A: Fermi GBM Observation
  99. GRB 260522B: NuSTAR detection of prompt emission
  100. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28

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