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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"

32490 results found.

  1. GRB 260604C: Jinshan optical observations
  2. GRB 260604C: Fermi GBM Observation
  3. EP260602d: J-band upper limit with WINTER
  4. EP260602b: J-band upper limit with WINTER
  5. GRB 260604C: LAST detection of optical counterpart candidate
  6. Fermi GRB 260604C: Global MASTER-Net observations report
  7. Fermi GRB 260604C: Global MASTER-Net observations report
  8. GRB 260604C: SVOM detection of a long burst
  9. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  10. GRB 260603A: NOT optical observations
  11. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  12. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  13. EP260602a: EP-FXT follow-up observation
  14. EP260603a: Global MASTER-Net observations report
  15. EP260602d: Optical Upper limits with kinder observations
  16. EP260602b: Liverpool Telescope observations
  17. EP260602a: Liverpool Telescope optical upper limits
  18. EP260602b: Liverpool Telescope and LCO observations
  19. EP260602a: GTC and Liverpool Telescope optical observations
  20. Konus-Wind detection of GRB 260601B/EP260601a
  21. GRB 260603A: EP-FXT follow-up observation
  22. EP260601a/GRB 260601B: EP-FXT follow-up observation
  23. GRB 260601B / EP260601a: Mondy optical upper limit
  24. EP260602b: EP-FXT follow-up observation
  25. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  26. GRB 260603A: Kilonova-Catcher optical upper limit
  27. GRB 260603A: SVOM/VT optical observations
  28. EP260602a: NOT NIR J-band observations
  29. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  30. EP260602d: Einstein Probe detection of a fast X-ray transient
  31. EP260602a: SVOM/VT optical magnitudes correction
  32. GRB 260601A: SVOM/GRM observation of a short burst
  33. EP260602c: Einstein Probe detection of a fast X-ray transient
  34. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  35. EP260602a: COLIBRÍ optical observations
  36. GRB260601B/EP260601a: NOT near-infrared observations
  37. EP260602b: Einstein Probe detection of a fast X-ray transient
  38. GRB 260601B/EP260601a: Insight-HXMT detection
  39. Fermi GRB 260602B: Global MASTER-Net observations report
  40. Fermi GRB 260602B: Global MASTER-Net observations report
  41. EP260602a: SVOM/VT optical candidate
  42. GRB 260601A: GECAM-B observation of a short burst
  43. GRB 260601B/EP260601a: J-band upper limit with WINTER
  44. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  45. EP260530a/AT 2026nwl: KAIT optical observations
  46. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  47. EP260602a: Optical upper limits with Kinder observations
  48. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  49. GRB 260601B/EP260601a: SVOM/VT optical observations
  50. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  51. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  52. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  53. GRB 260601A: Glowbug gamma-ray detection of a short burst
  54. GRB 260531B: Glowbug gamma-ray detection
  55. GRB 260516D: VLA radio detection
  56. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  57. Fermi GRB 260601A: Global MASTER-Net observations report
  58. GRB 260531B: GECAM-B observation
  59. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  60. AT 2026nuz: COLIBRÍ optical observations
  61. IPN triangulation of GRB 260527A / EP260527a
  62. EP260527a/GRB 260527A: further FTW optical and NIR observations
  63. GRB 260527A / EP260527a: VLA radio detection
  64. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  65. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  66. GRB 260529A: GOTO tentative optical afterglow candidate
  67. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  68. GRB 260527A/EP260527a: Insight-HXMT detection
  69. Fermi GRB 260529A: Global MASTER-Net observations report
  70. EP260526a: SVOM/VT optical upper limits
  71. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  72. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  73. EP260527a / GRB 260527A: NOT optical observations
  74. GRB 260527A/EP260527a: FTW optical and NIR observations
  75. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  76. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  77. EP260527a/GRB 260527A: EP-FXT follow-up observation
  78. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  79. GRB 260526A: GECAM-B observation
  80. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  81. EP260526a: EP-FXT follow-up observation
  82. EP260527a: SVOM/VT optical observation
  83. EP260527a: COLIBRÍ optical detection
  84. EP260526a: LCO optical upper limits
  85. EP260526a: Einstein Probe detection of a fast X-ray transient
  86. GRB 260525A: AstroSat CZTI detection
  87. The EP-WXT trigger 01709266106 is not a real source
  88. Fermi GRB 260526A: Global MASTER-Net observations report
  89. Fermi GRB 260525A: Global MASTER-Net observations report
  90. GRB 260523B: AstroSat CZTI detection
  91. GRB 260523B: GECAM-B observation
  92. Fermi GRB 260523A: Global MASTER-Net observations report
  93. GRB 260522A: Fermi GBM Observation
  94. GRB 260522B: NuSTAR detection of prompt emission
  95. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  96. GRB 260522A: GOTO optical upper limit
  97. Fermi GRB 260522A: Global MASTER-Net observations report
  98. GRB 260522A: Fermi-LAT detection
  99. GRB 260519C: SVOM/GRM observation
  100. GRB 260511A: iTelescope T-75 optical detection

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