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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"

27470 results found.

  1. GRB 260604C: 6 GHz VLA observations
  2. GRB 260504C: SAO RAS optical observations
  3. GRB 260604B: SVOM/GRM detection
  4. EP260605a: Einstein Probe detection of a fast X-ray transient
  5. EP260603a: COLIBRÍ optical upper limit
  6. GRB 260604A: Glowbug gamma-ray detection
  7. GRB 260604C: LCO optical upper limit
  8. EP260602d: EP-FXT follow-up observation
  9. EP260602c: EP-FXT follow-up observation
  10. GRB 260601B / EP260601a: AstroSat CZTI detection
  11. GRB 260527A/EP260527a: 6 GHz VLA observations
  12. GRB 260604C: Kilonova-Catcher optical afterglow detection
  13. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  14. GRB 260604C: Jinshan optical observations
  15. GRB 260604C: Fermi GBM Observation
  16. EP260602d: J-band upper limit with WINTER
  17. EP260602b: J-band upper limit with WINTER
  18. GRB 260604C: LAST detection of optical counterpart candidate
  19. Fermi GRB 260604C: Global MASTER-Net observations report
  20. Fermi GRB 260604C: Global MASTER-Net observations report
  21. SVOM GRB260604.85: Global MASTER-Net observations report
  22. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  23. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  24. EP260602a: EP-FXT follow-up observation
  25. EP260603a: Global MASTER-Net observations report
  26. EP260603a: Einstein Probe detection of a fast X-ray transient
  27. EP260602d: Optical Upper limits with kinder observations
  28. EP260602b: Liverpool Telescope observations
  29. EP260602a: Liverpool Telescope optical upper limits
  30. EP260602b: Liverpool Telescope and LCO observations
  31. EP260602a: GTC and Liverpool Telescope optical observations
  32. EP260601a/GRB 260601B: EP-FXT follow-up observation
  33. GRB 260601B / EP260601a: Mondy optical upper limit
  34. EP260602b: EP-FXT follow-up observation
  35. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  36. GRB 260603A: Kilonova-Catcher optical upper limit
  37. GRB 260603A: SVOM/VT optical observations
  38. EP260602a: NOT NIR J-band observations
  39. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  40. EP260602d: Einstein Probe detection of a fast X-ray transient
  41. Fermi trigger No 802141998: Global MASTER-Net observations report
  42. GRB 260601A: SVOM/GRM observation of a short burst
  43. EP260602c: Einstein Probe detection of a fast X-ray transient
  44. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  45. EP260602a: COLIBRÍ optical observations
  46. GRB260601B/EP260601a: NOT near-infrared observations
  47. SVOM GRB260603.23: Global MASTER-Net observations report
  48. GRB 260603A: SVOM detection of a burst
  49. EP260602b: Einstein Probe detection of a fast X-ray transient
  50. Fermi GRB 260602B: Global MASTER-Net observations report
  51. Fermi GRB 260602B: Global MASTER-Net observations report
  52. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  53. EP260602a: SVOM/VT optical candidate
  54. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  55. GRB 260601B/EP260601a: J-band upper limit with WINTER
  56. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  57. EP260530a/AT 2026nwl: KAIT optical observations
  58. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  59. EP260602a: Optical upper limits with Kinder observations
  60. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  61. EP260602a: Einstein Probe detection of a fast X-ray transient
  62. GRB 260601B/EP260601a: SVOM/VT optical observations
  63. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  64. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  65. EP260601a: Einstein Probe detection of an X-ray transient
  66. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  67. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  68. GRB 260601A: Glowbug gamma-ray detection of a short burst
  69. GRB 260531B: Glowbug gamma-ray detection
  70. GRB 260601A: Fermi GBM Observation
  71. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  72. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  73. Fermi GRB 260601A: Global MASTER-Net observations report
  74. GRB 260601A: Fermi GBM Final Real-time Localization
  75. The EP-WXT trigger 01709266272 is likely a flaring star
  76. AT2026nik: EP-FXT X-ray counterpart
  77. Fermi trigger No 801900520: Global MASTER-Net observations report
  78. GRB 260531A: MAXI/GSC detection
  79. AT 2026nuz: COLIBRÍ optical observations
  80. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  81. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  82. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  83. Fermi GRB 260529A: Global MASTER-Net observations report
  84. EP260526a: SVOM/VT optical upper limits
  85. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  86. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  87. EP260527a/GRB 260527A: EP-FXT follow-up observation
  88. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  89. EP260527a: SVOM/VT optical observation
  90. EP260527a: COLIBRÍ optical detection
  91. EP260527a: Einstein Probe detection of a fast X-ray transient
  92. Fermi trigger No 801580882: Global MASTER-Net observations report
  93. EP260526a: LCO optical upper limits
  94. EP260526a: Einstein Probe detection of a fast X-ray transient
  95. EP260526.405: COLIBRÍ optical upper limits
  96. The EP-WXT trigger 01709266106 is not a real source
  97. Fermi GRB 260526A: Global MASTER-Net observations report
  98. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  99. EP-WXT 01709266106: NOT optical upper limits
  100. Fermi GRB 260525A: Global MASTER-Net observations report

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