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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"
  1. IPN triangulation of GRB 240615A (short)
  2. X-ray transient EP240618a: Fermi/GBM non-detection
  3. GRB 240619A: GRBAlpha detection
  4. EP240618a: Swift/XRT upper limit
  5. EP240617a: tentative Swift/XRT detection of the afterglow
  6. GRB 240619A: Swift-XRT probable afterglow detection
  7. GRB 240619A: Swift ToO observations
  8. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  9. GRB 240619C: NuSTAR automated detection of the GRB
  10. GRB 240619A: Fermi GBM Observation
  11. Fermi GBM Sub-Threshold Detection of GRB 240619C
  12. GRB 240619A: GOTO candidate optical afterglow
  13. EP240618a: Abastumani optical observationsEP240618a
  14. GRB 240615A: NOT optical observations
  15. EP240618a: GRANDMA Optical Upper Limits
  16. GRB 240619C: AstroSat CZTI detection
  17. EP240618a: TRT optical upper limit
  18. Fermi trigger No 740474239: Global MASTER-Net observations report
  19. Fermi GRB 240619A: Global MASTER-Net observations report
  20. EP240617a: STEP/T80S optical limits
  21. GRB 240615A: possible transient detection from Wendelstein observations
  22. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  23. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  24. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  25. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  26. EP240618a: BOOTES-6/DPRT optical upper limit
  27. Fermi Gamma-ray Burst Monitor trigger 740474239/240619304 is not a GRB
  28. GRB 240619B: Fermi GBM Final Real-time Localization
  29. LIGO/Virgo S240615dg: Swift XRT observations, 39 X-ray sources
  30. Fermi trigger No 740430582: Global MASTER-Net observations report
  31. GRB240615A: 1.3m DFOT optical upper limit
  32. GRB 240619A: BALROG localization (Fermi Trigger 740461416 / GRB 240619155)
  33. GRB 240619A: Fermi GBM Final Real-time Localization
  34. EP240617a: BOOTES-6/DPRT optical upper limit
  35. EP240617a is likely a GRB event
  36. EP240617a: EP-WXT detection of a fast X-ray transient
  37. EP240618a: EP-WXT detection of a fast X-ray transient and EP-FXT quick follow-up
  38. LIGO/Virgo/KAGRA S240618ah: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S240615ea: Upper limits from Swift/BAT-GUANO
  40. LIGO/Virgo/KAGRA S240615dg: Upper limits from Swift/BAT-GUANO
  41. GRB 240615A: J-band upper limits from WINTER
  42. GRB 240615A: Fermi GBM Observation
  43. LIGO/Virgo/KAGRA S240615ea: Updated Sky localization
  44. GRB 240615A: Swift-XRT observations
  45. GRB 240615A: GECAM detection
  46. X-ray transient EP240414a: Chandra late time observation
  47. GRB 240615A: FLWO-1.2m optical upper limits
  48. Fermi trigger No 740221779: Global MASTER-Net observations report
  49. Fermi GRB 240616A: Global MASTER-Net observations report
  50. Konus-Wind detection of GRB 240615A (short/hard)
  51. GRB 240615A: GOTO optical upper limits
  52. Fermi trigger No 740166710: Global MASTER-Net observations report
  53. GRB 240616A: Fermi GBM Final Real-time Localization
  54. GRB 240615A: Swift ToO observations
  55. GRB 240615A: Swift/BAT-GUANO arcminute localization of a short burst
  56. GRB 240615A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S240615ea: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S240615dg: Identification of a GW compact binary merger candidate
  59. GRB 240603A: VZLUSAT-2 detection
  60. GRB 240612A: GRBAlpha detection
  61. GRB 240613A: Fermi GBM Final Real-time Localization
  62. Fermi GRB 240612B: Global MASTER-Net observations report
  63. Fermi GRB 240612A: Global MASTER-Net observations report
  64. GRB 240612B: Fermi GBM Final Real-time Localization
  65. GRB 240612A: Fermi GBM Final Real-time Localization
  66. GRB 240607A: GECAM detection of a bright long burst
  67. Fermi GRB 240611A: Global MASTER-Net observations report
  68. Konus-Wind detection of GRB 240607A
  69. GRB 240611A: Fermi GBM Final Real-time Localization
  70. EXO 0748-676: Swift-BAT refined analysis
  71. GRB240529A: 3.6m TNG NIR detection 8d after the burst
  72. GRB 240529A: LBT optical detection and late temporal decay
  73. GRB 240529A : MITSuME Akeno optical afterglow detection
  74. Trigger 1236151: Swift detection of EXO 0748-676
  75. Fermi GRB 240610A: Global MASTER-Net observations report
  76. GRB 240610A: Fermi GBM Final Real-time Localization
  77. IPN triangulation of GRB 240607A
  78. Fermi Gamma-ray Burst Monitor trigger 739632045/240609556 is not a GRB
  79. Fermi trigger No 739632045: Global MASTER-Net observations report
  80. Fermi GRB 240608A: Global MASTER-Net observations report
  81. Konus-Wind detection of GRB 240606B
  82. Fermi trigger No 739506569: Global MASTER-Net observations report
  83. GRB 240608A: Fermi GBM Final Real-time Localization
  84. Fermi GRB 240607A: Global MASTER-Net observations report
  85. GRB 240529A: NOEMA detection
  86. GRB 240607A: Fermi GBM Observation
  87. GRB 240606B: Fermi GBM Observation
  88. Swift Trigger 1235109: consistent with noise and not astrophysical
  89. GRB 240607A: AstroSat CZTI detection of bright long burst
  90. GRB 240607A: Fermi GBM detection of a very bright burst
  91. GRB 240529A: radio detection with AMI-LA
  92. GRB 240607A: BALROG localization (Fermi Trigger 739450879 / GRB 240607459)
  93. GRB 240607A: Fermi GBM Final Real-time Localization
  94. GRB 240606B: GECAM-B detection a long burst
  95. Fermi trigger No 739373591: Global MASTER-Net observations report
  96. GRB 240606B: Swift-XRT afterglow detection
  97. Swift GRB240606.15: Global MASTER-Net observations report
  98. GRB 240606B: Swift ToO observations
  99. GRB 240606B: Swift/BAT-GUANO arcminute localization of a burst
  100. Konus-Wind detection of GRB 240603A

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