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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').
  1. Fermi trigger No 740744838: Global MASTER-Net observations report
  2. EP240618a: NOT optical counterpart candidate
  3. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  4. GRB 240529A: JinShan optical observations
  5. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  6. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  7. EP240618a: GSP optical upper limit
  8. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  10. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  12. IPN triangulation of GRB 240615A (short)
  13. X-ray transient EP240618a: Fermi/GBM non-detection
  14. GRB 240619A: GRBAlpha detection
  15. EP240618a: Swift/XRT upper limit
  16. EP240617a: tentative Swift/XRT detection of the afterglow
  17. GRB 240619A: Swift-XRT probable afterglow detection
  18. GRB 240619A: Swift ToO observations
  19. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 240619C: NuSTAR automated detection of the GRB
  21. GRB 240619A: Fermi GBM Observation
  22. Fermi GBM Sub-Threshold Detection of GRB 240619C
  23. GRB 240619A: GOTO candidate optical afterglow
  24. EP240618a: Abastumani optical observationsEP240618a
  25. GRB 240615A: NOT optical observations
  26. EP240618a: GRANDMA Optical Upper Limits
  27. GRB 240619C: AstroSat CZTI detection
  28. EP240618a: TRT optical upper limit
  29. Fermi trigger No 740474239: Global MASTER-Net observations report
  30. Fermi GRB 240619A: Global MASTER-Net observations report
  31. EP240617a: STEP/T80S optical limits
  32. GRB 240615A: possible transient detection from Wendelstein observations
  33. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  34. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  35. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  36. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  37. EP240618a: BOOTES-6/DPRT optical upper limit
  38. Fermi Gamma-ray Burst Monitor trigger 740474239/240619304 is not a GRB
  39. GRB 240619B: Fermi GBM Final Real-time Localization
  40. LIGO/Virgo S240615dg: Swift XRT observations, 39 X-ray sources
  41. Fermi trigger No 740430582: Global MASTER-Net observations report
  42. GRB240615A: 1.3m DFOT optical upper limit
  43. GRB 240619A: BALROG localization (Fermi Trigger 740461416 / GRB 240619155)
  44. GRB 240619A: Fermi GBM Final Real-time Localization
  45. EP240617a: BOOTES-6/DPRT optical upper limit
  46. EP240617a is likely a GRB event
  47. EP240617a: EP-WXT detection of a fast X-ray transient
  48. EP240618a: EP-WXT detection of a fast X-ray transient and EP-FXT quick follow-up
  49. LIGO/Virgo/KAGRA S240618ah: Identification of a GW compact binary merger candidate
  50. LIGO/Virgo/KAGRA S240615ea: Upper limits from Swift/BAT-GUANO
  51. LIGO/Virgo/KAGRA S240615dg: Upper limits from Swift/BAT-GUANO
  52. GRB 240615A: J-band upper limits from WINTER
  53. GRB 240615A: Fermi GBM Observation
  54. LIGO/Virgo/KAGRA S240615ea: Updated Sky localization
  55. GRB 240615A: Swift-XRT observations
  56. GRB 240615A: GECAM detection
  57. X-ray transient EP240414a: Chandra late time observation
  58. GRB 240615A: FLWO-1.2m optical upper limits
  59. Fermi trigger No 740221779: Global MASTER-Net observations report
  60. Fermi GRB 240616A: Global MASTER-Net observations report
  61. Konus-Wind detection of GRB 240615A (short/hard)
  62. GRB 240615A: GOTO optical upper limits
  63. Fermi trigger No 740166710: Global MASTER-Net observations report
  64. GRB 240616A: Fermi GBM Final Real-time Localization
  65. GRB 240615A: Swift ToO observations
  66. GRB 240615A: Swift/BAT-GUANO arcminute localization of a short burst
  67. GRB 240615A: Fermi GBM Final Real-time Localization
  68. LIGO/Virgo/KAGRA S240615ea: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S240615dg: Identification of a GW compact binary merger candidate
  70. GRB 240603A: VZLUSAT-2 detection
  71. GRB 240612A: GRBAlpha detection
  72. GRB 240613A: Fermi GBM Final Real-time Localization
  73. Fermi GRB 240612B: Global MASTER-Net observations report
  74. Fermi GRB 240612A: Global MASTER-Net observations report
  75. GRB 240612B: Fermi GBM Final Real-time Localization
  76. GRB 240612A: Fermi GBM Final Real-time Localization
  77. GRB 240607A: GECAM detection of a bright long burst
  78. Fermi GRB 240611A: Global MASTER-Net observations report
  79. Konus-Wind detection of GRB 240607A
  80. GRB 240611A: Fermi GBM Final Real-time Localization
  81. EXO 0748-676: Swift-BAT refined analysis
  82. GRB240529A: 3.6m TNG NIR detection 8d after the burst
  83. GRB 240529A: LBT optical detection and late temporal decay
  84. GRB 240529A : MITSuME Akeno optical afterglow detection
  85. Trigger 1236151: Swift detection of EXO 0748-676
  86. Fermi GRB 240610A: Global MASTER-Net observations report
  87. GRB 240610A: Fermi GBM Final Real-time Localization
  88. IPN triangulation of GRB 240607A
  89. Fermi Gamma-ray Burst Monitor trigger 739632045/240609556 is not a GRB
  90. Fermi trigger No 739632045: Global MASTER-Net observations report
  91. Fermi GRB 240608A: Global MASTER-Net observations report
  92. Konus-Wind detection of GRB 240606B
  93. Fermi trigger No 739506569: Global MASTER-Net observations report
  94. GRB 240608A: Fermi GBM Final Real-time Localization
  95. Fermi GRB 240607A: Global MASTER-Net observations report
  96. GRB 240529A: NOEMA detection
  97. GRB 240607A: Fermi GBM Observation
  98. GRB 240606B: Fermi GBM Observation
  99. Swift Trigger 1235109: consistent with noise and not astrophysical
  100. GRB 240607A: AstroSat CZTI detection of bright long burst

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