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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 Gamma-ray Burst Monitor trigger 745811685 / 240820080 is not a GRB
  2. GRB 240820A: Fermi GBM Final Real-time Localization
  3. GRB 240819A: Swift ToO observations
  4. GRB 240814A: SVOM/GRM observation
  5. EP240816b: Liverpool Telescope optical follow-up observations
  6. GRB 240814C: SVOM/GRM observation
  7. EP240816a: BOOTES-6/DPRT optical upper limit
  8. GRB 240815A: SVOM/GRM observation
  9. GRB 240817A: Fermi GBM Final Real-time Localization
  10. Integral GRB240816.79: Global MASTER-Net observations report
  11. IceCube-240721A: AT2023qqp and AT2024pge likely unrelated
  12. GRB GRB 240809A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  13. IBAS Alert n.10856: not a GRB
  14. GRB 240805B: Osservatorio Astronomico Nastro Verde upper limit
  15. EP240816b: KAIT optical upper limit
  16. GRB 240814B: GRBAlpha detection
  17. Fermi trigger No 745501396: Global MASTER-Net observations report
  18. EP240816a: EP detection of a fast X-ray transient and follow-up observation
  19. EP EP240816b: Global MASTER-Net observations report
  20. EP240816b: TRT optical upper limit
  21. EP240816b: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  22. Fermi GRB 240814A: Global MASTER-Net observations report
  23. Fermi GRB 240814C: Global MASTER-Net observations report
  24. Fermi trigger No 745306088: Global MASTER-Net observations report
  25. GRB 240814C: Fermi GBM Final Real-time Localization
  26. Fermi GRB 240814B: Global MASTER-Net observations report
  27. GRB 240812B: SVOM/GRM observation
  28. EP240802a: Kinder optical, SWIFT-UVOT, and SWIFT-XRT upper limits 6 days after the WXT detection
  29. GRB 240814B: Fermi GBM Final Real-time Localization
  30. GRB 240814A: Fermi GBM Final Real-time Localization
  31. LIGO/Virgo/KAGRA S240813d: Updated Sky localization
  32. Fermi trigger No 745220784: Global MASTER-Net observations report
  33. Konus-Wind detection of GRB 240811A
  34. Konus-Wind detection of GRB 240810A
  35. Fermi Gamma-ray Burst Monitor trigger 745220784/240813240 is not a GRB
  36. LIGO/Virgo/KAGRA S240813d: Identification of a GW compact binary merger candidate
  37. LIGO/Virgo/KAGRA S240813c: Updated Sky localization
  38. LIGO/Virgo/KAGRA S240813c: Identification of a GW compact binary merger candidate
  39. GRB 240809A: Correction to the VLA source position in GCN 37158
  40. GRB 240810A: SVOM/GRM observation
  41. Fermi Gamma-ray Burst Monitor trigger 240812940/745194848 is not a GRB
  42. Fermi Gamma-ray Burst Monitor trigger 240812917/745192855 is not a GRB
  43. Fermi Gamma-ray Burst Monitor trigger 240812917/745192855 is not a GRB
  44. GRB 240809A: ATA radio non-detection
  45. GRB 240812D: Fermi GBM Final Real-time Localization
  46. GRB 240812C: Fermi GBM Final Real-time Localization
  47. GRB 240809A : RAPAS follow-up observations
  48. GRB 240809A: VLA detection
  49. GRB 240809A: ALMA detection
  50. IPN triangulation of GRB 240810A (short)
  51. GRB 240811A: Swift-BAT refined analysis
  52. GRB 240809A: Swift-BAT refined analysis
  53. EP240807a: PRIME H-band upper limits
  54. GRB 240812B: AstroSat CZTI detection of a long burst
  55. IceCube-240808A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 240811A: Bassano Bresciano Observatory upper limit
  57. GRB 240811A: Swift-XRT refined Analysis
  58. Fermi Gamma-ray Burst Monitor trigger 745135620/240812255 is not a GRB
  59. GRB 240811A: Swift/UVOT Upper Limits
  60. EP240801a: Assy-Turgen optical observations
  61. Fermi GRB 240810A: Global MASTER-Net observations report
  62. Fermi Gamma-ray Burst Monitor trigger 240812094/745121685 is not a GRB
  63. GRB 240812A: Fermi GBM Final Real-time Localization
  64. GRB 240811A: LCOGT Optical Upper Limit
  65. GRB 240811A: Enhanced Swift-XRT position
  66. GRB 240811A: Upper limits with Mephisto
  67. Konus-Wind detection of GRB 240809A
  68. Fermi trigger No 745057312: Global MASTER-Net observations report
  69. Swift GRB 240811A: Global MASTER-Net observations report
  70. GRB 240811A: Swift detection of a burst
  71. Fermi Gamma-ray Burst Monitor trigger 745050426/240811269 is not a GRB
  72. GRB240809A: Liverpool Telescope optical follow-up observations
  73. GRB 240810A: Fermi GBM Final Real-time Localization
  74. GRB 240809A: REM detection of the optical afterglow
  75. GRB 240809A: Bassano Bresciano Observatory optical observations
  76. Konus-Wind detection of GRB 240807A (a counterpart of EP240807a)
  77. GRB 240809A: Conclusive redshift from VLT
  78. Fermi-LAT gamma-ray observations of IceCube-240808A
  79. GRB 240809A: KAIT optical observations
  80. GRB 240808A: AstroSat CZTI detection
  81. GRB 240809A: GIT afterglow observations
  82. GRB 240809B: MAXI/GSC detection
  83. GRB 240809A: Swift/UVOT Detection
  84. GRB 240809A: Tentative redshift from NOT
  85. GRB 240809A: Swift-XRT refined Analysis
  86. IPN triangulation of GRB 240807A / EP 240807a
  87. LIGO/Virgo/KAGRA S240807h: Updated Sky localization and EM Bright Classification
  88. X-ray Transient EP240807a: PRIME near-infrared upper limits
  89. Swift GRB 240809A: Global MASTER-Net observations report
  90. GRB 240809A: JinShan optical observations
  91. GRB 240809A: Enhanced Swift-XRT position
  92. GRB 240809A: Skynet & Photon Ranch Optical Afterglow Observations
  93. GRB 240809A: SVOM/GRM observation
  94. GRB 240808A: SVOM/GRM observation
  95. GRB 240807A: SVOM/GRM observation
  96. GRB 240809A: Swift detection of a burst with a bright optical counterpart
  97. EP-WXT trigger 01709018832: SVOM/C-GFT observations of the star flare
  98. EP240807a: STEP/T80S optical limits
  99. GRB 240807B: AstroSat CZTI detection of a short burst
  100. IceCube Alert 240808.27: Global MASTER-Net observations report

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