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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 741448122/240630575 is not a GRB
  2. GRB 240627A: CALET Gamma-Ray Burst Monitor detection
  3. Fermi trigger No 741448122: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S240630t: Updated Sky localization
  5. LIGO/Virgo/KAGRA S240629by: Updated Sky localization
  6. LIGO/Virgo/KAGRA S240630t: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S240629by: Upper limits from Fermi-GBM Observations
  8. LIGO/Virgo/KAGRA S240629by: Coverage and upper limits from MAXI/GSC observations
  9. Fermi trigger No 741356809: Global MASTER-Net observations report
  10. Fermi GRB 240629A: Global MASTER-Net observations report
  11. Fermi Gamma-ray Burst Monitor trigger 741362867/240629589 is not a GRB
  12. Fermi Gamma-ray Burst Monitor trigger 741288821/240628732 is not a GRB
  13. GRB 240629A: BALROG localization (Fermi Trigger 741372837 / GRB 240629704)
  14. GRB 240629A: Fermi GBM Final Real-time Localization
  15. Fermi Gamma-ray Burst Monitor trigger 741356809/240629519 is not a GRB
  16. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  17. Fermi trigger No 741296200: Global MASTER-Net observations report
  18. Fermi trigger No 741251380: Global MASTER-Net observations report
  19. IPN triangulation of GRB 240619C
  20. IceCube-Cascade 240626A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 240628A: BALROG localization (Fermi Trigger 741288821 / GRB 240628732)
  22. GRB 240627A: NuSTAR Detection of the long GRB
  23. GRB 240615A: SAI CMO J- band observations
  24. GRB 240627A: AstroSat CZTI detection
  25. Fermi trigger No 741211696: Global MASTER-Net observations report
  26. EP240626a: Montarrenti Observatory optical upper limit
  27. EP240626a: KAIT optical upper limit
  28. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  29. EP240625a: GRANDMA Optical Upper Limits
  30. EP240626a: EP-FXT detection of the X-ray emission
  31. GRB 240624A: Swift-BAT refined analysis
  32. Konus-Wind detection of GRB 240619A
  33. EP240626a: BOOTES-7 optical upper limit
  34. EP240626a: EP-WXT detection of a fast X-ray transient
  35. Fermi GRB 240625B: Global MASTER-Net observations report
  36. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  37. GRB 240625B: Fermi GBM Final Real-time Localization
  38. GRB 240625A: Fermi GBM Observation
  39. EP240625a: NOT optical counterpart candidate
  40. EP240625a: EP-FXT detection of the X-ray emission
  41. GRB 240624B: GRBAlpha detection
  42. GRB 240625A: Fermi GBM Final Real-time Localization
  43. EP240625a: EP-WXT detection of a fast X-ray transient
  44. GRB240624A: Fermi GBM Observation
  45. LIGO/Virgo/KAGRA S240622h: Upper limits from Swift/BAT-GUANO
  46. LIGO/Virgo/KAGRA S240621dy: Upper limits from Swift/BAT-GUANO
  47. LIGO/Virgo/KAGRA S240618ah: Upper limits from Swift/BAT-GUANO
  48. Swift GRB 240624A: Global MASTER-Net observations report
  49. GRB240615A: Gemini-North observations of the BAT and XRT positions
  50. Fermi GRB 240624A: Global MASTER-Net observations report
  51. GRB 240624B: Fermi GBM Final Real-time Localization
  52. Fermi trigger No 740949590: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S240624cd: Retraction of GW unmodeled transient candidate
  54. GRB240615A: Gemini-North observations of the BAT and XRT positions
  55. GRB 240624A: Fermi GBM Final Real-time Localization
  56. GRB 240619A: detection of a radio counterpart with AMI-LA
  57. GRB 240624A: Swift detection of a burst
  58. LIGO/Virgo/KAGRA S240623dg: Retraction of GW compact binary merger candidate
  59. EP240618a: NOT further optical observations
  60. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  61. GRB 240619A: J-band detection with WINTER
  62. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification
  63. Fermi trigger No 740744838: Global MASTER-Net observations report
  64. EP240618a: NOT optical counterpart candidate
  65. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  66. GRB 240529A: JinShan optical observations
  67. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  68. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  69. EP240618a: GSP optical upper limit
  70. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  71. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  74. IPN triangulation of GRB 240615A (short)
  75. X-ray transient EP240618a: Fermi/GBM non-detection
  76. GRB 240619A: GRBAlpha detection
  77. EP240618a: Swift/XRT upper limit
  78. EP240617a: tentative Swift/XRT detection of the afterglow
  79. GRB 240619A: Swift-XRT probable afterglow detection
  80. GRB 240619A: Swift ToO observations
  81. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  82. GRB 240619C: NuSTAR automated detection of the GRB
  83. GRB 240619A: Fermi GBM Observation
  84. Fermi GBM Sub-Threshold Detection of GRB 240619C
  85. GRB 240619A: GOTO candidate optical afterglow
  86. EP240618a: Abastumani optical observationsEP240618a
  87. GRB 240615A: NOT optical observations
  88. EP240618a: GRANDMA Optical Upper Limits
  89. GRB 240619C: AstroSat CZTI detection
  90. EP240618a: TRT optical upper limit
  91. Fermi trigger No 740474239: Global MASTER-Net observations report
  92. Fermi GRB 240619A: Global MASTER-Net observations report
  93. EP240617a: STEP/T80S optical limits
  94. GRB 240615A: possible transient detection from Wendelstein observations
  95. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  96. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  97. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  98. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  99. EP240618a: BOOTES-6/DPRT optical upper limit
  100. Fermi Gamma-ray Burst Monitor trigger 740474239/240619304 is not a GRB

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