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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. GRB 240629A: Fermi GBM Final Real-time Localization
  2. Fermi Gamma-ray Burst Monitor trigger 741356809/240629519 is not a GRB
  3. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  4. Fermi trigger No 741296200: Global MASTER-Net observations report
  5. Fermi trigger No 741251380: Global MASTER-Net observations report
  6. IPN triangulation of GRB 240619C
  7. IceCube-Cascade 240626A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 240628A: BALROG localization (Fermi Trigger 741288821 / GRB 240628732)
  9. GRB 240627A: NuSTAR Detection of the long GRB
  10. GRB 240615A: SAI CMO J- band observations
  11. GRB 240627A: AstroSat CZTI detection
  12. Fermi trigger No 741211696: Global MASTER-Net observations report
  13. EP240626a: Montarrenti Observatory optical upper limit
  14. EP240626a: KAIT optical upper limit
  15. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  16. EP240625a: GRANDMA Optical Upper Limits
  17. EP240626a: EP-FXT detection of the X-ray emission
  18. GRB 240624A: Swift-BAT refined analysis
  19. Konus-Wind detection of GRB 240619A
  20. EP240626a: BOOTES-7 optical upper limit
  21. EP240626a: EP-WXT detection of a fast X-ray transient
  22. Fermi GRB 240625B: Global MASTER-Net observations report
  23. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  24. GRB 240625B: Fermi GBM Final Real-time Localization
  25. GRB 240625A: Fermi GBM Observation
  26. EP240625a: NOT optical counterpart candidate
  27. EP240625a: EP-FXT detection of the X-ray emission
  28. GRB 240624B: GRBAlpha detection
  29. GRB 240625A: Fermi GBM Final Real-time Localization
  30. EP240625a: EP-WXT detection of a fast X-ray transient
  31. GRB240624A: Fermi GBM Observation
  32. LIGO/Virgo/KAGRA S240622h: Upper limits from Swift/BAT-GUANO
  33. LIGO/Virgo/KAGRA S240621dy: Upper limits from Swift/BAT-GUANO
  34. LIGO/Virgo/KAGRA S240618ah: Upper limits from Swift/BAT-GUANO
  35. Swift GRB 240624A: Global MASTER-Net observations report
  36. GRB240615A: Gemini-North observations of the BAT and XRT positions
  37. Fermi GRB 240624A: Global MASTER-Net observations report
  38. GRB 240624B: Fermi GBM Final Real-time Localization
  39. Fermi trigger No 740949590: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S240624cd: Retraction of GW unmodeled transient candidate
  41. GRB240615A: Gemini-North observations of the BAT and XRT positions
  42. GRB 240624A: Fermi GBM Final Real-time Localization
  43. GRB 240619A: detection of a radio counterpart with AMI-LA
  44. GRB 240624A: Swift detection of a burst
  45. LIGO/Virgo/KAGRA S240623dg: Retraction of GW compact binary merger candidate
  46. EP240618a: NOT further optical observations
  47. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  48. GRB 240619A: J-band detection with WINTER
  49. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification
  50. Fermi trigger No 740744838: Global MASTER-Net observations report
  51. EP240618a: NOT optical counterpart candidate
  52. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  53. GRB 240529A: JinShan optical observations
  54. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  55. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  56. EP240618a: GSP optical upper limit
  57. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  61. IPN triangulation of GRB 240615A (short)
  62. X-ray transient EP240618a: Fermi/GBM non-detection
  63. GRB 240619A: GRBAlpha detection
  64. EP240618a: Swift/XRT upper limit
  65. EP240617a: tentative Swift/XRT detection of the afterglow
  66. GRB 240619A: Swift-XRT probable afterglow detection
  67. GRB 240619A: Swift ToO observations
  68. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  69. GRB 240619C: NuSTAR automated detection of the GRB
  70. GRB 240619A: Fermi GBM Observation
  71. Fermi GBM Sub-Threshold Detection of GRB 240619C
  72. GRB 240619A: GOTO candidate optical afterglow
  73. EP240618a: Abastumani optical observationsEP240618a
  74. GRB 240615A: NOT optical observations
  75. EP240618a: GRANDMA Optical Upper Limits
  76. GRB 240619C: AstroSat CZTI detection
  77. EP240618a: TRT optical upper limit
  78. Fermi trigger No 740474239: Global MASTER-Net observations report
  79. Fermi GRB 240619A: Global MASTER-Net observations report
  80. EP240617a: STEP/T80S optical limits
  81. GRB 240615A: possible transient detection from Wendelstein observations
  82. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  83. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  84. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  85. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  86. EP240618a: BOOTES-6/DPRT optical upper limit
  87. Fermi Gamma-ray Burst Monitor trigger 740474239/240619304 is not a GRB
  88. GRB 240619B: Fermi GBM Final Real-time Localization
  89. LIGO/Virgo S240615dg: Swift XRT observations, 39 X-ray sources
  90. Fermi trigger No 740430582: Global MASTER-Net observations report
  91. GRB240615A: 1.3m DFOT optical upper limit
  92. GRB 240619A: BALROG localization (Fermi Trigger 740461416 / GRB 240619155)
  93. GRB 240619A: Fermi GBM Final Real-time Localization
  94. EP240617a: BOOTES-6/DPRT optical upper limit
  95. EP240617a is likely a GRB event
  96. EP240617a: EP-WXT detection of a fast X-ray transient
  97. EP240618a: EP-WXT detection of a fast X-ray transient and EP-FXT quick follow-up
  98. LIGO/Virgo/KAGRA S240618ah: Identification of a GW compact binary merger candidate
  99. LIGO/Virgo/KAGRA S240615ea: Upper limits from Swift/BAT-GUANO
  100. LIGO/Virgo/KAGRA S240615dg: Upper limits from Swift/BAT-GUANO

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