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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. LIGO/Virgo S240615dg: Swift XRT observations, 28 futher X-ray sources
  2. EP240703b: GSP optical upper limit
  3. Fermi Gamma-ray Burst Monitor trigger 741911057/240705933 is not a GRB
  4. GRB 240705A: Fermi GBM Final Real-time Localization
  5. EP240703b: TRT optical upper limits
  6. EP240703a: TRT further optical observation
  7. EP240702a: TRT optical upper limits
  8. Konus-Wind detection of GRB 240627A
  9. IPN triangulation of GRB 240628B (short)
  10. LIGO/Virgo/KAGRA S240705at: Updated Sky localization
  11. EP240703a and EP240703b: Swift/XRT upper limits
  12. LIGO/Virgo/KAGRA S240705at: Identification of a GW compact binary merger candidate
  13. EP240703a: KAIT optical upper limit
  14. EP240703a: BTA observations
  15. EP240703c: Kinder optical follow-up and Swift XRT observations
  16. EP240703a: BOOTES-3 optical upper limit
  17. EP240703a: Liverpool Telescope optical follow-up observations
  18. EP240703a/GRB 240703A: TRT optical candidate likely not real
  19. EP240703a: Kinder optical follow-up observations
  20. EP240703c: EP-WXT detection of an X-ray transient
  21. LIGO/Virgo/KAGRA S240703ad: Updated Sky localization
  22. LIGO/Virgo/KAGRA S240703ad: Identification of a GW compact binary merger candidate
  23. EP240703a/GRB 240703A: TRT and JinShan decaying optical afterglow candidate
  24. IPN triangulation of GRB 240627A
  25. GRB 240619A: Host galaxy redshift from VLT/X-shooter
  26. LIGO/Virgo/KAGRA S240422ed: Updated significance estimate
  27. The first three GRBs detected by SVOM: X-ray Upper Limits from EP-WXT
  28. EP240703b: EP-WXT detection of a fast X-ray transient
  29. Konus-Wind detection of GRB 240703A (a counterpart of EP240703a)
  30. EP240702a: Swift/XRT upper limit
  31. EP240703a: EP-WXT detection of a fast X-ray transient
  32. EP240702a: GSP optical upper limit
  33. The first three GRBs detected by SVOM: GRB 240627B, GRB 240629A and GRB 240702A
  34. GRB 240702A: BALROG localization (Fermi Trigger / GRB 240702885)
  35. Fermi GRB 240702A: Global MASTER-Net observations report
  36. GRB 240702A: Fermi GBM Final Real-time Localization
  37. EP240702a: EP-WXT detection of a fast X-ray transient
  38. LIGO/Virgo/KAGRA S240627by: Upper limits from Swift/BAT-GUANO
  39. Fermi Gamma-ray Burst Monitor trigger 741448122/240630575 is not a GRB
  40. GRB 240627A: CALET Gamma-Ray Burst Monitor detection
  41. Fermi trigger No 741448122: Global MASTER-Net observations report
  42. LIGO/Virgo/KAGRA S240630t: Updated Sky localization
  43. LIGO/Virgo/KAGRA S240629by: Updated Sky localization
  44. LIGO/Virgo/KAGRA S240630t: Identification of a GW compact binary merger candidate
  45. LIGO/Virgo/KAGRA S240629by: Upper limits from Fermi-GBM Observations
  46. LIGO/Virgo/KAGRA S240629by: Coverage and upper limits from MAXI/GSC observations
  47. Fermi trigger No 741356809: Global MASTER-Net observations report
  48. Fermi GRB 240629A: Global MASTER-Net observations report
  49. Fermi Gamma-ray Burst Monitor trigger 741362867/240629589 is not a GRB
  50. Fermi Gamma-ray Burst Monitor trigger 741288821/240628732 is not a GRB
  51. GRB 240629A: BALROG localization (Fermi Trigger 741372837 / GRB 240629704)
  52. GRB 240629A: Fermi GBM Final Real-time Localization
  53. Fermi Gamma-ray Burst Monitor trigger 741356809/240629519 is not a GRB
  54. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  55. Fermi trigger No 741296200: Global MASTER-Net observations report
  56. Fermi trigger No 741251380: Global MASTER-Net observations report
  57. IPN triangulation of GRB 240619C
  58. IceCube-Cascade 240626A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 240628A: BALROG localization (Fermi Trigger 741288821 / GRB 240628732)
  60. GRB 240627A: NuSTAR Detection of the long GRB
  61. GRB 240615A: SAI CMO J- band observations
  62. GRB 240627A: AstroSat CZTI detection
  63. Fermi trigger No 741211696: Global MASTER-Net observations report
  64. EP240626a: Montarrenti Observatory optical upper limit
  65. EP240626a: KAIT optical upper limit
  66. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  67. EP240625a: GRANDMA Optical Upper Limits
  68. EP240626a: EP-FXT detection of the X-ray emission
  69. GRB 240624A: Swift-BAT refined analysis
  70. Konus-Wind detection of GRB 240619A
  71. EP240626a: BOOTES-7 optical upper limit
  72. EP240626a: EP-WXT detection of a fast X-ray transient
  73. Fermi GRB 240625B: Global MASTER-Net observations report
  74. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  75. GRB 240625B: Fermi GBM Final Real-time Localization
  76. GRB 240625A: Fermi GBM Observation
  77. EP240625a: NOT optical counterpart candidate
  78. EP240625a: EP-FXT detection of the X-ray emission
  79. GRB 240624B: GRBAlpha detection
  80. GRB 240625A: Fermi GBM Final Real-time Localization
  81. EP240625a: EP-WXT detection of a fast X-ray transient
  82. GRB240624A: Fermi GBM Observation
  83. LIGO/Virgo/KAGRA S240622h: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S240621dy: Upper limits from Swift/BAT-GUANO
  85. LIGO/Virgo/KAGRA S240618ah: Upper limits from Swift/BAT-GUANO
  86. Swift GRB 240624A: Global MASTER-Net observations report
  87. GRB240615A: Gemini-North observations of the BAT and XRT positions
  88. Fermi GRB 240624A: Global MASTER-Net observations report
  89. GRB 240624B: Fermi GBM Final Real-time Localization
  90. Fermi trigger No 740949590: Global MASTER-Net observations report
  91. LIGO/Virgo/KAGRA S240624cd: Retraction of GW unmodeled transient candidate
  92. GRB240615A: Gemini-North observations of the BAT and XRT positions
  93. GRB 240624A: Fermi GBM Final Real-time Localization
  94. GRB 240619A: detection of a radio counterpart with AMI-LA
  95. GRB 240624A: Swift detection of a burst
  96. LIGO/Virgo/KAGRA S240623dg: Retraction of GW compact binary merger candidate
  97. EP240618a: NOT further optical observations
  98. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  99. GRB 240619A: J-band detection with WINTER
  100. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification

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