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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').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. LIGO/Virgo/KAGRA S240630t: Updated Sky localization
  2. LIGO/Virgo/KAGRA S240629by: Updated Sky localization
  3. LIGO/Virgo/KAGRA S240630t: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S240629by: Upper limits from Fermi-GBM Observations
  5. LIGO/Virgo/KAGRA S240629by: Coverage and upper limits from MAXI/GSC observations
  6. Fermi trigger No 741356809: Global MASTER-Net observations report
  7. Fermi GRB 240629A: Global MASTER-Net observations report
  8. Fermi Gamma-ray Burst Monitor trigger 741362867/240629589 is not a GRB
  9. Fermi Gamma-ray Burst Monitor trigger 741288821/240628732 is not a GRB
  10. GRB 240629A: BALROG localization (Fermi Trigger 741372837 / GRB 240629704)
  11. GRB 240629A: Fermi GBM Final Real-time Localization
  12. Fermi Gamma-ray Burst Monitor trigger 741356809/240629519 is not a GRB
  13. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  14. Fermi trigger No 741296200: Global MASTER-Net observations report
  15. Fermi trigger No 741251380: Global MASTER-Net observations report
  16. IPN triangulation of GRB 240619C
  17. IceCube-Cascade 240626A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 240628A: BALROG localization (Fermi Trigger 741288821 / GRB 240628732)
  19. GRB 240627A: NuSTAR Detection of the long GRB
  20. GRB 240615A: SAI CMO J- band observations
  21. GRB 240627A: AstroSat CZTI detection
  22. Fermi trigger No 741211696: Global MASTER-Net observations report
  23. EP240626a: Montarrenti Observatory optical upper limit
  24. EP240626a: KAIT optical upper limit
  25. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  26. EP240625a: GRANDMA Optical Upper Limits
  27. EP240626a: EP-FXT detection of the X-ray emission
  28. GRB 240624A: Swift-BAT refined analysis
  29. Konus-Wind detection of GRB 240619A
  30. EP240626a: BOOTES-7 optical upper limit
  31. EP240626a: EP-WXT detection of a fast X-ray transient
  32. Fermi GRB 240625B: Global MASTER-Net observations report
  33. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  34. GRB 240625B: Fermi GBM Final Real-time Localization
  35. GRB 240625A: Fermi GBM Observation
  36. EP240625a: NOT optical counterpart candidate
  37. EP240625a: EP-FXT detection of the X-ray emission
  38. GRB 240624B: GRBAlpha detection
  39. GRB 240625A: Fermi GBM Final Real-time Localization
  40. EP240625a: EP-WXT detection of a fast X-ray transient
  41. GRB240624A: Fermi GBM Observation
  42. LIGO/Virgo/KAGRA S240622h: Upper limits from Swift/BAT-GUANO
  43. LIGO/Virgo/KAGRA S240621dy: Upper limits from Swift/BAT-GUANO
  44. LIGO/Virgo/KAGRA S240618ah: Upper limits from Swift/BAT-GUANO
  45. Swift GRB 240624A: Global MASTER-Net observations report
  46. GRB240615A: Gemini-North observations of the BAT and XRT positions
  47. Fermi GRB 240624A: Global MASTER-Net observations report
  48. GRB 240624B: Fermi GBM Final Real-time Localization
  49. Fermi trigger No 740949590: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S240624cd: Retraction of GW unmodeled transient candidate
  51. GRB240615A: Gemini-North observations of the BAT and XRT positions
  52. GRB 240624A: Fermi GBM Final Real-time Localization
  53. GRB 240619A: detection of a radio counterpart with AMI-LA
  54. GRB 240624A: Swift detection of a burst
  55. LIGO/Virgo/KAGRA S240623dg: Retraction of GW compact binary merger candidate
  56. EP240618a: NOT further optical observations
  57. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  58. GRB 240619A: J-band detection with WINTER
  59. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification
  60. Fermi trigger No 740744838: Global MASTER-Net observations report
  61. EP240618a: NOT optical counterpart candidate
  62. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  63. GRB 240529A: JinShan optical observations
  64. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  65. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  66. EP240618a: GSP optical upper limit
  67. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  69. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  70. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  71. IPN triangulation of GRB 240615A (short)
  72. X-ray transient EP240618a: Fermi/GBM non-detection
  73. GRB 240619A: GRBAlpha detection
  74. EP240618a: Swift/XRT upper limit
  75. EP240617a: tentative Swift/XRT detection of the afterglow
  76. GRB 240619A: Swift-XRT probable afterglow detection
  77. GRB 240619A: Swift ToO observations
  78. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 240619C: NuSTAR automated detection of the GRB
  80. GRB 240619A: Fermi GBM Observation
  81. Fermi GBM Sub-Threshold Detection of GRB 240619C
  82. GRB 240619A: GOTO candidate optical afterglow
  83. EP240618a: Abastumani optical observationsEP240618a
  84. GRB 240615A: NOT optical observations
  85. EP240618a: GRANDMA Optical Upper Limits
  86. GRB 240619C: AstroSat CZTI detection
  87. EP240618a: TRT optical upper limit
  88. Fermi trigger No 740474239: Global MASTER-Net observations report
  89. Fermi GRB 240619A: Global MASTER-Net observations report
  90. EP240617a: STEP/T80S optical limits
  91. GRB 240615A: possible transient detection from Wendelstein observations
  92. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  93. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  94. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  95. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  96. EP240618a: BOOTES-6/DPRT optical upper limit
  97. Fermi Gamma-ray Burst Monitor trigger 740474239/240619304 is not a GRB
  98. GRB 240619B: Fermi GBM Final Real-time Localization
  99. LIGO/Virgo S240615dg: Swift XRT observations, 39 X-ray sources
  100. Fermi trigger No 740430582: Global MASTER-Net observations report

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