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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. EP240703c: EP-WXT detection of an X-ray transient
  2. LIGO/Virgo/KAGRA S240703ad: Updated Sky localization
  3. LIGO/Virgo/KAGRA S240703ad: Identification of a GW compact binary merger candidate
  4. EP240703a/GRB 240703A: TRT and JinShan decaying optical afterglow candidate
  5. IPN triangulation of GRB 240627A
  6. GRB 240619A: Host galaxy redshift from VLT/X-shooter
  7. LIGO/Virgo/KAGRA S240422ed: Updated significance estimate
  8. The first three GRBs detected by SVOM: X-ray Upper Limits from EP-WXT
  9. EP240703b: EP-WXT detection of a fast X-ray transient
  10. Konus-Wind detection of GRB 240703A (a counterpart of EP240703a)
  11. EP240702a: Swift/XRT upper limit
  12. EP240703a: EP-WXT detection of a fast X-ray transient
  13. EP240702a: GSP optical upper limit
  14. The first three GRBs detected by SVOM: GRB 240627B, GRB 240629A and GRB 240702A
  15. GRB 240702A: BALROG localization (Fermi Trigger / GRB 240702885)
  16. Fermi GRB 240702A: Global MASTER-Net observations report
  17. GRB 240702A: Fermi GBM Final Real-time Localization
  18. EP240702a: EP-WXT detection of a fast X-ray transient
  19. LIGO/Virgo/KAGRA S240627by: Upper limits from Swift/BAT-GUANO
  20. Fermi Gamma-ray Burst Monitor trigger 741448122/240630575 is not a GRB
  21. GRB 240627A: CALET Gamma-Ray Burst Monitor detection
  22. Fermi trigger No 741448122: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S240630t: Updated Sky localization
  24. LIGO/Virgo/KAGRA S240629by: Updated Sky localization
  25. LIGO/Virgo/KAGRA S240630t: Identification of a GW compact binary merger candidate
  26. LIGO/Virgo/KAGRA S240629by: Upper limits from Fermi-GBM Observations
  27. LIGO/Virgo/KAGRA S240629by: Coverage and upper limits from MAXI/GSC observations
  28. Fermi trigger No 741356809: Global MASTER-Net observations report
  29. Fermi GRB 240629A: Global MASTER-Net observations report
  30. Fermi Gamma-ray Burst Monitor trigger 741362867/240629589 is not a GRB
  31. Fermi Gamma-ray Burst Monitor trigger 741288821/240628732 is not a GRB
  32. GRB 240629A: BALROG localization (Fermi Trigger 741372837 / GRB 240629704)
  33. GRB 240629A: Fermi GBM Final Real-time Localization
  34. Fermi Gamma-ray Burst Monitor trigger 741356809/240629519 is not a GRB
  35. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  36. Fermi trigger No 741296200: Global MASTER-Net observations report
  37. Fermi trigger No 741251380: Global MASTER-Net observations report
  38. IPN triangulation of GRB 240619C
  39. IceCube-Cascade 240626A: Upper limits from a search for additional neutrino events in IceCube
  40. GRB 240628A: BALROG localization (Fermi Trigger 741288821 / GRB 240628732)
  41. GRB 240627A: NuSTAR Detection of the long GRB
  42. GRB 240615A: SAI CMO J- band observations
  43. GRB 240627A: AstroSat CZTI detection
  44. Fermi trigger No 741211696: Global MASTER-Net observations report
  45. EP240626a: Montarrenti Observatory optical upper limit
  46. EP240626a: KAIT optical upper limit
  47. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  48. EP240625a: GRANDMA Optical Upper Limits
  49. EP240626a: EP-FXT detection of the X-ray emission
  50. GRB 240624A: Swift-BAT refined analysis
  51. Konus-Wind detection of GRB 240619A
  52. EP240626a: BOOTES-7 optical upper limit
  53. EP240626a: EP-WXT detection of a fast X-ray transient
  54. Fermi GRB 240625B: Global MASTER-Net observations report
  55. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  56. GRB 240625B: Fermi GBM Final Real-time Localization
  57. GRB 240625A: Fermi GBM Observation
  58. EP240625a: NOT optical counterpart candidate
  59. EP240625a: EP-FXT detection of the X-ray emission
  60. GRB 240624B: GRBAlpha detection
  61. GRB 240625A: Fermi GBM Final Real-time Localization
  62. EP240625a: EP-WXT detection of a fast X-ray transient
  63. GRB240624A: Fermi GBM Observation
  64. LIGO/Virgo/KAGRA S240622h: Upper limits from Swift/BAT-GUANO
  65. LIGO/Virgo/KAGRA S240621dy: Upper limits from Swift/BAT-GUANO
  66. LIGO/Virgo/KAGRA S240618ah: Upper limits from Swift/BAT-GUANO
  67. Swift GRB 240624A: Global MASTER-Net observations report
  68. GRB240615A: Gemini-North observations of the BAT and XRT positions
  69. Fermi GRB 240624A: Global MASTER-Net observations report
  70. GRB 240624B: Fermi GBM Final Real-time Localization
  71. Fermi trigger No 740949590: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S240624cd: Retraction of GW unmodeled transient candidate
  73. GRB240615A: Gemini-North observations of the BAT and XRT positions
  74. GRB 240624A: Fermi GBM Final Real-time Localization
  75. GRB 240619A: detection of a radio counterpart with AMI-LA
  76. GRB 240624A: Swift detection of a burst
  77. LIGO/Virgo/KAGRA S240623dg: Retraction of GW compact binary merger candidate
  78. EP240618a: NOT further optical observations
  79. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  80. GRB 240619A: J-band detection with WINTER
  81. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification
  82. Fermi trigger No 740744838: Global MASTER-Net observations report
  83. EP240618a: NOT optical counterpart candidate
  84. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  85. GRB 240529A: JinShan optical observations
  86. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  87. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  88. EP240618a: GSP optical upper limit
  89. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  91. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  93. IPN triangulation of GRB 240615A (short)
  94. X-ray transient EP240618a: Fermi/GBM non-detection
  95. GRB 240619A: GRBAlpha detection
  96. EP240618a: Swift/XRT upper limit
  97. EP240617a: tentative Swift/XRT detection of the afterglow
  98. GRB 240619A: Swift-XRT probable afterglow detection
  99. GRB 240619A: Swift ToO observations
  100. GRB 240619A: CALET Gamma-Ray Burst Monitor detection

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