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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. Fermi trigger No 722977823: Global MASTER-Net observations report
  2. GRB 231129B: Tiled Swift observations
  3. GRB 231129B: MAXI/GSC detection
  4. Fermi-LAT gamma-ray observations of IceCube-231125A
  5. Integral GRB231129.21: Global MASTER-Net observations report
  6. LIGO/Virgo/KAGRA S231129ac: Identification of a GW compact binary merger candidate
  7. GRB 231129A: GECAM-C detection of a long burst
  8. GRB 231129A: INTEGRAL detection of a long GRB
  9. GRB 231129A: Swift detection of a burst
  10. LIGO/Virgo/KAGRA S231127cg: Updated Sky localization
  11. GRB 231128A: Fermi GBM Final Real-time Localization
  12. GRB 231123C: Fermi GBM Observation
  13. GRB 231123B: Fermi GBM Observation
  14. IceCube-231125A: Upper limits from a search for additional neutrino events in IceCube
  15. LIGO/Virgo/KAGRA S231127cg: Identification of a GW compact binary merger candidate
  16. GRB 231117A: MeerKAT 1.3GHz detection
  17. GRB 231127A: CALET Gamma-Ray Burst Monitor detection
  18. GRB 231125A: GRBAlpha detection
  19. GRB 231125A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 231127A: AstroSat CZTI detection
  21. GRB 231125A (short): Glowbug gamma-ray detection
  22. GRB 231123B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  23. Update of IceCube-231125A - Corrected errors
  24. GRB 231124A: GRBAlpha detection
  25. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  26. Fermi trigger No 722653947: Global MASTER-Net observations report
  27. GRB 231125A: AstroSat CZTI detection of a short burst
  28. GRB 231111A: Optical follow-up observations at Terskol, AbAO, Maidanak, Mondy, Assy
  29. GRB 231126A: Fermi GBM Final Real-time Localization
  30. GRB 231123C: Insight-HXMT/HE detection
  31. Fermi trigger No 722460326: Global MASTER-Net observations report
  32. Fermi trigger No 722507896: Global MASTER-Net observations report
  33. GRB 231123C (short): Glowbug gamma-ray detection
  34. GRB 231124A: Glowbug gamma-ray detection
  35. GRB230728A: VIRT optical upper limit
  36. GRB230506C: VIRT optical upper limit
  37. GRB230506B: VIRT optical upper limit
  38. GRB 231123C: Swift/BAT-GUANO detection of a short burst likely outside the coded FOV
  39. Fermi trigger No 722462310: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S231118an: Updated Sky localization and EM Bright Classification
  41. GRB 231124A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 231115A: XMM-Newton observation
  43. GRB 231124A: Fermi GBM Final Real-time Localization
  44. GRB 231123A: AstroSat CZTI detection
  45. GRB 231117A: Mondy optical observations
  46. GRB 231123C: Fermi GBM Final Real-time Localization
  47. GRB 231123B: Fermi GBM Final Real-time Localization
  48. Fermi trigger No 722400249: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S231123cg: Identification of a GW compact binary merger candidate
  50. GRB 231118A: REM optical afterglow detection
  51. GRB 231122B: AstroSat CZTI detection
  52. GRB 231122B: CALET Gamma-Ray Burst Monitor detection
  53. GRB 231122B: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  54. GRB 231117A: Chandra afterglow detection
  55. GRB 231123A: Fermi GBM Final Real-time Localization
  56. GRB 231122B: Glowbug gamma-ray detection
  57. GRB 231117A: Continued GTC Observations
  58. Fermi trigger No 722349867: Global MASTER-Net observations report
  59. GRB 231122A: GECAM detection
  60. GRB 231122B: GECAM detection
  61. GRB 231122A: Fermi GBM Final Real-time Localization
  62. GRB 231118A: ATCA detection of radio counterpart
  63. GRB 231117A: Swift/UVOT late time observations
  64. GRB 231117A: GTC Near-Infrared Observations
  65. GRB 231117A: Swift-BAT refined analysis
  66. GRB 231118A: GRBAlpha detection
  67. LIGO/Virgo/KAGRA S231118d: Upper limits from Swift/BAT-GUANO
  68. LIGO/Virgo/KAGRA S231118an: Upper limits from Swift/BAT-GUANO
  69. LIGO/Virgo/KAGRA S231114n: Upper limits from Swift/BAT-GUANO
  70. LIGO/Virgo/KAGRA S231113bb: Upper limits from Swift/BAT-GUANO
  71. LIGO/Virgo/KAGRA S231119u: Updated Sky localization and Source Classification
  72. LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification
  73. LIGO/Virgo/KAGRA S231118d: Updated Sky localization and Source Classification
  74. GRB 231118A: VZLUSAT-2 detection
  75. GRB 231117A: AMI-LA radio observations
  76. GRB 231118A: Swift-BAT refined analysis
  77. Konus-Wind detection of GRB 231020A
  78. GRB 231117A: LDT Confirmation of Optical Fading
  79. GRB 231117A: Wendelstein Confirmation of Fading of the Optical Afterglow
  80. GRB 231118B: CALET Gamma-Ray Burst Monitor detection
  81. GRB 231117A: CALET Gamma-Ray Burst Monitor detection
  82. 231118A: Swift-UVOT Detection
  83. GRB231117A: Swift-UVOT detection
  84. GRB 231117A : MITSuME Akeno optical afterglow candidate detection
  85. GRB 231118B: Fermi GBM observation
  86. GRB 231118A: Fermi GBM observation
  87. LIGO/Virgo/KAGRA S231119ab: Coverage and upper limits from MAXI/GSC observations
  88. GRB 231120A: Fermi GBM Final Real-time Localization
  89. GRB 231117A: Swift-XRT refined Analysis
  90. GRB 231118A: Swift-XRT refined Analysis
  91. GRB 231118A: MeerLICHT afterglow detection
  92. LIGO/Virgo/KAGRA S231119u: One counterpart neutrino candidate from IceCube neutrino searches
  93. GRB 231117A: OHP/T120 optical observations
  94. GRB 231118A: VLT/X-shooter redshift
  95. Fermi trigger No 722039659: Global MASTER-Net observations report
  96. GRB 231117A: Pan-STARRS1 follow-up confirms rapid fading
  97. LIGO/Virgo/KAGRA S231119u: Identification of a GW compact binary merger candidate
  98. GRB 231117A: MAAO 0.7-m telescope optical upper limit
  99. GRB 231117A: AKO Follow-Up Observation
  100. GRB 231117A: GECAM-C detection

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