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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. IceCube-231125A: Upper limits from a search for additional neutrino events in IceCube
  2. LIGO/Virgo/KAGRA S231127cg: Identification of a GW compact binary merger candidate
  3. GRB 231117A: MeerKAT 1.3GHz detection
  4. GRB 231127A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 231125A: GRBAlpha detection
  6. GRB 231125A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 231127A: AstroSat CZTI detection
  8. GRB 231125A (short): Glowbug gamma-ray detection
  9. GRB 231123B: Swift/BAT-GUANO detection of a burst outside the coded FOV
  10. Update of IceCube-231125A - Corrected errors
  11. GRB 231124A: GRBAlpha detection
  12. IceCube-231125A - IceCube observation of a high-energy neutrino candidate track-like event
  13. Fermi trigger No 722653947: Global MASTER-Net observations report
  14. GRB 231125A: AstroSat CZTI detection of a short burst
  15. GRB 231111A: Optical follow-up observations at Terskol, AbAO, Maidanak, Mondy, Assy
  16. GRB 231126A: Fermi GBM Final Real-time Localization
  17. GRB 231123C: Insight-HXMT/HE detection
  18. Fermi trigger No 722460326: Global MASTER-Net observations report
  19. Fermi trigger No 722507896: Global MASTER-Net observations report
  20. GRB 231123C (short): Glowbug gamma-ray detection
  21. GRB 231124A: Glowbug gamma-ray detection
  22. GRB230728A: VIRT optical upper limit
  23. GRB230506C: VIRT optical upper limit
  24. GRB230506B: VIRT optical upper limit
  25. GRB 231123C: Swift/BAT-GUANO detection of a short burst likely outside the coded FOV
  26. Fermi trigger No 722462310: Global MASTER-Net observations report
  27. LIGO/Virgo/KAGRA S231118an: Updated Sky localization and EM Bright Classification
  28. GRB 231124A: CALET Gamma-Ray Burst Monitor detection
  29. GRB 231115A: XMM-Newton observation
  30. GRB 231124A: Fermi GBM Final Real-time Localization
  31. GRB 231123A: AstroSat CZTI detection
  32. GRB 231117A: Mondy optical observations
  33. GRB 231123C: Fermi GBM Final Real-time Localization
  34. GRB 231123B: Fermi GBM Final Real-time Localization
  35. Fermi trigger No 722400249: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S231123cg: Identification of a GW compact binary merger candidate
  37. GRB 231118A: REM optical afterglow detection
  38. GRB 231122B: AstroSat CZTI detection
  39. GRB 231122B: CALET Gamma-Ray Burst Monitor detection
  40. GRB 231122B: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  41. GRB 231117A: Chandra afterglow detection
  42. GRB 231123A: Fermi GBM Final Real-time Localization
  43. GRB 231122B: Glowbug gamma-ray detection
  44. GRB 231117A: Continued GTC Observations
  45. Fermi trigger No 722349867: Global MASTER-Net observations report
  46. GRB 231122A: GECAM detection
  47. GRB 231122B: GECAM detection
  48. GRB 231122A: Fermi GBM Final Real-time Localization
  49. GRB 231118A: ATCA detection of radio counterpart
  50. GRB 231117A: Swift/UVOT late time observations
  51. GRB 231117A: GTC Near-Infrared Observations
  52. GRB 231117A: Swift-BAT refined analysis
  53. GRB 231118A: GRBAlpha detection
  54. LIGO/Virgo/KAGRA S231118d: Upper limits from Swift/BAT-GUANO
  55. LIGO/Virgo/KAGRA S231118an: Upper limits from Swift/BAT-GUANO
  56. LIGO/Virgo/KAGRA S231114n: Upper limits from Swift/BAT-GUANO
  57. LIGO/Virgo/KAGRA S231113bb: Upper limits from Swift/BAT-GUANO
  58. LIGO/Virgo/KAGRA S231119u: Updated Sky localization and Source Classification
  59. LIGO/Virgo/KAGRA S231118ab: Updated Sky localization and Source Classification
  60. LIGO/Virgo/KAGRA S231118d: Updated Sky localization and Source Classification
  61. GRB 231118A: VZLUSAT-2 detection
  62. GRB 231117A: AMI-LA radio observations
  63. GRB 231118A: Swift-BAT refined analysis
  64. Konus-Wind detection of GRB 231020A
  65. GRB 231117A: LDT Confirmation of Optical Fading
  66. GRB 231117A: Wendelstein Confirmation of Fading of the Optical Afterglow
  67. GRB 231118B: CALET Gamma-Ray Burst Monitor detection
  68. GRB 231117A: CALET Gamma-Ray Burst Monitor detection
  69. 231118A: Swift-UVOT Detection
  70. GRB231117A: Swift-UVOT detection
  71. GRB 231117A : MITSuME Akeno optical afterglow candidate detection
  72. GRB 231118B: Fermi GBM observation
  73. GRB 231118A: Fermi GBM observation
  74. LIGO/Virgo/KAGRA S231119ab: Coverage and upper limits from MAXI/GSC observations
  75. GRB 231120A: Fermi GBM Final Real-time Localization
  76. GRB 231117A: Swift-XRT refined Analysis
  77. GRB 231118A: Swift-XRT refined Analysis
  78. GRB 231118A: MeerLICHT afterglow detection
  79. LIGO/Virgo/KAGRA S231119u: One counterpart neutrino candidate from IceCube neutrino searches
  80. GRB 231117A: OHP/T120 optical observations
  81. GRB 231118A: VLT/X-shooter redshift
  82. Fermi trigger No 722039659: Global MASTER-Net observations report
  83. GRB 231117A: Pan-STARRS1 follow-up confirms rapid fading
  84. LIGO/Virgo/KAGRA S231119u: Identification of a GW compact binary merger candidate
  85. GRB 231117A: MAAO 0.7-m telescope optical upper limit
  86. GRB 231117A: AKO Follow-Up Observation
  87. GRB 231117A: GECAM-C detection
  88. GRB 231118A: AstroSat CZTI detection
  89. GRB 231115A: Upper limit from CALET Gamma-Ray Burst Monitor
  90. GRB 231117A: 10 GHz VLA detection
  91. GRB 231118A: Las Cumbres optical detection
  92. GRB 231118B: BALROG localization (Fermi Trigger 722039659 / GRB 231118940)
  93. GRB 231118B: Fermi GBM Final Real-time Localization
  94. GRB 231118A: LCOGT Optical Observations
  95. GRB 231118A: MASTER OT observation
  96. GRB 231118A: Continued Skynet Observations
  97. Swift GRB231118.72: Global MASTER-Net observations report
  98. GRB 231118A: Enhanced Swift-XRT position
  99. GRB 231117A: Kinder observations with Lulin observatory for AT 2023yba without fading in r band
  100. GRB 231118A: Swift-XRT position

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