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

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