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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 210802A: DDOTI Upper Limits
  2. GRB 210802A: BOOTES-2/TELMA optical upper limit
  3. GRB 210802A: Swift-XRT afterglow detection
  4. GRB 210802A: Fermi GBM detection
  5. GRB 210802A: Fermi-LAT detection
  6. GRB 210803A: BALROG localization (Fermi Trigger 649684549 / GRB 210803497)
  7. GRB 210802A: Tiled Swift observations
  8. Fermi trigger No 649627691: Global MASTER-Net observations report
  9. GRB 210801A: Fermi GBM detection
  10. GRB 210731A: continued GROND observations
  11. GRB 210731A: VLT/X-shooter redshift
  12. GRB 210731A: KAIT Optical Detection
  13. IceCube-210730A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  14. GRB 210731A: Swift-BAT refined analysis
  15. Fermi trigger No 649524889: Global MASTER-Net observations report
  16. GRB 210731A: MASTER optical afterglow detection
  17. GRB 210801A: BALROG localization (Fermi Trigger 649519043 / GRB 210801581)
  18. GRB 210731A: Swift-XRT refined Analysis
  19. Fermi trigger No 649519043: Global MASTER-Net observations report
  20. GRB 210731A: GROND observations
  21. GRB 210731A: Fermi GBM Observation
  22. GRB 210731A: Swift/UVOT Detection of an optical afterglow
  23. Swift GRB210731.62: Global MASTER-Net observations report
  24. GRB 210731A: MeerLICHT optical afterglow detection
  25. GRB210731A: Enhanced Swift-XRT position
  26. GRB 210731A: Swift detection of a burst
  27. Swift GRB210731.93: Global MASTER-Net observations report
  28. Fermi-LAT Gamma-ray Observations of IceCube-210730A
  29. Trigger 1062273: Swift detection of 4U 1700-377
  30. GRB 210730A: Campo Imperatore optical observations
  31. GRB 210730A: BOOTES-5/JGT and 2.2m CAHA telescopes optical limit
  32. Swift GRB 210730A: Global MASTER-Net observations report
  33. Fermi trigger No 649390368: Global MASTER-Net observations report
  34. GRB 210730A: TNG optical observations
  35. IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
  36. GRB 210726A: Chandra detection of the X-ray afterglow
  37. GRB 210730A: Fermi GBM observation
  38. Fermi trigger No 649313854: Global MASTER-Net observations report
  39. GRB 210730A: AstroSat CZTI detection
  40. GRB 210730A: Swift-BAT refined analysis
  41. GRB 210730A: Swift-XRT refined Analysis
  42. GRB 210730A: Swift/UVOT Upper Limits
  43. GRB 210724A: Early CAHA 2.2m limit
  44. GRB 210730A: Enhanced Swift-XRT position
  45. GRB 210727A: AstroSat CZTI detection
  46. GRB 210730A: Swift detection of a burst near M82
  47. GRB 210724A: Corrected Swift-XRT enhanced position
  48. Fermi GBM Sub-Threshold Detection of GRB 210725B
  49. GRB 210726A: OSIRIS/GTC observations
  50. GRB 210727A: CALET Gamma-Ray Burst Monitor detection
  51. GRB 210726A: Deep CAHA 2.2m limit
  52. GRB 210726A: 6 GHz VLA radio upper limit
  53. IPN triangulation of GRB 210727A (short)
  54. Fermi GBM Sub-Threshold Detection of GRB 210726A
  55. GRB 210714A: Fermi GBM observation
  56. GRB 210702A: MeerKAT radio detection
  57. GRB 210726A: Swift-XRT refined Analysis
  58. GRB 210726A: Swift-BAT refined analysis
  59. GRB 210726A: Likely a short burst
  60. GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy
  61. GRB 210727A: AGILE/MCAL detection
  62. Fermi trigger No 649072251: Global MASTER-Net observations report
  63. GRB 210727A: BALROG localization (Fermi Trigger 649072251 / GRB 210727410)
  64. GRB 210725A: AbAO optical upper limit
  65. GRB 210724A: Swift/UVOT Upper Limits
  66. GRB 210723A: Swift/UVOT Upper Limits
  67. GRB 210725A: Swift/UVOT Upper Limits
  68. GRB 210725B: Swift/UVOT Upper Limits
  69. GRB 210726A: CAHA 2.2m telescope optical limit
  70. GRB 210726A: Enhanced Swift-XRT position
  71. GRB 210726A: Swift detection of a burst
  72. Swift GRB210726.80: Global MASTER-Net observations report
  73. Fermi trigger No 648959581: Global MASTER-Net observations report
  74. GRB 210725B: Swift-XRT refined Analysis
  75. GRB 210725A: Fermi GBM detection
  76. GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
  77. GRB 210725A: Swift-XRT refined Analysis
  78. GRB 210725B: Swift-BAT refined analysis
  79. GRB 210724A: Swift-XRT refined Analysis
  80. GRB 210725A: Swift-BAT refined analysis
  81. GRB 210724A: Swift-BAT refined analysis
  82. Swift GRB 210725B: Global MASTER-Net observations report
  83. GRB 210724A: Afterglow candidate from OSIRIS/GTC
  84. GRB 210725B: Enhanced Swift-XRT position
  85. GRB 210725A: MITSuME Akeno optical upper limits
  86. GRB 210725B: Swift detection of a burst
  87. GRB 210725A: CALET Gamma-Ray Burst Monitor detection
  88. GRB 210723A: CALET Gamma-Ray Burst Monitor detection
  89. GRB 210722A: continued Assy optical observations
  90. GRB 210722A: Nanshan/NEXT further optical observations
  91. GRB 210725A: KAIT Optical Upper Limit
  92. Fermi trigger No 648868114: Global MASTER-Net observations report
  93. GRB 210725A: Swift detection of a burst
  94. Swift GRB210725.16: Global MASTER-Net observations report
  95. GRB 210723A: Fermi GBM Observation
  96. GRB210724A: MeerLICHT upper limits
  97. GRB 210724A: Swift detection of a burst
  98. Swift GRB210724.84: Global MASTER-Net observations report
  99. GRB 210723A: Swift-BAT refined analysis
  100. GRB 210722A: continued Assy optical observations

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