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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 210205A: Swift-BAT refined analysis
  2. IPN triangulation of GRB 210204A
  3. GRB 210205A: Swift-XRT refined Analysis
  4. GRB 210205A: MITSuME Ishigaki optical observation
  5. ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
  6. GRB 210205B: AGILE/MCAL detection of a burst
  7. GRB 210205A: Swift/UVOT Upper Limits
  8. Swift GRB 210205A: Global MASTER-Net observations report
  9. GRB 210205A: Nanshan/NEXT optical upper limit
  10. GRB 210205A: BOOTES-4/MET optical upper limit
  11. GRB 210205A: Enhanced Swift-XRT position
  12. GRB 210205A： GWAC-F60A optical upper limit
  13. GRB 210205A: Swift detection of a burst
  14. Fermi GRB 210204B: Global MASTER-Net observations report
  15. Fermi GRB 210204A: Global MASTER-Net observations report
  16. GRB 210204B: Fermi GBM Final Real-time Localization
  17. GRB 210204: Fermi GBM observation
  18. GRB 210204A: GECAM detection
  19. GRB 210204A: BALROG localization (Fermi Trigger 634112970 / GRB 210204270)
  20. GRB 210204A: Fermi GBM Final Real-time Localization
  21. GRB 210202A: AGILE/MCAL detection
  22. Fermi GBM Observations of a bright burst from SGR J1935+2154
  23. GRB 210202A: Fermi GBM detection
  24. GRB 210202A: Fermi-LAT detection
  25. Fermi GRB 210202A: Global MASTER-Net observations report
  26. Fermi trigger No 633963272: Global MASTER-Net observations report
  27. Recent activity of SGR 1935+2154 as observed by CGBM
  28. GRB 210202A: BALROG localization (Fermi Trigger / GRB 210202841)
  29. INTEGRAL detection of a short burst from SGR 1935+2154
  30. GRB 210202A: Fermi GBM Final Real-time Localization
  31. GRB 210131A: GECAM detection
  32. Fermi trigger No 633879387: Global MASTER-Net observations report
  33. GECAM observations of SGR 1935+2154
  34. GRB 210129A: Insight-HXMT/HE detection
  35. Continued Chandra observations of GW170817 at ~3.3 years since merger
  36. Fermi GBM Observations of SGR J1935+2154
  37. Konus-Wind detection of two bright bursts from SGR 1935+2154
  38. GRB 140330A: Swift-XRT refined Analysis
  39. GRB 140320B: Swift-XRT refined Analysis
  40. GRB 140402A: Swift-XRT refined Analysis
  41. GRB 140104B: Swift-XRT refined Analysis
  42. GRB 210126A: AstroSat CZTI detection
  43. GRB 210124B: AstroSat CZTI detection
  44. GRB 210123A: AstroSat CZTI detection
  45. IPN triangulation of a bright burst from SGR 1935+2154
  46. ZTF21aaeyldq: Observations with the 3.6m DOT
  47. GECAM detection of a short burst probably from SGR 1935+2154
  48. GRB 210127A: Fermi GBM Final Real-time Localization
  49. GRB 210120A: Fermi GBM detection
  50. Fermi trigger No 633348010: Global MASTER-Net observations report
  51. HAWC Transient event on 2021/01/25
  52. Konus-Wind detection of GRB 210121A
  53. Konus-Wind detection of GRB 210124B
  54. GRB 210126A: GECAM detection
  55. IPN triangulation of GRB 210124B (short)
  56. GRB 210126A: BALROG localization (Fermi Trigger / GRB 210126417)
  57. GRB 210124B: Insight-HXMT/HE detection
  58. Fermi trigger No 633257525: Global MASTER-Net observations report
  59. GRB 210123A: Fermi GBM Final Localization
  60. GECAM detection of a burst possibly from the X-ray burster 4U 0614+09 or GRB 210124A
  61. GRB 210123A: Insight-HXMT/HE detection
  62. IPN triangulation of GRB 210121A
  63. GRB 210121A: GECAM detection
  64. GRB 210121A: Insight-HXMT/HE detection
  65. GRB 210120A : 1.3m DFOT optical observations
  66. ZTF21aaeyldq: GROND and CAHA jet break confirmation
  67. ZTF20aaeyldq: VLA radio detection
  68. GRB 210116A: AstroSat CZTI detection
  69. GRB 210120A(MASTER OT J105242.66+152355.0 / AT2021axc): Mondy optical observations
  70. GRB 210116: AstroSat LAXPC detection
  71. GRB 210120A: MASTER OT (possibly) discovery
  72. GECAM In-Flight Trigger of GRB 210120A
  73. GRB 210104A: 3.6m DOT optical upper limit
  74. Fermi GRB 210120A: Global MASTER-Net observations report
  75. GRB 210120A: BALROG localization (Fermi Trigger 632819449 / GRB 210120299)
  76. GRB 210120A: Fermi GBM Final Real-time Localization
  77. GRB 210112A: 3.6m DOT optical detection
  78. GRB 210119A (Swift J1851.2-6148): Swift-BAT refined analysis
  79. GECAM detection of a short GRB 210119A or a new SGR candidate Swift J1851.2-6148
  80. ZTF21aaeyldq: GROND observations
  81. GRB 210119A: Insight-HXMT/HE detection
  82. GRB 210119A: Fermi GBM observation
  83. ZTF21aaeyldq: LBT near-infrared observations
  84. GRB 210112A: Insight-HXMT/HE detection
  85. Short Fermi GRB 210119A or new SGR Swift J1851.2-6148: Possible MASTER Short OT detection
  86. Fermi GRB 210119A: Global MASTER-Net observations report
  87. Swift detection of a new SGR Swift J1851.2-6148 or a short GRB 210119A
  88. GRB 210119A: Fermi GBM Final Real-time Localization
  89. ZTF21aaeyldq CAHA 2.2m detection and power-law decay
  90. GRB 200613A: Host galaxy redshift from OSIRIS/GTC
  91. GRB 210112A: Deep CAHA 2.2m detection
  92. GRB 210104A: Late-time CAHA 2.2m detection
  93. Fermi trigger No 632573937: Global MASTER-Net observations report
  94. ZTF21aaeyldq: KPED observations
  95. Konus-Wind detection of GRB 210112A
  96. Correction to GCN 29288: NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS observation
  97. ZTF21aaeyldq (AT2021any): Detection of X-ray Emission with Swift/XRT
  98. ZTF21aaeyldq: 2.2m CAHA BVRI optical observations
  99. GRB 201221D: near-infrared observation with LBT
  100. ZTF21aaeyldq: NOT optical observations

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