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GCN Circulars are now part of the new GCN! See news and announcements

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').
  1. GRB 230328B: GIT optical follow-up
  2. GRB 230328B: OASDG optical observations
  3. GRB 230328B: Nanshan/NEXT optical upper limit
  4. GRB 230328B: Swift-XRT refined Analysis
  5. GRB 230328B: AstroSat CZTI detection
  6. GRB 230328B: Fermi GBM observation
  7. GRB 230328B: Mondy, AbAO and Kitab optical observations
  8. GRB 230328B: Enhanced Swift-XRT position
  9. GRB 230328B: Mondy optical afterglow confirmation
  10. GRB 230328B: Swift detection of a burst with an optical afterglow
  11. GRB 230328B: Fermi GBM Final Real-time Localization
  12. Fermi GRB 230328A: Global MASTER-Net observations report
  13. GRB 230328A: Fermi GBM Final Real-time Localization
  14. GRB 230325A: Swift-BAT refined analysis
  15. GRB 230325A: Swift/UVOT Upper Limits
  16. GRB 230325A: X-shooter optical afterglow and redshift
  17. GRB 230325A: Swift-XRT refined Analysis
  18. GRB 230322B: Swift-BAT refined analysis
  19. GRB 230325A: Enhanced Swift-XRT position
  20. GRB 230325A: Prompt enhanced Swift-XRT position
  21. GRB 230325A: Swift detection of a burst
  22. GRB 230320B: Fermi GBM Observation
  23. Fermi trigger No 701313046: Global MASTER-Net observations report
  24. Fermi trigger No 701321709: Global MASTER-Net observations report
  25. GRB 230322B: Swift/UVOT Detection
  26. Konus-Wind detection of GRB 230309A
  27. Konus-Wind detection of GRB 230308A
  28. Konus-Wind detection of GRB 230304B
  29. GRB 230322B: Swift-XRT refined Analysis
  30. GRB 230322B: Enhanced Swift-XRT position
  31. Swift GRB 230322B: Global MASTER-Net observations report
  32. GRB 230322B: Swift detection of a burst with optical counterpart
  33. GRB 230322A: Fermi GBM Final Real-time Localization
  34. GRB 230320B: GRBAlpha detection
  35. GRB 230321A: CALET Gamma-Ray Burst Monitor detection
  36. GRB 230320B: CALET Gamma-Ray Burst Monitor detection
  37. Fermi trigger No 701071944: Global MASTER-Net observations report
  38. GRB 230320B: Swift/BAT-GUANO detection outside the coded FOV
  39. Fermi GRB 230320A: Global MASTER-Net observations report
  40. Fermi GRB 230321A: Global MASTER-Net observations report
  41. Fermi trigger No 701058254: Global MASTER-Net observations report
  42. SGR 1806-20: Correction to GCN 33494
  43. INTEGRAL detection of a burst from SGR 1806-200
  44. GRB 230321B: AstroSat CZTI detection
  45. GRB 230320B: AstroSat CZTI detection
  46. GRB 230321A: BALROG localization (Fermi Trigger 701065308 / GRB 230321182)
  47. GRB 230321A: Fermi GBM Final Real-time Localization
  48. GRB 230320A: Fermi GBM Final Real-time Localization
  49. GRB 230314A: TURBO Optical Upper Limit
  50. Trigger 1160641: Swift detection of 4U 1630-472 (a.k.a. SWIFT J1633.8-4724A)
  51. Fermi trigger No 700976129: Global MASTER-Net observations report
  52. GRB 230307A: Continued Gemini-South observations confirm rapid optical fading
  53. IPN triangulation of GRB 230309A
  54. Fermi GRB 230316A: Global MASTER-Net observations report
  55. GRB 230304D: AstroSat CZTI detection
  56. GRB 230316A: Fermi GBM Final Real-time Localization
  57. IPN triangulation of GRB 230304B
  58. GRB 230313A: AstroSat CZTI detection
  59. GRB 230307A: Far off-axis NuSTAR detection of the GRB
  60. IPN triangulation of GRB 230308A (short/bright)
  61. Fermi GRB 230314A: Global MASTER-Net observations report
  62. GRB 230307A: ATCA radio detection
  63. GRB 230314A: Fermi GBM Final Real-time Localization
  64. VZLUSAT-2 detection of SGR 1806-20
  65. GRB 230307A: INTEGRAL upper limit on Hard X-ray afterglow
  66. GRB 230307A: Swift/UVOT detection
  67. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230313A
  68. GRB 230313A: BALROG localization (Fermi Trigger 700400328 / GRB 230313485)
  69. Fermi GRB 230313A: Global MASTER-Net observations report
  70. GRB 230313A: Fermi GBM Final Real-time Localization
  71. GRB 230307A: soft X-ray detection with LEIA
  72. GRB 230307A: Swift-XRT afterglow detection
  73. GRB 230309A: AstroSat CZTI detection of a bright long GRB
  74. Swift GRB230311.85: Global MASTER-Net observations report
  75. Swift GRB230311.83: Global MASTER-Net observations report
  76. Further improved IPN localization for GRB 230307A
  77. Swift GRB230311.81: Global MASTER-Net observations report
  78. GRB 230307A: SOAR/Goodman detection of the possible host galaxy
  79. Swift GRB230311.84: Global MASTER-Net observations report
  80. Swift Trigger 1159438 is also due to the Star Tracker loss of lock.
  81. Swift GRB230311.82: Global MASTER-Net observations report
  82. Triggers 1159434, 1159435 and 1159437: Swift detection of Sco X-1 due to Star Tracker loss of lock
  83. Alert from the HAWC Burst Monitor HAWC-230311A
  84. TESS Detection of the Optical Afterglow of GRB230307A
  85. GRB 230308A: CALET Gamma-Ray Burst Monitor detection
  86. Trigger 1159327: Swift detection of SGR1806-20
  87. GRB 230310A: AstroSat CZTI detection
  88. GRB 230307A: GECKO optical observations and detections of the afterglow
  89. GRB 230307A: MAXI/GSC upper limit
  90. GRB 230307A: Gemini-South Confirmation of the Optical Afterglow
  91. Fermi GRB 230310A: Global MASTER-Net observations report
  92. GRB 230310A: Fermi GBM Final Real-time Localization
  93. GRB 230307A: AGILE/MCAL analysis
  94. GRB 230307A: ATLAS information on the ULTRACAM optical afterglow candidate
  95. GRB 230307A: Erratum of the GCN 33441
  96. GRB 230204B: MASTER detection of an object near NTT Optical Afterglow Candidate
  97. GRB 230308A: Fermi GBM detection
  98. GRB 230307A: Possible optical afterglow
  99. GRB 230307A: ASO-S/HXI detection
  100. GRB 230307A: AstroSat LAXPC detection
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