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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 210725A: MITSuME Akeno optical upper limits
  2. GRB 210725B: Swift detection of a burst
  3. GRB 210725A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 210723A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 210722A: continued Assy optical observations
  6. GRB 210722A: Nanshan/NEXT further optical observations
  7. GRB 210725A: KAIT Optical Upper Limit
  8. Fermi trigger No 648868114: Global MASTER-Net observations report
  9. GRB 210725A: Swift detection of a burst
  10. Swift GRB210725.16: Global MASTER-Net observations report
  11. GRB 210723A: Fermi GBM Observation
  12. GRB210724A: MeerLICHT upper limits
  13. GRB 210724A: Swift detection of a burst
  14. Swift GRB210724.84: Global MASTER-Net observations report
  15. GRB 210723A: Swift-BAT refined analysis
  16. GRB 210722A: continued Assy optical observations
  17. GRB 210723A: Swift-XRT refined Analysis
  18. GRB 210722A: D50 optical detection
  19. Swift GRB 210723A: Global MASTER-Net observations report
  20. GRB 210722A: Fermi GBM observation
  21. GRB 210722A: Swift-BAT refined analysis
  22. GRB 210722A: Kitab optical observations, light curve
  23. GRB 210722A: Redshift from OSIRIS/GTC
  24. GRB 210723A: Prompt enhanced Swift-XRT position
  25. GRB 210723A: Swift detection of a burst
  26. GRB 210722A: RATIR Optical Observations
  27. GRB 210722A: Swift-XRT refined Analysis
  28. GRB 210722A: Swift/UVOT Detection
  29. GRB 210722A: GIT optical detection and preliminary analysis
  30. Swift GRB 210722A: Global MASTER-Net observations report
  31. GRB 210702A: ALMA detection of mm-band rebrightening
  32. GRB 210722A: Assy optical detection
  33. GRB 210702A: ATCA detection of radio rebrightening
  34. GRB 210722A: Nanshan/NEXT optical afterglow observations
  35. GRB 210722A: Swift detection of a burst with a bright optical counterpart
  36. Fermi trigger No 648602917: Global MASTER-Net observations report
  37. Fermi-LAT Gamma-ray Observations of IceCube-210717A
  38. GRB 210719A: GECAM detection
  39. IceCube-210717A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  40. Fermi trigger No 648359752: Global MASTER-Net observations report
  41. Fermi trigger No 648278666: Global MASTER-Net observations report
  42. IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
  43. Konus-Wind detection of GRB 210714A
  44. Fermi trigger No 647942198: MASTER optical afterglow detection
  45. GRB 210704A: Zeiss-1000/SAO-RAS optical observations
  46. GRB 210715B: DDOTI Upper Limits on the Afterglow
  47. Fermi trigger No 648033323: Global MASTER-Net observations report
  48. Fermi trigger No 648024201: Global MASTER-Net observations report
  49. Fermi trigger No 647942198: Global MASTER-Net observations report
  50. GRB 210712A: Swift-BAT refined analysis
  51. GECAM detection of a short burst from SGR J1935+2154
  52. Recent activity of SGR 1935+2154 as observed by CGBM
  53. GRB 210712A: Swift-XRT refined Analysis
  54. GRB 210712A: Swift/UVOT Upper Limits
  55. GRB 210712A: BOOTES-3/YA optical upper limit
  56. Fermi trigger No 647805873: Global MASTER-Net observations report
  57. GRB 210712A: Enhanced Swift-XRT position
  58. GRB 210704A: classification as long GRB and redshift estimating
  59. GRB 210704A: Lowell Discovery Telescope Optical Observations
  60. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 July 10
  61. GECAM detection of a short burst from SGR J1935+2154
  62. Fermi trigger No 647775795: Global MASTER-Net observations report
  63. GRB 210712A: Swift detection of a burst
  64. GRB 210709A: AstroSat CZTI detection
  65. GRB 210704A: Continued Gemini-North NIR K-band Detections
  66. GRB 210704A: INTEGRAL observations
  67. GRB 210704A: NOT optical observations and color change
  68. GRB210704A: Gemini near-infrared upper limits
  69. Fermi trigger No 647653174: Global MASTER-Net observations report
  70. GRB 210704A: Assy optical afterglow upper limit
  71. Fermi trigger No 647641569: Global MASTER-Net observations report
  72. Fermi trigger No 647624281: Global MASTER-Net observations report
  73. GECAM detection of a short burst from SGR J1935+2154
  74. GRB 210704A: OSIRIS/GTC Observations and Archival Detection of the Possible Host Galaxy
  75. MAXI GRB210709.93: Global MASTER-Net observations report
  76. Fermi trigger No 647522278: Global MASTER-Net observations report
  77. GRB 210704A: Gemini-North Infrared Source Detection
  78. GRB 210704A: further TNG optical observations
  79. GRB 210706A: Swift/XRT afterglow confirmation
  80. GECAM detection of a short burst from SGR 1935+2154
  81. GRB 210708B: Swift-BAT refined analysis
  82. Fermi GRB 210709A: Global MASTER-Net observations report
  83. GRB 210709A: Fermi GBM Final Real-time Localization
  84. Swift GRB 210708B: Global MASTER-Net observations report
  85. GRB 210708A: Swift/UVOT Upper Limits
  86. GRB 210702A: ATCA detection
  87. GRB 210702A: ALMA detection
  88. GRB 210708A: Swift-BAT refined analysis
  89. Fermi GBM Sub-Threshold Detection of GRB 210708A
  90. Fermi GBM Sub-Threshold Detection of GRB 210707A
  91. IceCube-210629A - Spectroscopic observation of AT2021osi
  92. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 July 7
  93. GRB 210708B: Swift detection of a possible burst
  94. GRB 210708A: Swift-XRT refined Analysis
  95. GECAM detection of a short burst from SGR 1935+2154
  96. GRB 210707A: A long GRB detected by INTEGRAL
  97. GRB 210708A: Swift detection of a burst
  98. Swift GRB210708.10: Global MASTER-Net observations report
  99. GRB 210704A: CAHA 2.2m telescope optical limit
  100. Fermi trigger No 647365516: Global MASTER-Net observations report

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