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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. EP240801a: SAO RAS optical observations
  2. GRB 240801B: AstroSat CZTI Updated classification - likely a solar flare
  3. EP240801a: JinShan optical observations
  4. GRB 240727C: SVOM/GRM observation
  5. EP240801a: NOT optical observations
  6. EP240801a: follow-up observation with LCOGT
  7. Fermi GBM trigger 744179961 / 240801194 can not be confirmed as a GRB
  8. GRB 240730A: Swift-BAT refined analysis
  9. EP240801a: GSP follow-up observations of the candidate counterpart
  10. Fermi trigger No 744204856: Global MASTER-Net observations report
  11. EP240801a: Kinder follow-up observations of the candidate counterpart
  12. EP240708a: Kinder follow-up observations of the candidate counterpart (duplicate submission of GCN 37002)
  13. EP240801a: KAIT optical counterpart observations
  14. EP240801a: GMG observation
  15. EP240801a: TRT optical counterpart detection
  16. EP240801a: EP-WXT detection and EP-FXT follow-up observation of a fast X-ray transient
  17. GRB 240801B: AstroSat CZTI detection of a bright long burst
  18. Fermi GRB 240801A: Global MASTER-Net observations report
  19. GRB 240801A: Fermi GBM Final Real-time Localization
  20. GRB 240730C: AstroSat CZTI detection of a long burst
  21. GRB 240731A: Fermi GBM Final Localization
  22. Fermi trigger No 744128417: Global MASTER-Net observations report
  23. Fermi trigger No 744083370: Global MASTER-Net observations report
  24. GRB 240731A: AstroSat CZTI detection
  25. GRB 240730A: Osservatorio Astronomico Nastro Verde upper limit
  26. GRB240730A: BOOTES-5/JGT early optical upper limit
  27. Fermi Gamma-ray Burst Monitor trigger 744061103/240730818 is not a GRB
  28. Fermi GRB 240730B: Global MASTER-Net observations report
  29. GRB 240730B: Fermi GBM Final Real-time Localization
  30. Swift GRB 240730A: Global MASTER-Net observations report
  31. GRB 240730A: Swift-XRT refined Analysis
  32. GRB 240715A: Swift-XRT afterglow detection
  33. GRB 240730A: KAIT Optical Upper Limit
  34. GRB 240727C: GRBAlpha detection
  35. GRB 240730A: Swift/UVOT Upper Limits
  36. GRB 240730A: Enhanced Swift-XRT position
  37. GRB 240730A: Swift detection of a burst
  38. Fermi trigger No 743953682: Global MASTER-Net observations report
  39. GRB 240727A: Swift-BAT refined analysis
  40. Fermi Gamma-ray Burst Monitor trigger 743953682/240729575 is not a GRB
  41. LIGO/Virgo/KAGRA S240615dg: GRAWITA wide-field optical observations
  42. GRB 240727A: observations of optical counterpart.
  43. GRB 240727B: Swift-XRT observations
  44. Fermi GRB 240727A: Global MASTER-Net observations report
  45. GRB 240727A: Swift/UVOT detection
  46. Fermi trigger No 743868421: Global MASTER-Net observations report
  47. Fermi Gamma-ray Burst Monitor trigger 743868421/240728588 is not a GRB
  48. GRB 240727A: Correction to time in GCN36960
  49. GRB 240727A: Osservatorio Astronomico Nastro Verde upper limit
  50. EP-WXT trigger 01709002661 is not a real source
  51. GRB 240727A: NOT optical observation
  52. GRB 240727A: JinShan optical upper limits
  53. GRB 240727A Bassano Bresciano Observatory upper limit
  54. GRB 240727D: Correction to the GRB name in GCN 36958
  55. GRB 240727A: Fermi GBM Final Real-time Localization
  56. GRB 240727C: AstroSat CZTI detection of a long burst
  57. GRB 240727A: Swift-XRT refined Analysis
  58. GRB 240720B: GRBAlpha detection
  59. GRB 240718A: GRBAlpha detection
  60. GRB 240710B: GRBAlpha detection
  61. GRB 240627A: GRBAlpha detection
  62. Fermi GRB 240726A: Global MASTER-Net observations report
  63. GRB 240727A: Enhanced Swift-XRT position
  64. GRB 240727B: Fermi GBM Observation
  65. Swift GRB240727.16: Global MASTER-Net observations report
  66. GRB240529A: VIRT optical transient detection
  67. GRB 240727B: Swift ToO observations
  68. GRB 240727B: Swift/BAT-GUANO arcminute localization of a long burst
  69. GRB 240726A: SVOM/GRM observation
  70. GRB 240727B: AstroSat CZTI detection
  71. GRB 240726B: AstroSat CZTI detection of a short burst
  72. GRB240727A: Skynet Optical Afterglow Observations
  73. GRB 240727A: TRT optical afterglow detection
  74. GRB 240727A: KAIT Optical Afterglow Candidate
  75. GRB 240727A: Swift detection of a burst
  76. GRB 240726A: AstroSat CZTI detection of a short burst
  77. IceCube-240725A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 240726A: Fermi GBM Final Real-time Localization
  79. Fermi-LAT gamma-ray observations of IceCube-240725A
  80. IceCube Alert 240725.22: Global MASTER-Net observations report
  81. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  82. Swift Trigger 1244778 is not a GRB
  83. Swift GRB240725.11: Global MASTER-Net observations report
  84. IceCube-240721A: Two candidates from the Zwicky Transient Facility
  85. GRB 240720A: Swift-BAT refined analysis
  86. IceCube-240721A: Upper limits from a search for additional neutrino events in IceCube
  87. Fermi trigger No 743418632: Global MASTER-Net observations report
  88. Fermi trigger No 743315411: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S240716b: Upper limits from Swift/BAT-GUANO
  90. LIGO/Virgo/KAGRA S240703ad: Upper limits from Swift/BAT-GUANO
  91. Fermi trigger No 743345551: Global MASTER-Net observations report
  92. Fermi-LAT gamma-ray observations of IceCube-240721A
  93. Fermi Gamma-ray Burst Monitor trigger 743271526/240721680 is not a GRB
  94. Fermi trigger No 743219692: Global MASTER-Net observations report
  95. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  96. IceCube Alert 240721.68: Global MASTER-Net observations report
  97. Fermi Gamma-ray Burst Monitor trigger 743243582/240721356 (GRB 240721A) is not a GRB
  98. GRB 240720B: SVOM/GRM observation
  99. GRB 240721A: Fermi GBM Final Real-time Localization
  100. GRB 240720B: AstroSat CZTI detection of a short burst

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