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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. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  2. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  3. GRB 231024A: AKO Optical Counterpart Candidate
  4. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  5. Fermi GRB 231030A: Global MASTER-Net observations report
  6. GRB 231030A: Fermi GBM Final Real-time Localization
  7. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  8. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  9. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  10. GRID detection of GRB 231020A
  11. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  12. GRB 231028A: AstroSat CZTI detection
  13. GRB 231028A: Glowbug gamma-ray detection
  14. GRB 231028A: Fermi GBM Detection
  15. Fermi trigger No 720224759: Global MASTER-Net observations report
  16. Swift GRB 231028A: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  18. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  19. GRB 231028A: Swift detection of a burst
  20. GRB 231028A: Fermi GBM Final Real-time Localization
  21. IceCube Alert 231027.18: Global MASTER-Net observations report
  22. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  23. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  25. GRB 231019A: Glowbug gamma-ray detection
  26. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  27. GRB 231025A: Fermi GBM Observation
  28. GRB 231024A: Fermi GBM Observation
  29. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  30. GRB 231025A: Fermi GBM Final Localization
  31. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  32. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  33. GRB 231020A: AstroSat CZTI detection
  34. GRB 231020B: AstroSat CZTI detection
  35. GRB 231024A: GOTO optical counterpart candidate
  36. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  37. GRB 231024A: Fermi GBM Final Localization
  38. Fermi trigger No 719846439: Global MASTER-Net observations report
  39. The photometry of the transient in Messier 31 field: GMG observation
  40. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  41. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  42. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  43. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  44. GRB 231020A: Fermi GBM Detection
  45. GRID detection of GRB 231004A
  46. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  47. GRB 231019A: VZLUSAT-2 detection
  48. GRB 231018A: VZLUSAT-2 detection
  49. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  50. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  51. GRB 231020B: Fermi GBM Final Real-time Localization
  52. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  53. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  54. GRB 231015A: NuSTAR Detection of Prompt Emission
  55. Fermi GRB 231020A: Global MASTER-Net observations report
  56. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  57. GRB 231020A: Fermi GBM Final Real-time Localization
  58. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  59. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  60. GRB 231017A: 1.3m DFOT Optical upper limit
  61. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  62. IceCube-231004A: Upper limits from Fermi-GBM Observations
  63. GRB 231018A: GRBAlpha detection
  64. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  65. Fermi GRB 231019A: Global MASTER-Net observations report
  66. GRB 231018A: Glowbug gamma-ray detection
  67. Konus-Wind detection of GRB 231018A
  68. IPN triangulation of GRB 231018A
  69. GRB 231017A: Swift/UVOT Upper Limit
  70. GRB 230911C: ATCA detection of possible radio counterpart
  71. GRB 231019A: Fermi GBM Final Real-time Localization
  72. GRB 231017A: GOTO optical upper limits
  73. GRB 231017A: JinShan optical upper limit
  74. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  75. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  76. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  77. GRB 231017A: Las Cumbres optical upper limit
  78. GRB 231015A: Glowbug gamma-ray detection
  79. GRB 231017A: LCOGT Optical Upper Limits
  80. GRB231017A: GROWTH-India upper limits on the optical afterglow
  81. GRB 231015A: AstroSat CZTI detection
  82. GRB 231018A: Fermi GBM Detection
  83. GRB 231017A: Fermi GBM Detection
  84. GRB 231017A: Swift-XRT observations
  85. GRB 231012B may not be a GRB
  86. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  87. GRB 231018A: Fermi GBM Final Real-time Localization
  88. GRB 231017A: Swift ToO observations
  89. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  90. Fermi-LAT gamma-ray observations of IceCube-231014A
  91. GRB231017A: Fermi GBM Final Localization
  92. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  93. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  94. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  95. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  96. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  97. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  98. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  99. GRB 231012A: Fermi GBM Final Real-time Localization
  100. GRB 231012A: Fermi GBM Final Real-time Localization

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