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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 231030B: Fermi GBM Detection
  2. GRB 231030B: AstroSat CZTI detection
  3. Fermi GRB 231030B: Global MASTER-Net observations report
  4. IPN triangulation of GRB 231020A
  5. GRB 231030B: BALROG localization (Fermi Trigger 720388704 / GRB 231030832)
  6. GRB 231030B: Fermi GBM Final Real-time Localization
  7. GRB 231028A: Swift-BAT refined analysis
  8. IceCube-231027A: Upper limits from a search for additional neutrino events in IceCube
  9. LIGO/Virgo/KAGRA S231029y: Upper limits from Swift/BAT-GUANO
  10. LIGO/Virgo/KAGRA S231030av: Retraction of GW compact binary merger candidate
  11. GRB 231024A: AKO Optical Counterpart Candidate
  12. GRB 231028A: CALET Gamma-Ray Burst Monitor detection
  13. Fermi GRB 231030A: Global MASTER-Net observations report
  14. GRB 231030A: Fermi GBM Final Real-time Localization
  15. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  16. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  18. GRID detection of GRB 231020A
  19. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  20. GRB 231028A: AstroSat CZTI detection
  21. GRB 231028A: Glowbug gamma-ray detection
  22. GRB 231028A: Fermi GBM Detection
  23. Fermi trigger No 720224759: Global MASTER-Net observations report
  24. Swift GRB 231028A: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  26. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  27. GRB 231028A: Swift detection of a burst
  28. GRB 231028A: Fermi GBM Final Real-time Localization
  29. IceCube Alert 231027.18: Global MASTER-Net observations report
  30. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  31. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  33. GRB 231019A: Glowbug gamma-ray detection
  34. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  35. GRB 231025A: Fermi GBM Observation
  36. GRB 231024A: Fermi GBM Observation
  37. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  38. GRB 231025A: Fermi GBM Final Localization
  39. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  40. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  41. GRB 231020A: AstroSat CZTI detection
  42. GRB 231020B: AstroSat CZTI detection
  43. GRB 231024A: GOTO optical counterpart candidate
  44. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  45. GRB 231024A: Fermi GBM Final Localization
  46. Fermi trigger No 719846439: Global MASTER-Net observations report
  47. The photometry of the transient in Messier 31 field: GMG observation
  48. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  49. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  50. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  51. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  52. GRB 231020A: Fermi GBM Detection
  53. GRID detection of GRB 231004A
  54. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  55. GRB 231019A: VZLUSAT-2 detection
  56. GRB 231018A: VZLUSAT-2 detection
  57. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  58. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  59. GRB 231020B: Fermi GBM Final Real-time Localization
  60. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  61. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  62. GRB 231015A: NuSTAR Detection of Prompt Emission
  63. Fermi GRB 231020A: Global MASTER-Net observations report
  64. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  65. GRB 231020A: Fermi GBM Final Real-time Localization
  66. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  67. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  68. GRB 231017A: 1.3m DFOT Optical upper limit
  69. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  70. IceCube-231004A: Upper limits from Fermi-GBM Observations
  71. GRB 231018A: GRBAlpha detection
  72. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  73. Fermi GRB 231019A: Global MASTER-Net observations report
  74. GRB 231018A: Glowbug gamma-ray detection
  75. Konus-Wind detection of GRB 231018A
  76. IPN triangulation of GRB 231018A
  77. GRB 231017A: Swift/UVOT Upper Limit
  78. GRB 230911C: ATCA detection of possible radio counterpart
  79. GRB 231019A: Fermi GBM Final Real-time Localization
  80. GRB 231017A: GOTO optical upper limits
  81. GRB 231017A: JinShan optical upper limit
  82. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  83. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  84. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  85. GRB 231017A: Las Cumbres optical upper limit
  86. GRB 231015A: Glowbug gamma-ray detection
  87. GRB 231017A: LCOGT Optical Upper Limits
  88. GRB231017A: GROWTH-India upper limits on the optical afterglow
  89. GRB 231015A: AstroSat CZTI detection
  90. GRB 231018A: Fermi GBM Detection
  91. GRB 231017A: Fermi GBM Detection
  92. GRB 231017A: Swift-XRT observations
  93. GRB 231012B may not be a GRB
  94. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  95. GRB 231018A: Fermi GBM Final Real-time Localization
  96. GRB 231017A: Swift ToO observations
  97. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  98. Fermi-LAT gamma-ray observations of IceCube-231014A
  99. GRB231017A: Fermi GBM Final Localization
  100. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube

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