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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 231028A: CALET Gamma-Ray Burst Monitor detection
  2. Fermi GRB 231030A: Global MASTER-Net observations report
  3. GRB 231030A: Fermi GBM Final Real-time Localization
  4. LIGO/Virgo/KAGRA S231029y: One counterpart neutrino candidate from IceCube neutrino searches
  5. LIGO/Virgo/KAGRA S231029ai: Global MASTER-Net observations report
  6. LIGO/Virgo/KAGRA S231029y: Identification of a GW compact binary merger candidate
  7. GRID detection of GRB 231020A
  8. LIGO/Virgo/KAGRA S231029k: Global MASTER-Net observations report
  9. GRB 231028A: AstroSat CZTI detection
  10. GRB 231028A: Glowbug gamma-ray detection
  11. GRB 231028A: Fermi GBM Detection
  12. Fermi trigger No 720224759: Global MASTER-Net observations report
  13. Swift GRB 231028A: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S231028bg: Updated Sky localization
  15. LIGO/Virgo/KAGRA S231028bg: Identification of a GW compact binary merger candidate
  16. GRB 231028A: Swift detection of a burst
  17. GRB 231028A: Fermi GBM Final Real-time Localization
  18. IceCube Alert 231027.18: Global MASTER-Net observations report
  19. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  20. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  21. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  22. GRB 231019A: Glowbug gamma-ray detection
  23. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  24. GRB 231025A: Fermi GBM Observation
  25. GRB 231024A: Fermi GBM Observation
  26. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  27. GRB 231025A: Fermi GBM Final Localization
  28. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  29. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  30. GRB 231020A: AstroSat CZTI detection
  31. GRB 231020B: AstroSat CZTI detection
  32. GRB 231024A: GOTO optical counterpart candidate
  33. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  34. GRB 231024A: Fermi GBM Final Localization
  35. Fermi trigger No 719846439: Global MASTER-Net observations report
  36. The photometry of the transient in Messier 31 field: GMG observation
  37. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  38. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  39. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  40. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  41. GRB 231020A: Fermi GBM Detection
  42. GRID detection of GRB 231004A
  43. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  44. GRB 231019A: VZLUSAT-2 detection
  45. GRB 231018A: VZLUSAT-2 detection
  46. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  47. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  48. GRB 231020B: Fermi GBM Final Real-time Localization
  49. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  50. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  51. GRB 231015A: NuSTAR Detection of Prompt Emission
  52. Fermi GRB 231020A: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  54. GRB 231020A: Fermi GBM Final Real-time Localization
  55. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  56. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  57. GRB 231017A: 1.3m DFOT Optical upper limit
  58. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  59. IceCube-231004A: Upper limits from Fermi-GBM Observations
  60. GRB 231018A: GRBAlpha detection
  61. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  62. Fermi GRB 231019A: Global MASTER-Net observations report
  63. GRB 231018A: Glowbug gamma-ray detection
  64. Konus-Wind detection of GRB 231018A
  65. IPN triangulation of GRB 231018A
  66. GRB 231017A: Swift/UVOT Upper Limit
  67. GRB 230911C: ATCA detection of possible radio counterpart
  68. GRB 231019A: Fermi GBM Final Real-time Localization
  69. GRB 231017A: GOTO optical upper limits
  70. GRB 231017A: JinShan optical upper limit
  71. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  72. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  73. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  74. GRB 231017A: Las Cumbres optical upper limit
  75. GRB 231015A: Glowbug gamma-ray detection
  76. GRB 231017A: LCOGT Optical Upper Limits
  77. GRB231017A: GROWTH-India upper limits on the optical afterglow
  78. GRB 231015A: AstroSat CZTI detection
  79. GRB 231018A: Fermi GBM Detection
  80. GRB 231017A: Fermi GBM Detection
  81. GRB 231017A: Swift-XRT observations
  82. GRB 231012B may not be a GRB
  83. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  84. GRB 231018A: Fermi GBM Final Real-time Localization
  85. GRB 231017A: Swift ToO observations
  86. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  87. Fermi-LAT gamma-ray observations of IceCube-231014A
  88. GRB231017A: Fermi GBM Final Localization
  89. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  90. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  91. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  92. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  93. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  94. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  95. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  96. GRB 231012A: Fermi GBM Final Real-time Localization
  97. GRB 231012A: Fermi GBM Final Real-time Localization
  98. GRB 231004A: Glowbug gamma-ray detection
  99. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  100. IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility

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