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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. IceCube-231027A - IceCube observation of a high-energy neutrino candidate track-like event
  2. LIGO/Virgo/KAGRA S231025t: Global MASTER-Net observations report
  3. LIGO/Virgo/KAGRA S231025a: Global MASTER-Net observations report
  4. GRB 231019A: Glowbug gamma-ray detection
  5. IC231004A: GRANDMA observations of AT2023uqf/ZTF23abidzvf candidate
  6. GRB 231025A: Fermi GBM Observation
  7. GRB 231024A: Fermi GBM Observation
  8. GRB 231025A: Swift/BAT-GUANO detection of a likely short burst
  9. GRB 231025A: Fermi GBM Final Localization
  10. GRB 231024A: X-shooter spectroscopy of AT2023vuc/GOTO23baj reveals a young supernova with flash ionisation features
  11. GRB 231024A: LCOGT and ZTF detections of the GOTO optical counterpart candidate
  12. GRB 231020A: AstroSat CZTI detection
  13. GRB 231020B: AstroSat CZTI detection
  14. GRB 231024A: GOTO optical counterpart candidate
  15. LIGO/Virgo/KAGRA S231025a: two counterpart neutrino candidates from IceCube neutrino searches
  16. GRB 231024A: Fermi GBM Final Localization
  17. Fermi trigger No 719846439: Global MASTER-Net observations report
  18. The photometry of the transient in Messier 31 field: GMG observation
  19. GRB 231018A: Swift/BAT-GUANO detection of a long burst outside the coded FOV
  20. LIGO/Virgo/KAGRA S231020bw: Upper limits from Swift/BAT-GUANO
  21. LIGO/Virgo/KAGRA S231021az: Coverage and upper limits from MAXI/GSC observations
  22. LIGO/Virgo/KAGRA S231020bw: Updated Sky localization
  23. GRB 231020A: Fermi GBM Detection
  24. GRID detection of GRB 231004A
  25. GRB 231017A: Mondy optical observations. A possible candidate for an afterglow or host galaxy.
  26. GRB 231019A: VZLUSAT-2 detection
  27. GRB 231018A: VZLUSAT-2 detection
  28. GRB 231020B: BALROG localization (Fermi Trigger 719530557 / GRB 231020900)
  29. LIGO/Virgo/KAGRA S231020ba: Updated Sky localization and EM Bright Classification
  30. GRB 231020B: Fermi GBM Final Real-time Localization
  31. GRB 231020A: BALROG localization (Fermi Trigger / GRB 231020790)
  32. LIGO/Virgo/KAGRA S231020ba: Upper limits from Fermi-GBM Observations
  33. GRB 231015A: NuSTAR Detection of Prompt Emission
  34. Fermi GRB 231020A: Global MASTER-Net observations report
  35. LIGO/Virgo/KAGRA S231020bw: Identification of a GW compact binary merger candidate
  36. GRB 231020A: Fermi GBM Final Real-time Localization
  37. GRB 231012A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 705709044)
  38. LIGO/Virgo/KAGRA S231020ba: Coverage and upper limits from MAXI/GSC observations
  39. GRB 231017A: 1.3m DFOT Optical upper limit
  40. LIGO/Virgo/KAGRA S231020ba: Identification of a GW compact binary merger candidate
  41. IceCube-231004A: Upper limits from Fermi-GBM Observations
  42. GRB 231018A: GRBAlpha detection
  43. GRB 231018A: CALET Gamma-Ray Burst Monitor detection
  44. Fermi GRB 231019A: Global MASTER-Net observations report
  45. GRB 231018A: Glowbug gamma-ray detection
  46. Konus-Wind detection of GRB 231018A
  47. IPN triangulation of GRB 231018A
  48. GRB 231017A: Swift/UVOT Upper Limit
  49. GRB 230911C: ATCA detection of possible radio counterpart
  50. GRB 231019A: Fermi GBM Final Real-time Localization
  51. GRB 231017A: GOTO optical upper limits
  52. GRB 231017A: JinShan optical upper limit
  53. GRB 231018A: GROWTH-India Follow-Up of a Fermi Long GRB
  54. LIGO/Virgo/KAGRA S231018cb: One counterpart neutrino candidate event from an IceCube neutrino search
  55. IC231004A: Classification of AT2023uqf/ZTF23abidzvf as a rapidly-evolving supernova with CSM interaction
  56. GRB 231017A: Las Cumbres optical upper limit
  57. GRB 231015A: Glowbug gamma-ray detection
  58. GRB 231017A: LCOGT Optical Upper Limits
  59. GRB231017A: GROWTH-India upper limits on the optical afterglow
  60. GRB 231015A: AstroSat CZTI detection
  61. GRB 231018A: Fermi GBM Detection
  62. GRB 231017A: Fermi GBM Detection
  63. GRB 231017A: Swift-XRT observations
  64. GRB 231012B may not be a GRB
  65. GRB 231018A: BALROG localization (Fermi Trigger / GRB 231018521)
  66. GRB 231018A: Fermi GBM Final Real-time Localization
  67. GRB 231017A: Swift ToO observations
  68. GRB 231017A: Swift/BAT-GUANO candidate arcminute localization of a burst
  69. Fermi-LAT gamma-ray observations of IceCube-231014A
  70. GRB231017A: Fermi GBM Final Localization
  71. IceCube-231014A: Upper limits from a search for additional neutrino events in IceCube
  72. LIGO/Virgo/KAGRA S231014r: Upper limits from Swift/BAT-GUANO
  73. (correction) Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field
  74. Discovery of an optical transient with strong flaring activity: a new blazar candidate in the Messier 31 field.
  75. IceCube-231014A - IceCube observation of a high-energy neutrino candidate track-like event
  76. LIGO/Virgo/KAGRA S231014r: Identification of a GW compact binary merger candidate
  77. Correction in GCN 34814: GRB 231012B (not GRB 231012A)
  78. GRB 231012A: Fermi GBM Final Real-time Localization
  79. GRB 231012A: Fermi GBM Final Real-time Localization
  80. GRB 231004A: Glowbug gamma-ray detection
  81. LIGO/Virgo/KAGRA S231001aq: Updated Sky localization
  82. IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility
  83. LIGO/Virgo/KAGRA S231005j: Upper limits from Swift/BAT-GUANO
  84. LIGO/Virgo/KAGRA S231008ap: Updated Sky localization
  85. LIGO/Virgo/KAGRA S231008ap: Identification of a GW compact binary merger candidate
  86. IceCube-231004A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-231004A: No significant detection in HAWC
  88. GRB 231004A: CALET Gamma-Ray Burst Monitor detection
  89. Fermi-LAT gamma-ray observations of IceCube-231004A
  90. LIGO/Virgo/KAGRA S231005ah: Updated Sky localization
  91. LIGO/Virgo/KAGRA S231005ah: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S231005j: Updated Sky localization
  93. LIGO/Virgo/KAGRA S231005j: Identification of a GW compact binary merger candidate
  94. Update of IceCube-231004A - Corrected direciton
  95. IceCube-231004A - IceCube observation of a high-energy neutrino candidate track-like event
  96. transient AT2023sva: radio observations with AMI-LA
  97. GRB 231004A: Fermi GBM Final Real-time Localization
  98. GRB 231003A is not a GRB
  99. GRB 231003A: Fermi GBM Final Real-time Localization
  100. LIGO/Virgo/KAGRA S231001aq: Upper limits from Swift/BAT-GUANO

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