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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"

7447 results found.

  1. GRB 220921A: LCOGT Optical Observations
  2. GRB 220926A: Swift detection of a burst
  3. IceCube-220907A: Classification of AT2022oyn as a Type Ia supernova
  4. GRB 220921A: Tiled Swift observations
  5. IceCube-220918A - IceCube observation of a high-energy neutrino candidate track-like event
  6. GRB 220909A: Swift ToO observations
  7. GRB 220909A: Swift/BAT-GUANO candidate arcminute localization
  8. IceCube-220907A: One Candidate Counterpart from the Zwicky Transient Facility
  9. GRB 220831A: ATCA 5/9 GHz radio observations
  10. IceCube-220907A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 220831A: Swift-UVOT Upper Limits
  12. Introducing Self-Service Configuration of GCN Notices over Email for Transient Alerts
  13. GRB 220831A: DECam detection of a possible optical counterpart
  14. GRB 220831A: Swift ToO observations
  15. IceCube-220822A: Classification of AT2022saw as a Type Ia supernova
  16. GRB 220826A: Swift detection of a burst with an optical counterpart
  17. IceCube-220822A: One Candidate Counterpart from the Zwicky Transient Facility
  18. IceCube-220822A - IceCube observation of a high-energy neutrino candidate track-like event
  19. GRB 220810A: Further Swift-XRT observations
  20. GRB 220813A: Swift detection of a burst with an optical counterpart
  21. GRB 220810A: Swift-XRT observations
  22. GRB 220810A: Swift ToO observations
  23. GRB 220810A: MeerLICHT detection of two afterglow candidates
  24. GRB 220730A: Swift detection of a short hard burst
  25. Introducing new GCN Kafka broker and web site for transient alerts, https://gcn.nasa.gov
  26. GRB 220715B: Swift detection of a burst
  27. GRB 220714B: UVOT afterglow discovery
  28. GRB 220714B: Swift detection of a burst
  29. GRB 220712B: NOT optical afterglow confirmation
  30. GRB 220710A: Swift ToO observations
  31. GRB 220711B: NOT optical observations
  32. GRB 220711B: Swift detection of a burst
  33. IceCube-220624A: Classification of AT2022nit as a type Ia supernova and AT2021bei as an AGN
  34. GRB 220708B: Swift ToO observations
  35. GRB 220627A: ATCA detection of radio counterpart
  36. GRB 220706A: Swift detection of a burst
  37. GRB 220701A: Keck/LRIS Optical Upper Limit
  38. GRB 200701A: KAIT Optical Upper Limit
  39. GRB 220701A: Swift detection of a burst
  40. Fermi-LAT Gamma-ray Observations of IceCube-220627A
  41. IceCube-220629A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 220627A: Swift-XRT afterglow detection
  43. IceCube-220624A: One Candidate Counterpart from Swift/XRT follow up observations
  44. GRB 220627A: VLT MUSE redshift
  45. GRB 220627A: MeerLICHT candidate optical afterglow
  46. Fermi-LAT Gamma-ray Observations of IceCube-220624A and and detection of a new gamma-ray source, Fermi J1458.0+4119
  47. GRB 220627A: Swift ToO observations
  48. GRB 220627A: MeerLICHT detection of two afterglow candidates
  49. IceCube-220627A - IceCube observation of a high-energy neutrino candidate track-like event
  50. IceCube-220624A: No Candidate Counterparts from the Zwicky Transient Facility
  51. IceCube-220624A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 220617A: TNG optical observations
  53. GRB 220611A optical counterpart
  54. GRB 220618A: Swift detection of a burst
  55. GRB 220617B: Swift ToO observations
  56. GRB 220611A: Swift detection of a burst
  57. GRB 220606B: Gemini South Optical Observations
  58. GRB 220606B: Swift follow-up observations
  59. GRB 220606B: GUANO coordinate correction to GCN 32167
  60. GRB 220606B: Swift ToO observations
  61. GRB 220606B: Swift/BAT-GUANO candidate arcminute localization of a short burst
  62. GRB 220527A: Swift ToO observations
  63. IceCube-220524A - IceCube observation of a high-energy neutrino candidate track-like event
  64. VLA observations of GW170817 at ~4.8 years after the merger
  65. GRB 220521A: Swift detection of a burst
  66. Continued Chandra monitoring of GW170817 at ~4.8 yr post-merger
  67. GRB 220518A: Swift detection of a burst
  68. GRB 220514B: Tiled Swift observations
  69. GRB 220514A: MeerLICHT optical afterglow candidate
  70. IceCube-220513A: No Candidate Counterparts from the Zwicky Transient Facility
  71. IceCube-220513A - IceCube observation of a high-energy neutrino candidate track-like event
  72. GRB 220511A: Swift ToO observations
  73. IceCube-220509A - IceCube observation of a high-energy neutrino candidate track-like event
  74. GRB 220506A: Tiled Swift observations
  75. IceCube-220405B - ZTF19aavnpjv unrelated
  76. IceCube-220501A: No Candidate Counterparts from the Zwicky Transient Facility
  77. IceCube-220501A - IceCube observation of a high-energy neutrino candidate track-like event
  78. GRB 220430A: CAHA 2.2m telescope optical limit
  79. GRB 220430A: Swift detection of a burst or Swift J0630.4+0932
  80. GRB 220426A: Tiled Swift observations
  81. GRB 220427A: Swift detection of a burst with an optical counterpart
  82. Fermi-LAT Gamma-ray Observations of IceCube-220425A
  83. IceCube-220425A: MASTER: flaring blazar TXS 1742-078 as the possible neutrino source candidate
  84. IceCube-220425A - IceCube observation of a high-energy neutrino candidate track-like event
  85. IceCube-220424A - IceCube observation of a high-energy neutrino candidate track-like event
  86. IceCube-220421A - IceCube observation of a high-energy neutrino candidate track-like event
  87. GRB 220418B: Swift ToO observations
  88. GRB 220418B: Swift/BAT-GUANO candidate arcminute localization of a short burst
  89. GRB 220412B: TNG optical observations
  90. GRB 220412A: Continued RATIR Observations and Steepening of the Light Curve
  91. GRB 220412A: BOOTES-network optical upper limits
  92. GRB 220412A: RATIR Observations of the Fading Afterglow
  93. GRB 220412B: Swift detection of a short burst
  94. GRB 220412A: RATIR Afterglow Candidate
  95. GRB 220412A: Swift detection of a burst
  96. GRB 220408A: NOT optical observations and archival detection
  97. GRB 220403C: Swift ToO observations
  98. GRB 220408A: Swift detection of a burst with an optical counterpart, possibly associated with M51
  99. IceCube-220405A: No Candidate Counterparts from the Zwicky Transient Facility
  100. IceCube-220405B: No Candidate Counterparts from the Zwicky Transient Facility

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