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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"

28051 results found.

  1. GRB 251230A: Enhanced Swift-XRT position
  2. GRB 251230A: Early optical counterpart detection by LCO.
  3. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  4. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  5. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  6. Swift GRB 251230A: Global MASTER-Net observations report
  7. EP251229a: Global MASTER-Net observations report
  8. EP251229a: Einstein Probe detection of an X-ray transient
  9. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  10. GRB 251226A: Glowbug gamma-ray detection
  11. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  12. Fermi GRB 251228A: Global MASTER-Net observations report
  13. GRB 251226A: SVOM/GRM observation
  14. GRB 251226A: GECAM-B detection
  15. SVOM GRB251227.07: Global MASTER-Net observations report
  16. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  17. IceCube Alert 251225.84: Global MASTER-Net observations report
  18. GRB 251222A/EP251222b: Optical detection with Kinder observations
  19. EP251222a: Optical upper limit with Kinder observations
  20. GRB 251221A: Swift-BAT refined analysis
  21. GRB 251205A: Kilonova-Catcher optical afterglow detection
  22. GRB 251222A: AbAO optical observations
  23. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  24. GRB 251222A: ZTSH BVRI optical observations
  25. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  26. GRB 251222A: Continued 1.3m DFOT optical observation
  27. EP251220a: 3.6m DOT optical afterglow detection
  28. GRB 251222A: Fermi GBM Observation
  29. EP251220a: CrAO ZTSh optical observations
  30. EP251221a: PRIME upper limit
  31. EP251222a: Global MASTER-Net observations report
  32. EP251221a: Liverpool Telescope upper limits
  33. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  34. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 251222A: Swift-XRT afterglow detection
  36. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  37. EP251222a: NTT/ULTRACAM optical observations
  38. GRB 251222A / EP251222b: GOTO optical counterpart detection
  39. GRB 251222A / EP251222b: LCO optical observations
  40. GRB 251222A: 1.3m DFOT optical detection
  41. GRB251221A: 7DT optical upper limits
  42. EP251222a: GSP Optical Counterpart Detection
  43. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  44. EP251222a: Einstein Probe detection of an X-ray transient
  45. EP251221a: Global MASTER-Net observations report
  46. GRB 251222A: PRIME near-infrared detection
  47. EP251221a: NOT optical upper limit
  48. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  49. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  50. IPN triangulation of GRB 251220B (short)
  51. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  52. GRB 251222A: SVOM/VT optical candidate
  53. GRB 251222A: SVOM detection of a long burst
  54. SVOM GRB251222A: Global MASTER-Net observations report
  55. EP251220a: PRIME upper limit
  56. GRB 251221A: PRIME near-infrared observation
  57. GRB 251221A: UAFO and Mondy optical upper limit
  58. GRB 251221A: Swift-XRT refined Analysis
  59. EP251221a: Einstein Probe detection of a fast X-ray transient
  60. GRB 251221A: Swift/UVOT Upper Limits
  61. GRB 251221A: Enhanced Swift-XRT position
  62. GRB 251221A: Fermi GBM Observation
  63. GRB 251220B: SVOM/GRM observation of a short burst
  64. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  65. EP 251220a: GOTO optical counterpart detection
  66. GRB 251221A: COLIBRÍ detection of the optical counterpart
  67. EP 251220a: COLIBRÍ detection of the optical counterpart
  68. GRB 251221A: Swift detection of a burst
  69. Swift GRB251221A: Global MASTER-Net observations report
  70. EP251220a: Global MASTER-Net observations report
  71. EP251220a: EP detection of a fast X-ray transient
  72. SVOM GRB251220.98: Global MASTER-Net observations report
  73. GRB 251219A: SVOM/GRM observation of a short burst
  74. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  75. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  76. GRB 251220A: MAXI/GSC detection
  77. GRB 251215A: Swift-XRT afterglow detection
  78. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  79. IceCube-251218A: COLIBRÍ optical upper limits
  80. SVOM GRB251219.11: Global MASTER-Net observations report
  81. IceCube Alert 251218.85: Global MASTER-Net observations report
  82. GRB 251214B: VIRT Optical Upper Limit
  83. Fermi trigger No 787736968: Global MASTER-Net observations report
  84. Fermi GRB 251217A: Global MASTER-Net observations report
  85. GRB 251215A: Swift/UVOT Upper LImits
  86. GRB 251215A: Fermi GBM Observation
  87. Fermi GRB 251216A: Global MASTER-Net observations report
  88. GRB 251202A/EP251202a: Koshka optical upper limit
  89. GRB 251214B: Mondy optical upper limit
  90. GRB 251215A: COLIBRÍ optical upper limit
  91. EP251214b: KAIT optical upper limit
  92. GRB 251215A: Swift-XRT observations
  93. Fermi GRB 251215A: Global MASTER-Net observations report
  94. EP251214a: Optical upper limit with Kinder observations
  95. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  96. GRB 251215A: Glowbug gamma-ray detection
  97. GRB 251214B: UAFO optical upper limit
  98. GRB 251214B: VLT/X-shooter observations
  99. GRB 251214B: Swift-BAT refined analysis
  100. GRB 251202A: radio detection with the VLA

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