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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"

28049 results found.

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

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