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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"

31737 results found.

  1. Fermi GRB 260104B: Global MASTER-Net observations report
  2. Swift GRB 260104A: Global MASTER-Net observations report
  3. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  4. GRB 260101A: Swift/UVOT Detection
  5. GRB 260103A: GECAM-B observation of a burst
  6. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  7. GRB 260101A: COLIBRÍ optical observations
  8. Fermi GBM Sub-Threshold Detection of GRB 260102A
  9. GRB 260102A: EP-FXT follow-up observation
  10. EP260101a: Global MASTER-Net observations report
  11. GRB 260102A: LCO optical upper limits
  12. GRB 260102A: Swift-XRT observations
  13. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  14. GRB 251230A / EP251230a: GECAM-B detection
  15. GRB 260102A: SVOM/VT optical counterpart
  16. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  17. GRB 260102A: Swift ToO observations
  18. GRB 260101A: Fermi GBM Observation
  19. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 260101A: GECAM-B detection
  21. GRB 260101A: NOT spectroscopic observations
  22. GRB 260101A: SVOM/GRM observation
  23. Swift GRB 260101A: Global MASTER-Net observations report
  24. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  25. GRB 260101A: LCO detection of the optical counterpart
  26. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  27. GRB 251230A: GRANDMA/TAROT Early Detection
  28. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  29. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  30. EP251229a: Optical upper limit with Kinder observations
  31. GRB 251230A: 1.3m DFOT optical upper limit
  32. GRB 251222A: Mondy Optical Observations
  33. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  34. GRB 251230A: Swift/UVOT detection
  35. GRB251230A: 7DT optical upper limits
  36. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  37. EP251229a: BOOTES-2 early optical upper limit
  38. GRB 251230A: GOTO optical upper limit
  39. EP251229a: NOT optical upper limits
  40. GRB 251230A / EP251230a: SVOM/VT optical observation
  41. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 251230A: Early optical counterpart detection by LCO.
  43. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  44. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  45. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  46. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  47. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  48. Swift GRB 251230A: Global MASTER-Net observations report
  49. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  50. EP251229a: Global MASTER-Net observations report
  51. GRB 251226A: Glowbug gamma-ray detection
  52. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  53. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  54. Fermi GRB 251228A: Global MASTER-Net observations report
  55. GRB 251226A: SVOM/GRM observation
  56. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 251222A: NUTTelA-TAO Early Measurements
  58. GRB 251222A/EP251222b: Optical detection with Kinder observations
  59. EP251222a: Optical upper limit with Kinder observations
  60. GRB 251221A: Swift-BAT refined analysis
  61. GRB 251222A/EP251222b: FTW optical and NIR observations
  62. EP251222a: FTW optical and NIR observations
  63. GRB 251205A: Kilonova-Catcher optical afterglow detection
  64. GRB 251222A: AbAO optical observations
  65. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  66. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  67. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  68. GRB 251222A: ZTSH BVRI optical observations
  69. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  70. GRB 251222A: Continued 1.3m DFOT optical observation
  71. EP251220a: 3.6m DOT optical afterglow detection
  72. GRB 251222A: Fermi GBM Observation
  73. EP251220a: CrAO ZTSh optical observations
  74. EP251221a: PRIME upper limit
  75. EP251222a: Global MASTER-Net observations report
  76. GRB 251222A / EP251222b: GECAM-B observation
  77. EP251221a: Liverpool Telescope upper limits
  78. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  79. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  80. Konus-Wind detection of GRB 251222A / EP251222b
  81. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  82. EP251222a: NTT/ULTRACAM optical observations
  83. EP251222a: GOTO optical upper limit
  84. GRB 251222A / EP251222b: GOTO optical counterpart detection
  85. GRB 251222A / EP251222b: LCO optical observations
  86. GRB 251222A: 1.3m DFOT optical detection
  87. GRB251221A: 7DT optical upper limits
  88. EP251222a: GSP Optical Counterpart Detection
  89. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  90. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  91. EP251222b/GRB 251222A: SVOM/GRM observation
  92. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  93. EP251221a: Global MASTER-Net observations report
  94. GRB 251222A: PRIME near-infrared detection
  95. EP251221a: NOT optical upper limit
  96. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  97. GRB 251222A: NOT optical observations
  98. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  99. IPN triangulation of GRB 251220B (short)
  100. GRB 251222A: Swift ToO observations

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