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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. EP251229a: Optical upper limit with Kinder observations
  2. GRB 251230A: 1.3m DFOT optical upper limit
  3. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  4. GRB 251230A: Swift-XRT refined Analysis
  5. GRB 251231A: Fermi GBM Final Real-time Localization
  6. GRB 251222A: Mondy Optical Observations
  7. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 251230A: Swift/UVOT detection
  9. GRB251230A: 7DT optical upper limits
  10. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  11. EP251229a: BOOTES-2 early optical upper limit
  12. GRB 251230A: GOTO optical upper limit
  13. EP251229a: NOT optical upper limits
  14. GRB 251230A / EP251230a: SVOM/VT optical observation
  15. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 251230A: Enhanced Swift-XRT position
  17. GRB 251230A: Early optical counterpart detection by LCO.
  18. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  19. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  20. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  21. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  22. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  23. Swift GRB 251230A: Global MASTER-Net observations report
  24. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  25. EP251229a: Global MASTER-Net observations report
  26. EP251229a: Einstein Probe detection of an X-ray transient
  27. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  28. GRB 251226A: Glowbug gamma-ray detection
  29. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  30. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  31. Fermi GRB 251228A: Global MASTER-Net observations report
  32. The EP-WXT trigger 01709250662 is likely a flaring star
  33. GRB 251228A: Fermi GBM Final Real-time Localization
  34. GRB 251226A: SVOM/GRM observation
  35. GRB 251226A: GECAM-B detection
  36. SVOM GRB251227.07: Global MASTER-Net observations report
  37. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  38. The EP-WXT trigger 01709250617 is likely a flaring star
  39. IceCube Alert 251225.84: Global MASTER-Net observations report
  40. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  41. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  42. GRB 251222A: NUTTelA-TAO Early Measurements
  43. GRB 251222A/EP251222b: Optical detection with Kinder observations
  44. EP251222a: Optical upper limit with Kinder observations
  45. GRB 251221A: Swift-BAT refined analysis
  46. GRB 251222A/EP251222b: FTW optical and NIR observations
  47. EP251222a: FTW optical and NIR observations
  48. GRB 251205A: Kilonova-Catcher optical afterglow detection
  49. GRB 251222A: AbAO optical observations
  50. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  51. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  52. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  53. GRB 251222A: ZTSH BVRI optical observations
  54. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. GRB 251222A: Continued 1.3m DFOT optical observation
  56. EP251220a: 3.6m DOT optical afterglow detection
  57. GRB 251222A: Fermi GBM Observation
  58. EP251220a: CrAO ZTSh optical observations
  59. EP251221a: PRIME upper limit
  60. EP251222a: Global MASTER-Net observations report
  61. GRB 251222A / EP251222b: GECAM-B observation
  62. EP251221a: Liverpool Telescope upper limits
  63. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  65. Konus-Wind detection of GRB 251222A / EP251222b
  66. GRB 251222A: Swift-XRT afterglow detection
  67. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  68. EP251222a: NTT/ULTRACAM optical observations
  69. EP251222a: GOTO optical upper limit
  70. GRB 251222A / EP251222b: GOTO optical counterpart detection
  71. GRB 251222A / EP251222b: LCO optical observations
  72. GRB 251222A: 1.3m DFOT optical detection
  73. GRB251221A: 7DT optical upper limits
  74. EP251222a: GSP Optical Counterpart Detection
  75. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  76. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  77. EP251222b/GRB 251222A: SVOM/GRM observation
  78. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  79. EP251222a: Einstein Probe detection of an X-ray transient
  80. The EP-WXT trigger 01709250397 is likely a flaring star
  81. EP251221a: Global MASTER-Net observations report
  82. GRB 251222A: PRIME near-infrared detection
  83. EP251221a: NOT optical upper limit
  84. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  85. GRB 251222A: NOT optical observations
  86. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  87. IPN triangulation of GRB 251220B (short)
  88. GRB 251222A: Swift ToO observations
  89. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  90. GRB 251222A: SVOM/VT optical candidate
  91. GRB 251222A: SVOM detection of a long burst
  92. SVOM GRB251222A: Global MASTER-Net observations report
  93. GRB 251222A: Fermi GBM Final Real-time Localization
  94. EP251220a: PRIME upper limit
  95. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  96. GRB 251221A: PRIME near-infrared observation
  97. EP251220a: NOT optical observations
  98. EP251220a: FTW optical and NIR observations
  99. GRB 251221A: UAFO and Mondy optical upper limit
  100. GRB 251221A: Swift-XRT refined Analysis

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