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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"

41710 results found.

  1. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  2. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  3. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  4. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  5. Swift GRB 251230A: Global MASTER-Net observations report
  6. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  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. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  13. Fermi GRB 251228A: Global MASTER-Net observations report
  14. The EP-WXT trigger 01709250662 is likely a flaring star
  15. GRB 251228A: Fermi GBM Final Real-time Localization
  16. GRB 251226A: SVOM/GRM observation
  17. GRB 251226A: GECAM-B detection
  18. SVOM GRB251227.07: Global MASTER-Net observations report
  19. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  20. The EP-WXT trigger 01709250617 is likely a flaring star
  21. IceCube Alert 251225.84: Global MASTER-Net observations report
  22. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 251222A: NUTTelA-TAO Early Measurements
  24. GRB 251222A/EP251222b: Optical detection with Kinder observations
  25. EP251222a: Optical upper limit with Kinder observations
  26. GRB 251222A/EP251222b: FTW optical and NIR observations
  27. EP251222a: FTW optical and NIR observations
  28. GRB 251205A: Kilonova-Catcher optical afterglow detection
  29. GRB 251222A: AbAO optical observations
  30. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  31. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  32. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  33. GRB 251222A: ZTSH BVRI optical observations
  34. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  35. GRB 251222A: Continued 1.3m DFOT optical observation
  36. EP251220a: 3.6m DOT optical afterglow detection
  37. GRB 251222A: Fermi GBM Observation
  38. EP251220a: CrAO ZTSh optical observations
  39. EP251221a: PRIME upper limit
  40. EP251222a: Global MASTER-Net observations report
  41. GRB 251222A / EP251222b: GECAM-B observation
  42. EP251221a: Liverpool Telescope upper limits
  43. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  44. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  45. Konus-Wind detection of GRB 251222A / EP251222b
  46. GRB 251222A: Swift-XRT afterglow detection
  47. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  48. EP251222a: NTT/ULTRACAM optical observations
  49. EP251222a: GOTO optical upper limit
  50. GRB 251222A / EP251222b: GOTO optical counterpart detection
  51. GRB 251222A / EP251222b: LCO optical observations
  52. GRB 251222A: 1.3m DFOT optical detection
  53. GRB251221A: 7DT optical upper limits
  54. EP251222a: GSP Optical Counterpart Detection
  55. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  56. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  57. EP251222b/GRB 251222A: SVOM/GRM observation
  58. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  59. EP251222a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709250397 is likely a flaring star
  61. EP251221a: Global MASTER-Net observations report
  62. GRB 251222A: PRIME near-infrared detection
  63. EP251221a: NOT optical upper limit
  64. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  65. GRB 251222A: NOT optical observations
  66. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  67. IPN triangulation of GRB 251220B (short)
  68. GRB 251222A: Swift ToO observations
  69. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  70. GRB 251222A: SVOM/VT optical candidate
  71. GRB 251222A: SVOM detection of a long burst
  72. SVOM GRB251222A: Global MASTER-Net observations report
  73. GRB 251222A: Fermi GBM Final Real-time Localization
  74. EP251220a: PRIME upper limit
  75. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  76. GRB 251221A: PRIME near-infrared observation
  77. EP251220a: NOT optical observations
  78. EP251220a: FTW optical and NIR observations
  79. GRB 251221A: UAFO and Mondy optical upper limit
  80. GRB 251221A: Swift-XRT refined Analysis
  81. EP251221a: Einstein Probe detection of a fast X-ray transient
  82. GRB 251221A: Swift/UVOT Upper Limits
  83. GRB 251221A: Enhanced Swift-XRT position
  84. GRB 251221A: Fermi GBM Observation
  85. GRB 251221B: Fermi GBM Final Real-time Localization
  86. EP251220a: EP-FXT follow-up observation
  87. GRB 251220B: SVOM/GRM observation of a short burst
  88. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  89. EP 251220a: GOTO optical counterpart detection
  90. GRB 251221A: COLIBRÍ detection of the optical counterpart
  91. EP 251220a: COLIBRÍ detection of the optical counterpart
  92. GRB 251221A: Swift detection of a burst
  93. Swift GRB251221A: Global MASTER-Net observations report
  94. GRB 251221A: Fermi GBM Final Real-time Localization
  95. EP251220a: Global MASTER-Net observations report
  96. EP251220a: EP detection of a fast X-ray transient
  97. SVOM GRB251220.98: Global MASTER-Net observations report
  98. GRB 251220B: Fermi GBM Final Real-time Localization
  99. GRB 251219A: SVOM/GRM observation of a short burst
  100. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645

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