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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"

28053 results found.

  1. GRB 251230A: Swift/UVOT detection
  2. GRB251230A: 7DT optical upper limits
  3. GRB 251230A: GOTO optical upper limit
  4. EP251229a: NOT optical upper limits
  5. GRB 251230A / EP251230a: SVOM/VT optical observation
  6. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 251230A: Enhanced Swift-XRT position
  8. GRB 251230A: Early optical counterpart detection by LCO.
  9. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  10. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  11. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  12. Swift GRB 251230A: Global MASTER-Net observations report
  13. EP251229a: Global MASTER-Net observations report
  14. EP251229a: Einstein Probe detection of an X-ray transient
  15. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  16. GRB 251226A: Glowbug gamma-ray detection
  17. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  18. Fermi GRB 251228A: Global MASTER-Net observations report
  19. GRB 251226A: SVOM/GRM observation
  20. GRB 251226A: GECAM-B detection
  21. SVOM GRB251227.07: Global MASTER-Net observations report
  22. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  23. IceCube Alert 251225.84: Global MASTER-Net observations report
  24. GRB 251222A/EP251222b: Optical detection with Kinder observations
  25. EP251222a: Optical upper limit with Kinder observations
  26. GRB 251221A: Swift-BAT refined analysis
  27. GRB 251205A: Kilonova-Catcher optical afterglow detection
  28. GRB 251222A: AbAO optical observations
  29. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  30. GRB 251222A: ZTSH BVRI optical observations
  31. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  32. GRB 251222A: Continued 1.3m DFOT optical observation
  33. EP251220a: 3.6m DOT optical afterglow detection
  34. GRB 251222A: Fermi GBM Observation
  35. EP251220a: CrAO ZTSh optical observations
  36. EP251221a: PRIME upper limit
  37. EP251222a: Global MASTER-Net observations report
  38. EP251221a: Liverpool Telescope upper limits
  39. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  40. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 251222A: Swift-XRT afterglow detection
  42. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  43. EP251222a: NTT/ULTRACAM optical observations
  44. GRB 251222A / EP251222b: GOTO optical counterpart detection
  45. GRB 251222A / EP251222b: LCO optical observations
  46. GRB 251222A: 1.3m DFOT optical detection
  47. GRB251221A: 7DT optical upper limits
  48. EP251222a: GSP Optical Counterpart Detection
  49. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  50. EP251222a: Einstein Probe detection of an X-ray transient
  51. EP251221a: Global MASTER-Net observations report
  52. GRB 251222A: PRIME near-infrared detection
  53. EP251221a: NOT optical upper limit
  54. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  55. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  56. IPN triangulation of GRB 251220B (short)
  57. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  58. GRB 251222A: SVOM/VT optical candidate
  59. GRB 251222A: SVOM detection of a long burst
  60. SVOM GRB251222A: Global MASTER-Net observations report
  61. EP251220a: PRIME upper limit
  62. GRB 251221A: PRIME near-infrared observation
  63. GRB 251221A: UAFO and Mondy optical upper limit
  64. GRB 251221A: Swift-XRT refined Analysis
  65. EP251221a: Einstein Probe detection of a fast X-ray transient
  66. GRB 251221A: Swift/UVOT Upper Limits
  67. GRB 251221A: Enhanced Swift-XRT position
  68. GRB 251221A: Fermi GBM Observation
  69. GRB 251220B: SVOM/GRM observation of a short burst
  70. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  71. EP 251220a: GOTO optical counterpart detection
  72. GRB 251221A: COLIBRÍ detection of the optical counterpart
  73. EP 251220a: COLIBRÍ detection of the optical counterpart
  74. GRB 251221A: Swift detection of a burst
  75. Swift GRB251221A: Global MASTER-Net observations report
  76. EP251220a: Global MASTER-Net observations report
  77. EP251220a: EP detection of a fast X-ray transient
  78. SVOM GRB251220.98: Global MASTER-Net observations report
  79. GRB 251219A: SVOM/GRM observation of a short burst
  80. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  81. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  82. GRB 251220A: MAXI/GSC detection
  83. GRB 251215A: Swift-XRT afterglow detection
  84. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  85. IceCube-251218A: COLIBRÍ optical upper limits
  86. SVOM GRB251219.11: Global MASTER-Net observations report
  87. IceCube Alert 251218.85: Global MASTER-Net observations report
  88. GRB 251214B: VIRT Optical Upper Limit
  89. Fermi trigger No 787736968: Global MASTER-Net observations report
  90. Fermi GRB 251217A: Global MASTER-Net observations report
  91. GRB 251215A: Swift/UVOT Upper LImits
  92. GRB 251215A: Fermi GBM Observation
  93. Fermi GRB 251216A: Global MASTER-Net observations report
  94. GRB 251202A/EP251202a: Koshka optical upper limit
  95. GRB 251214B: Mondy optical upper limit
  96. GRB 251215A: COLIBRÍ optical upper limit
  97. EP251214b: KAIT optical upper limit
  98. GRB 251215A: Swift-XRT observations
  99. Fermi GRB 251215A: Global MASTER-Net observations report
  100. EP251214a: Optical upper limit with Kinder observations

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