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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"

28056 results found.

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

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