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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"

32503 results found.

  1. GRB251230A: 7DT optical upper limits
  2. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  3. EP251229a: BOOTES-2 early optical upper limit
  4. GRB 251230A: GOTO optical upper limit
  5. EP251229a: NOT optical upper limits
  6. GRB 251230A / EP251230a: SVOM/VT optical observation
  7. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 251230A: Early optical counterpart detection by LCO.
  9. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  10. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  11. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  12. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  13. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  14. Swift GRB 251230A: Global MASTER-Net observations report
  15. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  16. EP251229a: Global MASTER-Net observations report
  17. GRB 251226A: Glowbug gamma-ray detection
  18. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  19. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  20. Fermi GRB 251228A: Global MASTER-Net observations report
  21. GRB 251226A: SVOM/GRM observation
  22. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  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 251221A: Swift-BAT refined analysis
  27. GRB 251222A/EP251222b: FTW optical and NIR observations
  28. EP251222a: FTW optical and NIR observations
  29. GRB 251205A: Kilonova-Catcher optical afterglow detection
  30. GRB 251222A: AbAO optical observations
  31. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  32. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  33. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  34. GRB 251222A: ZTSH BVRI optical observations
  35. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  36. GRB 251222A: Continued 1.3m DFOT optical observation
  37. EP251220a: 3.6m DOT optical afterglow detection
  38. GRB 251222A: Fermi GBM Observation
  39. EP251220a: CrAO ZTSh optical observations
  40. EP251221a: PRIME upper limit
  41. EP251222a: Global MASTER-Net observations report
  42. GRB 251222A / EP251222b: GECAM-B observation
  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. Konus-Wind detection of GRB 251222A / EP251222b
  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. EP251221a: Global MASTER-Net observations report
  60. GRB 251222A: PRIME near-infrared detection
  61. EP251221a: NOT optical upper limit
  62. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. GRB 251222A: NOT optical observations
  64. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  65. IPN triangulation of GRB 251220B (short)
  66. GRB 251222A: Swift ToO observations
  67. GRB 251222A: SVOM/VT optical candidate
  68. GRB 251222A: SVOM detection of a long burst
  69. EP251220a: PRIME upper limit
  70. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  71. GRB 251221A: PRIME near-infrared observation
  72. EP251220a: NOT optical observations
  73. EP251220a: FTW optical and NIR observations
  74. GRB 251221A: UAFO and Mondy optical upper limit
  75. GRB 251221A: Swift/UVOT Upper Limits
  76. GRB 251221A: Fermi GBM Observation
  77. EP251220a: EP-FXT follow-up observation
  78. GRB 251220B: SVOM/GRM observation of a short burst
  79. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  80. EP 251220a: GOTO optical counterpart detection
  81. GRB 251221A: COLIBRÍ detection of the optical counterpart
  82. EP 251220a: COLIBRÍ detection of the optical counterpart
  83. EP251220a: Global MASTER-Net observations report
  84. GRB 251219A: SVOM/GRM observation of a short burst
  85. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  86. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-251218A: COLIBRÍ optical upper limits
  88. GRB 251214B: VIRT Optical Upper Limit
  89. Fermi GRB 251217A: Global MASTER-Net observations report
  90. GRB 251215A: Swift/UVOT Upper LImits
  91. GRB 251215A: Fermi GBM Observation
  92. Fermi GRB 251216A: Global MASTER-Net observations report
  93. GRB 251202A/EP251202a: Koshka optical upper limit
  94. GRB 251214B: Mondy optical upper limit
  95. GRB 251215A: COLIBRÍ optical upper limit
  96. EP251214b: KAIT optical upper limit
  97. Fermi GRB 251215A: Global MASTER-Net observations report
  98. EP251214a: Optical upper limit with Kinder observations
  99. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  100. GRB 251215A: Glowbug gamma-ray detection

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