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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"

20967 results found.

  1. SVOM GRB260102A: Global MASTER-Net observations report
  2. EP260101a: Global MASTER-Net observations report
  3. GRB 260102A: Swift-XRT observations
  4. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. GRB 260102A: Swift ToO observations
  6. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260101A: NOT spectroscopic observations
  8. Swift GRB 260101A: Global MASTER-Net observations report
  9. GRB 260101A: LCO detection of the optical counterpart
  10. SVOM GRB251231.57: Global MASTER-Net observations report
  11. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  12. GRB 251230A: GRANDMA/TAROT Early Detection
  13. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  14. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  15. EP251229a: Optical upper limit with Kinder observations
  16. GRB 251230A: 1.3m DFOT optical upper limit
  17. GRB 251222A: Mondy Optical Observations
  18. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  19. GRB 251230A: Swift/UVOT detection
  20. GRB251230A: 7DT optical upper limits
  21. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  22. EP251229a: BOOTES-2 early optical upper limit
  23. GRB 251230A: GOTO optical upper limit
  24. EP251229a: NOT optical upper limits
  25. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 251230A: Early optical counterpart detection by LCO.
  27. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  28. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  29. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  30. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  31. Swift GRB 251230A: Global MASTER-Net observations report
  32. EP251229a: Global MASTER-Net observations report
  33. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  34. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  35. Fermi GRB 251228A: Global MASTER-Net observations report
  36. SVOM GRB251227.07: Global MASTER-Net observations report
  37. IceCube Alert 251225.84: Global MASTER-Net observations report
  38. GRB 251222A: NUTTelA-TAO Early Measurements
  39. GRB 251222A/EP251222b: Optical detection with Kinder observations
  40. EP251222a: Optical upper limit with Kinder observations
  41. GRB 251222A/EP251222b: FTW optical and NIR observations
  42. EP251222a: FTW optical and NIR observations
  43. GRB 251205A: Kilonova-Catcher optical afterglow detection
  44. GRB 251222A: AbAO optical observations
  45. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  46. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  47. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  48. GRB 251222A: ZTSH BVRI optical observations
  49. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  50. GRB 251222A: Continued 1.3m DFOT optical observation
  51. EP251220a: 3.6m DOT optical afterglow detection
  52. EP251220a: CrAO ZTSh optical observations
  53. EP251221a: PRIME upper limit
  54. EP251222a: Global MASTER-Net observations report
  55. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 251222A: Swift-XRT afterglow detection
  58. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  59. EP251222a: NTT/ULTRACAM optical observations
  60. EP251222a: GOTO optical upper limit
  61. GRB 251222A / EP251222b: GOTO optical counterpart detection
  62. GRB 251222A / EP251222b: LCO optical observations
  63. GRB 251222A: 1.3m DFOT optical detection
  64. GRB251221A: 7DT optical upper limits
  65. EP251222a: GSP Optical Counterpart Detection
  66. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  67. EP251221a: Global MASTER-Net observations report
  68. GRB 251222A: PRIME near-infrared detection
  69. EP251221a: NOT optical upper limit
  70. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  71. GRB 251222A: NOT optical observations
  72. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  73. GRB 251222A: Swift ToO observations
  74. SVOM GRB251222A: Global MASTER-Net observations report
  75. EP251220a: PRIME upper limit
  76. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  77. GRB 251221A: PRIME near-infrared observation
  78. EP251220a: NOT optical observations
  79. EP251220a: FTW optical and NIR observations
  80. GRB 251221A: UAFO and Mondy optical upper limit
  81. GRB 251221A: Swift/UVOT Upper Limits
  82. EP251220a: EP-FXT follow-up observation
  83. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  84. EP 251220a: GOTO optical counterpart detection
  85. EP 251220a: COLIBRÍ detection of the optical counterpart
  86. Swift GRB251221A: Global MASTER-Net observations report
  87. EP251220a: Global MASTER-Net observations report
  88. SVOM GRB251220.98: Global MASTER-Net observations report
  89. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  90. GRB 251215A: Swift-XRT afterglow detection
  91. IceCube-251218A: COLIBRÍ optical upper limits
  92. SVOM GRB251219.11: Global MASTER-Net observations report
  93. IceCube Alert 251218.85: Global MASTER-Net observations report
  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. Fermi GRB 251216A: Global MASTER-Net observations report
  98. GRB 251215A: COLIBRÍ optical upper limit
  99. GRB 251215A: Swift-XRT observations
  100. Fermi GRB 251215A: Global MASTER-Net observations report

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