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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"

26164 results found.

  1. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  2. GRB 251201B: Swift-XRT refined Analysis
  3. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  4. GRB 251202A: Fermi GBM Final Real-time Localization
  5. GRB 251201A: SVOM/GRM observation of a burst
  6. GRB 251201B: SVOM/VT optical fading
  7. Swift GRB 251201B : MASTER optical counterpart detection
  8. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  9. Swift GRB 251201B: Global MASTER-Net observations report
  10. GRB 251201B: Swift detection of a burst with an optical counterpart
  11. GRB 251201B: Fermi GBM Final Real-time Localization
  12. EP251130a: Optical detections with Kinder observations
  13. SVOM GRB251201.19: Global MASTER-Net observations report
  14. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  15. EP251130A: Optical observation from 1.3m DFOT
  16. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  17. Fermi GRB 251130B: Global MASTER-Net observations report
  18. GRB 251127A: SVOM/GRM observation
  19. IceCube Alert 251130.75: Global MASTER-Net observations report
  20. EP251130a: Swift-XRT counterpart detection
  21. GRB 251130B: Fermi GBM Final Localization Correction
  22. EP251130a: Global MASTER-Net observations report
  23. GRB 251130B: Fermi GBM Final Real-time Localization
  24. EP251130a: COLIBRÍ optical counterpart candidate
  25. EP251130a: Einstein Probe detection of an X-ray transient
  26. EP251129a/GRB 251129A: EP-FXT follow-up observations
  27. GRB 251130A: Fermi GBM Final Real-time Localization
  28. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  29. GRB 251128A: GECAM-B detection
  30. GRB 251128A: SVOM/GRM observation of a long burst
  31. SVOM GRB 251129A : MASTER optical counterpart detection
  32. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  33. Swift trigger 1418333 is not an astrophysical source
  34. GRB 251129A / EP251129a: SVOM/VT optical fading
  35. EP251129a: Global MASTER-Net observations report
  36. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  37. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  38. GRB 251128A: Fermi GBM Observation
  39. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  40. GRB 251129A: SVOM detection of a burst
  41. SVOM GRB251129A: Global MASTER-Net observations report
  42. GRB 251129A: SVOM detection of a burst
  43. GRB 251126A: Swift-BAT refined analysis
  44. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  45. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  46. Fermi GRB 251128A: Global MASTER-Net observations report
  47. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  48. GRB 251126A NUTTelA-TAO Early Measurements
  49. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  50. GRB251126A: MAO/AZT-22 optical observations
  51. GRB 251128A: Fermi GBM Final Real-time Localization
  52. GRB251126A: Continued optical observation from 1.3m DFOT
  53. GRB 251126A: Swift/UVOT Detection
  54. GRB 251126A: Mondy and SAO RAS optical observations
  55. GRB 251126A: Swift-XRT refined Analysis
  56. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  57. GRB 251126A: NOT optical observations
  58. GRB 251126A: 1.3m DFOT optical afterglow detection
  59. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  60. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  61. GRB 251125B: GECAM-B detection
  62. Fermi GRB 251127A: Global MASTER-Net observations report
  63. GRB 251127A: Fermi GBM Final Real-time Localization
  64. GRB 251126A: Kilonova-Catcher optical afterglow detection
  65. GRB 251126A: Asiago i-band detection
  66. GRB 251126A: Nanshan/HMT optical afterglow detection
  67. Swift GRB 251126A: Global MASTER-Net observations report
  68. GRB 251121A: Fermi GBM Observation
  69. GRB 251126A: GIT discovery of the likely optical afterglow
  70. GRB 251126A: Swift detection of a burst
  71. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  72. EP251124b follow-up observation by EP-FXT
  73. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  74. EP251124b: NOT r- and z-band optical upper limits
  75. Fermi GRB 251125B: Global MASTER-Net observations report
  76. GRB 251125B: Fermi GBM Final Real-time Localization
  77. EP251124b: Global MASTER-Net observations report
  78. EP251124b: EP-WXT detection of a fast X-ray transient
  79. EP251124a: Xinglong GWAC-F60A optical observation
  80. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  81. Fermi GRB 251125A: Global MASTER-Net observations report
  82. GRB 251125A: Fermi GBM Final Real-time Localization
  83. EP251124a: NOT r- and z-band optical upper limits
  84. EP251124a: Global MASTER-Net observations report
  85. EP251124a: Swift-XRT observations
  86. GRB 251124A: Fermi GBM Localization by automated pipeline
  87. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  88. EP251124a: Optical upper limit with Kinder observations
  89. GRB 251122B: Fermi GBM Final Localization
  90. EP251118A: 6 GHz VLA Detection
  91. Fermi GRB 251124a: Global MASTER-Net observations report
  92. GRB 251124a: Fermi GBM Final Localization
  93. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  94. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  95. EP251124a: GROWTH-India Telescope optical upper limits
  96. EP251124a: Einstein Probe detection of an X-ray transient
  97. GRB 251122A/EP251122a: FTW optical and NIR observations
  98. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  99. The EP-WXT trigger 01709248783 is likely a flaring star
  100. GRB 251122A / EP251122a: Xinglong 2.16m optical observation

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