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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"
  1. EP251130a: Swift-XRT counterpart detection
  2. GRB 251130B: Fermi GBM Final Localization Correction
  3. EP251130a: Global MASTER-Net observations report
  4. GRB 251130B: Fermi GBM Final Real-time Localization
  5. EP251130a: COLIBRÍ optical counterpart candidate
  6. EP251130a: Einstein Probe detection of an X-ray transient
  7. EP251129a/GRB 251129A: EP-FXT follow-up observations
  8. GRB 251130A: Fermi GBM Final Real-time Localization
  9. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  10. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  11. GRB 251128A: AstroSat CZTI detection
  12. GRB 251129A / EP251129a: SAO RAS optical observations
  13. GRB 251126A: SAO RAS optical observations
  14. GRB 251128A: GECAM-B detection
  15. GRB 251128A: SVOM/GRM observation of a long burst
  16. GRB 251128A: Insight-HXMT/HE detection
  17. SVOM GRB 251129A : MASTER optical counterpart detection
  18. GRB 251129A: Swift-XRT afterglow detection
  19. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  20. Swift trigger 1418333 is not an astrophysical source
  21. GRB 251129A: Swift ToO observations
  22. GRB 251129A / EP251129a: SVOM/VT optical fading
  23. EP251129a: Global MASTER-Net observations report
  24. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  25. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  26. GRB 251129A: Correction to the position of the optical counterpar
  27. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  28. GRB 251128A: Fermi GBM Observation
  29. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  30. GRB 251129A: SVOM detection of a burst
  31. SVOM GRB251129A: Global MASTER-Net observations report
  32. GRB 251129A: SVOM detection of a burst
  33. GRB 251126A: Swift-BAT refined analysis
  34. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  35. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  36. Fermi GRB 251128A: Global MASTER-Net observations report
  37. GRB 251127A: Glowbug gamma-ray detection
  38. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  39. GRB 251126A: further SAO RAS optical observations
  40. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  41. GRB 251126A NUTTelA-TAO Early Measurements
  42. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  43. GRB251126A: MAO/AZT-22 optical observations
  44. GRB 251128A: Fermi GBM Final Real-time Localization
  45. GRB251126A: Continued optical observation from 1.3m DFOT
  46. GRB 251126A: Swift/UVOT Detection
  47. EP251124a: Pan-STARRS ri-band imaging and photometry
  48. GRB 251126A: Mondy and SAO RAS optical observations
  49. GRB 251126A: Swift-XRT refined Analysis
  50. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  51. GRB 251126A: NOT optical observations
  52. GRB 251126A: 1.3m DFOT optical afterglow detection
  53. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  54. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  55. GRB 251125B: GECAM-B detection
  56. Fermi GRB 251127A: Global MASTER-Net observations report
  57. GRB 251127A: Fermi GBM Final Real-time Localization
  58. GRB 251126A: Enhanced Swift-XRT position
  59. GRB 251126A: Kilonova-Catcher optical afterglow detection
  60. GRB 251126A: Asiago i-band detection
  61. GRB 251126A: Nanshan/HMT optical afterglow detection
  62. Swift GRB 251126A: Global MASTER-Net observations report
  63. GRB 251121A: Fermi GBM Observation
  64. GRB 251126A: Prompt enhanced Swift-XRT position
  65. GRB 251126A: GIT discovery of the likely optical afterglow
  66. GRB 251126A: Swift detection of a burst
  67. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  68. EP251124b follow-up observation by EP-FXT
  69. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  70. EP251124b: NOT r- and z-band optical upper limits
  71. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  72. Fermi GRB 251125B: Global MASTER-Net observations report
  73. GRB 251125B: Fermi GBM Final Real-time Localization
  74. EP251124b: Global MASTER-Net observations report
  75. EP251124b: EP-WXT detection of a fast X-ray transient
  76. EP251124a: Xinglong GWAC-F60A optical observation
  77. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  78. Fermi GRB 251125A: Global MASTER-Net observations report
  79. GRB 251125A: Fermi GBM Final Real-time Localization
  80. EP251124a: NOT r- and z-band optical upper limits
  81. EP251124a: Global MASTER-Net observations report
  82. EP251124a: Swift-XRT observations
  83. GRB 251124A: Fermi GBM Localization by automated pipeline
  84. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  85. EP251124a: Optical upper limit with Kinder observations
  86. GRB 251122B: Fermi GBM Final Localization
  87. EP251118A: 6 GHz VLA Detection
  88. Fermi GRB 251124a: Global MASTER-Net observations report
  89. GRB 251124a: Fermi GBM Final Localization
  90. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  91. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  92. EP251124a: GROWTH-India Telescope optical upper limits
  93. EP251124a: Einstein Probe detection of an X-ray transient
  94. GRB 251116C: Swift-XRT confirmation of fading
  95. GRB 251122A/EP251122a: FTW optical and NIR observations
  96. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  97. The EP-WXT trigger 01709248783 is likely a flaring star
  98. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  99. EP251118A: 3.6m DOT optical afterglow detection
  100. GRB 251122A / EP251122a: EP-FXT counterpart detection

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