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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"

44490 results found.

  1. Fermi GRB 251130B: Global MASTER-Net observations report
  2. GRB 251127A: SVOM/GRM observation
  3. IceCube Alert 251130.75: Global MASTER-Net observations report
  4. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  5. EP251130a: Swift-XRT counterpart detection
  6. GRB 251130B: Fermi GBM Final Localization Correction
  7. EP251130a: Global MASTER-Net observations report
  8. GRB 251130B: Fermi GBM Final Real-time Localization
  9. EP251130a: COLIBRÍ optical counterpart candidate
  10. EP251130a: Einstein Probe detection of an X-ray transient
  11. EP251129a/GRB 251129A: EP-FXT follow-up observations
  12. GRB 251130A: Fermi GBM Final Real-time Localization
  13. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  14. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  15. GRB 251128A: AstroSat CZTI detection
  16. GRB 251129A / EP251129a: SAO RAS optical observations
  17. GRB 251126A: SAO RAS optical observations
  18. GRB 251128A: GECAM-B detection
  19. GRB 251128A: SVOM/GRM observation of a long burst
  20. GRB 251128A: Insight-HXMT/HE detection
  21. SVOM GRB 251129A : MASTER optical counterpart detection
  22. GRB 251129A: Swift-XRT afterglow detection
  23. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  24. Swift trigger 1418333 is not an astrophysical source
  25. GRB 251129A: Swift ToO observations
  26. GRB 251129A / EP251129a: SVOM/VT optical fading
  27. EP251129a: Global MASTER-Net observations report
  28. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  29. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  30. GRB 251129A: Correction to the position of the optical counterpar
  31. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  32. GRB 251128A: Fermi GBM Observation
  33. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  34. GRB 251129A: SVOM detection of a burst
  35. SVOM GRB251129A: Global MASTER-Net observations report
  36. GRB 251129A: SVOM detection of a burst
  37. GRB 251126A: Swift-BAT refined analysis
  38. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  39. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  40. Fermi GRB 251128A: Global MASTER-Net observations report
  41. GRB 251127A: Glowbug gamma-ray detection
  42. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  43. GRB 251126A: further SAO RAS optical observations
  44. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  45. GRB 251126A NUTTelA-TAO Early Measurements
  46. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  47. GRB251126A: MAO/AZT-22 optical observations
  48. GRB 251128A: Fermi GBM Final Real-time Localization
  49. GRB251126A: Continued optical observation from 1.3m DFOT
  50. GRB 251126A: Swift/UVOT Detection
  51. EP251124a: Pan-STARRS ri-band imaging and photometry
  52. GRB 251126A: Mondy and SAO RAS optical observations
  53. GRB 251126A: Swift-XRT refined Analysis
  54. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  55. GRB 251126A: NOT optical observations
  56. GRB 251126A: 1.3m DFOT optical afterglow detection
  57. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  58. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  59. GRB 251125B: GECAM-B detection
  60. Fermi GRB 251127A: Global MASTER-Net observations report
  61. GRB 251127A: Fermi GBM Final Real-time Localization
  62. GRB 251126A: Enhanced Swift-XRT position
  63. GRB 251126A: Kilonova-Catcher optical afterglow detection
  64. GRB 251126A: Asiago i-band detection
  65. GRB 251126A: Nanshan/HMT optical afterglow detection
  66. Swift GRB 251126A: Global MASTER-Net observations report
  67. GRB 251121A: Fermi GBM Observation
  68. GRB 251126A: Prompt enhanced Swift-XRT position
  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 : MASTER OT J155558.56+581224.1 optical counterpart discovery
  76. Fermi GRB 251125B: Global MASTER-Net observations report
  77. GRB 251125B: Fermi GBM Final Real-time Localization
  78. EP251124b: Global MASTER-Net observations report
  79. EP251124b: EP-WXT detection of a fast X-ray transient
  80. EP251124a: Xinglong GWAC-F60A optical observation
  81. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  82. Fermi GRB 251125A: Global MASTER-Net observations report
  83. GRB 251125A: Fermi GBM Final Real-time Localization
  84. EP251124a: NOT r- and z-band optical upper limits
  85. EP251124a: Global MASTER-Net observations report
  86. EP251124a: Swift-XRT observations
  87. GRB 251124A: Fermi GBM Localization by automated pipeline
  88. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  89. EP251124a: Optical upper limit with Kinder observations
  90. GRB 251122B: Fermi GBM Final Localization
  91. EP251118A: 6 GHz VLA Detection
  92. Fermi GRB 251124a: Global MASTER-Net observations report
  93. GRB 251124a: Fermi GBM Final Localization
  94. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  95. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  96. EP251124a: GROWTH-India Telescope optical upper limits
  97. EP251124a: Einstein Probe detection of an X-ray transient
  98. GRB 251116C: Swift-XRT confirmation of fading
  99. GRB 251122A/EP251122a: FTW optical and NIR observations
  100. GRB 251122A/EP251122A: 1.3m DFOT optical detection

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