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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. GRB 251129A: Correction to the position of the optical counterpar
  2. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  3. GRB 251128A: Fermi GBM Observation
  4. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  5. GRB 251129A: SVOM detection of a burst
  6. SVOM GRB251129A: Global MASTER-Net observations report
  7. GRB 251129A: SVOM detection of a burst
  8. GRB 251126A: Swift-BAT refined analysis
  9. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  10. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  11. Fermi GRB 251128A: Global MASTER-Net observations report
  12. GRB 251127A: Glowbug gamma-ray detection
  13. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  14. GRB 251126A: further SAO RAS optical observations
  15. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  16. GRB 251126A NUTTelA-TAO Early Measurements
  17. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  18. GRB251126A: MAO/AZT-22 optical observations
  19. GRB 251128A: Fermi GBM Final Real-time Localization
  20. GRB251126A: Continued optical observation from 1.3m DFOT
  21. GRB 251126A: Swift/UVOT Detection
  22. EP251124a: Pan-STARRS ri-band imaging and photometry
  23. GRB 251126A: Mondy and SAO RAS optical observations
  24. GRB 251126A: Swift-XRT refined Analysis
  25. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  26. GRB 251126A: NOT optical observations
  27. GRB 251126A: 1.3m DFOT optical afterglow detection
  28. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  29. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  30. GRB 251125B: GECAM-B detection
  31. Fermi GRB 251127A: Global MASTER-Net observations report
  32. GRB 251127A: Fermi GBM Final Real-time Localization
  33. GRB 251126A: Enhanced Swift-XRT position
  34. GRB 251126A: Kilonova-Catcher optical afterglow detection
  35. GRB 251126A: Asiago i-band detection
  36. GRB 251126A: Nanshan/HMT optical afterglow detection
  37. Swift GRB 251126A: Global MASTER-Net observations report
  38. GRB 251121A: Fermi GBM Observation
  39. GRB 251126A: Prompt enhanced Swift-XRT position
  40. GRB 251126A: GIT discovery of the likely optical afterglow
  41. GRB 251126A: Swift detection of a burst
  42. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  43. EP251124b follow-up observation by EP-FXT
  44. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  45. EP251124b: NOT r- and z-band optical upper limits
  46. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  47. Fermi GRB 251125B: Global MASTER-Net observations report
  48. GRB 251125B: Fermi GBM Final Real-time Localization
  49. EP251124b: Global MASTER-Net observations report
  50. EP251124b: EP-WXT detection of a fast X-ray transient
  51. EP251124a: Xinglong GWAC-F60A optical observation
  52. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  53. Fermi GRB 251125A: Global MASTER-Net observations report
  54. GRB 251125A: Fermi GBM Final Real-time Localization
  55. EP251124a: NOT r- and z-band optical upper limits
  56. EP251124a: Global MASTER-Net observations report
  57. EP251124a: Swift-XRT observations
  58. GRB 251124A: Fermi GBM Localization by automated pipeline
  59. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  60. EP251124a: Optical upper limit with Kinder observations
  61. GRB 251122B: Fermi GBM Final Localization
  62. EP251118A: 6 GHz VLA Detection
  63. Fermi GRB 251124a: Global MASTER-Net observations report
  64. GRB 251124a: Fermi GBM Final Localization
  65. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  66. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  67. EP251124a: GROWTH-India Telescope optical upper limits
  68. EP251124a: Einstein Probe detection of an X-ray transient
  69. GRB 251116C: Swift-XRT confirmation of fading
  70. GRB 251122A/EP251122a: FTW optical and NIR observations
  71. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  72. The EP-WXT trigger 01709248783 is likely a flaring star
  73. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  74. EP251118A: 3.6m DOT optical afterglow detection
  75. GRB 251122A / EP251122a: EP-FXT counterpart detection
  76. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  77. GRB 251122A / EP251122a: WFST optical observations
  78. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  79. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  80. GRB 251122A / EP251122a: LCO optical upper limits
  81. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  82. EP251122a: Global MASTER-Net observations report
  83. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  84. GRB 251122A / EP251122a: SVOM detection of a long burst
  85. EP251122a: Einstein Probe detection of an X-ray transient
  86. EP251118a: Continued Optical Detection with Kinder observations
  87. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  88. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  89. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  90. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  91. EP251118a: Xinglong-2.16m optical observation
  92. GRB 251115A: Fermi GBM Observation
  93. The EP-WXT trigger 01709248635 is likely a flaring star
  94. GRB 251121A: Fermi GBM Final Real-time Localization
  95. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  96. Fermi trigger No 785388351: Global MASTER-Net observations report
  97. EP251118A: 1.3m DFOT optical afterglow detection
  98. GRB 251118A: Swift/UVOT Detection
  99. EP251118a / GRB 251118C: SAO RAS optical observations
  100. GRB 251118A: Glowbug gamma-ray detection

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