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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: Optical Observations via Virtual Telescope Project, Italy
  2. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  3. GRB 251129A: Correction to the position of the optical counterpar
  4. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  5. GRB 251128A: Fermi GBM Observation
  6. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  7. GRB 251129A: SVOM detection of a burst
  8. SVOM GRB251129A: Global MASTER-Net observations report
  9. GRB 251129A: SVOM detection of a burst
  10. GRB 251126A: Swift-BAT refined analysis
  11. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  12. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  13. Fermi GRB 251128A: Global MASTER-Net observations report
  14. GRB 251127A: Glowbug gamma-ray detection
  15. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  16. GRB 251126A: further SAO RAS optical observations
  17. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  18. GRB 251126A NUTTelA-TAO Early Measurements
  19. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  20. GRB251126A: MAO/AZT-22 optical observations
  21. GRB 251128A: Fermi GBM Final Real-time Localization
  22. GRB251126A: Continued optical observation from 1.3m DFOT
  23. GRB 251126A: Swift/UVOT Detection
  24. EP251124a: Pan-STARRS ri-band imaging and photometry
  25. GRB 251126A: Mondy and SAO RAS optical observations
  26. GRB 251126A: Swift-XRT refined Analysis
  27. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  28. GRB 251126A: NOT optical observations
  29. GRB 251126A: 1.3m DFOT optical afterglow detection
  30. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  31. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  32. GRB 251125B: GECAM-B detection
  33. Fermi GRB 251127A: Global MASTER-Net observations report
  34. GRB 251127A: Fermi GBM Final Real-time Localization
  35. GRB 251126A: Enhanced Swift-XRT position
  36. GRB 251126A: Kilonova-Catcher optical afterglow detection
  37. GRB 251126A: Asiago i-band detection
  38. GRB 251126A: Nanshan/HMT optical afterglow detection
  39. Swift GRB 251126A: Global MASTER-Net observations report
  40. GRB 251121A: Fermi GBM Observation
  41. GRB 251126A: Prompt enhanced Swift-XRT position
  42. GRB 251126A: GIT discovery of the likely optical afterglow
  43. GRB 251126A: Swift detection of a burst
  44. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  45. EP251124b follow-up observation by EP-FXT
  46. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  47. EP251124b: NOT r- and z-band optical upper limits
  48. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  49. Fermi GRB 251125B: Global MASTER-Net observations report
  50. GRB 251125B: Fermi GBM Final Real-time Localization
  51. EP251124b: Global MASTER-Net observations report
  52. EP251124b: EP-WXT detection of a fast X-ray transient
  53. EP251124a: Xinglong GWAC-F60A optical observation
  54. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  55. Fermi GRB 251125A: Global MASTER-Net observations report
  56. GRB 251125A: Fermi GBM Final Real-time Localization
  57. EP251124a: NOT r- and z-band optical upper limits
  58. EP251124a: Global MASTER-Net observations report
  59. EP251124a: Swift-XRT observations
  60. GRB 251124A: Fermi GBM Localization by automated pipeline
  61. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  62. EP251124a: Optical upper limit with Kinder observations
  63. GRB 251122B: Fermi GBM Final Localization
  64. EP251118A: 6 GHz VLA Detection
  65. Fermi GRB 251124a: Global MASTER-Net observations report
  66. GRB 251124a: Fermi GBM Final Localization
  67. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  68. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  69. EP251124a: GROWTH-India Telescope optical upper limits
  70. EP251124a: Einstein Probe detection of an X-ray transient
  71. GRB 251116C: Swift-XRT confirmation of fading
  72. GRB 251122A/EP251122a: FTW optical and NIR observations
  73. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  74. The EP-WXT trigger 01709248783 is likely a flaring star
  75. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  76. EP251118A: 3.6m DOT optical afterglow detection
  77. GRB 251122A / EP251122a: EP-FXT counterpart detection
  78. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 251122A / EP251122a: WFST optical observations
  80. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  81. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  82. GRB 251122A / EP251122a: LCO optical upper limits
  83. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  84. EP251122a: Global MASTER-Net observations report
  85. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  86. GRB 251122A / EP251122a: SVOM detection of a long burst
  87. EP251122a: Einstein Probe detection of an X-ray transient
  88. EP251118a: Continued Optical Detection with Kinder observations
  89. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  90. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  91. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  92. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  93. EP251118a: Xinglong-2.16m optical observation
  94. GRB 251115A: Fermi GBM Observation
  95. The EP-WXT trigger 01709248635 is likely a flaring star
  96. GRB 251121A: Fermi GBM Final Real-time Localization
  97. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  98. Fermi trigger No 785388351: Global MASTER-Net observations report
  99. EP251118A: 1.3m DFOT optical afterglow detection
  100. GRB 251118A: Swift/UVOT Detection

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