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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"

27039 results found.

  1. EP251129a/GRB 251129A: EP-FXT follow-up observations
  2. GRB 251130A: Fermi GBM Final Real-time Localization
  3. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  4. GRB 251128A: GECAM-B detection
  5. GRB 251128A: SVOM/GRM observation of a long burst
  6. SVOM GRB 251129A : MASTER optical counterpart detection
  7. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  8. Swift trigger 1418333 is not an astrophysical source
  9. GRB 251129A / EP251129a: SVOM/VT optical fading
  10. EP251129a: Global MASTER-Net observations report
  11. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  12. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  13. GRB 251128A: Fermi GBM Observation
  14. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  15. GRB 251129A: SVOM detection of a burst
  16. SVOM GRB251129A: Global MASTER-Net observations report
  17. GRB 251129A: SVOM detection of a burst
  18. GRB 251126A: Swift-BAT refined analysis
  19. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  20. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  21. Fermi GRB 251128A: Global MASTER-Net observations report
  22. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  23. GRB 251126A NUTTelA-TAO Early Measurements
  24. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  25. GRB251126A: MAO/AZT-22 optical observations
  26. GRB 251128A: Fermi GBM Final Real-time Localization
  27. GRB251126A: Continued optical observation from 1.3m DFOT
  28. GRB 251126A: Swift/UVOT Detection
  29. GRB 251126A: Mondy and SAO RAS optical observations
  30. GRB 251126A: Swift-XRT refined Analysis
  31. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  32. GRB 251126A: NOT optical observations
  33. GRB 251126A: 1.3m DFOT optical afterglow detection
  34. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  35. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  36. GRB 251125B: GECAM-B detection
  37. Fermi GRB 251127A: Global MASTER-Net observations report
  38. GRB 251127A: Fermi GBM Final Real-time Localization
  39. GRB 251126A: Kilonova-Catcher optical afterglow detection
  40. GRB 251126A: Asiago i-band detection
  41. GRB 251126A: Nanshan/HMT optical afterglow detection
  42. Swift GRB 251126A: Global MASTER-Net observations report
  43. GRB 251121A: Fermi GBM Observation
  44. GRB 251126A: GIT discovery of the likely optical afterglow
  45. GRB 251126A: Swift detection of a burst
  46. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  47. EP251124b follow-up observation by EP-FXT
  48. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  49. EP251124b: NOT r- and z-band optical upper limits
  50. Fermi GRB 251125B: Global MASTER-Net observations report
  51. GRB 251125B: Fermi GBM Final Real-time Localization
  52. EP251124b: Global MASTER-Net observations report
  53. EP251124b: EP-WXT detection of a fast X-ray transient
  54. EP251124a: Xinglong GWAC-F60A optical observation
  55. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  56. Fermi GRB 251125A: Global MASTER-Net observations report
  57. GRB 251125A: Fermi GBM Final Real-time Localization
  58. EP251124a: NOT r- and z-band optical upper limits
  59. EP251124a: Global MASTER-Net observations report
  60. EP251124a: Swift-XRT observations
  61. GRB 251124A: Fermi GBM Localization by automated pipeline
  62. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  63. EP251124a: Optical upper limit with Kinder observations
  64. GRB 251122B: Fermi GBM Final Localization
  65. EP251118A: 6 GHz VLA Detection
  66. Fermi GRB 251124a: Global MASTER-Net observations report
  67. GRB 251124a: Fermi GBM Final Localization
  68. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  69. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  70. EP251124a: GROWTH-India Telescope optical upper limits
  71. EP251124a: Einstein Probe detection of an X-ray transient
  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: LCO optical upper limits
  82. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  83. EP251122a: Global MASTER-Net observations report
  84. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  85. GRB 251122A / EP251122a: SVOM detection of a long burst
  86. EP251122a: Einstein Probe detection of an X-ray transient
  87. EP251118a: Continued Optical Detection with Kinder observations
  88. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  89. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  90. EP251118a: Xinglong-2.16m optical observation
  91. GRB 251115A: Fermi GBM Observation
  92. The EP-WXT trigger 01709248635 is likely a flaring star
  93. GRB 251121A: Fermi GBM Final Real-time Localization
  94. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  95. Fermi trigger No 785388351: Global MASTER-Net observations report
  96. EP251118A: 1.3m DFOT optical afterglow detection
  97. GRB 251118A: Swift/UVOT Detection
  98. GRB 251118A: Glowbug gamma-ray detection
  99. GRB 251118A: Fermi GBM Observation
  100. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis

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