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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"

27405 results found.

  1. EP251130A: Optical observation from 1.3m DFOT
  2. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP251130a: JinShan optical observations
  4. GRB 251201A: MAXI/GSC detection
  5. Fermi GRB 251130B: Global MASTER-Net observations report
  6. GRB 251127A: SVOM/GRM observation
  7. IceCube Alert 251130.75: Global MASTER-Net observations report
  8. EP251130a: Swift-XRT counterpart detection
  9. EP251130a: Global MASTER-Net observations report
  10. EP251130a: COLIBRÍ optical counterpart candidate
  11. EP251130a: Einstein Probe detection of an X-ray transient
  12. GRB 251129A / EP251129a: SAO RAS optical observations
  13. GRB 251126A: SAO RAS optical observations
  14. GRB 251128A: SVOM/GRM observation of a long burst
  15. SVOM GRB 251129A : MASTER optical counterpart detection
  16. GRB 251129A: Swift-XRT afterglow detection
  17. EP251129a: Global MASTER-Net observations report
  18. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  19. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  20. GRB 251128A: Fermi GBM Observation
  21. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  22. GRB 251129A: SVOM detection of a burst
  23. SVOM GRB251129A: Global MASTER-Net observations report
  24. GRB 251129A: SVOM detection of a burst
  25. GRB 251126A: Swift-BAT refined analysis
  26. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  27. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  28. Fermi GRB 251128A: Global MASTER-Net observations report
  29. GRB 251127A: Glowbug gamma-ray detection
  30. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  31. GRB 251126A: further SAO RAS optical observations
  32. GRB 251126A NUTTelA-TAO Early Measurements
  33. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  34. GRB251126A: MAO/AZT-22 optical observations
  35. GRB251126A: Continued optical observation from 1.3m DFOT
  36. GRB 251126A: Swift/UVOT Detection
  37. GRB 251126A: Mondy and SAO RAS optical observations
  38. GRB 251126A: Swift-XRT refined Analysis
  39. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  40. GRB 251126A: NOT optical observations
  41. GRB 251126A: 1.3m DFOT optical afterglow detection
  42. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  43. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  44. Fermi GRB 251127A: Global MASTER-Net observations report
  45. GRB 251126A: Enhanced Swift-XRT position
  46. GRB 251126A: Kilonova-Catcher optical afterglow detection
  47. GRB 251126A: Nanshan/HMT optical afterglow detection
  48. Swift GRB 251126A: Global MASTER-Net observations report
  49. GRB 251121A: Fermi GBM Observation
  50. GRB 251126A: GIT discovery of the likely optical afterglow
  51. GRB 251126A: Swift detection of a burst
  52. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  53. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  54. EP251124b: NOT r- and z-band optical upper limits
  55. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  56. Fermi GRB 251125B: Global MASTER-Net observations report
  57. EP251124b: Global MASTER-Net observations report
  58. EP251124b: EP-WXT detection of a fast X-ray transient
  59. EP251124a: Xinglong GWAC-F60A optical observation
  60. Fermi GRB 251125A: Global MASTER-Net observations report
  61. EP251124a: NOT r- and z-band optical upper limits
  62. EP251124a: Global MASTER-Net observations report
  63. EP251124a: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  65. EP251124a: Optical upper limit with Kinder observations
  66. Fermi GRB 251124a: Global MASTER-Net observations report
  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: 1.3m DFOT optical detection
  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. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  89. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  90. EP251118a: Xinglong-2.16m optical observation
  91. GRB 251115A: Fermi GBM Observation
  92. Fermi trigger No 785388351: Global MASTER-Net observations report
  93. EP251118A: 1.3m DFOT optical afterglow detection
  94. GRB 251118A: Swift/UVOT Detection
  95. EP251118a / GRB 251118C: SAO RAS optical observations
  96. GRB 251118A: Glowbug gamma-ray detection
  97. GRB 251118A: Fermi GBM Observation
  98. GRB 251118A: Swift-XRT afterglow detection
  99. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  100. EP251118a: Optical detection with Kinder observations

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