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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"

20539 results found.

  1. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  2. GRB 251129A / EP251129a: SAO RAS optical observations
  3. GRB 251126A: SAO RAS optical observations
  4. GRB 251129A: Swift-XRT afterglow detection
  5. GRB 251129A: Swift ToO observations
  6. EP251129a: Global MASTER-Net observations report
  7. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  8. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  9. SVOM GRB251129A: Global MASTER-Net observations report
  10. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  11. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  12. Fermi GRB 251128A: Global MASTER-Net observations report
  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. GRB251126A: Continued optical observation from 1.3m DFOT
  20. GRB 251126A: Swift/UVOT Detection
  21. GRB 251126A: Mondy and SAO RAS optical observations
  22. GRB 251126A: NOT optical observations
  23. GRB 251126A: 1.3m DFOT optical afterglow detection
  24. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  25. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  26. Fermi GRB 251127A: Global MASTER-Net observations report
  27. GRB 251126A: Kilonova-Catcher optical afterglow detection
  28. GRB 251126A: Asiago i-band detection
  29. GRB 251126A: Nanshan/HMT optical afterglow detection
  30. Swift GRB 251126A: Global MASTER-Net observations report
  31. GRB 251126A: GIT discovery of the likely optical afterglow
  32. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  33. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  34. EP251124b: NOT r- and z-band optical upper limits
  35. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  36. Fermi GRB 251125B: Global MASTER-Net observations report
  37. EP251124b: Global MASTER-Net observations report
  38. Fermi GRB 251125A: Global MASTER-Net observations report
  39. EP251124a: NOT r- and z-band optical upper limits
  40. EP251124a: Global MASTER-Net observations report
  41. EP251124a: Swift-XRT observations
  42. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  43. EP251124a: Optical upper limit with Kinder observations
  44. EP251118A: 6 GHz VLA Detection
  45. Fermi GRB 251124a: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  47. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  48. GRB 251116C: Swift-XRT confirmation of fading
  49. GRB 251122A/EP251122a: FTW optical and NIR observations
  50. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  51. EP251118A: 3.6m DOT optical afterglow detection
  52. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 251122A / EP251122a: WFST optical observations
  54. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  55. GRB 251122A / EP251122a: LCO optical upper limits
  56. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  57. EP251122a: Global MASTER-Net observations report
  58. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  59. EP251118a: Continued Optical Detection with Kinder observations
  60. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  61. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  62. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  63. EP251118a: Xinglong-2.16m optical observation
  64. Fermi trigger No 785388351: Global MASTER-Net observations report
  65. EP251118A: 1.3m DFOT optical afterglow detection
  66. GRB 251118A: Swift/UVOT Detection
  67. EP251118a / GRB 251118C: SAO RAS optical observations
  68. GRB 251118A: Swift-XRT afterglow detection
  69. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  70. EP251118a: Optical detection with Kinder observations
  71. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  72. EP251118a / GRB 251118C: SVOM/VT optical observation
  73. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  74. GRB 251116C: NOT optical observations
  75. GRB 251117A: Swift-XRT observations
  76. EP251118A / GRB 251118C : MASTER optical counterpart observations
  77. EP251118a: FTW optical and NIR observations
  78. EP251118a: VLT near-infrared observation
  79. EP251118a: GOTO optical afterglow detection
  80. EP251118a: Global MASTER-Net observations report
  81. LAT GRB251118.86: Global MASTER-Net observations report
  82. EP251118a: NOT candidate optical counterpart
  83. GRB 251118A: Swift ToO observations
  84. EP251118a: Einstein Probe detected of a fast X-ray transient
  85. Fermi GRB 251118B: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  87. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  88. GRB 251116C: SVOM/ECLAIRs refined analysis
  89. GRB 251116B: SVOM/ECLAIRs refined analysis
  90. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  91. GRB 251115A: Swift-XRT observations
  92. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  93. GRB 251117A: Tiled Swift observations
  94. LAT GRB251117.51: Global MASTER-Net observations report
  95. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  96. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  97. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  98. GRB 251116C: Swift-XRT observations
  99. EP251023a: Assy AZT-20 optical observations
  100. EP251023a: UAFO and AbAO optical observations

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