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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"

20558 results found.

  1. GRB 251202A: Swift-XRT afterglow detection
  2. Fermi GRB 251202A: Global MASTER-Net observations report
  3. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  4. Swift GRB 251201B: Global MASTER-Net observations report
  5. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  6. EP251130a: Mondy optical observations
  7. EP251130a: Optical detections with Kinder observations
  8. SVOM GRB251201.19: Global MASTER-Net observations report
  9. EP251130a: SAO RAS optical observations
  10. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  11. EP251130a: KAIT optical observations
  12. EP251130A: Optical observation from 1.3m DFOT
  13. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP251130a: JinShan optical observations
  15. Fermi GRB 251130B: Global MASTER-Net observations report
  16. IceCube Alert 251130.75: Global MASTER-Net observations report
  17. EP251130a: Swift-XRT counterpart detection
  18. EP251130a: Global MASTER-Net observations report
  19. EP251129a/GRB 251129A: EP-FXT follow-up observations
  20. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  21. GRB 251129A / EP251129a: SAO RAS optical observations
  22. GRB 251126A: SAO RAS optical observations
  23. GRB 251129A: Swift-XRT afterglow detection
  24. GRB 251129A: Swift ToO observations
  25. EP251129a: Global MASTER-Net observations report
  26. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  27. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  28. SVOM GRB251129A: Global MASTER-Net observations report
  29. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  30. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  31. Fermi GRB 251128A: Global MASTER-Net observations report
  32. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  33. GRB 251126A: further SAO RAS optical observations
  34. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  35. GRB 251126A NUTTelA-TAO Early Measurements
  36. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  37. GRB251126A: MAO/AZT-22 optical observations
  38. GRB251126A: Continued optical observation from 1.3m DFOT
  39. GRB 251126A: Swift/UVOT Detection
  40. GRB 251126A: Mondy and SAO RAS optical observations
  41. GRB 251126A: NOT optical observations
  42. GRB 251126A: 1.3m DFOT optical afterglow detection
  43. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  44. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  45. Fermi GRB 251127A: Global MASTER-Net observations report
  46. GRB 251126A: Kilonova-Catcher optical afterglow detection
  47. GRB 251126A: Asiago i-band detection
  48. GRB 251126A: Nanshan/HMT optical afterglow detection
  49. Swift GRB 251126A: Global MASTER-Net observations report
  50. GRB 251126A: GIT discovery of the likely optical afterglow
  51. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  52. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  53. EP251124b: NOT r- and z-band optical upper limits
  54. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  55. Fermi GRB 251125B: Global MASTER-Net observations report
  56. EP251124b: Global MASTER-Net observations report
  57. Fermi GRB 251125A: Global MASTER-Net observations report
  58. EP251124a: NOT r- and z-band optical upper limits
  59. EP251124a: Global MASTER-Net observations report
  60. EP251124a: Swift-XRT observations
  61. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  62. EP251124a: Optical upper limit with Kinder observations
  63. EP251118A: 6 GHz VLA Detection
  64. Fermi GRB 251124a: Global MASTER-Net observations report
  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. GRB 251116C: Swift-XRT confirmation of fading
  68. GRB 251122A/EP251122a: FTW optical and NIR observations
  69. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  70. EP251118A: 3.6m DOT optical afterglow detection
  71. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 251122A / EP251122a: WFST optical observations
  73. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  74. GRB 251122A / EP251122a: LCO optical upper limits
  75. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  76. EP251122a: Global MASTER-Net observations report
  77. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  78. EP251118a: Continued Optical Detection with Kinder observations
  79. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  80. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  81. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  82. EP251118a: Xinglong-2.16m optical observation
  83. Fermi trigger No 785388351: Global MASTER-Net observations report
  84. EP251118A: 1.3m DFOT optical afterglow detection
  85. GRB 251118A: Swift/UVOT Detection
  86. EP251118a / GRB 251118C: SAO RAS optical observations
  87. GRB 251118A: Swift-XRT afterglow detection
  88. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  89. EP251118a: Optical detection with Kinder observations
  90. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  91. EP251118a / GRB 251118C: SVOM/VT optical observation
  92. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  93. GRB 251116C: NOT optical observations
  94. GRB 251117A: Swift-XRT observations
  95. EP251118A / GRB 251118C : MASTER optical counterpart observations
  96. EP251118a: FTW optical and NIR observations
  97. EP251118a: VLT near-infrared observation
  98. EP251118a: GOTO optical afterglow detection
  99. EP251118a: Global MASTER-Net observations report
  100. LAT GRB251118.86: Global MASTER-Net observations report

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