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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"

20966 results found.

  1. EP251130a: KAIT optical observations
  2. EP251130A: Optical observation from 1.3m DFOT
  3. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  4. EP251130a: JinShan optical observations
  5. Fermi GRB 251130B: Global MASTER-Net observations report
  6. IceCube Alert 251130.75: Global MASTER-Net observations report
  7. EP251130a: Swift-XRT counterpart detection
  8. EP251130a: Global MASTER-Net observations report
  9. EP251129a/GRB 251129A: EP-FXT follow-up observations
  10. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  11. GRB 251129A / EP251129a: SAO RAS optical observations
  12. GRB 251126A: SAO RAS optical observations
  13. GRB 251129A: Swift-XRT afterglow detection
  14. GRB 251129A: Swift ToO observations
  15. EP251129a: Global MASTER-Net observations report
  16. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  17. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  18. SVOM GRB251129A: Global MASTER-Net observations report
  19. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  20. Fermi GRB 251128A: Global MASTER-Net observations report
  21. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  22. GRB 251126A: further SAO RAS optical observations
  23. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  24. GRB 251126A NUTTelA-TAO Early Measurements
  25. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  26. GRB251126A: MAO/AZT-22 optical observations
  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: NOT optical observations
  31. GRB 251126A: 1.3m DFOT optical afterglow detection
  32. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  33. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  34. Fermi GRB 251127A: Global MASTER-Net observations report
  35. GRB 251126A: Kilonova-Catcher optical afterglow detection
  36. GRB 251126A: Asiago i-band detection
  37. GRB 251126A: Nanshan/HMT optical afterglow detection
  38. Swift GRB 251126A: Global MASTER-Net observations report
  39. GRB 251126A: GIT discovery of the likely optical afterglow
  40. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  41. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  42. EP251124b: NOT r- and z-band optical upper limits
  43. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  44. Fermi GRB 251125B: Global MASTER-Net observations report
  45. EP251124b: Global MASTER-Net observations report
  46. Fermi GRB 251125A: Global MASTER-Net observations report
  47. EP251124a: NOT r- and z-band optical upper limits
  48. EP251124a: Global MASTER-Net observations report
  49. EP251124a: Swift-XRT observations
  50. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  51. EP251124a: Optical upper limit with Kinder observations
  52. EP251118A: 6 GHz VLA Detection
  53. Fermi GRB 251124a: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  55. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  56. GRB 251116C: Swift-XRT confirmation of fading
  57. GRB 251122A/EP251122a: FTW optical and NIR observations
  58. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  59. EP251118A: 3.6m DOT optical afterglow detection
  60. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 251122A / EP251122a: WFST optical observations
  62. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  63. GRB 251122A / EP251122a: LCO optical upper limits
  64. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  65. EP251122a: Global MASTER-Net observations report
  66. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  67. EP251118a: Continued Optical Detection with Kinder observations
  68. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  69. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  70. EP251118a: Xinglong-2.16m optical observation
  71. Fermi trigger No 785388351: Global MASTER-Net observations report
  72. EP251118A: 1.3m DFOT optical afterglow detection
  73. GRB 251118A: Swift/UVOT Detection
  74. EP251118a / GRB 251118C: SAO RAS optical observations
  75. GRB 251118A: Swift-XRT afterglow detection
  76. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  77. EP251118a: Optical detection with Kinder observations
  78. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  79. EP251118a / GRB 251118C: SVOM/VT optical observation
  80. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  81. GRB 251116C: NOT optical observations
  82. GRB 251117A: Swift-XRT observations
  83. EP251118A / GRB 251118C : MASTER optical counterpart observations
  84. EP251118a: FTW optical and NIR observations
  85. EP251118a: VLT near-infrared observation
  86. EP251118a: GOTO optical afterglow detection
  87. EP251118a: Global MASTER-Net observations report
  88. LAT GRB251118.86: Global MASTER-Net observations report
  89. EP251118a: NOT candidate optical counterpart
  90. GRB 251118A: Swift ToO observations
  91. EP251118a: Einstein Probe detected of a fast X-ray transient
  92. Fermi GRB 251118B: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  94. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  95. GRB 251116C: SVOM/ECLAIRs refined analysis
  96. GRB 251116B: SVOM/ECLAIRs refined analysis
  97. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  98. GRB 251115A: Swift-XRT observations
  99. GRB 251117A: Tiled Swift observations
  100. LAT GRB251117.51: Global MASTER-Net observations report

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