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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"

20550 results found.

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

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