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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
  1. Swift GRB251003A: Global MASTER-Net observations report
  2. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  3. GRB 251002A: BOOTES-6 early optical detection
  4. GRB 251002A: SAO RAS optical observations
  5. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  6. GRB 251002A: FRAM-ORM afterglow detection
  7. GRB 251002A: LCO optical observation
  8. GRB 251002A: SVOM/VT optical observation
  9. GRB 251002A: SVOM detection of a burst
  10. Fermi GRB 251002A: Global MASTER-Net observations report
  11. GRB 251001B: Swift-BAT refined analysis
  12. GRB 251001A: SVOM/GRM observation
  13. GRB 251001A: Insight-HXMT detection
  14. GRB 251001B: Swift/UVOT Detection
  15. GRB 251001B: COLIBRÍ optical observations
  16. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  17. GRB 251001B: Swift-XRT refined Analysis
  18. GRB 251001B: SVOM/VT optical observation
  19. GRB 251001B: NOT optical observations
  20. GRB 251001C: Glowbug gamma-ray detection
  21. Swift GRB 251001B: Global MASTER-Net observations report
  22. GRB 251001B: Fermi GBM Observation
  23. GRB 251001B: Further GOTO observations of optical counterpart.
  24. GRB 251001B: Enhanced Swift-XRT position
  25. GRB 250930A: Fermi GBM Final Localization
  26. GRB 251001B: LCOGT Optical Observations
  27. GRB 250930A: SVOM/GRM observation
  28. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  29. GRB 251001B: GOTO optical counterpart detection
  30. GRB 251001B: Swift detection of a burst
  31. GRB 251001B: Fermi GBM Final Real-time Localization
  32. GRB 251001A: Fermi GBM Detection
  33. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  34. GRB 251001A: BALROG localization (Fermi Trigger 780979261 / GRB 251001112)
  35. GRB 251001A: Fermi GBM Final Real-time Localization
  36. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  37. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  38. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  39. GRB 250925A: MAO/AZT-22 optical observations
  40. Fermi GRB 250929A: Global MASTER-Net observations report
  41. GRB 250929A: Fermi GBM Final Real-time Localization
  42. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  43. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  44. GRB 250925A: Mondy I-band optical observations
  45. GRB 250916A: SVOM/VT optical observation
  46. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  47. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  48. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  49. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  50. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  51. GRB 250924A: SVOM/GRM observation
  52. GRB 250925A: Swift-XRT refined Analysis
  53. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  54. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  55. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250926A: Insight-HXMT detection
  57. GRB 250926B: Fermi GBM Final Localization
  58. Fermi trigger No 780609036: Global MASTER-Net observations report
  59. IceCube Alert 250926.52: Global MASTER-Net observations report
  60. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  61. GRB 250926A: AstroSat CZTI detection
  62. GRB 250925A: Swift/UVOT Upper Limits
  63. GRB 250925A: Swift-BAT refined analysis
  64. GRB 250925A: Mondy and AbAO optical observations
  65. GRB 250925A: COLIBRÍ photometric redshift
  66. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 250925A: SVOM/GWAC-F60A upper limit
  68. GRB 250925A/EP250925a: EP-WXT detection
  69. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  70. GRB 250925A : MITSuME Akeno optical upper limits
  71. GRB 250925A: JinShan optical observations
  72. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  73. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  74. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  75. Fermi GRB 250926A: Global MASTER-Net observations report
  76. GRB 250926A: Fermi GBM Final Real-time Localization
  77. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  78. GRB250925A: Liverpool Telescope optical observations
  79. GRB 250925A: NOT optical afterglow candidate
  80. GRB 250925A: Leavitt Observatory optical upper limit
  81. GRB 250925A: Enhanced Swift-XRT position
  82. GRB 250924A: Swift-BAT refined analysis
  83. GRB 250925A: GROWTH-India Telescope Upper Limits
  84. GRB 250925A: Swift detection of a burst
  85. Swift GRB 250925A: Global MASTER-Net observations report
  86. GRB 250922A: SVOM/GRM observation
  87. GRB 250924A: 1.6m Mephisto optical upper limits
  88. GRB 250924A: SAO RAS optical observations
  89. GRB 250924A: NOT optical observations
  90. GRB 250924A: AstroSat CZTI detection
  91. GRB 250914A: AstroSat CZTI detection
  92. GRB 250920B: AstroSat CZTI detection
  93. GRB 250924A: SVOM/VT optical observation
  94. GRB 250924A: Swift/UVOT Detection
  95. GRB 250924A: Swift-XRT refined Analysis
  96. GRB 250924A: Enhanced Swift-XRT position
  97. GRB 250924A: J-band detection with WINTER
  98. GRB 250924A: GROWTH-India Telescope Upper Limits
  99. GRB 250924A: KAIT optical observations
  100. GRB 250924A: Mondy optical observations, afterglow fading

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