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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 251003A: LCOGT Optical Detection
  2. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  3. GRB 251003A: 1.5m OSN afterglow candidate
  4. Swift GRB251003A: Global MASTER-Net observations report
  5. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  6. GRB 251002A: SAO RAS optical observations
  7. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  8. GRB 251002A: LCO optical observation
  9. Fermi GRB 251002A: Global MASTER-Net observations report
  10. GRB 251001B: Swift/UVOT Detection
  11. GRB 251001B: COLIBRÍ optical observations
  12. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  13. GRB 251001B: NOT optical observations
  14. Swift GRB 251001B: Global MASTER-Net observations report
  15. GRB 251001B: Further GOTO observations of optical counterpart.
  16. GRB 251001B: LCOGT Optical Observations
  17. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  18. GRB 251001B: GOTO optical counterpart detection
  19. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  20. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  21. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  22. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  23. GRB 250925A: MAO/AZT-22 optical observations
  24. Fermi GRB 250929A: Global MASTER-Net observations report
  25. GRB 250925A: Mondy I-band optical observations
  26. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  27. Fermi trigger No 780609036: Global MASTER-Net observations report
  28. IceCube Alert 250926.52: Global MASTER-Net observations report
  29. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  30. GRB 250925A: Swift/UVOT Upper Limits
  31. GRB 250925A: Mondy and AbAO optical observations
  32. GRB 250925A: COLIBRÍ photometric redshift
  33. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  34. GRB 250925A: JinShan optical observations
  35. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  36. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  37. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  38. Fermi GRB 250926A: Global MASTER-Net observations report
  39. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  40. GRB250925A: Liverpool Telescope optical observations
  41. GRB 250925A: NOT optical afterglow candidate
  42. GRB 250925A: Leavitt Observatory optical upper limit
  43. Swift GRB 250925A: Global MASTER-Net observations report
  44. GRB 250924A: 1.6m Mephisto optical upper limits
  45. GRB 250924A: SAO RAS optical observations
  46. GRB 250924A: NOT optical observations
  47. GRB 250924A: Swift/UVOT Detection
  48. GRB 250924A: J-band detection with WINTER
  49. GRB 250924A: GROWTH-India Telescope Upper Limits
  50. GRB 250924A: KAIT optical observations
  51. GRB 250924A: Mondy optical observations, afterglow fading
  52. GRB 250924A: Kilonova-Catcher optical afterglow detection
  53. GRB 250920C: Kilonova-Catcher optical afterglow detection
  54. GRB 250920C: TRT optical observation
  55. GRB 250924A: COLIBRÍ optical observations
  56. Swift GRB 250924A: Global MASTER-Net observations report
  57. GRB 250919A / EP250919a: further LCO optical observation
  58. GRB 250924A: DDOTI Detection of the Optical Counterpart
  59. GRB 250920C: KAIT optical observations
  60. GRB 250920C: VLT redshift confirmation z = 1.399
  61. EP250911a: e-MERLIN radio observations
  62. GRB 250920B: CrAO ZTSH optical observations
  63. GRB 250920C: SALT redshift confirmation
  64. GRB 250920C: COLIBRÍ optical observations
  65. Fermi GRB 250922B: Global MASTER-Net observations report
  66. GRB 250920B: SAO RAS optical observations
  67. GRB 250920C: NIR observations with WINTER
  68. GRB 250920B: NIR observations with WINTER
  69. Fermi trigger No 780156732: Global MASTER-Net observations report
  70. GRB 250920C: PRIME near-infrared detection
  71. GRB 250916A: Swift/UVOT Detection
  72. GRB 250916A: CrAO ZTSh R-band optical observations
  73. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  74. GRB 250920B: Asiago optical observations
  75. GRB 250920B: Kitab-ISON optical upper limit
  76. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  77. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  78. GRB 250920C: GROWTH-India Telescope optical observations
  79. GRB 250916A: FTW optical and NIR observations of the counterpart
  80. GRB 250920C: Swift/UVOT Detection
  81. Swift GRB 250920C: Global MASTER-Net observations report
  82. GRB 250920B: Swift/UVOT Detection
  83. GRB 250920B: FTW optical and NIR observations of the counterpart
  84. GRB 250920C: Optical counterpart detection by LCO
  85. GRB 250920B: SVOM/C-GFT optical observations
  86. GRB 250920C: GOTO optical counterpart candidate
  87. GRB 250919A / EP250919a: LCO optical observation
  88. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  89. Swift GRB 250920B: Global MASTER-Net observations report
  90. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  91. GRB 250916A: Mondy R-band optical observations
  92. Fermi GRB 250918A: Global MASTER-Net observations report
  93. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  94. GRB 250919A: Swift-XRT afterglow detection
  95. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  96. EP250919a: Global MASTER-Net observations report
  97. EP250919a: Einstein Probe detection of an X-ray transient
  98. Fermi GRB 250919A: Global MASTER-Net observations report
  99. GRB 250916A: KAIT optical observations
  100. GRB 250917B: VLT/HAWK-I near-infrared observations

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