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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"

32508 results found.

  1. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  2. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  3. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  4. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  5. GRB 251002A: EP-FXT counterpart detection
  6. GRB 251003A: LCOGT Optical Detection
  7. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  8. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  9. GRB 251002A: BOOTES-6 early optical detection
  10. GRB 251002A: SAO RAS optical observations
  11. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  12. GRB 251002A: FRAM-ORM afterglow detection
  13. GRB 251002A: LCO optical observation
  14. GRB 251002A: SVOM/VT optical observation
  15. GRB 251001B: Swift-BAT refined analysis
  16. GRB 251001A: SVOM/GRM observation
  17. GRB 251001A: Insight-HXMT detection
  18. GRB 251001B: Swift/UVOT Detection
  19. GRB 251001B: COLIBRÍ optical observations
  20. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  21. GRB 251001B: SVOM/VT optical observation
  22. GRB 251001B: NOT optical observations
  23. Swift GRB 251001B: Global MASTER-Net observations report
  24. GRB 251001B: Fermi GBM Observation
  25. GRB 251001B: Further GOTO observations of optical counterpart.
  26. GRB 251001B: LCOGT Optical Observations
  27. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  28. GRB 251001B: GOTO optical counterpart detection
  29. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  30. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  31. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  32. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  33. GRB 250925A: MAO/AZT-22 optical observations
  34. Fermi GRB 250929A: Global MASTER-Net observations report
  35. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  36. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  37. GRB 250925A: Mondy I-band optical observations
  38. GRB 250916A: SVOM/VT optical observation
  39. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  40. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  41. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  42. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  43. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  44. GRB 250924A: SVOM/GRM observation
  45. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  47. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  48. GRB 250926A: Insight-HXMT detection
  49. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  50. GRB 250926A: AstroSat CZTI detection
  51. GRB 250925A: Swift/UVOT Upper Limits
  52. GRB 250925A: Swift-BAT refined analysis
  53. GRB 250925A: Mondy and AbAO optical observations
  54. GRB 250925A: COLIBRÍ photometric redshift
  55. GRB 250925A: SVOM/GWAC-F60A upper limit
  56. GRB 250925A/EP250925a: EP-WXT detection
  57. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  58. GRB 250925A : MITSuME Akeno optical upper limits
  59. GRB 250925A: JinShan optical observations
  60. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  61. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  62. Fermi GRB 250926A: Global MASTER-Net observations report
  63. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  64. GRB250925A: Liverpool Telescope optical observations
  65. GRB 250925A: NOT optical afterglow candidate
  66. GRB 250925A: Leavitt Observatory optical upper limit
  67. GRB 250924A: Swift-BAT refined analysis
  68. GRB 250925A: GROWTH-India Telescope Upper Limits
  69. GRB 250922A: SVOM/GRM observation
  70. GRB 250924A: 1.6m Mephisto optical upper limits
  71. GRB 250924A: SAO RAS optical observations
  72. GRB 250924A: NOT optical observations
  73. GRB 250924A: AstroSat CZTI detection
  74. GRB 250914A: AstroSat CZTI detection
  75. GRB 250920B: AstroSat CZTI detection
  76. GRB 250924A: SVOM/VT optical observation
  77. GRB 250924A: Swift/UVOT Detection
  78. GRB 250924A: J-band detection with WINTER
  79. GRB 250924A: GROWTH-India Telescope Upper Limits
  80. GRB 250924A: KAIT optical observations
  81. GRB 250924A: Mondy optical observations, afterglow fading
  82. GRB 250924A: Kilonova-Catcher optical afterglow detection
  83. GRB 250920C: Kilonova-Catcher optical afterglow detection
  84. GRB 250922B: SVOM/GRM observation
  85. GRB 250920C: TRT optical observation
  86. GRB 250924A: COLIBRÍ optical observations
  87. Swift GRB 250924A: Global MASTER-Net observations report
  88. GRB 250919A / EP250919a: further LCO optical observation
  89. GRB 250924A: DDOTI Detection of the Optical Counterpart
  90. GRB 250920B: AbAO optical upper limits
  91. Konus-Wind detection of GRB 250920C
  92. GRB 250920C: KAIT optical observations
  93. GRB 250920C: VLT redshift confirmation z = 1.399
  94. EP250911a: e-MERLIN radio observations
  95. GRB 250920B: CrAO ZTSH optical observations
  96. GRB 250920C: SALT redshift confirmation
  97. GRB 250920C: COLIBRÍ optical observations
  98. Fermi GRB 250922B: Global MASTER-Net observations report
  99. GRB 250920B: SAO RAS optical observations
  100. GRB 250920C: NIR observations with WINTER

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