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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"

32505 results found.

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

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