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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"

32572 results found.

  1. GRB 250424A: likely host galaxy
  2. GRB 250424A: DDOTI Afterglow Detection
  3. GRB 250424A: REM optical/NIR afterglow detection
  4. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  5. EP250421a: Nickel optical upper limit
  6. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  7. EP250421a: Upper limits from Fermi-GBM Observations
  8. SVOM/sb25042207: XRT observations
  9. SVOM/sb25042207: BOOTES-2 early optical upper limit
  10. SVOM/sb25042207: GOTO optical upper limits
  11. GRB 250421A: AstroSat CZTI detection
  12. GRB250419A: VLA radio detection
  13. IceCube-250421A: DDOTI Detection of the LAST Candidate
  14. GRB 250419A: Mephisto Multi-band Optical Detection
  15. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  16. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  17. EP250421a: NOT optical observations
  18. GRB 250419A: Optical Observations via Virtual Telescope Project
  19. EP250421a: REM optical upper limit
  20. EP250421a: Swift/XRT counterpart detection
  21. EP250421A: COLIBRÍ Optical Upper Limit
  22. GRB 250419A: Mondy Continued Optical Observations
  23. Fermi GRB 250421A: Global MASTER-Net observations report
  24. EP250421a: Global MASTER-Net observations report
  25. EP250421a: Mephisto optical counterpart confirmation
  26. GRB 250419A: Liverpool Telescope observations
  27. GRB 250419A: LCO optical observation
  28. GRB 250419A: JinShan optical observations
  29. GRB 250419A: SVOM/VT optical continuous observations
  30. GRB 250419A: SVOM/C-GFT optical observations
  31. GRB 250419A: Swift/UVOT Follow up
  32. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  33. GRB 250419A: LCO optical afterglow multi-band observations
  34. GRB 250419A: Mondy and AbAO Optical Observations
  35. GRB 250419A: Liverpool Telescope observations
  36. GRB 250419A: AKO Optical Afterglow Detection
  37. GRB 250419A: MASTER optical afterglow observation
  38. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  39. GRB 250407A: rest-frame energetics from Konus-Wind observation
  40. GRB 250419A: Swift-XRT localisation
  41. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  42. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  43. GRB 250419A: Swift-XRT refined Analysis
  44. GRB 250419A: GOTO optical counterpart detection
  45. GRB 250419A: KAIT optical afterglow observations
  46. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  47. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  48. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  49. EP250416a: Swift/XRT counterpart fading
  50. EP250416a: refined EP-WXT and EP-FXT analysis
  51. Konus-Wind detection of GRB 250403A
  52. EP20250416a: Swift/XRT counterpart detection
  53. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  54. IceCube-250416A: DDOTI Optical Observations
  55. EP250416a: Gemini South-GMOS optical counterpart
  56. EP250225a: SVOM/VT optical brightening
  57. SVOM/sb25041603 is not a GRB
  58. EP250416a: GSP optical upper limit
  59. EP250416a: Global MASTER-Net observations report
  60. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  61. GRB 250413A: AstroSat CZTI detection
  62. EP250304a: ATCA radio observations
  63. EP250404a: Nanshan 0.43m Telescope optical observatios
  64. GRB 250411A: DDOTI Optical Observations
  65. Fermi GRB 250411A: Global MASTER-Net observations report
  66. GRB 250407A: Continued KAIT/Nickel optical observations
  67. GRB 250314A: e-MERLIN observations
  68. GRB 250407A: Mondy and AbAO Optical Observations
  69. EP250227a: Further NOT optical observations
  70. GRB 250320B: cubesat Avion detection
  71. IceCube-250406A: Swift-XRT observations
  72. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  73. IPN triangulation of GRB 250407A
  74. EP250407a: Global MASTER-Net observations report
  75. GRB 250407A: LCO detection of a fading optical counterpart
  76. Fermi-LAT gamma-ray observations of IceCube-250406A
  77. EP250407a: Swift-XRT observations
  78. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  79. Konus-Wind detection of GRB 250407A
  80. GRB 250407A: SVOM/GRM observation of a bright long burst
  81. GRB 250407A: EP-WXT afterglow detection
  82. EP250407a: EP-WXT detection of a fast X-ray transient
  83. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  84. GRB 250407A: KAIT Optical Afterglow Candidate
  85. IceCube-250406A: No candidates from the Zwicky Transient Facility
  86. GRB 250407A: Fermi GBM Detection
  87. GRB 250407A: Swift-XRT afterglow detection
  88. Fermi GRB 250407A: Global MASTER-Net observations report
  89. GRB 250407A: Swift ToO observations
  90. GRB 250407A: SRG/ART-XC afterglow detection
  91. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  92. Konus-Wind detection of GRB 250406B (short/hard)
  93. IPN triangulation of GRB 250406B (short/hard)
  94. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  95. GRB 250406A: AstroSat CZTI detection
  96. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  97. Fermi GRB 250406A: Global MASTER-Net observations report
  98. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  99. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  100. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit

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