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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"

28053 results found.

  1. GRB 250407A: Swift-XRT afterglow detection
  2. GRB 250407A: SRG/ART-XC afterglow detection
  3. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  4. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  5. IPN triangulation of GRB 250406B (short/hard)
  6. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  7. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  8. IceCube 250406.951: DDOTI Optical Observations
  9. GRB 250406A: AstroSat CZTI detection
  10. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  11. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  12. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  13. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  14. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  15. Konus-Wind detection of GRB 250404A / EP250404a
  16. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  18. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  19. EP250402a: Optical upper limit with PD 1.3m observations
  20. GRB 250404A / EP250404a: NOT optical observations
  21. GRB 250331D: Swift-XRT afterglow detection
  22. GRB 250404B: AstroSat CZTI detection of a short burst
  23. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  24. EP250404a: REM optical/NIR observations
  25. EP250404a: Seimei/TriCCS optical counterpart detection
  26. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  27. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  28. EP250404a: LCO optical counterpart detection
  29. EP250404a: Xinglong decaying optical counterpart
  30. GRB 250403A: Montarrenti Observatory optical detection
  31. GRB 250404A: Fermi GBM Detection
  32. GRB 250403A: KAIT optical observations
  33. EP250404a: AKO Optical Afterglow Detection
  34. EP250404a: LAST detection of optical counterpart
  35. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  36. GRB 250403A: Fermi GBM observations
  37. GRB 250327B: VIRT Optical Upper Limit
  38. EP250404a: Mephisto multi-band optical detection
  39. GRB 250331C Swift-BAT refined analysis
  40. GRB 250331B Swift-BAT refined analysis
  41. GRB 250330A Swift-BAT refined analysis
  42. EP250321A: J band upper limit by SYSU 80cm telescope
  43. EP250404a: Nanshan/HMT optical counterpart detection
  44. EP250404a: Einstein Probe detection of an X-ray transient
  45. GRB 250403A: Swift/UVOT Detection
  46. GRB 250402A: Swift/UVOT Upper Limits
  47. EP250402a: Optical upper limit with Kinder observations
  48. GRB 250403A: REM NIR afterglow detection
  49. GRB 250403A: LCO optical counterpart detection
  50. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  51. GRB 250403A: JinShan optical observations
  52. GRB 250403A: Optical counterpart detection by LCO.
  53. EP250402a: EP-FXT follow-up observations
  54. GRB 250403A: Swift-XRT observations
  55. GRB 250322A: 10 GHz VLA radio upper limits
  56. GRB 250403A: GMG Optical Observation
  57. GRB 250403A: 1.6m Mephisto multi-band optical detection
  58. GRB 250402A: Fermi GBM Observation
  59. GRB 250403A: SVOM/C-GFT optical observations
  60. GRB 250402A: Swift-XRT observations
  61. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  62. GRB 250402A: REM optical/NIR upper limits
  63. GRB 250402A: LCO optical counterpart detection
  64. EP250402a: Einstein Probe detection of a fast X-ray transient
  65. GRB 250402B: AstroSat CZTI detection of a short burst
  66. GRB 250402A: SVOM/VT optical counterpart
  67. GRB 250402A: SVOM detection of a burst
  68. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  69. GRB 250329B: Swift/UVOT Upper Limit
  70. GRB 250329A: Swift/UVOT Upper Limit
  71. GRB 250327B: Swift/UVOT Detection
  72. GRB 250327A: Swift/UVOT Upper Limits
  73. GRB 250331E: SVOM/GRM observation
  74. GRB 250327B: Kilonova-Catcher Observations
  75. GRB250331D: AbAO optical observations
  76. GRB 250331D: Fermi GBM observation
  77. GRB 250331C: Swift/UVOT Upper Limits
  78. GRB 250331B: Swift/UVOT Upper Limits
  79. GRB 250328A: AbAO AS-32 Optical Observations
  80. GRB 250219A: NOT candidate host galaxy detection
  81. GRB 250331D: Swift-XRT observations
  82. GRB 250331C: Swift-XRT refined Analysis
  83. GRB 250331B: Swift-XRT refined Analysis
  84. GRB 250331B: Swift-XRT refined Analysis
  85. GRB 250322B possible detection by the AstroSat Satellite
  86. GRB 250330B: SVOM/GRM observation of a short burst
  87. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  88. GRB 250330B: EIRSAT-1 GMOD Detection
  89. GRB 250327A Swift-BAT refined analysis
  90. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  91. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  92. Swift GRB 250331C: Global MASTER-Net observations report
  93. Swift GRB 250331B: Global MASTER-Net observations report
  94. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  95. GRB 250331C: Enhanced Swift-XRT position
  96. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  97. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  98. GRB 250331B: Enhanced Swift-XRT position
  99. GRB 250320C : SVOM detection of a burst through offline search
  100. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources

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