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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"

45431 results found.

  1. Fermi GRB 250404A: Global MASTER-Net observations report
  2. EP250404a: Xinglong decaying optical counterpart
  3. GRB 250403A: Montarrenti Observatory optical detection
  4. GRB 250404A: Fermi GBM Detection
  5. EP250404a: Global MASTER-Net observations report
  6. GRB 250403A: KAIT optical observations
  7. EP250404a: AKO Optical Afterglow Detection
  8. EP250404a: LAST detection of optical counterpart
  9. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  10. EP250404a: Xinglong-2.16m spectroscopic redshift
  11. GRB 250403A: Fermi GBM observations
  12. GRB 250327B: VIRT Optical Upper Limit
  13. EP250404a: Mephisto multi-band optical detection
  14. GRB 250331C Swift-BAT refined analysis
  15. GRB 250331B Swift-BAT refined analysis
  16. GRB 250330A Swift-BAT refined analysis
  17. EP250321A: J band upper limit by SYSU 80cm telescope
  18. EP250404a: BOOTES-4/JGT optical afterglow detection
  19. EP250404a: Nanshan/HMT optical counterpart detection
  20. EP250404a: Einstein Probe detection of an X-ray transient
  21. GRB 250404A: Fermi GBM Final Real-time Localization
  22. GRB 250402A: Mondy optical observations
  23. GRB 250403A: Swift/UVOT Detection
  24. GRB 250402A: Swift/UVOT Upper Limits
  25. EP250402a: Optical upper limit with Kinder observations
  26. GRB 250403A: SVOM/VT optical observation
  27. GRB 250403A: REM NIR afterglow detection
  28. GRB 250403A: LCO optical counterpart detection
  29. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  30. GRB 250403A: JinShan optical observations
  31. GRB 250402A: EP-FXT afterglow detection
  32. GRB 250403A: Optical counterpart detection by LCO.
  33. EP250402a: EP-FXT follow-up observations
  34. GRB 250403A: Swift-XRT observations
  35. GRB 250322A: 10 GHz VLA radio upper limits
  36. Fermi GRB 250403A: Global MASTER-Net observations report
  37. GRB 250403A: GOTO optical counterpart follow-up observations
  38. GRB 250402A: NUTTelA-TAO Early Optical Limits
  39. GRB 250403A: GMG Optical Observation
  40. GRB 250403A: 1.6m Mephisto multi-band optical detection
  41. GRB 250402A: Fermi GBM Observation
  42. GRB 250403A: SVOM/C-GFT optical observations
  43. GRB 250403A: GOTO detection of the optical afterglow
  44. GRB 250402A: Swift-XRT observations
  45. GRB 250403A : SVOM detection of a burst
  46. GRB 250403A: Fermi GBM Final Real-time Localization
  47. GRB 250225B: VLT host galaxy redshift z = 0.950
  48. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  49. GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
  50. GRB 250402A: REM optical/NIR upper limits
  51. GRB 250402A: LCO optical counterpart detection
  52. GRB 250402A: refined SVOM/MXT data analysis
  53. The EP-WXT trigger 01709133862 is a flaring star
  54. EP250402a: Einstein Probe detection of a fast X-ray transient
  55. GRB 250402B: AstroSat CZTI detection of a short burst
  56. GRB 250402A: SVOM/VT optical counterpart
  57. GRB 250402A: SVOM detection of a burst
  58. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  59. GRB 250314A: ALMA detection
  60. GRB 250329B: Swift/UVOT Upper Limit
  61. GRB 250329A: Swift/UVOT Upper Limit
  62. GRB 250327B: Swift/UVOT Detection
  63. GRB 250327A: Swift/UVOT Upper Limits
  64. GRB 250331E: SVOM/GRM observation
  65. GRB 250327B: Kilonova-Catcher Observations
  66. GRB250331D: AbAO optical observations
  67. GRB 250331D: Fermi GBM observation
  68. GRB 250331C: Swift/UVOT Upper Limits
  69. GRB 250331B: Swift/UVOT Upper Limits
  70. GRB 250328A: AbAO AS-32 Optical Observations
  71. GRB 250219A: NOT candidate host galaxy detection
  72. GRB 250322B: GRBAlpha detection
  73. GRB 250331D: Swift-XRT observations
  74. GRB 250331C: Swift-XRT refined Analysis
  75. GRB 250331B: Swift-XRT refined Analysis
  76. GRB 250331B: Swift-XRT refined Analysis
  77. GRB 250322B possible detection by the AstroSat Satellite
  78. GRB 250330B: SVOM/GRM observation of a short burst
  79. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  80. Fermi GRB 250331E: Global MASTER-Net observations report
  81. Fermi GRB 250331D: Global MASTER-Net observations report
  82. GRB 250330B: EIRSAT-1 GMOD Detection
  83. GRB 250331E: Fermi GBM Final Real-time Localization
  84. GRB 250327A Swift-BAT refined analysis
  85. LIGO/Virgo/KAGRA S250331o: Updated Sky localization
  86. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  87. Fermi trigger No 765078057: Global MASTER-Net observations report
  88. GRB 250329B: CAHA 2.2m telescope optical limit
  89. GRB 250331D: Swift ToO observations
  90. Swift GRB 250331C: Global MASTER-Net observations report
  91. Swift GRB 250331B: Global MASTER-Net observations report
  92. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  93. Konus-Wind detection of GRB 250327B
  94. GRB 250331C: Enhanced Swift-XRT position
  95. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  96. LIGO/Virgo/KAGRA S250331o: NED Galaxies in the 3-Initial Localization Volume
  97. GRB 250331B: Enhanced Swift-XRT position
  98. GRB 250320C : SVOM detection of a burst through offline search
  99. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  100. GRB 250329B: Swift-XRT confirmation of fading

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