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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"

37707 results found.

  1. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  2. GRB 250309B: Swift-XRT refined Analysis
  3. GRB 250309B / IceCube-250309A: GECAM-B observations
  4. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  5. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  6. GRB 250309B / AT2025dws: SAO RAS optical observations
  7. GRB 250309B / AT2025dws: Swift-UVOT detection
  8. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  9. GRB 250309B: Fermi GBM Observation
  10. Fermi GRB 250309B: Global MASTER-Net observations report
  11. Fermi GRB 250309A: Global MASTER-Net observations report
  12. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  13. Fermi-LAT gamma-ray observations of IceCube-250309A
  14. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  15. GRB 250309B: Fermi GBM Final Localization
  16. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  17. GRB 230509B: Tiled Swift observations
  18. GRB 250308A: SVOM/GRM observation of a bright short burst
  19. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  21. GRB 250309A: Fermi GBM Final Real-time Localization
  22. GRB 250306A: EIRSAT-1 GMOD detection
  23. Fermi GRB 250307A: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 250306A
  25. GRB 250307A: Fermi GBM Final Real-time Localization
  26. GRB 250306A: Swift-BAT refined analysis
  27. GRB 250306A: NuSTAR detection of the prompt emission
  28. GRB 250305A: AstroSat CZTI detection
  29. GRB 250306A: AstroSat CZTI detection
  30. Fermi trigger No 762963055: Global MASTER-Net observations report
  31. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  32. Swift GRB 250306A: Global MASTER-Net observations report
  33. GRB 250306A: Swift detection of a burst
  34. GRB 250305A: SVOM/GRM observation of a burst
  35. EP250304A: Upper limits from Fermi-GBM Observations
  36. Fermi GRB 250305A: Global MASTER-Net observations report
  37. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  38. GRB 250305A: Fermi GBM Final Real-time Localization
  39. EP250302a: Optical Observations at CrAO and SAO RAS
  40. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  41. EP 250304A: Optical counterpart detection by LCO
  42. Konus-Wind detection of GRB 250222A
  43. IPN triangulation of GRB 250222A
  44. EP250302a: Mondy Continued Optical Observations
  45. EP250304a: VLT/X-shooter redshift z = 0.200
  46. EP250302a: Mondy Observations and Optical Light Curve
  47. EP250302a: OHP/T193 optical and spectroscopic observations
  48. GRB 250226A: GRANDMA Optical Observations
  49. EP250302a: Montarrenti Observatory optical detection
  50. Fermi GRB 250302A: Global MASTER-Net observations report
  51. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  52. GRB 250302A: Fermi GBM Final Real-time Localization
  53. GRB 250228A: Fermi GBM Final Localization
  54. GRB 250225B: VLT near-infrared afterglow confirmation
  55. Konus-Wind detection of GRB 250226A
  56. GRB 250225B: EIRSAT-1 GMOD Detection
  57. GRB 250226A: KAO Optical Upper Limit
  58. GRB 250226A: AbAO AS-32 Optical Upper Limit
  59. EP250223A: Upper limits from Fermi-GBM Observations
  60. GRB 250225B: VLT/HAWKI near-infrared observations
  61. GRB 250226A: Fermi GBM Observation
  62. GRB 250226A / EP250226a: LCO detection of the afterglow
  63. GRB 250225B: VLT/Xshooter imaging
  64. GRB 250205A / EP250205A: further radio observations with the VLA
  65. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  66. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  67. GRB 250225B: INTEGRAL SPI-ACS detection
  68. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  69. EP250226a / GRB 250226A: SVOM/VT optical observations
  70. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  71. EP250226a/GRB 250226A: 1.6m Mephisto observations
  72. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  73. EP250226a/GRB 250226A: Kinder optical follow-up observations
  74. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  75. Fermi GRB 250226B: Global MASTER-Net observations report
  76. GRB 250226B: Fermi GBM Final Real-time Localization
  77. GRB 250225B: Fermi GBM Observation
  78. GRB 250221A: ATCA Detections and Upper Limits
  79. GRB 250225B: REM NIR upper limits
  80. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  81. Konus-Wind detection of GRB 250225B
  82. EP250223a: CrAO ZTSH optical observation
  83. GRB 250225B: VLT optical and near-infrared candidate counterpart
  84. GRB 250225B: VLT/FORS2 candidate optical afterglow
  85. GRB 250225B: SVOM/GRM observation of a long burst
  86. GRB 250226A: GECAM-B detection
  87. GRB 250221A: EP-FXT detection of the X-ray afterglow
  88. GRB 250214A: SVOM/GRM observation
  89. EP250226a/GRB 250226A: GSP detects optical counterpart
  90. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  91. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  92. EP250226a / GRB 250226A: TRT optical counterpart observation
  93. Swift GRB 250225B: Global MASTER-Net observations report
  94. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  95. Fermi GRB 250226A: Global MASTER-Net observations report
  96. Fermi trigger No 762205158: Global MASTER-Net observations report
  97. GRB 250226A: Fermi GBM Final Real-time Localization
  98. Fermi GRB 250225A: Global MASTER-Net observations report
  99. GRB 250225B: Swift detection of a burst
  100. GRB 250221A: Swift-BAT refined analysis

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