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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"

35427 results found.

  1. GRB 250309B / AT2025dws: SAO RAS optical observations
  2. GRB 250309B / AT2025dws: Swift-UVOT detection
  3. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  4. GRB 250309B: Fermi GBM Observation
  5. Fermi GRB 250309B: Global MASTER-Net observations report
  6. Fermi GRB 250309A: Global MASTER-Net observations report
  7. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  8. Fermi-LAT gamma-ray observations of IceCube-250309A
  9. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  10. GRB 250309B: Fermi GBM Final Localization
  11. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  12. GRB 230509B: Tiled Swift observations
  13. GRB 250308A: SVOM/GRM observation of a bright short burst
  14. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  16. GRB 250309A: Fermi GBM Final Real-time Localization
  17. GRB 250306A: EIRSAT-1 GMOD detection
  18. Fermi GRB 250307A: Global MASTER-Net observations report
  19. Konus-Wind detection of GRB 250306A
  20. GRB 250307A: Fermi GBM Final Real-time Localization
  21. GRB 250306A: Swift-BAT refined analysis
  22. GRB 250306A: NuSTAR detection of the prompt emission
  23. GRB 250305A: AstroSat CZTI detection
  24. GRB 250306A: AstroSat CZTI detection
  25. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  26. Swift GRB 250306A: Global MASTER-Net observations report
  27. GRB 250306A: Swift detection of a burst
  28. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  29. GRB 250305A: SVOM/GRM observation of a burst
  30. EP250304A: Upper limits from Fermi-GBM Observations
  31. Fermi GRB 250305A: Global MASTER-Net observations report
  32. GRB 250305A: Fermi GBM Final Real-time Localization
  33. EP250302a: Optical Observations at CrAO and SAO RAS
  34. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  35. EP 250304A: Optical counterpart detection by LCO
  36. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  37. Konus-Wind detection of GRB 250222A
  38. IPN triangulation of GRB 250222A
  39. EP250302a: Mondy Continued Optical Observations
  40. EP250304a: VLT/X-shooter redshift z = 0.200
  41. EP250302a: NUTTelA-TAO Early Measurments
  42. EP250302a: Mondy Observations and Optical Light Curve
  43. EP250302a: OHP/T193 optical and spectroscopic observations
  44. GRB 250226A: GRANDMA Optical Observations
  45. EP250302a: Montarrenti Observatory optical detection
  46. Fermi GRB 250302A: Global MASTER-Net observations report
  47. GRB 250302A: Fermi GBM Final Real-time Localization
  48. GRB 250228A: Fermi GBM Final Localization
  49. GRB 250225B: VLT near-infrared afterglow confirmation
  50. Konus-Wind detection of GRB 250226A
  51. GRB 250225B: EIRSAT-1 GMOD Detection
  52. GRB 250226A: KAO Optical Upper Limit
  53. GRB 250226A: AbAO AS-32 Optical Upper Limit
  54. EP250223A: Upper limits from Fermi-GBM Observations
  55. GRB 250225B: VLT/HAWKI near-infrared observations
  56. GRB 250226A: Fermi GBM Observation
  57. GRB 250226A / EP250226a: LCO detection of the afterglow
  58. GRB 250225B: VLT/Xshooter imaging
  59. GRB 250205A / EP250205A: further radio observations with the VLA
  60. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  61. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  62. GRB 250225B: INTEGRAL SPI-ACS detection
  63. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  64. EP250226a / GRB 250226A: SVOM/VT optical observations
  65. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  66. EP250226a/GRB 250226A: 1.6m Mephisto observations
  67. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  68. EP250226a/GRB 250226A: Kinder optical follow-up observations
  69. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  70. Fermi GRB 250226B: Global MASTER-Net observations report
  71. GRB 250226B: Fermi GBM Final Real-time Localization
  72. GRB 250225B: Fermi GBM Observation
  73. GRB 250221A: ATCA Detections and Upper Limits
  74. GRB 250225B: REM NIR upper limits
  75. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  76. Konus-Wind detection of GRB 250225B
  77. EP250223a: CrAO ZTSH optical observation
  78. GRB 250225B: VLT optical and near-infrared candidate counterpart
  79. GRB 250225B: VLT/FORS2 candidate optical afterglow
  80. GRB 250225B: SVOM/GRM observation of a long burst
  81. GRB 250226A: GECAM-B detection
  82. GRB 250221A: EP-FXT detection of the X-ray afterglow
  83. GRB 250214A: SVOM/GRM observation
  84. EP250226a/GRB 250226A: GSP detects optical counterpart
  85. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  86. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  87. EP250226a / GRB 250226A: TRT optical counterpart observation
  88. Swift GRB 250225B: Global MASTER-Net observations report
  89. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  90. Fermi GRB 250226A: Global MASTER-Net observations report
  91. GRB 250226A: Fermi GBM Final Real-time Localization
  92. Fermi GRB 250225A: Global MASTER-Net observations report
  93. GRB 250225B: Swift detection of a burst
  94. GRB 250221A: Swift-BAT refined analysis
  95. GRB 250223C: SVOM/GRM observation of a long burst
  96. GRB 250225A: Fermi GBM Final Real-time Localization
  97. GRB 250207a: ATCA Radio Upper Limits
  98. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  99. GRB 250119B: VZLUSAT-2 detection
  100. GRB 250223C: Fermi GBM Final Real-time Localization

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