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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"

35428 results found.

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

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