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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"

37512 results found.

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

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