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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"

39150 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. IceCube-250309A: No candidates 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. IceCube Alert 250309.32: Global MASTER-Net observations report
  17. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  18. EP250308a: Global MASTER-Net observations report
  19. EP250308a: GSP optical upper limit
  20. GRB 250309A: Fermi GBM Final Real-time Localization
  21. GRB 250306A: EIRSAT-1 GMOD detection
  22. Fermi GRB 250307A: Global MASTER-Net observations report
  23. Konus-Wind detection of GRB 250306A
  24. GRB 250307A: Fermi GBM Final Real-time Localization
  25. GRB 250306A: Swift-BAT refined analysis
  26. GRB 250306A: NuSTAR detection of the prompt emission
  27. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  28. GRB 250305A: AstroSat CZTI detection
  29. EP250302a:Xinglong optical observations
  30. GRB 250306A: AstroSat CZTI detection
  31. Fermi trigger No 762963055: Global MASTER-Net observations report
  32. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  33. Swift GRB 250306A: Global MASTER-Net observations report
  34. GRB 250306A: Swift detection of a burst
  35. GRB 250305A: SVOM/GRM observation of a burst
  36. EP250304A: Upper limits from Fermi-GBM Observations
  37. Fermi GRB 250305A: Global MASTER-Net observations report
  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. EP250302A: 1.3m DFOT optical afterglow detection
  43. Konus-Wind detection of GRB 250222A
  44. EP250304a: REM NIR upper limits
  45. IPN triangulation of GRB 250222A
  46. EP250302a: Mondy Continued Optical Observations
  47. EP250304a: VLT/X-shooter redshift z = 0.200
  48. EP250304a: TRT optical counterpart detection
  49. EP250304a: Global MASTER-Net observations report
  50. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  51. EP250302a : GIT optical follow-up
  52. EP250225a: the candidate optical counterpart is an AGN
  53. EP250302a: optical observation from the INAF Asiago Observatory
  54. EP250302a: REM NIR upper limits
  55. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  56. EP250302a: Mondy Observations and Optical Light Curve
  57. EP250302a: OHP/T193 optical and spectroscopic observations
  58. EP250302a: Global MASTER-Net observations report
  59. EP250302a: SVOM/C-GFT optical observations
  60. GRB 250226A: GRANDMA Optical Observations
  61. EP250302a: Montarrenti Observatory optical detection
  62. Fermi GRB 250302A: Global MASTER-Net observations report
  63. EP250302a: Nanshan/HMT optical counterpart detection
  64. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 250302A: Fermi GBM Final Real-time Localization
  66. GRB 250228A: Fermi GBM Final Localization
  67. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  68. GRB 250225B: VLT near-infrared afterglow confirmation
  69. Konus-Wind detection of GRB 250226A
  70. GRB 250225B: EIRSAT-1 GMOD Detection
  71. GRB 250226A: KAO Optical Upper Limit
  72. GRB 250226A: AbAO AS-32 Optical Upper Limit
  73. EP250227a: Global MASTER-Net observations report
  74. EP250223A: Upper limits from Fermi-GBM Observations
  75. EP250227a: TRT optical upper limit
  76. GRB 250225B: VLT/HAWKI near-infrared observations
  77. EP250227a: NOT optical observations
  78. GRB 250226A: Fermi GBM Observation
  79. EP250228a: Global MASTER-Net observations report
  80. GRB 250226A / EP250226a: LCO detection of the afterglow
  81. GRB 250225B: VLT/Xshooter imaging
  82. GRB 250205A / EP250205A: further radio observations with the VLA
  83. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  84. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  85. GRB 250225B: INTEGRAL SPI-ACS detection
  86. EP250225a: NOT optical candidate counterpart
  87. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  88. EP250226a / GRB 250226A: SVOM/VT optical observations
  89. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  90. EP250225a: TRT optical upper limits
  91. EP250226a/GRB 250226A: 1.6m Mephisto observations
  92. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  93. EP250226a/GRB 250226A: Kinder optical follow-up observations
  94. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  95. Fermi GRB 250226B: Global MASTER-Net observations report
  96. GRB 250226B: Fermi GBM Final Real-time Localization
  97. GRB 250225B: Fermi GBM Observation
  98. GRB 250221A: ATCA Detections and Upper Limits
  99. GRB 250225B: REM NIR upper limits
  100. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event

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