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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"

39162 results found.

  1. GRB 250309B / AT2025dws: further SAO RAS optical observations
  2. IceCube-250309A: Upper limits from Fermi-GBM Observations
  3. EP250308a: 1.6m Mephisto optical upper limits
  4. Konus-Wind detection of GRB 250309B
  5. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  6. IPN triangulation of GRB 250308A (short)
  7. IPN triangulation of GRB 250309B
  8. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  9. GRB 250309B: Swift-XRT refined Analysis
  10. GRB 250309B / IceCube-250309A: GECAM-B observations
  11. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  12. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  13. GRB 250309B / AT2025dws: SAO RAS optical observations
  14. GRB 250309B / AT2025dws: Swift-UVOT detection
  15. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  16. GRB 250309B: Fermi GBM Observation
  17. Fermi GRB 250309B: Global MASTER-Net observations report
  18. Fermi GRB 250309A: Global MASTER-Net observations report
  19. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  20. IceCube-250309A: No candidates from the Zwicky Transient Facility
  21. Fermi-LAT gamma-ray observations of IceCube-250309A
  22. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  23. GRB 250309B: Fermi GBM Final Localization
  24. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  25. GRB 230509B: Tiled Swift observations
  26. GRB 250308A: SVOM/GRM observation of a bright short burst
  27. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  28. IceCube Alert 250309.32: Global MASTER-Net observations report
  29. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  30. EP250308a: Global MASTER-Net observations report
  31. EP250308a: GSP optical upper limit
  32. GRB 250309A: Fermi GBM Final Real-time Localization
  33. GRB 250306A: EIRSAT-1 GMOD detection
  34. Fermi GRB 250307A: Global MASTER-Net observations report
  35. Konus-Wind detection of GRB 250306A
  36. GRB 250307A: Fermi GBM Final Real-time Localization
  37. GRB 250306A: Swift-BAT refined analysis
  38. GRB 250306A: NuSTAR detection of the prompt emission
  39. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  40. GRB 250305A: AstroSat CZTI detection
  41. EP250302a:Xinglong optical observations
  42. GRB 250306A: AstroSat CZTI detection
  43. Fermi trigger No 762963055: Global MASTER-Net observations report
  44. Fermi Gamma-ray Burst Monitor trigger 762963055/250306591 is not a GRB
  45. Swift GRB 250306A: Global MASTER-Net observations report
  46. GRB 250306A: Swift detection of a burst
  47. GRB 250305A: SVOM/GRM observation of a burst
  48. EP250304A: Upper limits from Fermi-GBM Observations
  49. Fermi GRB 250305A: Global MASTER-Net observations report
  50. GRB 250305A: Fermi GBM Final Real-time Localization
  51. EP250302a: Optical Observations at CrAO and SAO RAS
  52. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  53. EP 250304A: Optical counterpart detection by LCO
  54. EP250302A: 1.3m DFOT optical afterglow detection
  55. Konus-Wind detection of GRB 250222A
  56. EP250304a: REM NIR upper limits
  57. IPN triangulation of GRB 250222A
  58. EP250302a: Mondy Continued Optical Observations
  59. EP250304a: VLT/X-shooter redshift z = 0.200
  60. EP250304a: TRT optical counterpart detection
  61. EP250304a: Global MASTER-Net observations report
  62. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  63. EP250302a : GIT optical follow-up
  64. EP250225a: the candidate optical counterpart is an AGN
  65. EP250302a: optical observation from the INAF Asiago Observatory
  66. EP250302a: REM NIR upper limits
  67. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  68. EP250302a: Mondy Observations and Optical Light Curve
  69. EP250302a: OHP/T193 optical and spectroscopic observations
  70. EP250302a: Global MASTER-Net observations report
  71. EP250302a: SVOM/C-GFT optical observations
  72. GRB 250226A: GRANDMA Optical Observations
  73. EP250302a: Montarrenti Observatory optical detection
  74. Fermi GRB 250302A: Global MASTER-Net observations report
  75. EP250302a: Nanshan/HMT optical counterpart detection
  76. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  77. GRB 250302A: Fermi GBM Final Real-time Localization
  78. GRB 250228A: Fermi GBM Final Localization
  79. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  80. GRB 250225B: VLT near-infrared afterglow confirmation
  81. Konus-Wind detection of GRB 250226A
  82. GRB 250225B: EIRSAT-1 GMOD Detection
  83. GRB 250226A: KAO Optical Upper Limit
  84. GRB 250226A: AbAO AS-32 Optical Upper Limit
  85. EP250227a: Global MASTER-Net observations report
  86. EP250223A: Upper limits from Fermi-GBM Observations
  87. EP250227a: TRT optical upper limit
  88. GRB 250225B: VLT/HAWKI near-infrared observations
  89. EP250227a: NOT optical observations
  90. GRB 250226A: Fermi GBM Observation
  91. EP250228a: Global MASTER-Net observations report
  92. GRB 250226A / EP250226a: LCO detection of the afterglow
  93. GRB 250225B: VLT/Xshooter imaging
  94. GRB 250205A / EP250205A: further radio observations with the VLA
  95. GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
  96. EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
  97. GRB 250225B: INTEGRAL SPI-ACS detection
  98. EP250225a: NOT optical candidate counterpart
  99. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  100. EP250226a / GRB 250226A: SVOM/VT optical observations

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