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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"

27320 results found.

  1. GRB 250317B: Leavitt Observatory optical upper limit
  2. GRB 250317B: Mondy AZT-33IK Optical Observations
  3. GRB 250317B: NOT optical observations suggest an optical plateau phase
  4. GRB 250317C: GECAM-B detection
  5. GRB 250317B: OHP/T193 optical observations
  6. GRB250312A: Swift/UVOT Upper Limits
  7. GRB 250317B: REM optical/NIR observations
  8. GRB 250317B: Swift-XRT observations
  9. GRB 250316A: Swift/UVOT Upper Limits
  10. GRB 250314A: REM optical/NIR upper limits
  11. GRB 250316A: AbAO AS-32 Optical Upper Limit
  12. EP 250317B: Fading optical counterpart detection by LCO
  13. GRB 250316A: Swift-XRT afterglow detection
  14. GRB 250317B: LCO detection of the fading optical afterglow
  15. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  16. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  17. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  18. GRB 250317B: SVOM detection of a burst
  19. GRB 250316A: Fermi GBM Observation
  20. GRB 250316A: Swift-XRT observations
  21. GRB 250314A: SVOM/GRM analysis
  22. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  23. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  24. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  25. GRB 250314A: EP-FXT afterglow detection
  26. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  27. GRB 250314A: Swift/UVOT Upper Limits
  28. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  29. GRB 250314A: Swift XRT Detection
  30. EP250315a: optical counterpart candidate detected by Gemini North
  31. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  32. EP250315a: Einstein Probe detection of an X-ray transient
  33. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  34. SVOM/MXT upper limit on GRB 250314A
  35. GRB 250314A: SVOM/VT upper limit
  36. GRB 250314A: NOT near-infrared candidate counterpart
  37. GRB 250313A: Fermi GBM Detection
  38. GRB 250312B: Fermi GBM Observation
  39. GRB 250313A: Swift-XRT observations
  40. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  41. GRB 250314A: SVOM detection of a burst
  42. GRB 250313A: AstroSat CZTI detection of a bright long burst
  43. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  44. GRB 250313A: Fermi-LAT detection
  45. EP250304a: Pan-STARRS r and i-band imaging and photometry
  46. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  48. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  49. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  50. GRB 250312A: Swift-XRT refined Analysis
  51. GRB 250312A: Enhanced Swift-XRT position
  52. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  53. GRB 250226B: Fermi GBM Observation
  54. GRB 250302A: Fermi GBM Observation
  55. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  56. GRB 250312A: Swift detection of a burst
  57. GRB 241213A: VIRT Optical Upper Limit
  58. GRB 241228A: VIRT Optical Upper Limit
  59. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  60. GRB 250311A: Swift-XRT observations
  61. GRB 250309B: 1.3m DFOT Optical observations
  62. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  64. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  65. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  66. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  67. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  68. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  69. GRB 250309B: PRIME near-infrared detection
  70. GRB 250225B: Swift-BAT refined analysis
  71. GRB 250311A/EP250311a: TRT optical upper limit
  72. EP250311a/GRB 250311A: EP-WXT detection
  73. GRB 250311B: SVOM detection of a burst
  74. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  75. GRB 250309B / AT2025dws: further SAO RAS optical observations
  76. EP250308a: 1.6m Mephisto optical upper limits
  77. Konus-Wind detection of GRB 250309B
  78. IPN triangulation of GRB 250308A (short)
  79. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  80. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  81. GRB 250309B: Swift-XRT refined Analysis
  82. GRB 250309B / IceCube-250309A: GECAM-B observations
  83. GRB 250309B / AT2025dws: SAO RAS optical observations
  84. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  85. GRB 250309B: Fermi GBM Observation
  86. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  87. IceCube-250309A: No candidates from the Zwicky Transient Facility
  88. Fermi-LAT gamma-ray observations of IceCube-250309A
  89. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  90. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  91. EP250308a: GSP optical upper limit
  92. EP250308a: Einstein Probe detection of an X-ray transient
  93. EP250308a: NOT optical upper limit
  94. GRB 250306A: EIRSAT-1 GMOD detection
  95. GRB 250306A: Swift-BAT refined analysis
  96. GRB 250306A: NuSTAR detection of the prompt emission
  97. EP250304a: MeerKAT detection of a possible radio counterpart
  98. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  99. GRB 250305A: AstroSat CZTI detection
  100. EP250302a:Xinglong optical observations

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