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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

23577 results found.

  1. GRB 250321A: Swift-XRT refined Analysis
  2. EP 250321A: Optical counterpart detection by LCO.
  3. EP250321a: Kinder optical follow-up observations
  4. GRB 250321A: Swift/UVOT Upper Limits
  5. GRB 250320B: SVOM/GRM observation of a long burst
  6. EP250321a: LCO optical counterpart detection
  7. EP250321A: COLIBRÍ Optical Observations
  8. GRB 250320B: AstroSat CZTI detection
  9. EP250321a: REM optical/NIR afterglow detection
  10. EP250321a: TRT optical counterpart detection
  11. EP250321a: Einstein Probe detection of an X-ray transient
  12. GRB 250321A: GOTO optical upper limits
  13. GRB 250314A: Keck/NIRC2 J-band upper limit
  14. EP250226a/GRB 250226A: KAIT optical observations
  15. GRB 250321A: Swift detection of a burst
  16. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  17. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  18. FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
  19. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  20. GRB 250314A: ATCA radio upper limits
  21. LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
  22. GRB 250317C: SVOM/GRM observation of a long burst
  23. GRB 250317B: Leavitt Observatory optical upper limit
  24. GRB 250317B: Mondy AZT-33IK Optical Observations
  25. GRB 250317C: AstroSat CZTI detection
  26. GRB 250317B: NOT optical observations suggest an optical plateau phase
  27. GRB 250317B: OHP/T193 optical observations
  28. GRB250312A: Swift/UVOT Upper Limits
  29. GRB 250317B: REM optical/NIR observations
  30. GRB 250317B: Swift-XRT observations
  31. GRB 250316A: Swift/UVOT Upper Limits
  32. GRB 250314A: REM optical/NIR upper limits
  33. GRB 250316A: AbAO AS-32 Optical Upper Limit
  34. EP 250317B: Fading optical counterpart detection by LCO
  35. GRB 250316A: Swift-XRT afterglow detection
  36. GRB 250317B: LCO detection of the fading optical afterglow
  37. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  38. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  39. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  40. GRB 250317B: SVOM detection of a burst
  41. GRB 250316A: Swift-XRT observations
  42. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  43. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 250314A: Swift/UVOT Upper Limits
  45. GRB 250314A: Swift XRT Detection
  46. EP250315a: optical counterpart candidate detected by Gemini North
  47. EP250315a: Einstein Probe detection of an X-ray transient
  48. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  49. SVOM/MXT upper limit on GRB 250314A
  50. GRB 250314A: SVOM/VT upper limit
  51. GRB 250314A: NOT near-infrared candidate counterpart
  52. GRB 250313A: Swift-XRT observations
  53. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  54. GRB 250314A: SVOM detection of a burst
  55. GRB 250313A: AstroSat CZTI detection of a bright long burst
  56. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  57. EP250304a: Pan-STARRS r and i-band imaging and photometry
  58. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  59. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  60. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  61. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  62. GRB 250312A: Enhanced Swift-XRT position
  63. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  64. GRB 250312A: Swift detection of a burst
  65. GRB 241213A: VIRT Optical Upper Limit
  66. GRB 241228A: VIRT Optical Upper Limit
  67. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  68. GRB 250311A: Swift-XRT observations
  69. GRB 250309B: 1.3m DFOT Optical observations
  70. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  71. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  73. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  74. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  75. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  76. GRB 250309B: PRIME near-infrared detection
  77. GRB 250225B: Swift-BAT refined analysis
  78. GRB 250311A/EP250311a: TRT optical upper limit
  79. EP250311a/GRB 250311A: EP-WXT detection
  80. GRB 250309B / AT2025dws: further SAO RAS optical observations
  81. IceCube-250309A: Upper limits from Fermi-GBM Observations
  82. EP250308a: 1.6m Mephisto optical upper limits
  83. IPN triangulation of GRB 250308A (short)
  84. IPN triangulation of GRB 250309B
  85. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  86. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  87. GRB 250309B / IceCube-250309A: GECAM-B observations
  88. GRB 250309B / AT2025dws: SAO RAS optical observations
  89. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  90. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  91. IceCube-250309A: No candidates from the Zwicky Transient Facility
  92. EP250308a: FTW optical and NIR upper limits
  93. EP250308a: Einstein Probe detection of an X-ray transient
  94. EP250308a: NOT optical upper limit
  95. Konus-Wind detection of GRB 250306A
  96. EP250304a: MeerKAT detection of a possible radio counterpart
  97. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  98. EP250302a:Xinglong optical observations
  99. GRB 250306A: AstroSat CZTI detection
  100. GRB 250306A: Swift detection of a burst

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