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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

16112 results found.

  1. GRB 250316A: AbAO AS-32 Optical Upper Limit
  2. EP 250317B: Fading optical counterpart detection by LCO
  3. GRB 250317B: LCO detection of the fading optical afterglow
  4. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  5. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  6. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  7. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  8. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250314A: Swift/UVOT Upper Limits
  10. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  11. GRB 250314A: Swift XRT Detection
  12. EP250315a: optical counterpart candidate detected by Gemini North
  13. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  14. GRB 250314A: NOT near-infrared candidate counterpart
  15. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  16. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  17. EP250304a: Pan-STARRS r and i-band imaging and photometry
  18. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  19. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  20. EP250304a: SVOM/VT optical observation
  21. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  22. EP250302a: Chandra X-ray Detection
  23. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  24. GRB 241213A: VIRT Optical Upper Limit
  25. GRB 241228A: VIRT Optical Upper Limit
  26. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  27. GRB 250309B: 1.3m DFOT Optical observations
  28. GRB 250309B: PRIME near-infrared detection
  29. GRB 250311A/EP250311a: TRT optical upper limit
  30. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  31. GRB 250309B: SVOM/VT optical observation
  32. GRB 250309B / AT2025dws: further SAO RAS optical observations
  33. IceCube-250309A: Upper limits from Fermi-GBM Observations
  34. EP250308a: 1.6m Mephisto optical upper limits
  35. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  36. IPN triangulation of GRB 250309B
  37. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  38. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  39. GRB 250309B: Swift-XRT refined Analysis
  40. GRB 250309B / IceCube-250309A: GECAM-B observations
  41. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  42. GRB 250309B / AT2025dws: SAO RAS optical observations
  43. GRB 250309B / AT2025dws: Swift-UVOT detection
  44. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  45. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  46. IceCube-250309A: No candidates from the Zwicky Transient Facility
  47. EP250308a: GSP optical upper limit
  48. EP250308a: FTW optical and NIR upper limits
  49. EP250308a: NOT optical upper limit
  50. EP250304a: MeerKAT detection of a possible radio counterpart
  51. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  52. EP250302a:Xinglong optical observations
  53. GRB250101A: Radio upper limits from VLA observations
  54. GRB 250305A: SVOM/GRM observation of a burst
  55. EP250302a: Optical Observations at CrAO and SAO RAS
  56. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  57. EP 250304A: Optical counterpart detection by LCO
  58. EP250302A: 1.3m DFOT optical afterglow detection
  59. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  60. EP250304a: REM NIR upper limits
  61. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  62. EP250302a: Mondy Continued Optical Observations
  63. EP250304a: VLT/X-shooter redshift z = 0.200
  64. EP250304a: Swift-XRT detection of a fading X-ray source
  65. EP250304a: TRT optical counterpart detection
  66. EP250302a: SVOM/VT optical observation
  67. EP250302a: SAO RAS optical observations
  68. EP250302a : GIT optical follow-up
  69. EP250225a: the candidate optical counterpart is an AGN
  70. EP250302a: Kinder optical follow-up observations
  71. EP250302a: Swift/UVOT detection
  72. EP250302a: NUTTelA-TAO Early Measurments
  73. EP250302a: optical observation from the INAF Asiago Observatory
  74. EP250302a: REM NIR upper limits
  75. EP250302a: Mondy Observations and Optical Light Curve
  76. EP250302a: VLT/MUSE optical redshift z = 1.131
  77. EP250302A: VLT near-infrared observations
  78. EP250302A: VLT/X-shooter tentative redshift
  79. EP250302a: OHP/T193 optical and spectroscopic observations
  80. EP250302a: Xinglong F60B optical observation
  81. EP250302a: Swift-XRT observations of a fading X-ray source
  82. EP250302a: Einstein Probe detection of an X-ray transient
  83. EP250302a: SVOM/C-GFT optical observations
  84. GRB 250226A: GRANDMA Optical Observations
  85. EP250302a: Montarrenti Observatory optical detection
  86. EP250302a: FTW optical and NIR detection
  87. EP250302a: Nanshan/HMT optical counterpart detection
  88. EP250228a: Optical observations with Kinder and Swift/UVOT
  89. GRB 250226A: KAO Optical Upper Limit
  90. GRB 250226A: AbAO AS-32 Optical Upper Limit
  91. EP250227a: TRT optical upper limit
  92. GRB 250225B: VLT/HAWKI near-infrared observations
  93. EP250227a: Optical upper limits with Kinder observations
  94. EP250227a: NOT optical observations
  95. GRB 250226A: Fermi GBM Observation
  96. EP250223a: J band upper limit by SYSU 80cm telescope
  97. GRB 250226A / EP250226a: LCO detection of the afterglow
  98. GRB 250225B: VLT/Xshooter imaging
  99. EP250225a: NOT optical candidate counterpart
  100. EP250226a/GRB 250226A:Xinglong optical follow-up observations

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