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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"

16103 results found.

  1. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  2. GRB 250314A: Swift XRT Detection
  3. EP250315a: optical counterpart candidate detected by Gemini North
  4. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  5. GRB 250314A: NOT near-infrared candidate counterpart
  6. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  7. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  8. EP250304a: Pan-STARRS r and i-band imaging and photometry
  9. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  10. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  11. EP250304a: SVOM/VT optical observation
  12. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  13. EP250302a: Chandra X-ray Detection
  14. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  15. GRB 241213A: VIRT Optical Upper Limit
  16. GRB 241228A: VIRT Optical Upper Limit
  17. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  18. GRB 250309B: 1.3m DFOT Optical observations
  19. GRB 250309B: PRIME near-infrared detection
  20. GRB 250311A/EP250311a: TRT optical upper limit
  21. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  22. GRB 250309B: SVOM/VT optical observation
  23. GRB 250309B / AT2025dws: further SAO RAS optical observations
  24. IceCube-250309A: Upper limits from Fermi-GBM Observations
  25. EP250308a: 1.6m Mephisto optical upper limits
  26. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  27. IPN triangulation of GRB 250309B
  28. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  29. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  30. GRB 250309B: Swift-XRT refined Analysis
  31. GRB 250309B / IceCube-250309A: GECAM-B observations
  32. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  33. GRB 250309B / AT2025dws: SAO RAS optical observations
  34. GRB 250309B / AT2025dws: Swift-UVOT detection
  35. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  36. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  37. IceCube-250309A: No candidates from the Zwicky Transient Facility
  38. EP250308a: GSP optical upper limit
  39. EP250308a: FTW optical and NIR upper limits
  40. EP250308a: NOT optical upper limit
  41. EP250304a: MeerKAT detection of a possible radio counterpart
  42. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  43. EP250302a:Xinglong optical observations
  44. GRB250101A: Radio upper limits from VLA observations
  45. GRB 250305A: SVOM/GRM observation of a burst
  46. EP250302a: Optical Observations at CrAO and SAO RAS
  47. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  48. EP 250304A: Optical counterpart detection by LCO
  49. EP250302A: 1.3m DFOT optical afterglow detection
  50. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP250304a: REM NIR upper limits
  52. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  53. EP250302a: Mondy Continued Optical Observations
  54. EP250304a: VLT/X-shooter redshift z = 0.200
  55. EP250304a: Swift-XRT detection of a fading X-ray source
  56. EP250304a: TRT optical counterpart detection
  57. EP250302a: SVOM/VT optical observation
  58. EP250302a: SAO RAS optical observations
  59. EP250302a : GIT optical follow-up
  60. EP250225a: the candidate optical counterpart is an AGN
  61. EP250302a: Kinder optical follow-up observations
  62. EP250302a: Swift/UVOT detection
  63. EP250302a: NUTTelA-TAO Early Measurments
  64. EP250302a: optical observation from the INAF Asiago Observatory
  65. EP250302a: REM NIR upper limits
  66. EP250302a: Mondy Observations and Optical Light Curve
  67. EP250302a: VLT/MUSE optical redshift z = 1.131
  68. EP250302A: VLT near-infrared observations
  69. EP250302A: VLT/X-shooter tentative redshift
  70. EP250302a: OHP/T193 optical and spectroscopic observations
  71. EP250302a: Xinglong F60B optical observation
  72. EP250302a: Swift-XRT observations of a fading X-ray source
  73. EP250302a: Einstein Probe detection of an X-ray transient
  74. EP250302a: SVOM/C-GFT optical observations
  75. GRB 250226A: GRANDMA Optical Observations
  76. EP250302a: Montarrenti Observatory optical detection
  77. EP250302a: FTW optical and NIR detection
  78. EP250302a: Nanshan/HMT optical counterpart detection
  79. EP250228a: Optical observations with Kinder and Swift/UVOT
  80. GRB 250226A: KAO Optical Upper Limit
  81. GRB 250226A: AbAO AS-32 Optical Upper Limit
  82. EP250227a: TRT optical upper limit
  83. GRB 250225B: VLT/HAWKI near-infrared observations
  84. EP250227a: Optical upper limits with Kinder observations
  85. EP250227a: NOT optical observations
  86. GRB 250226A: Fermi GBM Observation
  87. EP250223a: J band upper limit by SYSU 80cm telescope
  88. GRB 250226A / EP250226a: LCO detection of the afterglow
  89. GRB 250225B: VLT/Xshooter imaging
  90. EP250225a: NOT optical candidate counterpart
  91. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  92. EP250226a / GRB 250226A: SVOM/VT optical observations
  93. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  94. EP250225a: TRT optical upper limits
  95. EP250226a/GRB 250226A: 1.6m Mephisto observations
  96. EP250226a/GRB 250226A: Kinder optical follow-up observations
  97. GRB 250225B: REM NIR upper limits
  98. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  99. EP250223a: CrAO ZTSH optical observation
  100. GRB 250225B: VLT optical and near-infrared candidate counterpart

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