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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"

15717 results found.

  1. EP250321a: SVOM/VT optical observation
  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: Swift-XRT detection of an X-ray source
  8. EP250321A: COLIBRÍ Optical Observations
  9. EP250321a: VLT/X-shooter redshift z = 4.368
  10. EP250321a: REM optical/NIR afterglow detection
  11. EP250321a: BOOTES-5/JGT optical afterglow detection
  12. EP250321a: TRT optical counterpart detection
  13. GRB 250321A: GOTO optical upper limits
  14. EP250226a/GRB 250226A: KAIT optical observations
  15. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  16. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  17. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  18. GRB 250314A: ATCA radio upper limits
  19. EP250302a: VLA observations
  20. GRB 250317B: OHP/T193 continued follow-up
  21. GRB 250317C: SVOM/GRM observation of a long burst
  22. GRB 250317B: Leavitt Observatory optical upper limit
  23. GRB 250309B/AT2025dws: further ATCA observations
  24. GRB 250317B: Mondy AZT-33IK Optical Observations
  25. GRB 250317B: NOT optical observations suggest an optical plateau phase
  26. GRB 250317B: OHP/T193 optical observations
  27. GRB250312A: Swift/UVOT Upper Limits
  28. GRB 250317B: REM optical/NIR observations
  29. GRB 250317B: Swift-XRT observations
  30. GRB 250316A: Swift/UVOT Upper Limits
  31. GRB 250314A: REM optical/NIR upper limits
  32. GRB 250316A: AbAO AS-32 Optical Upper Limit
  33. EP 250317B: Fading optical counterpart detection by LCO
  34. GRB 250317B: LCO detection of the fading optical afterglow
  35. GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
  36. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  37. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  38. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  39. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  40. GRB 250314A: Swift/UVOT Upper Limits
  41. GRB 250314A: Swift XRT Detection
  42. EP250315a: optical counterpart candidate detected by Gemini North
  43. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  44. GRB 250314A: NOT near-infrared candidate counterpart
  45. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  46. EP250304a: Pan-STARRS r and i-band imaging and photometry
  47. EP trigger ID 01709061302: Lick/Kast spectroscopy with the 3 m Shane telescope
  48. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  49. EP250304a: SVOM/VT optical observation
  50. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  51. EP250302a: Chandra X-ray Detection
  52. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  53. GRB 241213A: VIRT Optical Upper Limit
  54. GRB 241228A: VIRT Optical Upper Limit
  55. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  56. GRB 250309B: 1.3m DFOT Optical observations
  57. GRB 250309B: PRIME near-infrared detection
  58. GRB 250311A/EP250311a: TRT optical upper limit
  59. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  60. GRB 250309B: SVOM/VT optical observation
  61. GRB 250309B / AT2025dws: further SAO RAS optical observations
  62. IceCube-250309A: Upper limits from Fermi-GBM Observations
  63. EP250308a: 1.6m Mephisto optical upper limits
  64. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  65. IPN triangulation of GRB 250309B
  66. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  67. GRB 250309B: Swift-XRT refined Analysis
  68. GRB 250309B / IceCube-250309A: GECAM-B observations
  69. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  70. GRB 250309B / AT2025dws: SAO RAS optical observations
  71. GRB 250309B / AT2025dws: Swift-UVOT detection
  72. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  73. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  74. IceCube-250309A: No candidates from the Zwicky Transient Facility
  75. EP250308a: GSP optical upper limit
  76. EP250308a: FTW optical and NIR upper limits
  77. EP250308a: NOT optical upper limit
  78. EP250304a: MeerKAT detection of a possible radio counterpart
  79. EP250302a:Xinglong optical observations
  80. GRB250101A: Radio upper limits from VLA observations
  81. GRB 250305A: SVOM/GRM observation of a burst
  82. EP250302a: Optical Observations at CrAO and SAO RAS
  83. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  84. EP 250304A: Optical counterpart detection by LCO
  85. EP250302A: 1.3m DFOT optical afterglow detection
  86. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP250304a: REM NIR upper limits
  88. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  89. EP250302a: Mondy Continued Optical Observations
  90. EP250304a: VLT/X-shooter redshift z = 0.200
  91. EP250304a: Swift-XRT detection of a fading X-ray source
  92. EP250304a: TRT optical counterpart detection
  93. EP250302a: SVOM/VT optical observation
  94. EP250302a: SAO RAS optical observations
  95. EP250302a : GIT optical follow-up
  96. EP250225a: the candidate optical counterpart is an AGN
  97. EP250302a: Kinder optical follow-up observations
  98. EP250302a: Swift/UVOT detection
  99. EP250302a: NUTTelA-TAO Early Measurments
  100. EP250302a: optical observation from the INAF Asiago Observatory

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