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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"

16161 results found.

  1. GRB 250309B: PRIME near-infrared detection
  2. GRB 250311A/EP250311a: TRT optical upper limit
  3. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  4. GRB 250309B: SVOM/VT optical observation
  5. GRB 250309B / AT2025dws: further SAO RAS optical observations
  6. IceCube-250309A: Upper limits from Fermi-GBM Observations
  7. EP250308a: 1.6m Mephisto optical upper limits
  8. GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
  9. IPN triangulation of GRB 250309B
  10. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  11. GRB 250309B: Swift-XRT refined Analysis
  12. GRB 250309B / IceCube-250309A: GECAM-B observations
  13. Liverpool Telecope observations of AT 2025dws / GRB 250309B
  14. GRB 250309B / AT2025dws: SAO RAS optical observations
  15. GRB 250309B / AT2025dws: Swift-UVOT detection
  16. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  17. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  18. IceCube-250309A: No candidates from the Zwicky Transient Facility
  19. EP250308a: GSP optical upper limit
  20. EP250308a: FTW optical and NIR upper limits
  21. EP250308a: NOT optical upper limit
  22. EP250304a: MeerKAT detection of a possible radio counterpart
  23. EP250302a:Xinglong optical observations
  24. GRB250101A: Radio upper limits from VLA observations
  25. GRB 250305A: SVOM/GRM observation of a burst
  26. EP250302a: Optical Observations at CrAO and SAO RAS
  27. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  28. EP 250304A: Optical counterpart detection by LCO
  29. EP250302A: 1.3m DFOT optical afterglow detection
  30. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  31. EP250304a: REM NIR upper limits
  32. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  33. EP250302a: Mondy Continued Optical Observations
  34. EP250304a: VLT/X-shooter redshift z = 0.200
  35. EP250304a: Swift-XRT detection of a fading X-ray source
  36. EP250304a: TRT optical counterpart detection
  37. EP250302a: SVOM/VT optical observation
  38. EP250302a: SAO RAS optical observations
  39. EP250302a : GIT optical follow-up
  40. EP250225a: the candidate optical counterpart is an AGN
  41. EP250302a: Kinder optical follow-up observations
  42. EP250302a: Swift/UVOT detection
  43. EP250302a: NUTTelA-TAO Early Measurments
  44. EP250302a: optical observation from the INAF Asiago Observatory
  45. EP250302a: REM NIR upper limits
  46. EP250302a: Mondy Observations and Optical Light Curve
  47. EP250302a: VLT/MUSE optical redshift z = 1.131
  48. EP250302A: VLT near-infrared observations
  49. EP250302A: VLT/X-shooter tentative redshift
  50. EP250302a: OHP/T193 optical and spectroscopic observations
  51. EP250302a: Xinglong F60B optical observation
  52. EP250302a: Swift-XRT observations of a fading X-ray source
  53. EP250302a: Einstein Probe detection of an X-ray transient
  54. EP250302a: SVOM/C-GFT optical observations
  55. GRB 250226A: GRANDMA Optical Observations
  56. EP250302a: Montarrenti Observatory optical detection
  57. EP250302a: FTW optical and NIR detection
  58. EP250302a: Nanshan/HMT optical counterpart detection
  59. EP250228a: Optical observations with Kinder and Swift/UVOT
  60. GRB 250226A: KAO Optical Upper Limit
  61. GRB 250226A: AbAO AS-32 Optical Upper Limit
  62. EP250227a: TRT optical upper limit
  63. GRB 250225B: VLT/HAWKI near-infrared observations
  64. EP250227a: Optical upper limits with Kinder observations
  65. EP250227a: NOT optical observations
  66. GRB 250226A: Fermi GBM Observation
  67. EP250223a: J band upper limit by SYSU 80cm telescope
  68. GRB 250226A / EP250226a: LCO detection of the afterglow
  69. GRB 250225B: VLT/Xshooter imaging
  70. EP250225a: NOT optical candidate counterpart
  71. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  72. EP250226a / GRB 250226A: SVOM/VT optical observations
  73. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  74. EP250225a: TRT optical upper limits
  75. EP250226a/GRB 250226A: 1.6m Mephisto observations
  76. EP250226a/GRB 250226A: Kinder optical follow-up observations
  77. GRB 250225B: REM NIR upper limits
  78. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  79. EP250223a: CrAO ZTSH optical observation
  80. GRB 250225B: VLT optical and near-infrared candidate counterpart
  81. GRB 250225B: VLT/FORS2 candidate optical afterglow
  82. GRB 250225B: SVOM/GRM observation of a long burst
  83. GRB 250221A: EP-FXT detection of the X-ray afterglow
  84. EP250226a/GRB 250226A: GSP detects optical counterpart
  85. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  86. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  87. EP250226a / GRB 250226A: TRT optical counterpart observation
  88. EP250225a: GSP optical upper limit
  89. EP250223a: GMG Optical Observation
  90. EP250223a: GROWTH-India Telescope optical observations
  91. EP250215A: J band upper limit by SYSU 80cm telescope
  92. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  93. EP250223a: Kinder optical follow-up observations
  94. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  95. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  96. GRB 250219A: EP-FXT afterglow detection
  97. EP250223a: GOTO optical afterglow detections
  98. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  99. EP250223a: REM NIR upper limit
  100. EP250223a: TRT optical afterglow observation

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