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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"

15719 results found.

  1. EP250302a: NUTTelA-TAO Early Measurments
  2. EP250302a: optical observation from the INAF Asiago Observatory
  3. EP250302a: REM NIR upper limits
  4. EP250302a: Mondy Observations and Optical Light Curve
  5. EP250302a: VLT/MUSE optical redshift z = 1.131
  6. EP250302A: VLT near-infrared observations
  7. EP250302A: VLT/X-shooter tentative redshift
  8. EP250302a: OHP/T193 optical and spectroscopic observations
  9. EP250302a: Xinglong F60B optical observation
  10. EP250302a: Swift-XRT observations of a fading X-ray source
  11. EP250302a: Einstein Probe detection of an X-ray transient
  12. EP250302a: SVOM/C-GFT optical observations
  13. GRB 250226A: GRANDMA Optical Observations
  14. EP250302a: Montarrenti Observatory optical detection
  15. EP250302a: FTW optical and NIR detection
  16. EP250302a: Nanshan/HMT optical counterpart detection
  17. EP250228a: Optical observations with Kinder and Swift/UVOT
  18. GRB 250226A: KAO Optical Upper Limit
  19. GRB 250226A: AbAO AS-32 Optical Upper Limit
  20. EP250227a: TRT optical upper limit
  21. GRB 250225B: VLT/HAWKI near-infrared observations
  22. EP250227a: Optical upper limits with Kinder observations
  23. EP250227a: NOT optical observations
  24. GRB 250226A: Fermi GBM Observation
  25. EP250223a: J band upper limit by SYSU 80cm telescope
  26. GRB 250226A / EP250226a: LCO detection of the afterglow
  27. GRB 250225B: VLT/Xshooter imaging
  28. EP250225a: NOT optical candidate counterpart
  29. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  30. EP250226a / GRB 250226A: SVOM/VT optical observations
  31. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  32. EP250225a: TRT optical upper limits
  33. EP250226a/GRB 250226A: 1.6m Mephisto observations
  34. EP250226a/GRB 250226A: Kinder optical follow-up observations
  35. GRB 250225B: REM NIR upper limits
  36. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  37. EP250223a: CrAO ZTSH optical observation
  38. GRB 250225B: VLT optical and near-infrared candidate counterpart
  39. GRB 250225B: VLT/FORS2 candidate optical afterglow
  40. GRB 250225B: SVOM/GRM observation of a long burst
  41. GRB 250221A: EP-FXT detection of the X-ray afterglow
  42. EP250226a/GRB 250226A: GSP detects optical counterpart
  43. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  44. EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
  45. EP250226a / GRB 250226A: TRT optical counterpart observation
  46. EP250225a: GSP optical upper limit
  47. EP250223a: GMG Optical Observation
  48. EP250223a: GROWTH-India Telescope optical observations
  49. EP250215A: J band upper limit by SYSU 80cm telescope
  50. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Magellan upper limits.
  51. EP250223a: Kinder optical follow-up observations
  52. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  53. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  54. GRB 250219A: EP-FXT afterglow detection
  55. EP250223a: GOTO optical afterglow detections
  56. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  57. EP250223a: REM NIR upper limit
  58. EP250223a: TRT optical afterglow observation
  59. EP250223a: refined analysis of the EP-WXT and FXT observations
  60. EP250223a: 1.6m Mephisto and 50cm array observations
  61. GRB 250221A: TNOT detection of the optical counterpart
  62. EP250223a: SVOM/VT optical observation
  63. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  64. EP250223a: OASDG optical observations
  65. EP250223a: LCO detection of the afterglow
  66. EP250223a: early optical detection by BOOTES-4
  67. EP250223a: NOT redshift z = 2.756
  68. EP250223a: NOT optical afterglow candidate
  69. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  70. GRB 250221A: continued Mondy optical observations, brightening afterglow
  71. GRB 250221A: Optical counterpart detection by LCO.
  72. GRB 250221A: Mondy optical observations
  73. GRB 250221A: Assy optical observations
  74. EP250220a: FTW optical and NIR observations and upper limits
  75. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  76. GRB 250221A: VLT/X-shooter redshift z = 0.768
  77. GRB 250221A: GRANDMA/TAROT Detection
  78. GRB 250221A: NOT optical observations
  79. GRB 250221A: 1.6m Mephisto optical detection
  80. GRB 250221A: AKO Optical Upper Limit
  81. GRB 250221A: Swift/UVOT Detection
  82. EP250220a: Liverpool Telescope upper limits
  83. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  84. GRB 250221A: REM optical/NIR afterglow detection
  85. EP250220a: 1.6m Mephisto observations
  86. EP250220a: Liverpool Telescope optical upper limits
  87. EP250220a: Optical upper limit with Kinder observations
  88. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  89. GRB 250221A: Swift detection of a burst with an optical counterpart
  90. Swift GRB250221.15: Global MASTER-Net OT detection
  91. EP250220a: Xinglong optical upper limit
  92. GRB 250219A: OHP/T193 optical upper limit
  93. GRB 250219A: NOT optical observations
  94. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  95. GRB 250219A: 1.6m Mephisto optical upper limits
  96. GRB 250219A: SVOM/VT optical counterpart
  97. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  98. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  99. GRB 250217C: SVOM/GRM observation
  100. GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61

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