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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"

19573 results found.

  1. EP250302a: VLT/MUSE optical redshift z = 1.131
  2. EP250302A: VLT near-infrared observations
  3. EP250302A: VLT/X-shooter tentative redshift
  4. EP250302a: OHP/T193 optical and spectroscopic observations
  5. EP250302a: Swift-XRT observations of a fading X-ray source
  6. EP250302a: Einstein Probe detection of an X-ray transient
  7. EP250302a: SVOM/C-GFT optical observations
  8. GRB 250226A: GRANDMA Optical Observations
  9. EP250302a: Montarrenti Observatory optical detection
  10. EP250302a: Nanshan/HMT optical counterpart detection
  11. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  12. GRB 250225B: VLT near-infrared afterglow confirmation
  13. EP250228a: Optical observations with Kinder and Swift/UVOT
  14. Konus-Wind detection of GRB 250226A
  15. GRB 250226A: KAO Optical Upper Limit
  16. GRB 250226A: AbAO AS-32 Optical Upper Limit
  17. EP250227a: TRT optical upper limit
  18. GRB 250225B: VLT/HAWKI near-infrared observations
  19. EP250227a: Optical upper limits with Kinder observations
  20. EP250227a: NOT optical observations
  21. EP250227a: Einstein Probe detected of a fast X-ray transient
  22. EP250228a: updates on the EP observations
  23. EP250223a: J band upper limit by SYSU 80cm telescope
  24. EP250228a: Einstein Probe detection of an X-ray transient
  25. GRB 250225B: VLT/Xshooter imaging
  26. GRB 250205A / EP250205A: further radio observations with the VLA
  27. EP250225a: NOT optical candidate counterpart
  28. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  29. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  30. EP250225a: TRT optical upper limits
  31. EP250226a/GRB 250226A: 1.6m Mephisto observations
  32. EP250226a/GRB 250226A: Kinder optical follow-up observations
  33. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  34. GRB 250225B: REM NIR upper limits
  35. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  36. EP250223a: CrAO ZTSH optical observation
  37. GRB 250225B: VLT optical and near-infrared candidate counterpart
  38. GRB 250225B: SVOM/GRM observation of a long burst
  39. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  40. EP250226a / GRB 250226A: TRT optical counterpart observation
  41. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  42. EP250223a: GMG Optical Observation
  43. EP250225a: Einstein Probe detected of a fast X-ray transient
  44. EP250223a: GROWTH-India Telescope optical observations
  45. EP250215A: J band upper limit by SYSU 80cm telescope
  46. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  47. EP250223a: Kinder optical follow-up observations
  48. GRB 250222A: SVOM/GRM observation of a burst
  49. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  50. EP250223a: REM NIR upper limit
  51. EP250223a: TRT optical afterglow observation
  52. EP250223a: refined analysis of the EP-WXT and FXT observations
  53. EP250223a: 1.6m Mephisto and 50cm array observations
  54. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  55. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO trigger with ID 762004910: Identification of a GW compact binary merger candidate possibly associated with a sub-threshold Swift/BAT-GUANO trigger
  56. EP250223a: OASDG optical observations
  57. EP250223a: NOT optical afterglow candidate
  58. EP250223a: Einstein Probe detection of an X-ray transient
  59. GRB 250221A: Optical counterpart detection by LCO.
  60. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  61. GRB 250221A: GRANDMA/TAROT Detection
  62. GRB 250221A: 1.6m Mephisto optical detection
  63. GRB 250221A: AKO Optical Upper Limit
  64. GRB 250221A: Swift/UVOT Detection
  65. EP250220a: Liverpool Telescope upper limits
  66. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  67. GRB 250221A: REM optical/NIR afterglow detection
  68. GRB 250221A: Enhanced Swift-XRT position
  69. EP250220a: 1.6m Mephisto observations
  70. EP250220a: Liverpool Telescope optical upper limits
  71. EP250220a: Optical upper limit with Kinder observations
  72. SVOM trigger sb25022102 is not an astrophysical event
  73. SVOM/sb25022102: SVOM detection of an X-ray transient
  74. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  75. GRB 250221A: Swift detection of a burst with an optical counterpart
  76. EP250220a: Xinglong optical upper limit
  77. GRB 250219A: Swift/UVOT Upper Limits
  78. GRB 250219A: OHP/T193 optical upper limit
  79. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  80. GRB 250219A: 1.6m Mephisto optical upper limits
  81. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  82. GRB 250219A: Swift ToO observations
  83. GRB 250219A: SVOM detection of a burst
  84. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
  85. GRB 250217C: Swift-XRT observations
  86. SVOM/sb25021804: QSO variability in Liverpool Telescope observations
  87. GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
  88. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  89. GRB 250217C: SVOM/GRM observation
  90. GRB 250217C: Tiled Swift observations
  91. Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
  92. SVOM/sb25021804: SVOM detection of a long X-ray transient
  93. LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
  94. GRANDMA/OPD observations of GRB250215A
  95. GRB 250215A / EP250215a: LCO detection of the afterglow
  96. GRB 250215A: Swift/UVOT Upper Limits
  97. GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  98. GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
  99. GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
  100. GRB 250215A: SVOM/GRM observation

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