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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"

19576 results found.

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

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