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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"

19089 results found.

  1. EP 250304A: Optical counterpart detection by LCO
  2. EP250302A: 1.3m DFOT optical afterglow detection
  3. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  4. EP250304a: REM NIR upper limits
  5. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  6. EP250302a: Mondy Continued Optical Observations
  7. EP250304a: TRT optical counterpart detection
  8. EP250304a: Einstein Probe detection of an X-ray transient
  9. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  10. EP250302a: SAO RAS optical observations
  11. EP250302a : GIT optical follow-up
  12. EP250302a: Kinder optical follow-up observations
  13. EP250302a: Swift/UVOT detection
  14. EP250302a: optical observation from the INAF Asiago Observatory
  15. EP250302a: REM NIR upper limits
  16. EP250302a: Mondy Observations and Optical Light Curve
  17. EP250302a: VLT/MUSE optical redshift z = 1.131
  18. EP250302A: VLT near-infrared observations
  19. EP250302A: VLT/X-shooter tentative redshift
  20. EP250302a: OHP/T193 optical and spectroscopic observations
  21. EP250302a: Swift-XRT observations of a fading X-ray source
  22. EP250302a: Einstein Probe detection of an X-ray transient
  23. EP250302a: SVOM/C-GFT optical observations
  24. GRB 250226A: GRANDMA Optical Observations
  25. EP250302a: Montarrenti Observatory optical detection
  26. EP250302a: Nanshan/HMT optical counterpart detection
  27. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  28. GRB 250225B: VLT near-infrared afterglow confirmation
  29. EP250228a: Optical observations with Kinder and Swift/UVOT
  30. Konus-Wind detection of GRB 250226A
  31. GRB 250226A: KAO Optical Upper Limit
  32. GRB 250226A: AbAO AS-32 Optical Upper Limit
  33. EP250227a: TRT optical upper limit
  34. GRB 250225B: VLT/HAWKI near-infrared observations
  35. EP250227a: Optical upper limits with Kinder observations
  36. EP250227a: NOT optical observations
  37. EP250227a: Einstein Probe detected of a fast X-ray transient
  38. EP250228a: updates on the EP observations
  39. EP250223a: J band upper limit by SYSU 80cm telescope
  40. EP250228a: Einstein Probe detection of an X-ray transient
  41. GRB 250225B: VLT/Xshooter imaging
  42. GRB 250205A / EP250205A: further radio observations with the VLA
  43. EP250225a: NOT optical candidate counterpart
  44. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  45. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  46. EP250225a: TRT optical upper limits
  47. EP250226a/GRB 250226A: 1.6m Mephisto observations
  48. EP250226a/GRB 250226A: Kinder optical follow-up observations
  49. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  50. GRB 250225B: REM NIR upper limits
  51. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  52. EP250223a: CrAO ZTSH optical observation
  53. GRB 250225B: VLT optical and near-infrared candidate counterpart
  54. GRB 250225B: SVOM/GRM observation of a long burst
  55. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  56. EP250226a / GRB 250226A: TRT optical counterpart observation
  57. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  58. EP250223a: GMG Optical Observation
  59. EP250225a: Einstein Probe detected of a fast X-ray transient
  60. EP250223a: GROWTH-India Telescope optical observations
  61. EP250215A: J band upper limit by SYSU 80cm telescope
  62. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  63. EP250223a: Kinder optical follow-up observations
  64. GRB 250222A: SVOM/GRM observation of a burst
  65. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  66. EP250223a: REM NIR upper limit
  67. EP250223a: TRT optical afterglow observation
  68. EP250223a: refined analysis of the EP-WXT and FXT observations
  69. EP250223a: 1.6m Mephisto and 50cm array observations
  70. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  71. 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
  72. EP250223a: OASDG optical observations
  73. EP250223a: NOT optical afterglow candidate
  74. EP250223a: Einstein Probe detection of an X-ray transient
  75. GRB 250221A: Optical counterpart detection by LCO.
  76. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  77. GRB 250221A: GRANDMA/TAROT Detection
  78. GRB 250221A: 1.6m Mephisto optical detection
  79. GRB 250221A: AKO Optical Upper Limit
  80. GRB 250221A: Swift/UVOT Detection
  81. EP250220a: Liverpool Telescope upper limits
  82. GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
  83. GRB 250221A: REM optical/NIR afterglow detection
  84. GRB 250221A: Enhanced Swift-XRT position
  85. EP250220a: 1.6m Mephisto observations
  86. EP250220a: Liverpool Telescope optical upper limits
  87. EP250220a: Optical upper limit with Kinder observations
  88. SVOM trigger sb25022102 is not an astrophysical event
  89. SVOM/sb25022102: SVOM detection of an X-ray transient
  90. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  91. GRB 250221A: Swift detection of a burst with an optical counterpart
  92. EP250220a: Xinglong optical upper limit
  93. GRB 250219A: Swift/UVOT Upper Limits
  94. GRB 250219A: OHP/T193 optical upper limit
  95. GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  96. GRB 250219A: 1.6m Mephisto optical upper limits
  97. LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
  98. GRB 250219A: Swift ToO observations
  99. GRB 250219A: SVOM detection of a burst
  100. SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability

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