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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"

24594 results found.

  1. EP250302a: Swift/UVOT detection
  2. EP250302a: optical observation from the INAF Asiago Observatory
  3. EP250302a: REM NIR upper limits
  4. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  5. EP250302a: Mondy Observations and Optical Light Curve
  6. EP250302a: VLT/MUSE optical redshift z = 1.131
  7. EP250302A: VLT near-infrared observations
  8. EP250302A: VLT/X-shooter tentative redshift
  9. EP250302a: OHP/T193 optical and spectroscopic observations
  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: Nanshan/HMT optical counterpart detection
  16. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  17. GRB 250225B: VLT near-infrared afterglow confirmation
  18. EP250228a: Optical observations with Kinder and Swift/UVOT
  19. Konus-Wind detection of GRB 250226A
  20. GRB 250225B: EIRSAT-1 GMOD Detection
  21. GRB 250226A: KAO Optical Upper Limit
  22. GRB 250226A: AbAO AS-32 Optical Upper Limit
  23. EP250227a: Global MASTER-Net observations report
  24. EP250223A: Upper limits from Fermi-GBM Observations
  25. EP250227a: TRT optical upper limit
  26. GRB 250225B: VLT/HAWKI near-infrared observations
  27. EP250227a: Optical upper limits with Kinder observations
  28. EP250227a: NOT optical observations
  29. EP250227a: Einstein Probe detected of a fast X-ray transient
  30. EP250228a: updates on the EP observations
  31. GRB 250226A: Fermi GBM Observation
  32. EP250223a: J band upper limit by SYSU 80cm telescope
  33. EP250228a: Swift/XRT localisation
  34. EP250228a: Einstein Probe detection of an X-ray transient
  35. GRB 250226A / EP250226a: LCO detection of the afterglow
  36. LIGO/Virgo/KAGRA S250227e: Updated Sky localization
  37. LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
  38. GRB 250225B: VLT/Xshooter imaging
  39. GRB 250205A / EP250205A: further radio observations with the VLA
  40. EP250225a: NOT optical candidate counterpart
  41. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  42. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  43. EP250225a: TRT optical upper limits
  44. EP250226a/GRB 250226A: 1.6m Mephisto observations
  45. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  46. EP250226a/GRB 250226A: Kinder optical follow-up observations
  47. LIGO/Virgo/KAGRA S250223dk: Insight-HXMT/HE sub-threshold detection of a burst (HEB 250223501)
  48. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  49. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  50. GRB 250225B: Fermi GBM Observation
  51. GRB 250225B: REM NIR upper limits
  52. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  53. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  54. EP250223a: CrAO ZTSH optical observation
  55. GRB 250225B: VLT optical and near-infrared candidate counterpart
  56. GRB 250225B: SVOM/GRM observation of a long burst
  57. EP250226a/GRB 250226A: GSP detects optical counterpart
  58. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  59. EP250226a / GRB 250226A: TRT optical counterpart observation
  60. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  61. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  62. EP250225a: GSP optical upper limit
  63. EP250223a: GMG Optical Observation
  64. EP250225a: Einstein Probe detected of a fast X-ray transient
  65. GRB 250225B: Swift detection of a burst
  66. EP250223a: GROWTH-India Telescope optical observations
  67. GRB 250221A: Swift-BAT refined analysis
  68. EP250215A: J band upper limit by SYSU 80cm telescope
  69. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  70. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  71. EP250223a: Kinder optical follow-up observations
  72. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  73. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  74. GRB 250119B: VZLUSAT-2 detection
  75. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  76. GRB 250202B: VZLUSAT-2 detection
  77. GRB 250222A: SVOM/GRM observation of a burst
  78. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  79. GRB 250206A: VZLUSAT-2 detection
  80. EP250223a: REM NIR upper limit
  81. EP250223a: TRT optical afterglow observation
  82. EP250223a: refined analysis of the EP-WXT and FXT observations
  83. EP250223a: 1.6m Mephisto and 50cm array observations
  84. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  85. 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
  86. EP250223a: OASDG optical observations
  87. EP250223a: LCO detection of the afterglow
  88. EP250223a: Swift/XRT localization
  89. EP250223a: NOT optical afterglow candidate
  90. EP250223a: Einstein Probe detection of an X-ray transient
  91. LIGO/Virgo/KAGRA S250206dm: Upper limits from IceCube neutrino searches
  92. GRB 250221A: Optical counterpart detection by LCO.
  93. GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
  94. GRB 250221A: GRANDMA/TAROT Detection
  95. GRB 250221A: Swift-XRT refined Analysis
  96. GRB 250221A: NOT optical observations
  97. GRB 250221A: 1.6m Mephisto optical detection
  98. GRB 250221A: AKO Optical Upper Limit
  99. GRB 250221A: Swift/UVOT Detection
  100. EP250220a: Liverpool Telescope upper limits

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