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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"

16192 results found.

  1. GRB 250314A: REM optical/NIR upper limits
  2. GRB 250316A: AbAO AS-32 Optical Upper Limit
  3. EP 250317B: Fading optical counterpart detection by LCO
  4. GRB 250316A: Swift-XRT afterglow detection
  5. GRB 250317B: LCO detection of the fading optical afterglow
  6. GRB250317B: SVOM/VT detection of an optical candidate from VHF data
  7. GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
  8. GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
  9. GRB 250317B: SVOM detection of a burst
  10. GRB 250314A: SVOM/GRM analysis
  11. The EP-WXT trigger 01709132801 is likely a flaring star
  12. GRB 250314A: EP-FXT afterglow detection
  13. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 250314A: Swift/UVOT Upper Limits
  15. GRB 250314A: Swift XRT Detection
  16. EP250315a: optical counterpart candidate detected by Gemini North
  17. EP250315a: Einstein Probe detection of an X-ray transient
  18. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  19. SVOM/MXT upper limit on GRB 250314A
  20. GRB 250314A: SVOM/VT upper limit
  21. GRB 250314A: NOT near-infrared candidate counterpart
  22. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  23. GRB 250314A: SVOM detection of a burst
  24. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  25. EP250304a: Pan-STARRS r and i-band imaging and photometry
  26. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  27. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  28. EP250311a/GRB 250311A: EP-FXT follow-up observation
  29. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  30. GRB 250312A: Enhanced Swift-XRT position
  31. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  32. GRB 250312A: Swift detection of a burst
  33. GRB 241213A: VIRT Optical Upper Limit
  34. GRB 241228A: VIRT Optical Upper Limit
  35. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  36. GRB 230509B: 1.3m DFOT Optical observations
  37. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  38. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  39. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  40. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  41. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  42. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  43. GRB 250309B: PRIME near-infrared detection
  44. GRB 250225B: Swift-BAT refined analysis
  45. GRB 250311A/EP250311a: TRT optical upper limit
  46. EP250311a/GRB 250311A: EP-WXT detection
  47. The EP-WXT trigger 01709132425 is not a real source
  48. GRB 250309B / AT2025dws: further SAO RAS optical observations
  49. EP250308a: 1.6m Mephisto optical upper limits
  50. IPN triangulation of GRB 250308A (short)
  51. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  52. GRB 250309B / AT2025dws: SAO RAS optical observations
  53. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  54. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  55. IceCube-250309A: No candidates from the Zwicky Transient Facility
  56. IceCube Alert 250309.32: Global MASTER-Net observations report
  57. EP250308a: Global MASTER-Net observations report
  58. EP250308a: Einstein Probe detection of an X-ray transient
  59. EP250308a: NOT optical upper limit
  60. GRB 250309A: Fermi GBM Final Real-time Localization
  61. The EP-WXT trigger 01709132387 is likely a flaring star
  62. EP250304a: MeerKAT detection of a possible radio counterpart
  63. EP250302a:Xinglong optical observations
  64. GRB250101A: Radio upper limits from VLA observations
  65. GRB 250305A: SVOM/GRM observation of a burst
  66. The EP-WXT trigger 01709132323 is likely a flaring star
  67. EP250302a: Optical Observations at CrAO and SAO RAS
  68. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  69. EP 250304A: Optical counterpart detection by LCO
  70. EP250302A: 1.3m DFOT optical afterglow detection
  71. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP250304a: REM NIR upper limits
  73. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  74. EP250302a: Mondy Continued Optical Observations
  75. EP250304a: TRT optical counterpart detection
  76. EP250304a: Einstein Probe detection of an X-ray transient
  77. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  78. EP250302a: SAO RAS optical observations
  79. EP250302a : GIT optical follow-up
  80. EP250302a: Kinder optical follow-up observations
  81. EP250302a: Swift/UVOT detection
  82. EP250302a: optical observation from the INAF Asiago Observatory
  83. EP250302a: REM NIR upper limits
  84. EP250302a: Mondy Observations and Optical Light Curve
  85. EP250302a: VLT/MUSE optical redshift z = 1.131
  86. EP250302A: VLT near-infrared observations
  87. EP250302A: VLT/X-shooter tentative redshift
  88. EP250302a: OHP/T193 optical and spectroscopic observations
  89. EP250302a: Einstein Probe detection of an X-ray transient
  90. EP250302a: SVOM/C-GFT optical observations
  91. GRB 250226A: GRANDMA Optical Observations
  92. EP250302a: Montarrenti Observatory optical detection
  93. EP250302a: Nanshan/HMT optical counterpart detection
  94. The EP-WXT trigger 01709132140 is likely a flaring star
  95. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  96. GRB 250225B: VLT near-infrared afterglow confirmation
  97. EP250228a: Optical observations with Kinder and Swift/UVOT
  98. GRB 250226A: KAO Optical Upper Limit
  99. GRB 250226A: AbAO AS-32 Optical Upper Limit
  100. EP250227a: TRT optical upper limit

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