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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.

Lucene Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

23211 results found.

  1. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  2. GRB 250309B: Fermi GBM Observation
  3. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  4. IceCube-250309A: No candidates from the Zwicky Transient Facility
  5. Fermi-LAT gamma-ray observations of IceCube-250309A
  6. GRB 250308A: SVOM/GRM detection of QPO in the tail emission
  7. EP250308a: Einstein Probe detection of an X-ray transient
  8. EP250308a: NOT optical upper limit
  9. EP250304a: MeerKAT detection of a possible radio counterpart
  10. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  11. EP250302a:Xinglong optical observations
  12. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  13. GRB250101A: Radio upper limits from VLA observations
  14. GRB 250305A: SVOM/GRM observation of a burst
  15. The EP-WXT trigger 01709132323 is likely a flaring star
  16. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  17. EP250302a: Optical Observations at CrAO and SAO RAS
  18. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  19. EP 250304A: Optical counterpart detection by LCO
  20. EP250302A: 1.3m DFOT optical afterglow detection
  21. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  22. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  23. Konus-Wind detection of GRB 250222A
  24. EP250304a: REM NIR upper limits
  25. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  26. EP250302a: Mondy Continued Optical Observations
  27. EP250304a: Swift-XRT detection of a fading X-ray source
  28. EP250304a: TRT optical counterpart detection
  29. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  30. EP250304a: Einstein Probe detection of an X-ray transient
  31. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  32. EP250302a: SAO RAS optical observations
  33. EP250302a : GIT optical follow-up
  34. EP250302a: Kinder optical follow-up observations
  35. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  36. EP250302a: Swift/UVOT detection
  37. EP250302a: optical observation from the INAF Asiago Observatory
  38. EP250302a: REM NIR upper limits
  39. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  40. EP250302a: Mondy Observations and Optical Light Curve
  41. EP250302a: VLT/MUSE optical redshift z = 1.131
  42. EP250302A: VLT near-infrared observations
  43. EP250302A: VLT/X-shooter tentative redshift
  44. EP250302a: OHP/T193 optical and spectroscopic observations
  45. EP250302a: Swift-XRT observations of a fading X-ray source
  46. EP250302a: Einstein Probe detection of an X-ray transient
  47. EP250302a: SVOM/C-GFT optical observations
  48. GRB 250226A: GRANDMA Optical Observations
  49. EP250302a: Montarrenti Observatory optical detection
  50. EP250302a: Nanshan/HMT optical counterpart detection
  51. GRB 250302A: Fermi GBM Final Real-time Localization
  52. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  53. GRB 250225B: VLT near-infrared afterglow confirmation
  54. EP250228a: Optical observations with Kinder and Swift/UVOT
  55. GRB 250226A: KAO Optical Upper Limit
  56. GRB 250226A: AbAO AS-32 Optical Upper Limit
  57. EP250227a: TRT optical upper limit
  58. GRB 250225B: VLT/HAWKI near-infrared observations
  59. EP250227a: Optical upper limits with Kinder observations
  60. EP250227a: NOT optical observations
  61. EP250227a: Einstein Probe detected of a fast X-ray transient
  62. EP250228a: updates on the EP observations
  63. GRB 250226A: Fermi GBM Observation
  64. EP250225a: EP-FXT follow-up observation
  65. EP250223a: J band upper limit by SYSU 80cm telescope
  66. EP250228a: Swift/XRT localisation
  67. EP250228a: Einstein Probe detection of an X-ray transient
  68. GRB 250225B: VLT/Xshooter imaging
  69. GRB 250205A / EP250205A: further radio observations with the VLA
  70. EP250225a: NOT optical candidate counterpart
  71. EP250226a/GRB 250226A:Xinglong optical follow-up observations
  72. EP250226a/GRB 250226A: refined analysis of the EP-WXT and FXT observations
  73. EP250225a: TRT optical upper limits
  74. EP250226a/GRB 250226A: 1.6m Mephisto observations
  75. LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
  76. EP250226a/GRB 250226A: Kinder optical follow-up observations
  77. LIGO/Virgo/KAGRA S250227e: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  79. GRB 250225B: Fermi GBM Observation
  80. GRB 250225B: REM NIR upper limits
  81. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Updated Sky localization and Coincidence with External Event
  82. Konus-Wind detection of GRB 250225B
  83. LIGO/Virgo/KAGRA S250223dk: DECam optical detections of Swift X-ray sources
  84. EP250223a: CrAO ZTSH optical observation
  85. GRB 250225B: VLT optical and near-infrared candidate counterpart
  86. GRB 250225B: SVOM/GRM observation of a long burst
  87. GRB 250221A: EP-FXT detection of the X-ray afterglow
  88. EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  89. EP250226a / GRB 250226A: TRT optical counterpart observation
  90. LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
  91. EP250226a/GRB 250226A: EP-WXT detection and FXT follow-up observation of an X-ray transient
  92. EP250223a: GMG Optical Observation
  93. EP250225a: Einstein Probe detected of a fast X-ray transient
  94. EP250223a: GROWTH-India Telescope optical observations
  95. EP250215A: J band upper limit by SYSU 80cm telescope
  96. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  97. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  98. EP250223a: Kinder optical follow-up observations
  99. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Upper limits from Fermi-GBM Observations
  100. GRB 250119B: VZLUSAT-2 detection

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