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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"

2623 results found.

  1. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 241223A: GOTO optical observations summary
  3. GRB 241105A: JWST photometric observations of the host galaxy
  4. GRB 241209B: host galaxy detection and GTC/OSIRIS+ spectroscopy
  5. GRB 241218A: Swift-BAT refined analysis
  6. EP 241217a: NIR detection with P200/WIRC
  7. EP 241217a: Possible J-band detection with WINTER
  8. EP241217a: Kinder optical follow-up observations
  9. EP241107a: VLA Radio Observation
  10. GRB 241212A: Fermi GBM detection
  11. GRB 241206C: GRBAlpha detection
  12. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  13. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  14. EP241201a: 1.6m Mephisto Optical Upper Limits
  15. GRB 241201A: GRBAlpha detection
  16. EP241202b: Kinder optical counterpart candidate
  17. EP241201a: Kinder optical counterpart candidate
  18. Swift-XRT observations of IceCube -241127A
  19. IceCube-241127A: IceCube observation of a high-energy neutrino candidate track-like event
  20. EP241125a: EP detection of an X-ray transient
  21. Konus-Wind detection of GRB 241117A
  22. IPN triangulation of GRB 241117A
  23. EP241021a and EP241026b: Keck/LRIS spectroscopic observations
  24. EP trigger ID 01709065118: Keck/LRIS spectroscopic observations
  25. GRB 241120A: Mondy and AbAO optical observations
  26. GRB 241113A: Possible ATCA Radio detection
  27. EP241115a/GRB 241115D: Swift/XRT follow-up observation
  28. EP 241113a: LBT possible optical counterpart
  29. IceCube-241113A - IceCube observation of a high-energy neutrino candidate track-like event
  30. LIGO/Virgo/KAGRA S241109bn: ATLAS observations and discovery of the potential counterpart AT2024aawt
  31. GRB 241030A: Mondy optical observations
  32. LIGO/Virgo/KAGRA S241102br: OHP/T193 optical observations
  33. EP241101a: Possible detection of an optical counterpart with FTW
  34. GRB 241030A / EP241030a: GMG possible spectroscopic redshift at z ~ 1.4
  35. GRB 241030A: detection of the bright optical counterpart in ATLAS forced photometry
  36. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  37. EP 241026b: LBT possible optical counterpart (brightening source)
  38. GRB 240821A: Keck/LRIS spectroscopic observations
  39. GRB 241026A: SAO RAS observations of possible optical afterglow
  40. IceCube-241006A - IceCube observation of a high-energy neutrino candidate track-like event
  41. EP trigger ID 01709064214: GOTO confirms detection as a flare star
  42. IceCube-240929A - IceCube observation of a high-energy neutrino candidate track-like event
  43. EP240918a: Swift-XRT observation
  44. EP240918a: YAHPT Optical Upper Limit
  45. GRB 240912A: Swift-BAT refined analysis
  46. Fast X-ray Transient EP240801a: GMRT radio observations
  47. GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
  48. GRB 240819A as a likely X-Ray Flash
  49. GRB 240828B : Detection of a possible very soft X-ray transient by SVOM/ECLAIRs
  50. EP240801a: Keck/LRIS spectroscopic redshift confirmation
  51. IceCube-240808A - IceCube observation of a high-energy neutrino candidate track-like event
  52. The EP-WXT trigger 01709018832 on August 7th is likely a flaring star
  53. EP240801a: NOT optical observations
  54. IceCube-240725A - IceCube observation of a high-energy neutrino candidate track-like event
  55. IceCube-240721A - IceCube observation of a high-energy neutrino candidate track-like event
  56. EP240708a: X-ray follow-up observations with Swift/XRT
  57. The EP-WXT source triggered on July 14th is likely a flaring star
  58. GRB 240713A: J-band upper limit from WINTER
  59. GRB240713A: X-ray follow-up observation with EP-FXT
  60. EP240708a: X-ray follow-up observations with EP/FXT and Swift/XRT
  61. EP240703a and EP240703b: Swift/XRT upper limits
  62. EP240702a: Swift/XRT upper limit
  63. EP240626a: Montarrenti Observatory optical upper limit
  64. EP240618a: NOT further optical observations
  65. X-ray transient EP240618a: Fermi/GBM non-detection
  66. EP240618a: Swift/XRT upper limit
  67. EP240617a: tentative Swift/XRT detection of the afterglow
  68. GRB 240615A: possible transient detection from Wendelstein observations
  69. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  70. Swift Trigger 1235109: a possible GRB 240606A
  71. GRB 240603B: Swift detection of a possible burst
  72. GRB 240529A: MASTER prompt OT detection
  73. The EP-WXT source triggered on June 1st is likely a flaring star
  74. EP240518a: GSP optical upper limit
  75. EP240518a: possibly identified with a flare star by EP-FXT
  76. GRB 240514E: A possible candidate BD-21 1074
  77. GRB 240502C: Zeiss-1000 at Koshka observations of GOTO24bao optical counterpart candidate
  78. GRB 240514B: GOTO candidate optical counterpart
  79. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  80. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  81. GRB 240502C: Zeiss-1000 at Koshka observatory observations of GOTO optical counterpart candidates
  82. IPN triangulation of GRB 240501B and GRB 240501A - possible episodes of ultra long GRB
  83. GRB 240502C: GOTO possible optical counterpart candidates
  84. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  85. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  86. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  87. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  88. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  89. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  90. EP240426a: YAHPT optical upper limit
  91. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  92. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  93. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  94. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  95. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  96. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  97. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  98. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  99. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  100. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure

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